University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnThe Handbook: Prevention and Control of WildlifeDamage Wildlife Damage Management, Internet Center for

7-27-1994

Pocket GophersRonald M. CaseUniversity of Nebraska - Lincoln

Bruce A. JaschUniversity of Nebraska - Lincoln

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Case, Ronald M. and Jasch, Bruce A., "Pocket Gophers" (1994). The Handbook: Prevention and Control of Wildlife Damage. Paper 13.http://digitalcommons.unl.edu/icwdmhandbook/13

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POCKET GOPHERS

Damage Prevention andControl Methods

Exclusion

Generally not practical.Small mesh wire fence may provide

protection for ornamental trees andshrubs or flower beds.

Plastic netting protects seedlings.

Cultural Methods

Damage resistant varieties of alfalfa.Crop rotation.Grain buffer strips.Control of tap-rooted forbs.Flood irrigation.Plant naturally resistant varieties of

seedlings.

Repellents

Synthetic predator odors are all ofquestionable benefit.

Toxicants

Baits:Strychnine alkaloid.Zinc phosphide.Chlorophacinone.Diphacinone.

Fumigants:Carbon monoxide from engineexhaust.Others are not considered veryeffective, but some are used:

Aluminum phosphide.Gas cartridges.

Trapping

Various specialized gopher kill traps.Common spring or pan trap

(sizes No. 0 and No. 1).

Shooting

Not practical.

Other

Buried irrigation pipe or electrical cablescan be protected with cylindrical pipehaving an outside diameter of at least2.9 inches (7.4 cm).

Surrounding a buried cable with 6 to 8inches (15 to 20 cm) of coarse gravel(1 inch [2.5 cm] in diameter) mayprovide some protection.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Cooperative Extension DivisionInstitute of Agriculture and Natural ResourcesUniversity of Nebraska - Lincoln

United States Department of AgricultureAnimal and Plant Health Inspection ServiceAnimal Damage Control

Great Plains Agricultural CouncilWildlife Committee

Ronald M. CaseProfessor of Wildlife BiologyDepartment of Forestry, Fisheries

and WildlifeUniversity of NebraskaLincoln, Nebraska 68583-0819

Bruce A. JaschResearch AssistantDepartment of Forestry, Fisheries

and WildlifeUniversity of NebraskaLincoln, Nebraska 68583-0819

Fig. 1. Plains pocket gopher,Geomys bursarius

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sensory mechanism guiding gophers’backward movements. The tail is alsoimportant in thermoregulation, actingas a radiator.

Pocket gophers are medium-sizedrodents ranging from about 5 to nearly14 inches (13 to 36 cm) long (head andbody). Adult males are larger thanadult females. Their fur is very fine,soft, and highly variable in color.Colors range from nearly black to palebrown to almost white. The great vari-ability in size and color of pocketgophers is attributed to their low dis-persal rate and thus limited gene flow,resulting in adaptation to local condi-tions.

Thirty-four species of pocket gophers,represented by five genera, occupy thewestern hemisphere. In the UnitedStates there are 13 species and threegenera. The major features differentiat-ing these genera are the size of theirforefeet, claws, and front surfaces oftheir chisel-like incisors (Fig. 3).

Thomomys have smooth-faced incisorsand small forefeet with small claws.Northern pocket gophers (Thomomystalpoides) are typically from 6 1/2 to 10inches (17 to 25 cm) long. Their fur isvariable in color but is often yellowishbrown with pale underparts. Botta’s(or valley) pocket gophers (Thomomysbottae) are extremely variable in sizeand color. Botta’s pocket gophers are 5inches to about 13 1/2 inches (13 to 34cm) long. Their color varies fromalmost white to black.

Geomys have two grooves on eachupper incisor and large forefeet andclaws. Plains pocket gophers (Geomysbursarius) vary in length from almost 71/2 to 14 inches (18 to 36 cm). Theirfur is typically brown but may vary toblack. Desert pocket gophers (Geomysarenarius) are always brown and varyfrom nearly 8 3/4 to 11 inches (22 to 28cm) long. Texas pocket gophers(Geomys personatus) are also brown andare from slightly larger than 8 3/4 tonearly 13 inches (22 to 34 cm) long.Southeastern pocket gophers (Geomyspinetis) are of various shades of brown,depending on soil color, and are from9 to 13 1/4 inches (23 to 34 cm) long.

Pappogeomys have a single groove oneach upper incisor and, like Geomys,have large forefeet with large claws.Yellow-faced pocket gophers(Pappogeomys castanops) vary in lengthfrom slightly more than 5 1/2 to justless than 7 1/2 inches (14 to 19 cm).Their fur color varies from pale yellowto dark reddish brown. The under-parts vary from whitish to bright yel-lowish buff. Some hairs on the backand top of the head are dark-tipped.

Range

Pocket gophers are found only in theWestern Hemisphere. They range fromPanama in the south to Alberta in thenorth. With the exception of the south-eastern pocket gopher, they occurthroughout the western two-thirds ofthe United States.

Fig. 3. These three genera of pocket gophers can be differentiated by relative size of forefeet and front surfaces of upper incisors.

Thomomys PappogeomysGeomys

Incisors always exposed

Opening of fur-linedcheek pouch

Fig. 2. Pocket gopher characteristics.

Identification

Pocket gophers (Fig. 1) are fossorial(burrowing) rodents, so named be-cause they have fur-lined pouches out-side of the mouth, one on each side ofthe face (Fig. 2). These pockets, whichare capable of being turned inside out,are used for carrying food. Pocket go-phers are powerfully built in the fore-quarters and have a short neck; thehead is fairly small and flattened. Theforepaws are large-clawed and the lipsclose behind their large incisors, allmarvelous adaptations to their under-ground existence.

Gophers have small external ears andsmall eyes. As sight and sound areseverely limited, gophers are highlydependent on the sense of touch. Thevibrissae (whiskers) on their face arevery sensitive to touch and assistpocket gophers while traveling aboutin their dark tunnels. The tail issparsely haired and also serves as a

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Fig. 4a. Range of the plains pocket gopher(Geomys bursarius) (dark) and Botta’s pocketgopher (Thomomys bottae) (light) in NorthAmerica.

