Application Techniques, Chemicals and Control
Baits Used for Gopher Control
Strychnine is a white crystalline powder with a characteristic bitter taste and mild aroma. The bitter taste is significant. Although this apparently does not affect the acceptance of the bait to gophers the taste is a warning to applicators of exposure to the chemical. Humans can taste very small quantities of this chemical. Strychnine is one of the most toxic pesticides with an Acute oral LD50 0f a little less than 2 (Category 1 material). Since strychnine is not water soluble and the baits are very dry there is little danger from exposure through the skin.
There are a number of formulations of strychnine baits but most depend on the impregnation of this highly toxic material on grain bait. The baits vary considerably in percent strychnine of the final formulation ranging from .3 percent to 3 percent. Generally speaking the higher the concentration, the more effective is the bait. For the purpose of detection and possibly making them less attractive to nontarget organisms (e.g. birds) baits containing strychnine are marked with a green dye.
Human poisoning due to strychnine in adults is usually a result of suicide attempts or accidental ingestion by children. Again absorption through the skin when formulated as a bait and inhalation potential is very low; however, a certain amount of dust residue accumulates at the bottom of packaging that should be avoided when pouring from the original container.
Strychnine is extremely toxic when ingested and acts very rapidly with the onset of symptoms within 30 minutes or sooner. Symptoms begin as stiffness in the knees and muscle spasms in the arms and legs followed by muscle spasms, which eventually can lead to death due to respiratory failure. In the case of poisoning, once symptoms begin to appear, attempts to induce vomiting should be avoided as this in itself can result in convulsions. Bright light, excessive moving of the victim and loud noises may also increase the chances of convulsions.
Poisoning of domestic animals most frequently occurs when strychnine baits are added to meats (e.g. hamburger) and intentionally used to poison someone pet or pets. Because strychnine use for commercial and homeowner control is confined to gophers the chance of a non-target organism consuming a poisoned animal is quite low. Since strychnine is so fast acting almost all poisoned gophers die below ground. If a large number of gophers are killed in a short period of time this possibility still does exist.
Protective Equipment Required.
Long sleeve shirt and long pants.
Shoes and socks.
Application and Equipment. Application of the highest concentration (3%) is restricted to gopher burrow building machines. Baits containing a 1.8% concentration or lower can legally be applied with a long-handled spoon or hand held mechanically dispensing gopher probe.
Most companies that specialize in gopher control do not use hand held mechanically dispensing gopher probes but prefer non-mechanical probes (Figure 1) for locating the gopher’s tunnels and long handled spoons for application. The reason for this preference is that the mechanical probes (Figure 2) typically rely on dispensing the bait though a small opening located at the end of a rather large diameter probe. Two problems can occur when using this type of a probe. First of all, as indicated, the diameter of the probe is quite large (up to 1 inch or more). This large size makes it difficult to locate the gopher’s tunnel which can occur a foot or more below the ground. Secondly the small opening at the end of the probe frequently becomes plugged with earth thus preventing release of the chemical into the gopher’s tunnel.
Figure 1. A nonmechanical gopher probe.
Figure 2. A mechanical gopher probe.
The advantage of a non-mechanical probe is that the diameter of the probe is quite small thus making it more sensitive in finding the gopher’s tunnel. Once the tunnel is located the probe can be withdrawn, flipped around 180 degrees and used to expand the opening with the large end of the probe. This enlarged opening to the tunnel allows accurate spooning of the bait into the tunnel. It is extremely important that all the bait be placed into the gopher’s tunnel and that none is left above ground. Leaving and strychnine bail above ground is considered a serious violation by the California Department of Pesticide Regulations.
The normal suggested application of strychnine baits is several teaspoons per burrow system. In cases of very heavy infestations it is almost impossible to tell where one gopher system ends and another one begins. In this case where there are mounds “everywhere” it is suggest placing treatments in a grid-like fashion, namely treat every 10 feet at each corner of the subsections of the grid.
It is important to place all bait in the main run of a gopher’s burrowing system (Figure 3). The main run typically runs parallel to the surface and typically is found from 2 to 18 inches below the ground. Extending from the main run to the surface are one or more lateral runs. These are used by gophers to push excess soil from the tunnel to the surface. This activity results in the large mounds that are found above ground. If bait is mistakenly placed in the lateral runs the possibility exist that a gopher may push the bait above ground while removing soil from the tunnel. Lateral runs are typically filled with soil so it again points out the importance of using a sensitive probe to find the correct location for bait placement. A sensitive probe greatly increase the chance of determining the difference between a lateral run filled with loose soil and a main run the is void of loose soil. Even if bait place in the lateral run isn’t pushed above ground a gopher would have a hard time finding it since it would be buried in soil.
Figure 3. A diagrammatic representation of a mature gopher tunneling system.
The location of the below ground main run can frequently be ascertained by examination of the large above ground mounds. These mounds are typically horseshoe shaped with a high side and low side. There is also an earthen plug (located next to open end of horseshoe-Figure 4, 5) that occurs within mound that functions to close the entrance of the lateral run that leads to the main run.
Figure 4. A typical horseshoe shaped gopher mound. Top of image is high side of mound. Note the circular plug of earth that fills the entrance of lateral run. Large x indicates where main run is likely to occur below ground.
Figure 5. A diagrammatic illustration of how to find the main run. Also note the slightly expanded tip of the mechanical gopher probe. This tip in fact makes the probe very sensitive in find the run.
Considering the previous description the main run in the above diagram would likely occur approximately 1 foot out from the earthen plug or in the location marked by the big x. This would be the location where probing should begin and once found where bait should be placed.
Zinc Phosphide Baits
Zinc phosphide reacts with atmospheric moisture to slowly release phosphine (not phosgene), a toxic and flammable gas with an odor similar to garlic or onions. This is again a Category 1 material with an LD50 of around 30.When formulated as grain bait and exposed to normal atmospheric conditions the gas that is produced presents little hazard. However when exposed to acidic conditions (as in the stomach) the gas is released quickly accounting for the toxic nature of the chemical. Although zinc phosphide baits have a strong pungent odor this seems to attract rodents, especially rats, and apparently makes the bait unattractive to some other animals. Bait shyness is a problem if rodents are exposed to sub lethal amounts of the toxicant.
Under normal conditions there is only a small amount of deterioration of zinc phosphide baits due to the loss of phosphine gas. Under field conditions, zinc phosphide baits can remain active for several months until the grain rots or is carried off by harvester ants or other insects. Mineral oil is sometimes added to the grain baits, which gives a considerable amount of protection from moisture.
Animals that consume lethal amounts of zinc phosphide typically die within 30 hours. Early symptoms include nausea, tightness of the chest, excitement and an overall feeling of cold and vomiting of a black colored stomach contents and the garlic smell of phosphine gas. Advanced symptoms include convulsions, paralysis, coma and death due to respiratory failure. If symptoms extend for several days intoxication occurs with resultant heavy liver damage. Typically if an individual lives for 3-day recovery is complete. The odor and color of zinc phoshide baits (gray) are a supposed safety factor in some situations. However as little as a teaspoon of bait can cause toxic symptoms in a child who of course might not be deterred by the color odor.
The dust at the bottom of zinc phosphide container creates a potential hazard and every precaution should be maintained to inhaling this material when pouring from the original packaging. Zinc phosphide bait should not be handled without gloves. Oils and other liquid are used in the preparation of some bait. As a result repeated handling can results in small amount being absorbed through the skin.
Zinc phosphide is not stored in muscles or other tissues so true secondary poisoning (poisoning of non-target animals-dogs, cats) does not seem to be a problem with this chemical. However, if a non-target animal consumed enough poisoned rodent with bait in their stomachs problems could occur. I am aware of a least one situation where a very large number of gophers were poisoned with zinc phosphide and 2 foxes died the following day supposedly due to consuming a number of poisoned gophers. Since this is a slower acting than strychnine it is more probable that some of the animals would die above ground. Still zinc phosphide is considered one of the safest rodeticides from the standpoint of secondary kills. It has the additional safety factor of being an emetic and consequently will be regurgitated if consumed by non-target organisms.
The main formulation that is used as gopher bait is 2% zinc phosphide in an alfalfa pellet. Based on the authors experience this bait is far less effective for gopher control than the strychnine baits. On advantage is that is safer to use than strychnine.
Application. The same techniques used to apply strychnine baits apply to zinc phosphide bait.
Multiple Dose Anticoagulant Baits
Formulation and Toxicity. Chlorophacinone and diphacinone are the most commonly used of the multiple dose anticoagulants with diphacinone being the most commonly used of the 2. Anticoagulant baits are typically dyed blue, which serves as a marker for identification and supposedly makes them less attractive to seed feeding birds and other non-target organisms. As previously mentioned, these materials work by preventing clotting of the blood, rupturing capillary blood vessels and subsequently causing the animal to bleed to death internally. They are referred as multiple dose anticoagulants because in order to be effective an animal typically has to feed on them over a several day period. This is considered to be a slow, but painless death. In the uncommon instance of accidental poisoning there is an antidote, vitamin K.
Application. The same techniques outline for strychnine can be used for these baits. These baits are relatively safe to use and have little if any effect on nontarget organisms (when used below ground for gopher control). Generally speaking they are not that effective for control of these pests when compared to strychnine baits. The problem that exists is that in order to be effective a gopher must feed on them for several consecutive days. Under most conditions it is unlikely that grain based baits will remain attractive to these past for more than a few days. Under moist condition grain baits mold within a few day. This problem can be partially eliminated by treating in a dozen or more locations
daily within the tunneling system. There are also formulations of anticoagulant baits that are imbedded in a wax-like material. Of course in this case the idea is to prevent molding. The author is not aware of how attractive these wax coated baits are to gophers.