Plains pocket gophers (Geomysbursarius, Fig. 4a) are found in the cen-tral plains from Canada south throughTexas and Louisiana. Botta’s (or val-ley) pocket gophers (Thomomys bottae,Fig. 4a) are found in most of the south-ern half of the western United States.

Northern pocket gophers (Thomomystalpoides, Fig. 4b) range throughoutmost of the states in the northern halfof the western United States. Yellow-faced pocket gophers (Pappogeomyscastanops, Fig. 4b) occur from Mexico,along the western edge of Texas, east-ern New Mexico, southeastern Colo-rado, southwestern Kansas, and intothe panhandle of Oklahoma.

Southeastern pocket gophers (Geomyspinetis, Fig. 4c) are found in northernand central Florida, southern Georgia,and southeastern Alabama. Southernpocket gophers (Thomomys umbrinus,Fig. 4c) range primarily in CentralAmerica, but occur in extreme south-western New Mexico and southeasternArizona. Desert pocket gophers(Geomys arenarius) occur only in south-western New Mexico and the extremewestern edge of Texas. Mazamapocket gophers (Thomomys mazama,),mountain pocket gophers (Thomomysmonticola ), and Camas pocket gophers(Thomomys bulbivorus) have more lim-ited distributions in the extreme west-ern United States.

Habitat

A wide variety of habitats are occu-pied by pocket gophers. They occurfrom low coastal areas to elevations inexcess of 12,000 feet (3,600 m). Pocketgophers similarly are found in a widevariety of soil types and conditions.They reach their greatest densities onfriable, light-textured soils with goodherbage production, especially whenthat vegetation has large, fleshy roots,bulbs, tubers, or other undergroundstorage structures.

The importance of soil depth and tex-ture to the presence or absence ofgophers is both obvious and cryptic.Shallow soils may be subject to cave-ins and thus will not maintain a tunnel.Tunnels are deeper in very sandy soils

where soil moisture is sufficient tomaintain the integrity of the burrow. Aless visible requirement is that atmo-spheric and exhaled gases must diffusethrough the soil to and from thegopher’s tunnel. Thus light-textured,porous soils with good drainage allowfor good gas exchange between thetunnel and the atmosphere. Soils thathave a very high clay content or thosethat are continuously wet diffuse gasespoorly and are unsuitable for gophers.

Pocket gophers sometimes occupyfairly rocky habitats, although thosehabitats generally do not have morethan 10% rocks in the top 8 inches (20cm) of soil. Pocket gophers appear toburrow around rocks greater than 1inch (2.5 cm) in diameter, but smallerrocks are frequently pushed to thesurface.

Soil depth is also important in amelio-rating temperatures. Soils less than 4inches (10 cm) deep probably are toowarm during summers. Shallow tun-nels may also limit the presence ofgophers during cold temperatures,especially if an insulating layer ofsnow is absent.

Typically, only one species of pocketgopher is found in each locality. Soilfactors are important in limiting thedistributions of pocket gophers. Thelarger gophers are restricted to sandyand silty soils east of the Rockies.Smaller gophers of the genusThomomys have a broader tolerance tovarious soils.

Food Habits

Pocket gophers feed on plants in threeways: 1) they feed on roots that theyencounter when digging; 2) they maygo to the surface, venturing only abody length or so from their tunnelopening to feed on abovegroundvegetation; and 3) they pull vegetationinto their tunnel from below. Pocketgophers eat forbs, grasses, shrubs, andtrees. They are strict herbivores, andany animal material in their dietappears to result from incidentalingestion.

Alfalfa and dandelions are apparentlysome of the most preferred and nutri-

Fig. 4c. Range of the southeastern pocket gopher(Geomys pinetis) (dark) and southern pocketgopher (Thomomys umbrinus) (light) in NorthAmerica.

Fig. 4b. Range of the northern pocket gopher(Thomomys talpoides) (dark) and yellow-facedpocket gopher (Pappogeomys castanops) (light) inNorth America.

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tious foods for pocket gophers. Gener-ally, Thomomys prefer perennial forbs,but they will also eat annual plantswith fleshy underground storagestructures. Plains pocket gophers con-sume primarily grasses, especiallythose with rhizomes, but they seem toprefer forbs when they are succulent inspring and summer.

Portions of plants consumed also varyseasonally. Gophers utilize above-ground portions of vegetation mostlyduring the growing season, when thevegetation is green and succulent.Height and density of vegetation atthis time of year may also offer protec-tion from predators, reducing the riskof short surface trips. Year-round,however, roots are the major foodsource. Many trees and shrubs areclipped just above ground level. Thisoccurs principally during winter undersnow cover. Damage may reach ashigh as 10 feet (3 m) above ground.Seedlings also have their roots clippedby pocket gophers.

General Biology,Reproduction, andBehavior

Just as cheek pouches are used in iden-tification of pocket gophers, their fan-shaped soil mounds are characteristicevidence of their presence. Typically,there is only one gopher per burrowsystem. Obvious exceptions are whenmating occurs and when the female iscaring for her young.

All pocket gophers use their claws andteeth while digging. Geomys, however,are primarily claw diggers, whileThomomys do much more tooth dig-ging, and Pappogeomys are intermedi-ate between the two. Soil, rocks, andother items loosened by this means arekicked away from the digging areawith the hind feet. Gophers then turnover, making a sort of somersaultwithin the confines of their burrow,and use their forefeet and chest topush the materials out of the burrow.

The incisors of pocket gophers, as in allrodents, grow continuously to repairthe wear and tear on the teeth. On theother hand, gophers must gnaw con-

tinuously to keep their teeth ground toan appropriate length. Gophers exerttremendous pressure with their bite,up to 18,000 pounds per square inch(1,265 kg/cm2).

Burrow systems consist of a main bur-row, generally 4 to 18 inches (10 to 46cm) below and parallel to the groundsurface, with a variable number of lat-eral burrows off the main one. Theseend at the surface with a soil moundor sometimes only a soil plug. Thereare also deeper branches off the mainburrow that are used as nests and foodcaches. Enlargements along the maintunnel are probably feeding and rest-ing locations. Nest chambers havedried grasses and other grasslikeplants formed into a sphere. The maxi-mum depth of at least some portion ofa burrow may be as great as 5 or 6 feet(1.5 or 1.8 m). The diameter of a bur-row is about 3 inches (7.6 cm) but var-ies with the body size of the gopher.

Burrow systems may be linear orhighly branched. The more linear sys-tems may be those of reproductivemales, since this shape would increasethe likelihood of encountering afemale’s burrow. The number of soilmounds on the surface of the groundmay be as great as 300 per animal in ayear. Burrows are sometimes quitedynamic, with portions constantlybeing sealed off and new areas exca-vated. A single burrow system maycontain up to 200 yards (180 m) of tun-nels. The poorer the habitat, the largerthe burrow system required to providesufficient forage for its occupant.

The rate of mound building is highlyvariable. Estimates include an averageof 1 to 3 per day up to 70 mounds permonth. This activity brings largeamounts of soil to the surface, vari-ously estimated at 2 1/4 tons (2 mt)per gopher each year up to 46 3/4 tonsper acre (103.9 mt/ha) for a populationof 50 southern pocket gophers.

The tunnel system tells us much aboutits inhabitant. The system is rigorouslydefended against intruders and consti-tutes the home range of the pocketgopher, which may be up to 700square yards (560 m2).

Pocket gophers also tunnel throughsnow, above the ground. Soil frombelow ground is pushed into the snowtunnels, but mounds are not built.When the snow melts, the soil casts(tubes) remain on the ground untilthey weather away. Soil casts are leftby both Thomomys and Geomys in areaswhere snow cover is adequate forburrowing.

Pocket gophers do not hibernate. Someobservers believe their activities peakat dawn and dusk, but various studieshave shown them to be active through-out the day, with activity periods in-terspersed with rest. Mound buildingby plains pocket gophers increases inspring, frequently declines duringsummer, and increases again in fall. InThomomys, mound building increasesfrom spring through summer into fall.Tunneling underground is a tremen-dously demanding activity estimatedto require 360 to 3,400 times the energyof moving across the surface. Thus,this activity must be of great impor-tance to the pocket gopher’s survival,either increasing its chance of breedingor finding needed food resources.

Pocket gophers reach sexual maturityin the spring following their birth. Inthe northern part of their range theyhave 1 litter per year. In the southernportion they may have 2 litters peryear. One researcher has suggestedthat Thomomys in irrigated alfalfa inCalifornia may breed throughout theyear.

Litter sizes range from 1 to 10 but typi-cally average 3 to 4. In some southernportions of their range where 2 littersare born each year, litter size is usuallysmaller, averaging about 2. The breed-ing season also varies, but births typi-cally occur from March through June.The gestation period is 18 or 19 daysfor the northern pocket gopher, butperiods as long as 51 days for theplains pocket gopher have beenreported. Sex ratios are typically infavor of females, generally rangingfrom 55% to 60% females for Geomys.In Thomomys, the sex ratio is often50:50 but it varies seasonally. Theremay be more males than females inspring and the reverse for summer and

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fall. Pocket gophers have been thoughtto be polygamous (one male matingwith two or more females), but serialmonogamy may be the case. The malecohabits a tunnel system and may helpcare for young before moving on toanother female’s burrow system. Someresearchers believe both sexes movemainly underground from their ownto other burrows during the breedingseason.

Densities reported for various pocketgophers are highly variable. Densitiesof 16 to 20 per acre (40 to 49/ha) arevery common for Thomomys, but theymay attain densities up to 62 per acre(153/ha). For Geomys, 6 to 8 per acre(20/ha) are representative of high den-sities. Average life span of gophersappears to change inversely withpopulation density. Average longevityfor Thomomys ranges from just over 1year to nearly 3 years. Geomys may liveto an average age of 2 and reach amaximum age in the wild in excess of7 years.

Sharp declines in gopher populationshave been noted on several occasions.Usually some climatic factor is associ-ated with a marked decline. Anexample would be a heavy snowcover, then rapid snowmelt with aconcomitant rise in the water table.

External parasites are often found onpocket gophers. Lice are perhaps themost common, while ticks, fleas, andmites also occur. The contribution ofparasites to gopher mortality isunknown.

Numerous predators eat pocketgophers. Some of the predators pursuethe gopher in its tunnel system (wea-sels, perhaps spotted skunks, and sev-eral snakes including gopher, bull, andrattlesnakes). Badgers are adept at dig-ging out gophers, and a whole host ofpredators prey on gophers when theyare aboveground feeding, dispersing,or while they construct their mounds.Other mammalian predators includecoyotes, domestic dogs, foxes, housecats, striped skunks, and bobcats. Rap-tors that prey on gophers include sev-eral owls, especially great horned andbarn owls, and several hawks.

summer in Nebraska. Theseaboveground movements are a primereason for high mortality in denselypopulated areas.

Damage and DamageIdentification

Several mammals are sometimes con-fused with pocket gophers because ofvariations in common local terminol-ogy (Fig. 5). In addition, in the south-eastern United States, pocket gophersare called “salamanders,” (derivedfrom the term sandy mounder), whilethe term gopher refers to a tortoise.Pocket gophers can be distinguishedfrom the other mammals by their tell-tale signs as well as by their appear-ance. Pocket gophers leave soilmounds on the surface of the ground.The mounds are usually fan-shapedand tunnel entrances are plugged,keeping various intruders out of bur-rows.

Damage caused by gophers includesdestruction of underground utilitycables and irrigation pipe, direct con-sumption and smothering of forage byearthen mounds, and change in speciescomposition on rangelands by provid-ing seedbeds (mounds) for invadingannual plants. Gophers damage treesby stem girdling and clipping, rootpruning, and possibly root exposurecaused by burrowing. Gopher moundsdull and plug sicklebars when harvest-ing hay or alfalfa, and soil brought tothe surface as mounds is more likely toerode. In irrigated areas, gopher tun-nels can channel water runoff, causingloss of surface irrigation water. Gophertunnels in ditch banks and earthendams can weaken these structures,causing water loss by seepage and pip-ing through a bank or the completeloss or washout of a canal bank. Thepresence of gophers also increases thelikelihood of badger activity, whichcan also cause considerable damage.

Legal Status

Pocket gophers are not protected byfederal or state law.