Factors Effecting Success with Baits.
Many factors influence the success of control with baits. Dry, sandy soil collapses easily, burying the baits so it’s difficult for the gopher to find. Also in dry soil, gophers may not show signs of activity until moisture is available. On the other hand, excessive moisture can cause the bait to mildew quickly, making it unpalatable to gophers. In our experience, the types of available plants affect how quickly gophers accept bait. For example, gophers are controlled more easily with baits in turf than in O’Connor’s legume (a favored gopher food), as the latter is a preferred host.
Finally, gophers may become “bait shy” if they ingest sub-lethal amounts of bait and become sick. Because the animal associates the sickness with the taste of the bait, it will no longer feed on it. Once this occurs, other types of bait or alternative control method should be used. Bait shyness may develop rapidly in a few gophers; however, typically it takes many months, or even years, of repeated applications to occur in many individuals of a large population.
There are a number of different types of gas cartridges on the market that can be used for gopher control. These range in size from the small cartridges that can be purchased from home and garden center to the large commercial size that are available from The Department of Agriculture (Figure 6 ).
Figure 6 . A commercial gas bomb.
These typically come with a fuse. Once ignited the cartridges are placed in the tunneling system. The subsequent combustion produces a toxic gas-carbon monoxide primarily. Generally speaking these type devices are considered the least effective of the various gopher control techniques. The reason being is it is that gophers have a well-developed sense of smell and can quickly sense the presence of a burning bomb and simply shut off that end of the tunnel where it occurs.
There are two possible situations where control might be achieved with these devices. One would be where a gopher has recently moved into and formed a new tunnel. In this case the tunnel is very short (a few to several feet) and of course more chance of the gas quickly filling the entire tunnel. The other might be where a gopher is trapped between two or more bombs that have been placed in the tunnel.
Formulation-Toxicity. The most popular formulation of this material for use in outdoor vertebrate pest control is tablets, which are marble like in size. This material is a highly toxic fumigant (Category 1) but as it currently stands a gas mask is not required when used in an outdoor location for vertebrate pest control. To their author’s knowledge there are no cases of human death from the use of this highly toxic material when used outdoors for vertebrate pest control. Aluminum phosphide is also used indoor for grain fumigation and clearly presents more of a potential hazard in this situation.
These materials are packaged in an airtight aluminum canister (Figure 7). Once aluminum phosphide tablets are removed from their canister containers and come in contact with atmospheric or any type of moisture the highly toxic phosphine gas begins to be released. This gas is clear and odorless but due to certain contaminants normally has garlic-like smell. It is important to limit how long an individual canister is left open, as atmospheric moisture will react with the tablets in the canister and release gas. Once the canister is tightly closed available moisture is quickly used up and the additional pressure produced by the small amount of gas produced in the canister essentially stops any further release from the tablets.
Protective Equipment Required.
Cotton gloves only when used outdoor for vertebrate pest control.
Figure 7. A canister of Fumitoxin.
Application. Aluminum phosphide may be applied to underground burrow systems located in noncrop or crop areas occupied by woodchucks, yellowbelly marmots, prairie dogs, (except Utah prairie dogs), Norway rats, roof rats, house mice, ground squirrels, moles, voles or chipmunks. All applications must be made outside and not within 15 feet of inhabited structures and under no conditions can applications be made when a burrow system opens under an occupied building.
When opening an aluminum phosphide canister, one should do so with the opening pointed away from face and body and, if possible, in a crosswind. This will not only limit applicator exposure but will serve to protect in the unlikely event of a flash ignition. If large amounts of aluminum phosphide dust accumulate in the bottom of a canister, heat may be generated with a resultant flash when exposed to air. I have been working with this material for almost 20 years and this has never happened. The label also advises not to open canisters in a flammable situation. Because the amount of gas released from tablet or other formulation increases with available moisture (atmospheric or otherwise) some operators have attempted to add water to a treated area (e.g. adding water to a ground squirrel burrow). This is generally considered an unadvisable practice as it increases applicator exposure and the chance of ignition.
When properly used aluminum phosphide (Phostoxin, Gastoxin, Fumitoxin) is by far the most superior rodenticide used for gopher control. It is advisable to only remove the number of tablets that are going to be used within a short period, as this will limit applicator exposure. Cotton or leather gloves should be used when handling aluminum phosphide tablets. Recent experiments indicate that leather gloves (as opposed to cotton) may reduce applicator exposure.
The recommended rate for gophers is 2 to 3 tablets per burrow system. However, in cases of very heavy infestations it is almost impossible to tell where one gopher system ends and another one begins. In this case where there are mounds “everywhere” it is suggest placing treatments in a grid-like fashion, namely treat every 10 feet at each corner of the subsections of the grid.
This is an extremely effective material when used properly in certain environmental conditions. Ideal conditions for effective control include adequate soil moisture, heavy clay soil and access to the entire length of a gopher’s tunneling system.
Aluminum phosphide is generally less effective in sandy soil. The logical reason for this is that in this type of soil, a certain amount of gas escapes from the runs. If sandy soil exists, this problem can be partially alleviated if there is a high level of moisture in the soil, presumably sealing the runs and releasing the gas at a faster rate.
If the entire length of a gopher’s run is not treated, the gopher may escape the gas by plugging off one end of the tunneling system with soil. Best results are achieved by first placing a tablet at each end of the system and then as many as needed at intermittent intervals in between. For effective control, tablets should be applied at the rate of 2 to 4 per burrow system. With very heavily infestations (e.g. a mound ever 3 or 4 feet) the applicator really doesn’t know how many gopher systems there are in a given area. In this situation we have found treating the burrows with one tablet every 15 feet in a grid-like fashion typically will give good control.
Treatment consists of opening up the main runs with a metal probe and dropping a tablet into the tunnel and then closing off the opening. Some county Departments of Agriculture or other regulatory agencies insist that the tunnel be reclosed with a wad of paper and then a barrier of soil.
The possibility exists that endangered species may be found in or around the burrows of target pests. The applicator must always be aware that this possibility exists and take every step necessary to protect these federally and state protected animals when using this or any other pesticide. Generally speaking, information on endangered species can be obtained from a county or state department of agriculture office or from local, state or federal game offices.
Trapping, although effective, is time consuming and best used for small areas with light populations of gophers. In heavy infestations there may be hundreds of gophers per acre. Considering the reproductive capacity of these pests, it would be difficult (if not impossible) to control large populations with traps alone. A good trapper typically can set and later check 8 or 9 in an hour. An average catch rate would possibly be 50 %. Assuming there is a large area (10 acres) with a heavy gopher population and taking into account that the average female will produce 6 to 7 young every 4 months who within a few months will also begin reproducing, the numbers become astounding. In this type of situation it would take (according to my math) 3 people trapping 8 hours a day, 30 days a month to stay even with the population. Maybe my math isn’t that good but the point should be made. Traps do not give effective control with big populations of gophers!
One of our studies compared the effectiveness of several models of box and snap traps-the 2 basic trap types (Figure 8). As can be seen from the results in Figure 9, there was a large variation in the degree of effectiveness from model to model.
Figure 8. The two commonly used types of gopher traps. Image courtesy of California Department of Agriculture.
Normally traps are not baited with any food to attract the gopher. Gophers are normally attracted by light or run into the traps randomly. Typically, snap-type traps (Macabee, Victor) are best set in the main run while box traps are set in the lateral run or in the main run, if there is room (Figure 10).
Snap Traps* No. of sets Percentage Catch
Macabee 263 48.7
Victor Gopher 292 62.2
Newhouse 260 36.7
Box Traps **
Cook Box 294 42.2
Baitless Gopher 267 31.3
Go For Steel 292 16.1
Guardian 278 59.3
California Box 261 44.3
* One set of a snap traps is defined as one trap set in both directions of the main run.
**One set of a box trap is defined as a single trap set in the lateral run.
Figure 9. Comparative efficiency of various commercially available gopher traps. \
Figure 10. Typical locations when setting snap or box type gopher traps and proper placement of baits=bait should be placed in the main run (right). Image courtesy of California Department of Agriculture.
How to set a trap. If possible it is best to set a trap or traps in the main run. In some cases this may not be possible because available space (especially with larger box traps. Once the main run is exposed the trap or traps should be placed as far as possible into the tunnel. Any loose soil should be removed from the tunnel prior to placement. It’s best to work the trap down a little into the soil whenever possible. Snap traps should be secured to a stake with a small chain or wire. If not, a trapped gopher will likely drag the unsecured trap deep into its tunnel before dying. Once in place, soil should be used to close off the tunnel behind the traps. Gophers readily close off any light entering their tunnel system. . In the case of snap-type traps it is preferable to leave a pinpoint of light shining through this earthen closure. The theory is that if too much light (behind the trap) enters the tunnel, the gopher pushes dirt to close off the tunnel and merely sets off the trap with this soil. On the other hand, if a pinpoint of light is left behind the trap, the gopher will think (?) the opening is further down the tunnel and thus more readily blunder to the trap in its attempt to reach the distant opening.
Most box traps already have a hole in them to allow a certain amount of light into the tunnel. In the case of the Guardian box trap, there is a baffle at the back of the trap that covers the hole and permits a minimum amount of light into the tunnel but which supposedly allows a draft to enter. The theory behind this trap is that the draft attracts the gopher.