A great diversity of vertebrates hasbeen found in the burrows of pocketgophers. It is especially interesting tonote how gophers react to those ani-mals. Most amphibians and lizards arelargely ignored. Ground squirrels,kangaroo rats, and smaller rodentsgenerally avoid gophers, frequentlyleaving the tunnel system if occupiedby a gopher. Sometimes gophers blockthe exit of these rodents by construct-ing earthen plugs in the burrow sys-tem. When pocket gophers encountersnakes, weasels, or other threats, theytypically react by assuming a threaten-ing posture with the mouth open,vocalizing with panting sounds, andraising the front of the body slightlywith their claws extended forward.This behavior usually chases awayother gophers in the tunnel. If theintruder is a snake, many strikesbounce off the gopher’s incisors andclaws. In addition, the gopher may tryto block the intruder with a wall ofsoil.

Pocket gophers are capable of swim-ming. The southern pocket gopher hasthe greatest endurance of three speciesthat were tested in laboratory condi-tions. The plains pocket gopher isintermediate in its endurance betweenthe southern pocket gopher and theyellow-faced pocket gopher. The latteris a very poor swimmer. The superiorswimming ability of the southernpocket gopher may be an adaptation toits mountain habitat, which frequentlyundergoes flooding during snowmelt.Swimming during flooding may alsobe a method of pocket gopherdispersal.

Dispersal of young plains pocketgophers from their natal burrows hasbeen reported to begin in June in Colo-rado. Young apparently begin to dis-perse when they are only one-third theadult body size. Other indications ofaboveground dispersal of pocketgophers have been reported by inci-dental captures of gophers in driftfences set for snakes. A plains pocketgopher was reported a victim of anautomobile on a highway in Iowa, andplains pocket gophers are reportedfalling into window wells every

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Damage Prevention andControl Methods

Exclusion

Because of the expense and limitedpracticality, exclusion is of little use.Fencing of highly valued ornamentalshrubs or landscape trees may be justi-fied. The fence should be buried atleast 18 inches (46 cm). The meshshould be small enough to excludegophers: 1/4-inch or 1/2-inch (6- to13-mm) hardware cloth will suffice.Cylindrical plastic netting placed overthe entire seedling, including the bareroot, reduces damage to newly plantedforest seedlings significantly.

Cultural Methods and HabitatModification

These methods take advantage ofknowledge of the habitat requirementsof pocket gophers or their feedingbehavior to reduce or eliminatedamage.

Crop Varieties. In alfalfa, large tap-rooted plants may be killed or thevigor of the plant greatly reduced bypocket gophers feeding on the roots.Varieties with several large rootsrather than a single taproot suffer lesswhen gophers feed on them. Addition-ally, pocket gophers in alfalfa fieldswith fibrous-root systems may havesmaller ranges. This would reducegopher impact on yield.

Crop Rotation. There are many goodreasons for using a crop rotationscheme, not the least of which is mini-mizing problems with pocket gophers.When alfalfa is rotated with graincrops, the resultant habitat is incapableof supporting pocket gophers. Theannual grains do not establish largeunderground storage structures andthus there is insufficient food forpocket gophers to survive year-round.

Grain Buffer Strips. Planting 50-foot (15-m) buffer strips of grainaround hay fields provides unsuitablehabitat around the fields and can mini-mize immigration of gophers.

Weed Control. Chemical or mechani-cal control of forbs, which frequently

Fig. 5. Mammals that are sometimes called gophers. From top to bottom: Richardson ground squir-rel, thirteen-lined ground squirrel, vole, and mole.

have large underground storage struc-tures, can be an effective method ofminimizing damage by Thomomys torangelands. It may also be effective inmaking orchards and shelterbelts lesssuitable for pocket gophers. Themethod is less effective for plainspocket gophers as they survive quitenicely on grasses. The warm-seasonprairie grasses have large root-to-stemratios and these food sources areadequate for Geomys.

Flood Irrigation. Irrigating fields byflooding can greatly reduce habitatsuitability for pocket gophers. Watercan fill a gopher’s tunnel, thus causingthe occupant to drown or flee to thesurface, making it vulnerable to preda-tion. The soil may be so damp that itbecomes sticky. This will foul thepocket gopher’s fur and claws. As thesoil becomes saturated with water, thediffusion of gases into and out of the

gopher’s burrow is inhibited, creatingan inhospitable environment. Theeffectiveness of this method can beenhanced by removing high spots infields that may serve as refuges duringirrigation.

Damage-Resistant PlantVarieties. Tests of several prove-nances of ponderosa pine showed thatsome have natural resistance to gopherdamage.

Repellents

Some predator odors have been testedas gopher repellents and show somepromise. Commercially available sonicdevises are claimed to repel pocketgophers. There is, however, no scien-tific supporting evidence. The plantsknown as caper spurge, gopher purge,or mole plant (Euphorbia lathyrus) andthe castor-oil plant (Ricinus communis)have been promoted as gopher

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repellents, but there is no evidence oftheir effectiveness. In addition, theseare not recommended as they are bothpoisonous to humans and pets.

Toxicants

Several rodenticides currently arefederally registered and available forpocket gopher control. The mostwidely used and evaluated is strych-nine alkaloid (0.25 to 0.5% active ingre-dient) on grain baits. There is someconcern that pocket gophers may con-sume sublethal doses of strychnineand then develop bait shyness. Strych-nine acts very rapidly and gopherssometimes die within an hour afterconsuming a lethal dose. It is regis-tered for use for Geomys spp. andThomomys spp. If the label has direc-tions for use with a burrow buildermachine, then it is a Restricted UsePesticide. Zinc phosphide (2%) is lesseffective than strychnine for gophercontrol. Anticoagulants now are avail-able for pocket gopher control. Cur-rently, the only federally registeredproducts are chlorophacinone anddiphacinone.

To poison pocket gophers, the baitmust be placed in their tunnel systemsby hand or by a special machineknown as a burrow builder. Under-ground baiting for pocket gopher con-trol with strychnine presents minimalhazards to nontarget wildlife, either bydirect consumption of bait or by eatingpoisoned gophers. Poison bait spilledon the surface of the ground may behazardous to ground-feeding birdssuch as mourning doves.

The main drawback to grain baits istheir high susceptibility to decomposi-tion in the damp burrows. A newproduct that contains a grain mixtureplus the anticoagulant, diphacinone, ina paraffin block not only increases thebait’s effective life, but also makes itpossible for more than one gopher tobe killed with the same bait. Once theresident gopher ingests the toxicantand dies, it is typical for a neighboringgopher to take over the tunnel systemand thus to ingest the still-toxic bait.