A trap that recently caught a gopher can be reused without cleaning provided the previous occupant did not rot in the trap and leave an obvious odor. There is no need to use gloves when setting traps as human odor does not repel gophers.
Exclusion. Although not a means of controlling a gopher population, exclusion, as the name implies, is a technique that can be used to prevent gophers from reaching a property or plants in the first place. The use of this technique is typically limited to small-scale locations of relative high value. The most commonly used method of excluding gophers from a property is burying ¼-inch mesh hardware cloth to the depth of 2 feet around the entire perimeter of the property. A 6-inch high wall of the cloth should extend above ground to prevent gophers attaining access via this route. Of course the amount of screening necessary will vary tremendously depending of block fencing or other barriers. The bottom of the hardware cloth should be bent at 135-degree angle away from the property to be protected to reduce the possibility of a gopher working around the barrier. This is not a permanent solution but such a barrier will last several years or more depending on environmental conditions.
Factors that May Lead to Unsuccessful Gopher Control.
Mechanical handheld probes are most commonly used for injecting poison baits into the gophers’ burrows. Most mechanical probes have a large-diameter injecting end that can clog readily with damp soil. A plugged tip may go unnoticed, resulting in non-baited applications. The large tip can also make it more difficult to determine the location of an open tunnel as opposed to a tunnel that has been refilled with soil. Many commercial vertebrate pest control companies use a non-mechanical gopher probe with a narrow, more sensitive end to find the tunnel (Figure 1, 5). Once it is located, the tunnel can be opened wider with the opposite end of the probe and bait can be poured into it with a long handled spoon or then injected by mechanical probe.
Proper Placement of Bait or Aluminum Phosphide.
It is essential to place bait or aluminum phosphide in a main run rather than in a lateral run. This normally can be accomplished by probing 10 to 12 inches in front of the earthen plug of the large mounds. The lateral runs are partially filled with loose soil and placement here (in the soil) will prevent the gopher from finding the bait or prevent the gas from being released into the tunnel.
Adequate soil moisture is essential for effective gopher control. If there is not enough irrigation or rain, an attempt to control any sizable population of gophers is usually worthless. Without moisture the runs do not maintain their integrity, quickly collapse and cover baits and fumigant pellets. Gophers under these conditions also burrow deeper and make it difficult to find active systems.
It is harder to control gophers in very sandy soil. Aluminum phosphide and other fumigants typically do not work as well as they do in clay types of soil. Tunnels also collapse easily covering baits. In cases where there is not plenty of soil moisture, strychnine bait is preferable to aluminum phosphide.
In situations where the preferred host plants such as O’Connor’s legume and gazanias are present, baits may be less effective than when used in other types of ground cover. In these cases the gophers may prefer to eat the plants rather than the baits. In such situations aluminum phospide is by far the preferred product for control.
Undoubtly one of the major reasons why many gopher control programs fail is due to the personnel who are performing the work. In very large projects gopher control can be very hard work and unless one is especially motivated, the work is performed incorrectly or not at all. It is especially worthwhile to spend the extra money to hire someone who will do a good job.
GIMMICKS AND FOLKLORE
Electrical devices and whirling yellow pansies. There is and have been a number of probe-like electrical devices that produce a sound or beep and when inserted into the ground, are supposed to drive away or eliminate gophers (Figure 11). We are not aware of any scientific evidence that any of these work. I once walked into a customer’s backyard that had 8 of these devices placed in various locations in her backyard. The whole yard was beeping and the gopher was doing quite well, thank you. It should be mentioned that there are similar devices that can be used in the home for control of any of a variety of insects and vertebrates. Again, in the authors’ opinion and that of many other scientists, these devices are of little, if any, value. Whirling yellow daisies, sunflowers and happy faces, although attractive in the yard, pretty much have the same result.
Figure 11. One of many electrical devices for control of gophers and moles.
Gopher purge is a plant that is commonly planted in yards with the idea it will drive gophers away. Undoubtedly gophers do not prefer or will not eat these plants, but as far as driving gophers from a property, this seems very unlikely.
There are a number of home remedies that, again, have no validity but are at least interesting. One is that if a person catches a gopher, kills it and then puts it back into its tunnel, it will drive others away or keep gophers from reinfesting the same tunnel. It is true that gophers do reinfest abandoned tunnels. Generally speaking this occurs but typically it takes months. Also, as we know, there is normally only one gopher in each tunnel system. As a consequence, if you kill the only gopher in the tunnel and put its dead body back in, this will not drive away the other gophers, as there are none there in the first place. Additionally a dead gopher in a tunnel rots and is eaten by ants and other insects within less that 2 weeks.
Other remedies include putting a bottle in the tunnels. The theory here is that if a gopher sees its own reflection it will run away. Wrigley’s spearmint chewing gum, banana peels, mothballs and ground glass placed into the tunnel are equally worthless for control.
Placing a water hose in a gopher tunneling system may or may not produce results. If it is a new gopher with a relatively short tunneling system, this may drive the gopher above ground. If it has a well-developed tunneling system with drainage tunnels this typically has no effect as the water merely sinks into the soil, drains down the tunnel while the gopher may retreat to its nest, which is located above the main run and the water. Because excess water has to go somewhere, as it washes out at the other end of the tunnel, it carries dirt with it. This can undermine the tunnel, which sometimes collapses. This can lead to sunken areas on flat ground and devastating slope loss on hillsides.
Placing several road flares in the tunnel has been used for many years and is fairly effective when favorable conditions are present for the use of fumigants. Unlike the small incendiary gas bombs that are available at many garden centers, road flares produce a large amount of gas. These smaller gas bombs are typically only effective on newly established gophers with small runs. Of course the use of road flares over a large area is would be very costly.
Finally the authors are aware of more than one situation where a homeowner has poured gasoline down a gopher tunnel and then igniting its. In one situation the result was setting a field and a neighbor’s fence on fire and in another case (4 gallons were used in this case) the individual basically blew up his backyard and ended up in the hospital. I don’t know if the gopher survived or not but my guess is it did just fine (i.e.-Caddy shack).
Questions. Version. 1. Do Version 1of question unless otherwise indicated.
Gophers may become “bait shy” if they ingest sub-lethal amounts of bait and become sick.
Gas bombs and aluminum phosphide are less effective for gopher control in dry or sandy soil.
Other than aluminum phosphide the currently registered fumigants are not generally considered very effective for gopher control.
Baits containing single dose toxicants such as strychnine tend to be more effective for gopher control than baits containing multiple dose anticoagulants while the latter is considered safer from the standpoint of possible toxic effects on human and other non-target organisms
Experts in the field consider whirling yellow daises and electrical devices that produce a beeping sound in the gopher tunnel ineffective for gopher control.
6. It is essential to place bait or aluminum phosphide in a main run rather than in a lateral run. This normally can be accomplished by probing 10 to 12 inches in front of the earthen plug of the large mounds.
7. Aluminum phosphide is generally less effective in sandy soil. The logical reason for this is that in this type of soil, a certain amount of gas escapes from the runs. If sandy soil exists, this problem can be partially alleviated if there is a high level of moisture in the soil, presumably sealing the runs and releasing the gas at a faster rate.
8. Sandy soil is conducive to gopher control as it is easy to find the tunnels below ground.
9. In situations where the preferred host plants such as O’Connor’s legume and gazanias are present, baits may be less effective than when used in other types of ground cover.
10. Strychnine baits left above ground are considered a serious violation.
11. Adequate soil moisture is essential for effective gopher control.
12. Gophers are drawn to a trap by light.
13. It is important to use gloves when setting traps as human odor does repel gophers.
14. Gopher traps are a good way of controlling large populations of gophers.
15. The theory is that if too much light (behind the trap) enters the tunnel, the gopher pushes dirt to close off the tunnel and merely sets off the trap with this soil.
16. A good trapper typically can set and later check 8 or 9 in an hour. An average catch rate would possibly be 50 %.
17. For the purpose of detection and possibly making it less attractive to nontarget organisms (e.g. Birds) bait containing strychnine is marked with a green dye.
18. the most commonly used method of excluding gophers from a property is burying ¼-inch mesh.
19. Placing a water hose in a gopher tunneling system may or may not produce results. If it is a new gopher with a relatively short tunneling system, this may drive the gopher above ground
20. Placing several road flares in the tunnel has been used for many years and is fairly effective when favorable conditions are present for the use of fumigant.
Application Techniques, Chemicals and Control
A successful ground squirrel control program should incorporate more than one technique and a thorough knowledge of their biology. The most critical biological factor that should be considered is instigating control procedures when the entire squirrel population is active above ground. The 3 main periods when squirrels are most susceptible and available for control periods are: 1. During breeding season (very early spring) when equal numbers of male and females are active above ground, the male/female ratio can be monitored by trapping. Subsequent to breeding the females will not be available for a few months until they wean their young. 2. When the young appear above ground in the spring until aestivation. 3. In the fall of the year when adults emerge from aestivation and before they enter hibernation in the winter.
Anticoagulant Baits. The use of baits is the most common and efficient means of controlling large populations of ground squirrels. When using any pesticide it is imperative that label instruction be followed carefully to obtain maximum results with the highest degree of safety. The multiple dose anticoagulant baits containing the active ingredients chlorophacinone or diphacinone are the most commonly used bait for ground squirrel control. Anticoagulant baits work primarily by rupturing small blood vessels in the animal and preventing blood from coagulating consequently causing the animal to bleed to death internally. In order to be effective a squirrel needs to feed on these baits on 3 to 5 consecutive days.
There are a few labels that allow for broadcast application of these baits but in most cases it is required that these materials be used in baits stations. If the label reads the latter and these materials are broadcast or are placed in the squirrels’ tunnels this is considered a violation and will be cited (if detected) by the County Departments of Agriculture or other regulatory agencies. Because the eradication of even a relatively small population of ground squirrels will require a considerable amount of bait (up to 8 ounces of bait per adult) large bait stations are typically preferred.
The most commonly used type of bait station is the “T” made out of 3 inch PVC pipe (Figure 12). A lip or baffle should be constructed within the station to prevent spillage out to the entrances at each end. Constructing a 3-inch long section of the PVC pipe that is cut longitudinally on one side is an effective baffle. This piece can be inserted all the way to the base of the T, which will in turn only allow small amount of the grain into the arms at any time.
The Department of Pesticide Regulations considers bait stations a service container and therefore requires that they are labeled with the Name of the toxicant, Poison-Keep Out Of the Reach of Children; Name and Address of Company.
Because the U.S. EPA does not approve or disapprove the construction of bait boxes prior to use, pesticide enforcement personnel judge the adequacy of bait boxes. The EPA has adopted criteria for judgment regarding bait boxes containing treated bait. Based on this criteria tamper resistant bait boxes should be resistant to weather, strong enough to prohibit entry by large nontarget species, possess a secured lid or hatch for rebaiting, equipped with entrances which readily allow target animals access to baits while denying access to larger nontarget species, capable of being anchored securely and equipped with an internal structure (normally baffles) for containing baits.
Figure 12. A commonly used T-type ground squirrel baits station. Image courtesy of California Department of Agriculture.
One of the big reasons why baiting of this type fails is that moisture (from rain or irrigation) gets into the bait station and rots the grain. Squirrels will not readily accept rotting or soggy grain. It is therefore very important to make sure the 3 arms of the “T” are sealed to the base with waterproof adhesive. When placed in the field, each bait station should be secured with a stake and cord or some other device. Tamper free stations (commercially available) must be used in areas where children, dog or domestic animals may have access to the baits.
The number of stations and amount of bait needed is totally dependent on the size of the squirrel population. Because of potential predators and other factors squirrel normally do not forage for more than 150 yards from their burrows and correspondingly 200 yards between individual stations is a maximum. With large populations less distance is usually required. We have experienced situations where 2 bait stations place together at intervals of 50 yard have been emptied by squirrels on a daily basis. If desired the length of the vertical arm of the “T” can always increased to accommodate more bait but most labels call for 1 to 5 pound of baits per station.
Another reason why control with anticoagulant may be less effective is failure to make the baits continually available. Once filled the bait stations should always contained unspoiled bait for up to 2 weeks or until the squirrels no longer feed out of them. When placing a bait station in the field, do not place it immediately adjacent to an active tunneling system; squirrels will frequently attempt to bury it.
Finally the use of anticoagulants may be less effective at those times of the year (winter through early spring) when the squirrels are primarily feeding of green feed. The main antidote for anticoagulants is vitamin K and green feed in high in this vitamin thus somewhat inhibiting the effect if the anticoagulants.
Zinc Phosphide Bait.
Zinc phosphide is an acute dose rodenticide that is registered for ground squirrels control. Unlike the multiple dose anticoagulants, acute dose rodenticides will kill if enough is consumed in a single feeding. This material is normally applied as a broadcast application with a long handled spoon or mechanical applicator. It should never be applied in piles, as these are more accessible to dogs and other non-target animals.
This material is most effective when the squirrels are actively feeding on grain. This normally equates to the fall when the population has emerged from aestivation or in the summers, especially in the cooler areas where most of the squirrels do not aestivate. However, bait acceptances has been adequate during the breeding season in some areas. When in doubt test areas can be monitored for bait acceptance prior to wholesale application. Prebaiting (using untreated grain) may also be used to test for acceptance and can actually increase acceptance of the toxic baits and is required on some labels. It is imperative that enough bait be used to insure adequate kill. If not enough is used the squirrels can develop bait shyness. In this case they eat sublethal amounts of the bait, become sick from it and then associate the sickness with the taste of the bait. If this happens the squirrels will be much less likely to consume the bait again. Also this bait should only be used once a year in a given area as bait shyness may also develop from overuse.
There are certain situations where baits may not be advisable to use for squirrel control. Obviously in situations where children might be present because of its toxicity zinc phosphide bait should not be used. Also it might be wise not use the anticoagulants in areas where the general public will see the effect of this materials on the squirrels. Most squirrels will die in their burrows but prior to dying they become lethargic, may bleed from the mouth and generally are sickly in nature. This tends to upset some individuals and you probably don’t need the hassle.
Fumigants can be quite effective for ground squirrel control but because their use can be time consuming they are not normally used to control large populations of squirrels; however they are useful for cleanup purpose, for control of isolated populations or for use in situations where baits may not be advisable. The 2 main fumigants that are used today are those already discuss for gophers, namely aluminum phosphide and gas cartridges. Both types are most effective when there is a high degree of moisture in the soil and when squirrels the squirrels are not aestivating or hibernating. Moisture tends to seal the burrows and reduces loss of gas into the soil and of course when squirrels are hibernating or aestivating the gas cannot reach them due to earthen plugs.
Prior to an attempt to use fumigant it is advisable to shovel dirt into and close up all opening to the burrow systems. By doing this and returning the next days to see which tunnels have been reopen by the squirrels, it can be determine which systems are active and which aren’t.
Gas cartridges or smoke bombs when ignited with a fuse produce a large amount of toxic smoke. They are normally used by placing one of the large commercial cartridges (see gophers) deep into each opening of the tunnel system. Then the entrance is closed with a shovel full of soil. Since these cartridges produce a large amount of smoke any leaks coming from the tunneling system should immediately closed with more soil. Gas cartridges can ignite and produce a fire hazard and should not be used in areas where this possibility exists. We had a small incident on campus where a student was using gas bombs for squirrel control. She did everything right but the bomb ignited, lit the squirrel on fire which subsequently ran though the brush and started a small blaze.
When aluminum phosphide (Phostoxin, Gastoxin, Fumatoxin) is exposed to atmospheric or soil moisture, the toxic gas hydrogen phosphide is produced. The rate at which the gas is released from aluminum phosphide tablets is dependent on the moisture level and prevailing temperatures. Generally speaking the higher the moisture level and temperature the faster the gas is released and the better the control is achieved. The labels call for placement 2 to 4 tablets deeply into each opening followed by a tightly packed wad of newspaper. This in turn is buried with soil. The news paper supposedly seals the tunnels and retards the squirrel’s tendency to dig out. Also less dig outs will occur if control is attempted late in the morning or evening after the squirrel’s peak activity periods.
It is fairly simple to tell if control has been successful or if a tunneling system is inactive. If there are dead squirrels within a tunneling system the applicator will see metallic blowflies entering the tunnel. If a system is inactive there will normally be spider webs over or around the entrance.
21. Gas cartridges can ignite and produce a fire hazard and should not be used in areas where this possibility exists
22. The Department of Pesticide Regulations considers bait stations a service container and therefore requires that they are labeled with the Name of the toxicant, Poison-Keep Out Of the Reach of Children; Name and Address of Company.
23. Based on EPA criteria tamper resistant bait boxes should be resistant to weather, strong enough to prohibit entry by large nontarget species, possess a secured lid or hatch for rebaiting, equipped with entrances which readily allow target animals access to baits while denying access to larger nontarget species, capable of being anchored securely and equipped with an internal structure (normally baffles) for containing baits.
24. One of the big reasons why baiting of this type fails is that moisture (from rain or irrigation) gets into the bait station and rots the grain.
25. Ground squirrels when poisoned by anticoagulant baits mostly will die in their burrows but prior to dying they become lethargic, may bleed from the mouth and generally are sickly in nature. This tends to upset some individuals and you probably don’t need the hassle
26. When aluminum phosphide is used for ground squirrel control the higher the moisture level in the soil the faster the gas is released and the higher degree of resultant control.
27. When controlling ground squirrels with anticoagulant baits containing diphacinone or chlorophacinone one day of exposure to these materials will result in good to excellent control.
28. Because of potential predators and other factors ground squirrel normally do not forage for more than 50 yards from their burrows and correspondingly 50 yards between individual stations is a maximum.
29. The above two chemical work primarily by rupturing the small blood vessels of poisoned animals and preventing their blood from coagulating.
30. If there are dead squirrels within a tunneling system the applicator will see metallic blowflies entering the tunnel.
31. If a squirrel tunneling system is inactive there will normally be spider webs over or around the entrance.
32. When aluminum phosphide (Phostoxin, Gastoxin, Fumatoxin) is exposed to atmospheric or soil moisture, the toxic gas hydrogen phosphide is produced. The rate at which the gas is released from aluminum phosphide tablets is dependent on the moisture level and prevailing temperatures.
33. Prior to an attempt to use fumigant it is advisable to shovel dirt into and close up all opening to the burrow systems.
Voles or Meadow Mice
Of the many species of meadow mice found in the United States, only Microtus californicus and Microtus montanus are economically important in the west. Of these, 2 M. californicus has by far the widest distribution and therefore causes the most damage in both agricultural and urban situations. The biology and control of all species are quite similar. These rodents are typically larger than a house mouse but smaller than a medium sized rat (Figure 13). They have a relatively short bare tail and are typically uniformly brown in color with a white underside dorsally.
Figure 13. A typical vole or meadow mouse.