Hand Baiting. Bait can be placed ina burrow system by hand, using a

special hand-operated bait dispenserprobe, or by making an opening to theburrow system with a probe. Placingbait in the burrow by hand is moretime-consuming than either of theprobing methods, but there is nodoubt that the bait is delivered to thetunnel system.

The key to efficient and effective use ofthese methods is locating the burrowsystem. The main burrow generally isfound 12 to 18 inches (30 to 46 cm)away from the plug on the fan-shapedmounds (Fig. 6). If you use a trowel orshovel to locate the main burrow, dig12 to 18 inches (30 to 46 cm) awayfrom the plug. When the main burrowis located, place a rounded tablespoon(15 ml) of bait in each direction. Placethe bait well into each tunnel systemwith a long-handled spoon and thenblock off each tunnel with sod clumpsand soil. Bait blocks are also applied inthis manner. The reason for closing theburrow is that pocket gophers are at-tracted to openings in their systemwith the intent of closing them withsoil. Thus, if there is a detectable open-ing near the placement of poison, thepocket gopher may cover the bait withsoil as it plugs the opening. Pocketgophers normally travel all portions oftheir burrow system during a day.

Place a probe for pocket gopher tun-nels where you expect to locate themain burrow as described above(plans for making a probe and instruc-

tions for use are presented in figure 7).You will know you have located a bur-row by the decreased friction on theprobe. With a reservoir-type bait probedispenser (Fig. 8), a button is pushedwhen the probe is in a burrow and ametered dose of bait drops into theburrow. With the burrow probe (with-out a bait reservoir), make an openingfrom the surface of the ground to theburrow. Place about a tablespoon (15ml) of bait down the probe opening.This method is much quicker than dig-ging open the burrow tunnel. For bestcontrol, dose each burrow system intwo or three places. Be sure to coverthe probe hole with a sod clump sothat the pocket gopher does not coverthe bait when attracted to the openingin its burrow. Greater doses of chloro-phacinone or other locally registeredanticoagulants are recommended (1/2cup [120 ml]) at each of two or threelocations in each burrow. Also, sincesome gophers poisoned in this mannerdie aboveground, the area should bechecked periodically for 10 to 14 daysafter treatment. Any dead gophersfound should be buried or incinerated.

Mechanical Burrow Builder. Theburrow builder (Fig. 9) delivers baitunderground mechanically, so largeareas can be economically treated forpocket gopher control. It is tractor-drawn and is available in hydraulicallyoperated units or three-point hitchmodels.

Fig. 6. Characteristics of pocket gopher moundsand relation to tunnel system.

plug

plug

gopher tunnel and mound

gopher mound

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system to consume the bait. Recom-mended application rates of 1 to 2pounds per acre (1.1 to 2.2 kg/ha) of0.3 to 0.5% strychnine alkaloid grainshould provide an 85% to 95% reduc-tion in the gopher population (Table 1demonstrates how to calculate baitdelivery rates).

The burrows should be spaced at 20-to 25-foot (6- to 8-m) intervals. Toassure success:

1. Operate the burrow builder parallelto the ground surface, at a depthwhere gophers are active. It is es-sential to check the artificial burrow.If the soil is too dry, a good burrowwill not be formed; if the soil is toowet and sticky, soil will accumulateon packer wheels or even on theknife shank and the slot may notclose adequately.

2. Check periodically to note whetherbait is being dispensed. Sometimesthe tube gets clogged with soil.

3. Encircle the perimeter of the fieldwith artificial burrows to deterreinvasions.

4. Follow directions provided with theburrow builder machine.

It is especially important to scour thetorpedo assembly by pulling it throughsandy soils so that smooth burrowswill be constructed.

Fig. 7. Materials and construction plans for pocket gopher probes.

For extensive use in relatively soft soil, a durable probe may be made of 3/4-inch gas pipe—1 piece30 inches long. The 30-inch piece is threaded at both ends and the other pieces at one end only. Apiece of 1/2-inch round iron about 2 inches long is welded into the unthreaded end of the 14-inchpipe and bluntly pointed. The pieces are then arranged and fitted together with two 3/4-inchT-joints as shown here.

For use in hard soil, the probe may be made of the following materials:

1 piece of 1/2-inch galvanized pipe, 34 inches long1 piece of 1/2-inch galvanized pipe, 5 inches long1 1/2-inch galvanized T-joint1 piece of 1/2-inch round iron, 2 inches long1 piece of highly temperatured steel, 3/8-inch in diameter and 28 inches long1 3/8-inch set screw, 1 inch long1 3/8-inch nut1 reducer, 1/2 inch to 3/8 inch

The two pieces of pipe are each threaded at one end. The piece of round iron is welded into theunthreaded end of the 34-inch pipe and bluntly pointed. A 3/8-inch hole is bored in the T-joint, andthe 3/8-inch nut is brazed over this hole to accommodate the set screw. The piece of highly tem-pered steel is sharply pointed on one or both ends and held in place by the set screw. The pointedend of a hayrake tooth cut 28 inches long would serve well for this piece. These materials are thenassembled as shown here.

3/4" gas pipe

Round endsolid iron

14" 30"

The device consists of a knife and tor-pedo assembly that makes the artificialburrow at desired soil depths, acoulter blade that cuts roots of plantsahead of the knife, a seeder assemblyfor bait dispensing, and the packerwheel assembly to close the burrowbehind the knife. The seeder box has ametering device for dispensing varioustoxic baits at desired rates.

The artificial burrows should be con-structed at a depth similar to thoseconstructed by gophers in your area.The artificial burrows may interceptthe gopher burrows, or the gophersmay inquisitively enter the artificialburrows, gather bait in their cheekpouches, and return to their burrow

Fig. 9. A tractor-drawn mechanical burrowbuilder machine can be used to control pocketgophers. It automatically dispenses toxic baitinto the artificial burrow it creates.

Fig. 8. Automatic bait dispensing probe forpocket gopher control.

3/8" steel rod

3/8" set screw 3/8" nut

34"20"

5"1/2" gas pipe

Round end

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Table 1. Burrow builder machine bait application rate chart.