The 1-to-2 inch wide surface runways through grass and other low growing vegetation (Figure 14) indicates the presence of these mice. In an active infestation these trails are littered with feces and pieces of stems, leaves and other leftovers. The runways lead to underground burrows that consist of short branching tunnels, food storage areas and nests. Unlike gophers these tunnels are not plugged with earth. Meadow mice populations tend to be cyclic, reaching peak numbers every 3 or 4 years and then dropping drastically the next year.
Figure 14. Shallow runway indicative of meadow mice.
Control of voles or meadow mice is primarily dependent on either broadcast applications of zinc phosphide baits at the rate of 5 to 10 pound per acre or spot treatments using either zinc phosphide baits or anticoagulants. In the case of anticoagulants, spot treatments consist of lightly sprinkling tablespoon amounts in the active runways for 3 consecutive days. Zinc phosphide spots treatments are the same as anticoagulant treatments except in this case only one treatment is necessary. In all cases, treatment should be avoided in the case of impending rain or daily irrigation.
34. In all cases treatment with grin baits for voles should be avoided in the case of impending rain or daily irrigation.
35. As do gophers, voles close the openings of their tunnels with earthen plugs.
36. The runways of voles lead to underground burrows that consist of short branching tunnels, food storage areas and nests.
37. Another symptom of the presence of voles is shallow runways in grass and other vegetation.
38. Meadow mice populations tend to be cyclic, reaching peak numbers every 3 or 4 years and then dropping drastically the next year.
39. The main means of controlling large populations of voles is broadcasting zinc phosphide baits at 5 to 10 pound per acre or spot treatment with zinc phosphide anticoagulant baits (the later may not be time efficient).
Wood Rats, Pack Rats
There are many species of wood rats (Neotoma spp.) in United State (Figure 15). Even though their combined distribution represents a wide area, these rodents rarely cause any significant damage to agriculture or the homeowner. Normally they do not reach large populations and are typically not found in urbanized or agricultural areas (depending on species), but are found instead in locations such as heavy chaparral, streamside thickets, pine forests, rock slide areas of high elevation forests or desert floors.
In cases where damage does occur, much of it is due to the rat’s nest building behaviors. Neotoma nests are typically cone or dome shaped structures that may be as high and wide as 5 feet and are made out of twigs, rock, bark, manure, tin cans or any other objects that meets the rat’s requirements. When damage such as stripping of bark or cutting of side braches of citrus or conifers occurs, this is primarily done for nest building purposes. The name “pack rat” refers to the annoying habit of this rat taking shiny objects and storing them in its nest. This can be troublesome to the homeowner who starts missing jewelry, coins, watches, silverware and similar objects.
Figure 15. A wood or pack rat.
Compared to many rat species, wood rats are easily trapped. This can be accomplished by placing a standard wood based rattrap baited with a prune, nutmeats or raisins near the nest or runways. Havahart live traps are equally as effective.
The spot treating with zinc phosphide baits has also proven to be effective. Because the populations of these rats are typically small, broadcast treatment is generally not effective. Crimped whole oats or oat groats are the preferred grains for baiting. Scatter a small amount of bait on approximately a one square foot area near the nest or in a runway. Do this in the late afternoon so ants and other insects do not carry the grain away. With wood rats, leaving these baits for prolonged periods of time does not improve kill and increases the chance or poisoning non-target animals. The baits should be removed after 48 hours.
Anticoagulant baits such as chlorophacinone or diaphacinine are effective against wood rats. Broadcast treatment is inadvisable and these rats frequently fill standard bait stations with sticks and other debris. As a consequence, open faced bait stations can be used, provided they are covered by inverting a wooden crate or similar object that will allow rats to enter but exclude larger animals. Normally 4 to 16 ounces of bait are used per station with individual stations placed no more than 100 feet apart. This is all that is necessary considering the limited foraging range of the animals.
Anticoagulant paraffin bait blocks have proven effective in orchard situations. In this case the blocks can be secured to the limbs of trees where damage has occurred. These should be removed once control has been attained. It is extremely important to make sure these blocks are high enough in the trees so dogs and other animas cannot access them. Dogs readily eat these blocks.
40. Normally wood rats do not reach large populations and are typically not found in urbanized or agricultural areas (depending on species), but are found instead in locations such as heavy chaparral, streamside thickets, pine forests, rock slide areas of high elevation forests or desert floors.
41. Pack rats get their name from the fact that they will enter homes and steal shiny objects such as coins and jewelry.
42. Assassin or cone-nosed bugs are commonly found associated with pack rats.
43. Wood rats typically produce as many offspring per year as voles.
44. Compared to many rat species, wood rats are easily trapped. This can be accomplished by placing a standard wood based rattrap baited with a prune, nutmeats or raisins near the nest or runways
45. Anticoagulant baits such as chlorophacinone or diaphacinine are effective against wood rats.
46. Broadcast treatment is inadvisable and these rats frequently fill standard bait stations with sticks and other debris.
Moles have muscular shoulders, a short neck, stout head and shovel-like front legs which are equipped with strong claws and well adapted for digging (Figure 16). When moles dig it almost appears as they are swimming through the soil. The forefeet are held close to their head and are used to push the dirt aside. Their blackish plush fur lies flat when stroked from either direction, thus offering little or no resistance when the mole moves backwards of forward in its tunnel. As might be expected, these subterranean critters have tiny eyes with fused eyelids and poor vision. On the other hand, not only do they have a good sense of smell, but can readily detect any above ground movements with sensory hairs that are spread throughout the body.
Figure 16. A mole.
Moles are active year around and throughout the day or night except for the Townsend mole, which is primarily nocturnal. Many develop their own rhythm with some individuals of a species active at night and some during the day. They are almost totally subterranean except for the shrew mole that spends a considerable amount of time above ground foraging for food. As indicated these small creatures feed mainly on worms and insects that they encounter during their burrowing activity; however, most moles eat some plant material during their lives.
These critters are not as prolific as gophers and normally produce one generation of 2 to 6 young a year. The young are born in the spring with a gestation period of around one month. The offspring are born relatively large and reach sexual maturity within a few months. It is estimated that the average mole only lives a few years, although this is not well documented due to their secretive way of life.
Moles form 2 types of tunnels, the most obvious of which are the shallow temporary tunnels where the soil is raised in ridges (Figure 17) as the mole searches for food. More permanent tunnels, which can reach a depth of 18 or more inches, are used when the soil dries out, as a nesting location or as a retreat from potential predators. These are typically located near the above ground, cone shaped mounds that are produced as the moles excavate these permanent locations.
As with gophers moles are solitary although in large populations the Townsend mole occasionally uses common tunnels to access different areas.
Figure 17. Raised ridge that is typical of a mole’s temporary tunneling below ground in search of food.
Moles are much more difficult to control than gophers. This is due to any of a number of factors. Because they mainly eat worms and insect larvae, there are few, if any, effective commercially available baits. Some pest control operators have claimed to attain some degree of control with a variety of baits with best results occurring when these are placed in the more permanent deeper tunnels.
These vermin do not regularly reuse their temporary tunnels and typically frequent a relatively large area as they move around. Most success control are typically aimed at the more permanent tunnels located by deeply probing with a steel rod or gopher probe in the vicinity of the above ground conical shaped mounds. Aluminum phosphide should not be placed in the temporary tunnels as the gas will readily leak from the soil and certainly not be effective in killing moles in this location. Also dogs have been known to dig up and eat foreign smelling objects as these. This would result in certain death of the animal. Again this is not a recommended means of control because this chemical is not registered for mole control.
Elimination of the food source of moles is a preventative means of control, which has found some degree of effectiveness. This can be accomplished by using a soil drench insecticide at least once a year in the late summer months. These drenches are mainly aimed at scarab larvae and worms. There are two products which work well for this purpose; Tempo and Bifenthrin Granules. If both are use they will deliver a one two punch which works well in the long run. The liquid provides a quick knockdown and kills off active larva. Tempo is both easy to use and quick acting. It will last a month or two and its effect is to kill the grubs which moles are seeking. Although the Tempo will provide quick knockdown, the use of Bifenthrin Granules will provide a longer window of protection. This will prove helpful in controlling the larvae which hatch out after liquid treatments. This is important in some climates that have long mild seasons and eggs may be hatching more than one time a year. These granules are easy to apply and will last several months per application.
Trapping is a technique that can result in control moles. However, it is time consuming and relies on knowing which tunnels are currently being used. As a consequence the individual attempting control may have to return to the general location several times before this can be determined. As previously discussed moles dig a series of surface runs many of which may not be reused. In order to determine which runs are being used more than once, flatten short sections of several runs and return daily to determine if any of those sections have been re-elevated due to the activity of the mole. Once this has been determined on a few consecutive days, a trap can be set. There are a number of different mole traps but the 2 most commonly used in California are the Out-of Sight and the Reddick Harpoon or Spear Trap (Figure 18). These traps are either placed directly over (Reddick trap) or around (Out of Sight trap) an active tunnel and rely on the mole activating the trap by pushing a trigger located in or directly above the tunnel.
Figure 18. Two common types of mole traps. Left-Out of Sight Trap. Right-Spear Trap.
Some baits are much more effective than others. In fact some are not effective at all and have been taken off the market. Regardless of the type of bait one important factor in the baiting of moles is a lot of the bait should be used to insure they find it. Since moles only use tunnels once except for the main den bait placements made too far apart will be missed. Don't make your placements more than 10 feet apart and try to make the placements as close to the den or main tunnels as possible.
Another key to mole control is that baiting should be applied after application of chemicals for grub and worm control. Generally speaking if chemicals are used for control of grubs and worm baiting should be done at least a day later. This will allow the chemicals to dry and not impact the bait. Spraying over the bait might contaminate it therefore making it unacceptable to moles. On the other hand, if you only bait, expect to have more moles replace the ones you kill. This is due to the fact that you haven't dealt with the food supply. The possible exception to this is Southern California where moles are somewhat rare and replacement is unlikely. On the other hand in Northern California and Oregon moles are very common pests.
As indicated there are a number of types of mole bait on the market. An example of one such bait that has a rather unique design is Talpirid Mole Bait (Figure 19). The bait is a rubber worm - very similar to the kind used for fishing. Moles feeding on worms rely on feel for identifying their prey. Talpirid worms are placed in tunnels and burrows which are active and as a mole passes through it will reportedly grab the offering. These worms mimic real earthworms so well moles won't know the difference. Once found, the worm will be seized and chewed. At that point a lethal dose of bromethalin is ingested causing the mole to die in a day or two.
Figure 19. Taliprid mole bait.
All things considered, moles are fascinating animals.
- A 5 ounce mole will consume 45-50 lbs of worms and insects each year.
- Moles can dig surface tunnels at approximately 18 feet/hour.
- Moles travel through existing tunnels at about 80 feet/minute.
- Moles contain twice as much blood and twice as much hemoglobin as other mammals of similar size. This allows moles to breathe more easily in underground environments with low oxygen.
47. Moles have a good sense of smell, but can readily detect any above ground movements with sensory hairs that are spread throughout the body.
48. Mole mounds are typically cone shaped while the larger gopher mounds typically are horseshoe shaped.
49. Moles typically dig two types of tunnels, the more obvious of which is the shallow temporary tunnels that result in raised ridges at ground level. These type tunnels are not frequently reused.
50. Elimination of the mole’s food source by applying soil drench pesticides can result in a degree of control.
51. Moles are not as prolific as gophers and normally produce one generation of 2 to 6 young a year.
52. Trapping is a technique that can result in control of moles. However, it is time consuming and relies on knowing which tunnels are currently being used.
53. Moles contain twice as much blood and twice as much hemoglobin as other mammals of similar size. This allows moles to breathe more easily in underground environments with low oxygen.
54. Moles do not regularly reuse their temporary tunnels and typically frequent a relatively large area as they move around.
55. A 5 ounce mole will consume 45-50 lbs of worms and insects each year.
56. Moles travel through existing tunnels at about 80 feet/minute.
Raccoons and Opossums
Raccoons and Opossums (Figure 20) are covered together since they both do similar damage and control techniques are the same, basically trapping. One annoying and often damage from these pests is that the cooler winter months it is not uncommon for these pests to move into attics of homes (especially raccoons-Figure). In doing so they can do a tremendous amount of damage to roofing, insulation, chewed electrical wires and tremendous odors from their urine and excrement. They can also cause tremendous problems from their feeding activity and are especially fond of digging in gardens and lawns for grubs and worms. They are readily attracted to pet food, tear trash cans apart and love to feed on pet koi and turtles in decorative ponds. Many paints and varnish have minerals and other nutrient that seem to attract these critters. It is not uncommon for them to cause considerable damage due to their chewing activity on outdoor furniture. Finally raccoons pose a health rise from the standpoint of carriers of rabies
Figure 20. An opossum and Raccoon with babies.
There are a variety of repellent type chemicals that are commercially available that can be used to repel these critters from attics, and other locations and can be used to treat furniture and other affected areas. Although these have their place for the homeowner most pest control applicators rely on trapping to totally eliminate long term problems and/or treating lawns with soil drenches to eliminate grubs and worms and therefore reducing or eliminating the continuous digging of these pests. Lawn treatment is the same as previously described for moles.
If raccoons or opossum are living in the near vicinity of a home it is a good idea to trap them. Ultimately they will reproduce and their offspring at one time or another will eventually more inside the home with the attic being the most likely location. One common mistake once they have established inside the attic is to try to seal them off. Once inside sealing them off or even a bigger mistake, sealing them inside by mistake will undoubtedly cause more damage to the structure. Sealing them in will often make the animal angry, aggressive and they will do anything to escape, sometimes ending up inside the living quarters of the home. Animals sealed outside of the structure will just chew their way back in.
Unlike rats raccoons and opossums are relatively easy to trap. There are a number of commercial live traps that are available for this purpose (Figure 21). Trap placement doesn’t necessarily have to be in the established path of these animals. However, they should be placed in the vicinity of their activity. For example they could be placed in an attic, crawl space next to the foundation or even next to a tree that they are climbing to gain access to the attic. With raccoons it is advisable to secure the trap as these critters are known to tip over a trap to gain access to the bait.
Figure 21. One of many types of live traps.
There are commercial baits that are available but fresh bait is also quite effective. If the animals have been eating fruits or vegetables then it might be advisable to use similar items for bait. Raccoons are especially fond of eggs, meat and fish.
57. Many paints and varnish have minerals and other nutrient that seem to attract raccoons.
58. With raccoons it is advisable to secure the trap as these critters are known to tip over a trap to gain access to the bait.
59. Raccoons pose a health rise from the standpoint of carriers of rabies.
The roof rat, Norway rat and house mouse are frequently referred to as commensal rodents. In the strictest sense of the term this is somewhat of a misnomer. Commensal according to the dictionary refers to an organism (in this case the rodent) that lives in a symbiotic relationship where one species benefits (the rodents again) while other (humans) are not affected by their presence. Of course these rodents greatly benefit by the presence of humans but certainly their presence does adversely effects humans. Rats and mice have adapted to and benefit greatly by the presence of humans. In doing so they have become one of the most successful groups of wild mammals, at least from the standpoint of survival. This guide is not designed to recommend any pest control product. Products mentioned are given as examples only. Hopefully the guide will help the applicator to apply pest control techniques in a safe and effective manner.
Identification of Commensal Rodents.
Identification of the pest is an integral part of any pest control scheme. The 3 principal species of domestic rodents in the United States are the roof rat (Rattus rattus), Norway rat (Rattus norvegicus) and the house mouse (Mus musculus) (Figures 22, 23). These are fairly simple to distinguish from each other. The following descriptions are based on adults. The Norway rat is the largest of the 3 species and is also commonly known as the brown, house, wharf and sewer rat. Adult body length varies from 7 1/2 to 10 inches with a 6 to 8 ½ inch tail. The body fur is quite coarse and brown dorsally with black scattered hairs and a gray to white underside. The snout or muzzle is relatively blunt with small, closely set ears and a semi-naked bicolored tail (darker above and lighter below). Finally the Norway rat is considerably stockier than the roof rat weighing nearly twice as much.
Figure 22. Differences in appearance of commensal rodents.
The roof rat is smaller than the Norway with a combined head and body length of 6 to 8 ½ inches and tail length of 6 to 8 ½. Since there is an overlap in total head and body length between the two species a more reliable identifying characteristic is the ratio of head + body length to tail length. Most simply the tail of the roof rat is longer than its combine head-body length while that of the Norway rat is shorter (see Figure 1). In addition the snout-muzzle of the roof rate is pointed. Finally the roof rat’s ears are comparatively larger than those of the Norway.
Of course the house mouse is much smaller than adult rats with a head-body length ranging from 2 ½ to 3 ½ inches and tail length from 3 to 4 inches. The house mouse can be confused with young rats as both are similar in appearance. Mice eyes and feet are relatively smaller than those of young rats of approximately the same size.
Figure 23. Roof Rat (left), Norway rat (middle) and house mouse (right). Images courtesy of CDC.
Scats or Fecal Pellets. Since these critters are nocturnal and quite secretive the operator may need to determine the presence of rodents by means other than their physical presence. As these rodents move through a structure they indiscriminately drop fecal pellets or scats and readily urinate. One rat is capable dropping over 25,000 fecal pellets in a one year period (Figure 24). Adult Norway and roof rat scats are the shape of and about twice the size of a grain of rice; however, Norway rat droppings have smooth round ends while roof rat dropping have pointed ends. As might be expected the overall size of scats vary with the size and age of the rat but in any infestation there will likely be some adults present. Mice droppings are small, black, oval-shaped and about the size of a grain of rice. Large roach droppings look the same so be careful not to confuse the two. If in doubt a hand lens examination will reveal hair in mice scats while those of large cockroach exhibit longitudinal grooves.
Figure 24. An attic full of roof rat scats.
Once established rats develop favored runway as they travel throughout a structure. They rarely deviate from the runways. In addition these runways are typically located next to walls or other vertical surfaces. The body hairs of rats are fairly oily in nature: consequently, as the rat moves through the structure some of this oil rubs off onto the walls and other structures (Figure 25). Over time this oil will appear as smudge marks or dark streaks.
Figure 25. Smudge (oil) marks on pipe and an attic full of rat urine.
Under ultra violet light urine and to a lesser extent rat hairs will glow. Fresh urine appears as bluish-white while older urine glows yellow. These marks may be spotty or in some cases a “squiggly line” as rats urinated while moving. There are several hand-held ultra violet light devices available (Figure 26). There are other materials that also produce fluoresce under UV light which include bleached fabrics, bleaches and ever tar products to name a few. However, if an infestation is substantial there is no mistaking rat urine as it will be very prominent-to say the least.
Figure 26. A hand-help ultra violet light.