When bait-metering device Spacing between rows of artificial burrows (feet)

is adjustedto deliver: 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Pounds/1,000 feetof burrow Pounds of bait delivered per acre

0.1 0.44 0.36 0.31 0.27 0.24 0.22 0.20 0.18 0.17 0.16 0.15 0.14 0.13 0.120.2 0.87 0.73 0.62 0.54 0.48 0.44 0.40 0.36 0.34 0.31 0.29 0.27 0.26 0.240.3 1.30 1.10 0.93 0.82 0.73 0.65 0.59 0.54 0.50 0.47 0.44 0.41 0.38 0.360.4 1.70 1.50 1.20 1.10 0.97 0.87 0.79 0.73 0.67 0.62 0.58 0.54 0.51 0.480.5 2.20 1.80 1.60 1.40 1.20 1.10 0.99 0.91 0.84 0.78 0.73 0.68 0.64 0.61

0.6 2.60 2.20 1.90 1.60 1.50 1.30 1.20 1.10 1.00 0.93 0.87 0.82 0.77 0.730.7 3.00 2.50 2.20 1.90 1.70 1.50 1.40 1.30 1.20 1.10 1.00 0.95 0.90 0.850.8 3.50 2.90 2.50 2.20 1.90 1.70 1.60 1.50 1.30 1.20 1.20 1.10 1.00 0.970.9 3.90 3.30 2.80 2.50 2.20 2.00 1.80 1.60 1.50 1.40 1.30 1.20 1.20 1.101.0 4.40 3.60 3.10 2.70 2.40 2.20 2.00 1.80 1.70 1.60 1.50 1.40 1.30 1.20

1.1 4.80 4.00 3.40 3.00 2.70 2.40 2.20 2.00 1.80 1.70 1.60 1.50 1.40 1.301.2 5.20 4.40 3.70 3.30 2.90 2.60 2.40 2.20 2.00 1.90 1.70 1.60 1.50 1.501.3 5.70 4.70 4.00 3.50 3.10 2.80 2.60 2.40 2.20 2.00 1.90 1.80 1.70 1.601.4 6.10 5.10 4.40 3.80 3.40 3.00 2.80 2.50 2.30 2.20 2.00 1.90 1.80 1.701.5 6.50 5.40 4.70 4.10 3.60 3.30 3.00 2.70 2.50 2.30 2.20 2.00 1.90 1.80

1.6 7.00 5.80 5.00 4.40 3.90 3.50 3.20 2.90 2.70 2.50 2.30 2.20 2.00 1.901.7 7.40 6.20 5.30 4.60 4.10 3.70 3.40 3.10 2.80 2.60 2.50 2.30 2.20 2.101.8 7.80 6.50 5.60 4.90 4.40 3.90 3.60 3.30 3.00 2.80 2.60 2.40 2.30 2.201.9 8.30 6.90 5.90 5.20 4.60 4.10 3.80 3.40 3.20 3.00 2.80 2.60 2.40 2.302.0 8.70 7.30 6.20 5.40 4.80 4.40 4.00 3.60 3.40 3.10 2.90 2.70 2.60 2.40

2.1 9.10 7.60 6.50 5.70 5.10 4.60 4.20 3.80 3.50 3.30 3.00 2.90 2.70 2.502.2 9.60 8.00 6.80 6.00 5.30 4.80 4.40 4.00 3.70 3.40 3.20 3.00 2.80 2.702.3 10.00 8.30 7.20 6.30 5.60 5.00 4.60 4.20 3.90 3.60 3.30 3.10 2.90 2.802.4 10.50 8.70 7.50 6.50 5.80 5.20 4.80 4.40 4.00 3.70 3.50 3.30 3.10 2.902.5 10.90 9.10 7.80 6.80 6.10 5.40 5.00 4.50 4.20 3.90 3.60 3.40 3.20 3.00

2.6 11.30 9.40 8.10 7.10 6.30 5.70 5.10 4.70 4.40 4.00 3.80 3.50 3.30 3.102.7 11.80 9.80 8.40 7.40 6.50 5.90 5.30 4.90 4.50 4.20 3.90 3.70 3.50 3.302.8 12.20 10.20 8.70 7.60 6.80 6.10 5.50 5.10 4.70 4.40 4.10 3.80 3.60 3.402.9 12.60 10.50 9.00 7.90 7.00 6.30 5.70 5.30 4.90 4.50 4.20 3.90 3.70 3.503.0 13.10 10.90 9.30 9.20 7.30 6.50 5.90 5.40 5.00 4.70 4.40 4.10 3.80 3.60

EXAMPLE: To determine the amount of bait that will be delivered if a mechanical baiter is set to apply 0.5 pound per 1,000 feet of burrow, and is to beused between orchard rows with 22-foot spacings, read down row spacing column 22 until opposite the designated 0.5 pound. The answer (to the near-est hundredth) is 0.99 pound.

Fumigants

Federally registered fumigants includealuminum phosphide and gas car-tridges with various active ingredients.These fumigants usually are not verysuccessful in treating pocket gophersbecause the gas moves too slowlythrough the tunnel system. Unless thesoil is moist, the fumigant will diffusethrough the soil out of the gopher’stunnel.

Carbon monoxide from automobileexhaust is more effective than otherfumigants because of its greater vol-ume and pressure. Connect a piece of

hose or pipe to the engine exhaust, andplace it in a tunnel near a fresh soilmound. Pack soil around the hose orpipe and allow the engine to run forabout 3 minutes. The method is usu-ally 90% effective. The engines ofnewer vehicles with antipollutiondevices require a longer running timesince they do not produce as muchcarbon monoxide. This procedurerequires no registration.

Trapping

Trapping is extremely effective forpocket gopher control in small areas

and for removal of remaining animalsafter a poisoning control program.Some representative traps are illus-trated on the following page (Fig. 10)with instructions for setting them(Figs. 11 and 12).

Vulnerability to trapping differsamong species of pocket gophers andsometimes within the same species indifferent areas and at different timesof the year.

For effective trapping, the first requi-site is to find the tunnel. The proce-dure will vary depending on whether

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Fig. 10. Common types of traps for pocket gophers.

(a) Macabee® gopher trap

(b) Victor® Gopher Getter

flat metal piece

body shaft

thumb latch

trip lever

jaws

(c) Death-Klutch 1 gopher and mole trap

spring bar

hold-down bar

trigger wire

(d) Guardian (California box-type) gopher trap

Still holding frame down, place other end oftrigger (3) into small hole in plate.

Fig. 11. Instructions for setting Macabee®.