One sure sign of a rodent infestation is significant gnawing on any of a number of hard objects or items (Figure 27). One characteristic of rodents in general is their extraordinary hard incisor teeth, two uppers and two lowers that butt against each other. These teeth grow continuously and must wear down. As a result rat and mice continually gnaws to gain access into walls, doors, packages, water pipes and outdoor irrigation systems. They also use this gnawing to collect nesting materials.
Figure 27. Roof rat gnawing of PVC pipe.
Behaviors Important to Control.
As the term implies, neophobic mean the fear of new things. While roof rats and Norway rats are definitely neophobic, the house mouse exhibits almost the opposite behavior. While the house mouse is likely to poke around a newly placed bait station or trap, a rat is more likely to be very suspicious and avoid them when possible. When rats enter a new environment for nesting or feeding, they become very familiar with all objects and soon can move around by what is termed kinesthesis or muscular memory. Once establish they can quickly move through a structure with an automatic memory of what is in their path.
The inquisitive nature of the house mouse makes them easier to trap or bait than rats. A new trap in a mouse’s environment is readily inspected as are bait stations. On the other hand when a trap, glue board or bait station is first placed in the path of a rat it is normally avoided for the first few days. As the rat becomes more accustomed to its presence it will eventually be accepted. Of course this makes these rodents more difficult to control. On common trick that applicators frequently use when confronted with this behavior is to place a trap in the rat’s environment but not set it until the rat becomes accustomed to its presence. Of course the same thing can be accomplish by not uncovering a glue board for the first few days.
This reminds me of a story that was told to me by my friend Bert Lopez of Univar Corporation. He was called into a situation at one of the more popular restaurants in Southern California. Apparently there was a single dominant male rat in the restaurant that was raising total havoc. Several operators were called in but nobody could eliminate the rat. It was totally neophobic and had a total run of the restaurant knowing everything in the place very well. After much thought Bert found out that the main diet of the rat was pecan pies which were kept on a rack in the back of the restaurant. So Bert simply had the pastry chef bake a rat trap in a pecan pie. The pie was placed on the same location where the rat fed every night. He got him the first night.
Sense of Sight and Touch. Rats have poor eyesight and don’t rely on this sense to a great degree when moving around. The main senses they rely on for navigation is the previously sense of kinesthesis and the sense of touch. Rats have large oral vibrissae (whiskers) and many rather long stiff guard hairs that are mixed in with their fur. They rely on both of these types of hair to sense or feel their environment. Of course this is the reason why rats when moving around a structure stick closely to vertical surfaces (walls, foundations of the house, cupboard, boxes, etc.) when establishing their runways. They feel the structure next to them and avoid, if possible, moving away from their establish path.
This is of the reason why when a trap, glue board or bait station if used for control it is essential to place them in the rat’s already established path. Of course when the rat first encounters these new objects it is very wary. But on the other hand it is very reluctant to move around the object thus leaving it establish path. As a result it tests the new object to determine if it is safe to go over or through. It may nibble on it, feel it with its whiskers or sense it in some other way. Eventually depending on the age and experience of the rat it will eventually become accustomed to this presence. Older more experience rats tend to be more wary than younger ones.
Baits and Bait Stations.
There are dozens of rat and mouse bait brands available on the market. The toxicants in these baits fall into 2 broad categories, namely anticoagulants and non-anticoagulants. Anticoagulants kill by rupturing capillaries and preventing blood from clotting. As a result the effected rodents internally bleed to death. This type of death although sounding quite gruesome actually is quite painless. The anticoagulants fall into two categories also, namely first and second generation. The first generation anticoagulants, as their name implies, are the older of the two groups. These are sometimes also referred to as multiple feeding anticoagulants. This simply means that the concentration of the toxicant in the baits is low enough that the animal must feed on them on several consecutive days to result in death. These include Warfarin-the oldest, Diphacinone and Chlorophacinone-the latter two are discussed under gophers. The second generation anticoagulants include Brodifacoum, Bromadiolone and Difethialone. These are referred to as the single feeding anticoagulants. This means that the toxicants in baits are high enough that a single feed will typically result in death. Both types are somewhat slow acting requiring 3 to 10 days for death once a lethal dose is acquired.
There are 3 different toxicants used in rat and mouse baits that are nonanticoagulant in mode of action: however, the most common types used for control of these rodents are the anticoagulants. Some of the nonanticoagulant types are restricted to outdoor agricultural rodent control. These are zinc phosphid (discussed with gophers), cholorophacinione and bromethalin. As far as which toxicant is most effective this is a matter of opinion and the choice of which to use is up to the individual pest control company and beyond the scope of this article. In all cases if rodent baits are used the operator must read the label carefully. The pesticide label is backed by years and research as to how to use these chemical in a safe and effective manner. It cannot be emphasized enough-read the label carefully!
The use of poisons for control of rat in urban situations although effective does have some drawbacks. These are all also toxic to nontarget mammals. Dogs are readily attracted to many types of bait and can die from consumption of these materials-although much more would be required to cause death to these larger animals. Also other mammals such as raccoons and opossums will also readily consume many rat baits. As a result tamper resistant bait stations are now required for the use of rat bait in an outdoor situation. Although non-tamper resistant baits stations can still be legally used indoors with rat baits, it is advisable to use tamper resistant types of sturdy bait stations indoors to prevent nontarget animals from accessing baits.
The EPA has come out with somewhat rough guidelines as to what criteria must be met to make a tamper resistant bait station (Figure 29). They must be made of sturdy material that is not easily broken and fitted with internal devices (e.g. baffles) that keep the bait inside. In addition they must have a lid that cannot be easily removed and should be able be secured to the surface on which they sit. There are many types and sizes available. Non-tamper resistant bait stations, if used indoors, are normally required to be placed in inaccessible locations to prevent bait access to pets and children.
Figure 29. One of many types of tamper resistant bait stations.
A second problem exists with the use of rat baits especially in an indoor situation. Although not as much of a problem with mice, one or more dead rat can cause a considerable odor problem. This can occur in a wall void or any of a number of hard to reach areas in the home. Of course homeowners are not happy when this occurs. One false belief that has circulated around the industry is that rodents poisoned with anticoagulant baits actively search for water and therefore most often die outdoors. This of course has no validity. Another fallacy is that rats that are killed with anticoagulants tend to dehydrate or dry up and therefore do not produce an odor.
If odor problems do develop within a structure there are deodorized products (Figure 30) that are fairly effective in removing them. Some of these are enzyme based compounds that works two ways. Initially they "eats" the odor molecule which is a gaseous by-product emitted by the decaying rodent. Secondly they attach to and increase the density of the odor causing molecules. As a result the heavier molecules simply drop from the air. Best results occur when these products are sprayed directly on the area where the animal died. If not these products can be sprayed into crawl spaces, attics and wall voids where you think the animal died.
Figure 30. One of several brands of odor killers.
Solid rodent baits come in two forms. One form is basically pellets or grains that are impregnated with the toxicant that come in a variety of flavors. The choice of flavor depends partially on which commensal rodent is targeted. Norway rats reportedly prefer meat as they commonly eat large cockroaches and greases and other foods throw away in dumpsters. While roof rats commonly feed on fruits and nuts but also readily accept insects, snails and grain. Mice are grain feeders. Needless to say all three species are quite omnivorous. Choices as to which bait flavor to use may also depend on what the rodents are feeding upon at the initiation of the job.
The second formulation of rodent baits is produced by embedding the baits in paraffin block. These blocks are not only attractive to the rodents from feeding aspects but are also attractive due to their gnawing habits. These blocks have one advantage over the pelleted forms of bait. Commensal rodents, especially Norway rats instinctively prefer to take their food to familiar and secure locations. In addition they frequently hoard or store food in these locations. This behavior presents a potential problem to the applicator/operator. That is toxic baits are now removed from the bait stations and now is found in some unprotected location in the structure. Of course the paraffin blocks are more difficult to move to some other location and some baits station provided internal means of securing the blocks.
Another bait formulation that can be used for rodent control is liquid baits. Though not too effective for mice (since they are able to derive their water requirements from the food they eat), liquid bait works well for rats which are a problem in dry areas. Common areas where these might work well would be feed stores and pet shops. Like other poisons, placements must be away from children and pets. As with other types of baits there are tamper proof bait stations available for liquid baits. These stations should be placed up high, behind appliances, in cupboards, in attics or crawl spaces or generally out of the way where only rodents are likely to find them. This will help minimize accidental consumption by non-target animals.
Live Traps, Snap Traps and Glue Boards.
Live traps are more commonly and effectively used for mice than rats. Because these devices do not kill or harm the rodent, they will not become afraid of it. Live trapping mice is easy, inexpensive and without risk or danger to non-target animals. The latest design of traps will last a long time, catch many rodents and be able to catch even the most experienced and wary rodent. The Tin Cat (Figure 31) and Mouse Master offer multiple catch capability for mice. The author has used both Tin Cat and Mouse Monster and several times caught over 20 with one setting. Mice of course are very curious and will readily be drawn to these traps.
Figure 31. Tin Cat.
The great thing about these traps is that they don't kill the animals so others do not become wary or afraid. In fact, I have observed a trap with several mice in it seemingly lure new ones. The untrapped mouse would come and circle the holding area seemingly interested with the activity going on inside. The smell of food is so powerful that even after being trapped the mice do not become upset or frightened. However, if they are left for any length of time and the food supply runs out, they will become frantic and distressed. Be sure to place plenty of bait inside to insure the mice will remain quiet once trapped. If the animals are left to die, they will certainly smell and decay resulting tap avoidance by other mice. An important factor to remember when trapping mice is that they do not range far from their nest or center of activity. As a consequence it is important to place these trap in close vicinity where the applicator see their activity.