Press thumbs down, and with left index fingerguide hook on trigger (2) over end of frame oftrap.

Hold trap exactly as shown. Be sure left indexfinger holds trigger (1) in upright position.

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have success leaving tunnels com-pletely open when they set their traps;others, when they place traps in themain, close off the tunnel completely,and when trapping the lateral, closemost of the tunnel with sod. Traps canbe marked above ground with engi-neering flags and should be anchoredwith a stake and wire or chain so apredator does not carry off the catchand the trap.

Trapping can be done year-round be-cause gophers are always active, but aformidable effort is required for trap-ping when the soil is frozen. Trappingis most effective when gophers arepushing up new mounds, generally inspring and fall. If a trap is not visitedwithin 48 hours, move it to a new loca-tion. Leave traps set in a tunnel systemeven if you have trapped a gopher inspring and early summer, whengophers are most likely to share theirquarters.

Shooting

Since pocket gophers spend essentiallyall their time below ground, thismethod is impractical.

Other Methods

Buried utility cables and irrigationlines can be protected by enclosingthem in various materials, as long asthe outside diameter exceeds 2.9inches (7.4 cm). Gophers can opentheir mouths only wide enough toallow about a 1-inch (2.5-cm) spanbetween the upper and lower incisors.Thus, the recommended diameterpresents an essentially flat surface tomost pocket gophers. Cables can beprotected in this manner whether theyare armored or not. Soft metals such aslead and aluminum used for armoringcables are readily damaged by pocketgophers if the diameters are less thanthe suggested sizes.

Buried cables may be protected fromgopher damage by surrounding thecable with 6 to 8 inches (15 to 20 cm) ofcoarse gravel. Pocket gophers usuallyburrow around gravel 1 inch (2.5 cm)in diameter, whereas smaller pebblesmay be pushed to the surface.

Fig. 12. Instructions for setting the Death-Klutch 1gopher trap.

Pull thumb latch away from body shaft counter-clockwise (putting tension on spring), releasingfrom shipping position. Twist thumb clockwiseuntil thumb latch stops.

plug side. The lateral may be pluggedwith soil for several inches (cm) or sev-eral feet (m). However, fresh moundsare usually plugged only a few inches.

You may have to experiment with traptype and placement. Some trappers

With jaws in open position (as shown), hookcrooked end of trip lever over top of left jawwith long end under jaw. Push top of trip levertoward spring.

Slide flat metal piece toward jaws with pointsup. Put trip lever through large hole and moveflat metal piece up about 1 inch.

To apply spring tension, hold body shaft in righthand, catch thumb latch with left fore andmiddle fingers under spring. Hold firm andcrank body shaft clockwise one turn, and hookthumb latch back to body shaft. Caution: weargloves as finger may touch end of trip lever. Ifthis becomes a problem, trim tail of trip leverslightly.

Move flat metal piece to ear (away from jaws)near tip end of trip lever. Trap is now ready toplace into burrow.

traps are set in the main tunnel or inthe lateral tunnels (Fig. 13). To locatetraps in the main tunnel, refer to thesection on hand baiting. To locate thelateral tunnels, find a fresh mound andwith a trowel or shovel, dig severalinches away from the mound on the

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Mound

Lateral

Main tunnel

Hole dugwith shovel

currently troubled by pocket gopherscan gain tremendously by studying thegophers’ basic biology. They wouldgain economically by learning how tomanage their systems with pocketgophers in mind, and aesthetically byunderstanding how this interestinganimal “makes a living.”

The distribution of gophers makes itunlikely that control measures willthreaten them with extinction. Localeradication may be desirable and cost-effective in some small areas withhigh-value items. On the other hand, itmay be effective to simply reduce apopulation. There are also times whencontrol is not cost-effective and there-fore inadvisable. Complete controlmay upset the long-term integrity ofecosystems in a manner that we cannotpossibly predict from our currentknowledge of the structure and func-tion of those systems.

Acknowledgments

We thank the many researchers and managerswho have spent untold time studying theseextremely interesting rodents. Some are listed inthe reference section. Special thanks are due toScott Hygnstrom for his editorial assistance; toRex E. Marsh, Bob Timm, and Jan Hygnstromfor their helpful comments on an earlier draft,and to Diane Gronewold and Diana Smith fortheir technical assistance.

Figures 1, 2, and 6 from Schwartz and Schwartz(1981).

Figures 3 and 5 from Turner et al. (1973).

Figures 4a, 4b, and 4c after Hegdal and Harbour(1991), adapted by Bruce Jasch and Dave Thornhill.

Figures 7, 8, and 10 by Jill Sack Johnson.

Figure 9 courtesy of Elston Equipment Company.

Figure 11 courtesy of Z. A. Macabee GopherTrap Company.

Figure 12 courtesy of P-W ManufacturingCompany.

Figure 13 adapted from E. K. Boggess (1980),“Pocket Gophers,” in Handbook on Prevention andControl of Wildlife Damage, Kansas StateUniversity, Manhattan.

Table 1 taken from Marsh and Cummings (1977).

Economics of Damageand Control

It is relatively easy to determine thevalue of the forage lost to pocketgophers. Botta’s pocket gophers at adensity of 32 per acre (79/ha)decreased the forage yield by 25% onfoothill rangelands in California,where the plants were nearly allannuals. Plains pocket gophersreduced forage yield on rangelands inwestern Nebraska by 21% to 49% ondifferent range sites. Alfalfa yields ineastern Nebraska were reduced asmuch as 46% in dryland and 35% inirrigated alfalfa. Losses of 30% havebeen reported for hay meadows.

Calculating the cost of control opera-tions is only slightly more compli-cated. However, the benefit-costanalysis of control is still not straight-forward. More research data areneeded on managing the recovery offorage productivity. For example,should range be fertilized, rested, orlightly grazed? Should gopher moundson alfalfa be lightly harrowed? Astudy of northern pocket gopher con-trol on range production in southernAlberta indicated that forage yieldsincreased 16%, 3 months after treat-

ment. The potential for complete yieldrecovery the first year followinggopher removal has been noted for afibrous-rooted variety of alfalfa.

Economic assessment should also bemade to determine the cost of no con-trol, the speed of pocket gopher infes-tation, and the costs associated withdulled or plugged mowing machineryor mechanical breakdowns caused bythe mounds. Assessment could also bemade for damages to buried cable, irri-gation structures, trees, and so on.