Glue boards or sticky traps (Figure 32) add one more tool to the applicator’s arsenal of control techniques. These traps vary in size and are placed alongside walls, around cabinets, under furniture or refrigerators. With rats they should be placed in their establish runways. When the animal steps onto the glue they get stuck and cannot pull free. They usually will not quit, however, and many times will pull a leg, tail or section of their body apart in an effort to escape. This can cause a mess so be careful to use these devices where young children are not likely to stumble upon such a mess. The author has encountered several mice and rats caught on these traps which were screaming! It was a loud, almost humanlike. Generally speaking glue board and sticky trap will only work for a short time with significant rat populations. Normally the applicator might catch a few rats the first day or two but the remaining population will quickly adjust their behavior to avoid the traps. These are very smart animals.
Figure 32. One of many types of glue boards.
These domesticated rats do make nice pets as they are very intelligent, readily recognize their owners and are quite friendly. Actually they are the same species as wild Norway rats but certainly not the same animal. The wild Norway or roof rat is wary, readily bites and can vector several diseases to humans. However, some customers do not recognize the difference between the two. The point is that the white rat is a domesticated species and the other is wild. A similar correlation could be made between our regular honeybee (which has also been domesticated by humans) and the killer or Africanized bee. Almost everyone appreciate regular bees and the good they do but I doubt if anyone would want killer bees in their house. The point is that the applicator has to know their customer and situation and use those control techniques that best fit the situation. For example you probably wouldn’t want to use glue traps in an office full of individuals all with different feelings about rodents. It probably wouldn’t be good form for a rat or mouse lover or animal right activist to run across a glue trap full of screaming mice. It that case live trapping might be more acceptable. You can drown the critters once you take them out of the office!
There are a variety of snap traps that are available for rat and mouse control. All have basically the same design with a spring loaded lever that is pulled back and held in place with a trigger. With the original design the metal trigger was quite small. Newer more effective designs have an expanded trigger (Figure 33). Both mice and rats will easily clean the bait off the old metal trigger traps while this is more difficult with the new design. Another advantage is that these traps do not need bait. Just place them alongside the wall or other vertical surface where rats have established their runways. Be sure to locate the trigger closest to the wall. Such traps will catch one or two rodents (especially with rats) for initial cleanouts and preventive maintenance programs, but don't rely on them if you suspect more than a few animals. It is important to secure these traps. If a rat or mouse is caught but not killed it can pull the trap of to some undisclosed location. Then once it dies of course you again have a potential odor problem. Common locations for setting these traps for roof rats indoors include darkened corners of attics, suspended ceilings and other aerial locations where they feel safe. The use of baits with these traps will likely increase their catch ratio. Common baits for roof rat are fruits and nuts while nuts, bacon or other meats work well for Norway rats. Peanut butter is a favorite of all 3 species of commensal rodents. Some of the tamper-resistant bait stations are equipped with a compartment for snap traps. This is an added bonus when dealing with dicey situations where dogs or children has the potential of getting some part of their body trapped.
Figure 33. A snap trap with expanded trigger (yellow).
Norway rats are basically burrowing rodents and live in tunnels or dens in the ground. Under certain situation fumigation with aluminum phosphide (Fumitoxin, Phostoxin, Gastoxin) can be an effective control technique (see gophers). This is a Category 1 material and is a permit material in California. It should be remembered that this material cannot be used any closer than 15 feet from an occupied structure.
Exclusion and Sanitation.
Part of a successful rat or mouse control program should be multifold. With rats especially, a thorough examination of the property is advisable. This examination not only serves to help delineate where ongoing control efforts should be applied but may also be important from the standpoint of reinfestation. Certain conditions are conducive to the attraction of new rat problems once an existing infestation is eliminated. These areas may include dumpsters, standing water, creeks, streams, neighboring businesses, fruit trees, heavy vegetation and drainage systems to name a few. The most common attractant around the average home include either pet food or bird seed. The smells from these items is so strong it will attract several types of animals to your yard, including rats. Once they get a taste of these nutritious foods they will try to feed there daily. In homes that have pets there is a much more likelihood that rodent infestations will occur than in homes without. Pet food is packed with more nutrition now than ever as is bird seed and rodents are able to detect these food supplies.
If removal of some of these attractive food sources is going to be part of a rat pest management program it is important not to do this prior to elimination of the existing population. If done prior to control the rats will likely seek a new food source and of course the most desirable would be found inside the home.
Exclusion is undoubtedly one of the most important elements in a successful rodent control program. If in a populated area and there is a significant rodent (especially rats) problem you cannot expect to eradicate them all. Even if total control can be obtained in the structure reinfestation is likely to occur unless some type of exclusion programs is used. Such a program has to be very well designed as these rodents can enter a structure through the smallest openings. Adult rats can squeeze through a crack 1/2 inch wide and an adult house mouse can fit though a hole the diameter of a pencil. On part of exclusion techniques is to plug all gaps in the structure that exceed 1/2 inch and any hole larger than a quarter.
In addition exclusion techniques are aimed at preventing rats reaching the roof of structures (especially roof rats). This can be especially difficult since roof rats can jump straight up 2 feet and horizontally 5 feet. They are good swimmers and can climb most walls, telephone and electrical wires, trees and almost any other object in contact with the structure. Gaps can be filled with steel wool but this quickly rusts unless covered with cement, stuccos or similar materials. Copper wool or a copper based material called StufFits comes in a long role can be stuffed in holes or stretched across a wide gap. There are foam based gap fillers but these may be susceptible to rat gnawing.
Besides filling holes exclusion techniques can and should possibly include any for the following.
Metal Barrier when Wires (electrical, telephone) Run Close to Structure.
Hardware Cloth Curtain Wall on a Storage
Building. Top Edge Covered with Strip of
Blocking End Spaces of Wall Voids Using Sheet Metal, Brick or Cement Blocks
Rodent Proofing Openings around Pipes with
Sheet Metal (left) and Concrete (right).
Rodent Proofing\Drains with Hardware Cloth
Rodent Proofing a Door, Placing Sheet Metal
Channel at Bottom and Cuffs at Sides, over
Rodent Proofing Vent with 1/4th inch Hardware Cloth
Rodent Proofing Utility Wires to Limit Access
to Buildings Using Rolling Plastic Tubes
Made from Rectangular Sheets of Plastic.
The Tube Rolls When the Rodent Tries to
Walk Over It.
Rodent Proofing Air Vents and Chimneys
Using 1/4" Hardware Cloth.
It also important to advise customers on landscape design that should be changed, if possible. Large trees and shrubs immediately adjacent to a structure is an easy access to the roof. Ivey is a preferred habitat of rats and large areas should be cut back and possibly removed especially if it grows touching the home. Any debris and piles of fire wood stacked against the structure should be removed.
Final Test. T/F
60. The Norway is the largest of the 3 species of commensal rodents discussed in this document and is also commonly known as the brown, house, wharf and sewer rat.
61. One rat is capable dropping over 25,000 fecal pellets in a one year period.
62. Adult Norway and roof rat scats are the shape of and about twice the size of a grain of rice; however, Norway rat droppings have smooth pointed ends while the roof scats have round ends.
63. The body hairs of rats are fairly oily in nature: consequently, as a rat moves through a structure some of this oil rubs off onto the walls. Over time this oil will appear as smudge marks or dark streaks.
64. Under ultra violet light urine and to a lesser extent rat hairs will glow. Fresh urine appears as bluish-white while older urine glows as yellow. These marks may be spotty or in some cases a “squiggly line” as the rat urinated while moving.
65. There are other materials that fluoresce under UV light including bleached fabrics, bleaches and ever tar products to name a few.
66. Rat teeth grow continuously and must wear down. As a result rats and mice continually gnaw to gain access into walls, doors, packages, water pipes and outdoor irrigation systems.
67. While the house mouse is likely to poke around a newly placed bait station or trap, a rat is more likely to be very suspicious of new objects in its path and avoid them when possible.
68. The inquisitive nature of the house mouse makes them easier to trap or bait than rats.
69. On common trick that applicators frequently use when confronted with neophobic behavior is to place a trap in the rat’s environment but not set it until the rat becomes accustomed to its presence.
70. Trapping for rats in a house may be successful at first but over time will decrease considerably in efficacy.
71. Rats have poor eyesight and don’t rely on this sense to a great degree when moving around.
72. The main senses they rely on for navigation is the previously sense of kinesthesis and the sense of touch.
73. Rats have large oral vibrissae (whiskers) and many rather long stiff guard hairs that are mixed in with their fur. They rely on both of the types of hair to sense or feel their environment.
74. The concentration of the toxicant in first generation anticoagulants baits is low enough that the animal must feed on them on several consecutive days to result in death. These include Warfarin-the oldest, Diphacinone and Chlorophacinone.
75. Though not too effective for mice (since they are able to derive their water requirements from the food they eat), liquid bait works well for rats which are a problem in dry areas.
76. Common areas where these might work well would be feed stores and pet shops.
77. Fumitoxin cannot be used any closer than 15 feet from an occupied structure.
78. Live traps are more commonly and effectively used for mice than rats.
79. Adult rats can squeeze through a crack 1/2 inch wide and an adult house mouse can fit though a hole the diameter of a pencil. On part of exclusion techniques is to plug all gaps in the structure that exceed 1/2 in and any hole larger than a quarter.
80. Rats can jump straight up 2 feet and horizontally 5 feet. They are good swimmers and can climb most walls, telephone and electrical wires, trees and almost any other object in contact with the structure.