The benefits of pocket gophers alsocomplicate the economic analysis.Some of these benefits are: (1) in-creased soil fertility by adding organicmatter such as buried vegetation andfecal wastes; (2) increased soil aerationand decreased soil compaction; (3)increased water infiltration and thusdecreased runoff; and (4) increasedrate of soil formation by bringingsubsoil material to the surface of theground, subjecting it to weathering.

Decisions on whether or not to controlgophers may be influenced by the ani-mals’ benefits, which are long-termand not always readily recognized,and the damage they cause, which isobvious and sometimes substantial inthe short-term. Landowners who are

Fig. 13. Trap placement in lateral or main pocket gopher tunnels. Note that traps are staked.

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For AdditionalInformation

Alsager, D. E., ed. 1970. Control of pocketgophers. Alberta Department of Agriculture,Publication No. 686, 16 pp.

Alsager, D. E. 1977. Impact of pocket gophers(Thomomys talpoides) on the quantitativeproductivity of rangelands vegetation insouthern Alberta: A damage assessment tool.Pages. 47-57 in W. B. Jackson, and R. E.Marsh, eds. Test methods for vertebrate pestcontrol and management materials, ASTMSTP 625, Am. Soc. Testing Mater.Philadelphia, Pennsylvania.

Andersen, D. C. 1978. Observations onreproduction, growth, and behavior of thenorthern pocket gopher (Thomomys talpoides).J. Mammal. 59:418-422.

Anthony, R. M., V. G. Barnes, Jr., and J. Evans.1978. “Vexar” plastic netting to reducepocket gopher depredation of coniferseedlings. Proc. Vertebr. Pest Conf. 8:138-144.

Barnes, V. G., Jr. 1973. Pocket gophers andreforestation in the Pacific Northwest: aproblem analysis. US Fish Wildl. Serv.Special Sci. Rep. Wildl. No. 155. Washington,DC. 18 pp.

Chase, J. D., W. E. Howard, and J. T. Roseberry.1982. Pocket gophers. Pages. 239-255 in J. A.Chapman and G. A. Feldhamer, eds. Wildmammals of North America: biology,management, and economics. The JohnsHopkins Univ. Press, Baltimore, Maryland.

Connolly, R. A., and R. E. Landstrom. 1969.Gopher damage to buried cable materials.Mater. Res. Standards 9:13-18.

Corbet, G. B., and J. E. Hill. 1986. A world list ofmammalian species. 2d ed. Facts On FilePubl., New York. 254 pp.

Downhower, J. F., and E. R. Hall. 1966. Thepocket gopher in Kansas. Univ. KansasMuseum Nat. Hist., Misc. Publ. No. 44.32 pp.

Fitch, H. S., and J. R. Bentley. 1949. Use ofCalifornia annual-plant forage by rangerodents. Ecology. 30:306-321.

Foster, M. A., and J. Stubbendieck. 1980. Effectsof the plains pocket gopher (Geomysbursarius) on rangelands. J. Range Manage.33:74-78.

Hegdal, P. L., and T. A. Gatz. 1976. Hazards towildlife associated with undergroundstrychnine baiting for pocket gophers. Proc.Vertebr. Pest Conf. 7:158-266.

Hegdal, P. L., and A. J. Harbour. 1991. Pocketgophers. Pages 5-19 in Prevention andcontrol of animal damage to hydraulicstructures. United States Printing Office,Denver, Colorado.

Hickman, G. C. 1977. Geomyid interaction inburrow systems. Texas J. Sci. 29:235-243.

Hickman, G. C. 1977. Swimming behavior inrepresentative species of the three genera ofNorth American geomyids. Southwest Nat.21:531-538.

Howard, W. E. 1961. A pocket gopherpopulation crash. J. Mammal. 42:258-260.

Kennerly, T. E., Jr. 1958. Comparisons ofmorphology and life history of two speciesof pocket gophers. Texas J. Sci. 10:133-146.

Laycock, W. A., and B. Z. Richardson. 1975.Long-term effects of pocket gopher controlon vegetation and soils of a subalpinegrassland. J. Range Manage. 28:458-462.

Luce, D. G., R. M. Case, and J. Stubbendieck.1980. Food habits of the plains pocket gopheron western Nebraska rangelands. J. RangeManage. 33:129-131.

Luce, D. G., R. M. Case, and J. L. Stubbendieck.1981. Damage to alfalfa fields by plainspocket gophers. J. Wildl. Manage.45:258-260.

Marsh, R. E. 1992. Reflections on current (1992)pocket gopher control in California. Proc.Vertebr. Pest Conf. 15:289-295.

Marsh, R. E., and M. W. Cummings. 1977. Pocketgopher control with mechanical baitapplicator. Coop. Ext., Div. Agric. Sci., Univ.California Leaflet 2699. 7 pp.

Miller, M. A. 1957. Burrows of the SacramentoValley pocket gopher in flood-irrigatedalfalfa fields. Hilgardia 26:431-452.

Myers, G. T., and T. A. Vaughan. 1964. Foodhabits of the plains pocket gopher in easternColorado. J. Mammal. 45:588-598.

Radwan, M. A., G. L. Couch, C. A. Harrington,and W. D. Ellis. 1982. Terpenes of ponderosapine and feeding preferences by pocketgophers. J. Chem. Ecol. 8:241-253.

Reichman, O. J., T. G. Whitham, and G. A.Ruffner. 1982. Adaptive geometry of burrowspacing in two pocket gopher populations.Ecology. 63:687-695.

Schwartz, C. W., and E. R. Schwartz. 1981. Thewild mammals of Missouri, rev. ed. Univ.Missouri Press, Columbia. 356 pp.

Sudaman, P. D., J. C. Burns, and J. R. Choate.1986. Gestation and postnatal developmentof the plains pocket gopher. Texas J. Sci.38:91-94.

Turner, G. T., R. M. Hansen, V. H. Reid, H. P.Tietjen, and A. L. Ward. 1973. Pocketgophers and Colorado mountain rangelands.Colorado State Univ. Exp. Stn. Bulletin 554S.90 pp.

Vaughan, T. A. 1962. Reproduction in the plainspocket gopher in Colorado. J. Mammal.43:1-13.

EditorsScott E. HygnstromRobert M. TimmGary E. Larson

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