Safe efficacy of three strychnine alkaloid bait concentrations for hand-baiting control of plains pocket gophers

In November 1990, field efficacy studies using milo baits formulated with 0.35%, 0.75%, or 1.30% strychnine alkaloid were compared to a placebo (0.0% strychnine) for controlling plains pocket gophers (Geomys bursarius) near Pleasanton, Texas. These data were required by the US Environmental Protection Agency (EPA) as partial fulfillment for the maintenance of the rodenticide registrations of the US Department of Agriculture. Each of four treatment units (TUs) within a block (2) was randomly assigned one of the four baits. Within each TU, 15 gophers were captured (balanced roughly for gender) and instrumented with radio transmitters. Following a pretreatment acclimation averaging 4.1 days, bait (4 g) was placed in active pocket gopher burrows by hand-baiting. Pocket gopher mortality was measured by monitoring the fate of radio-equipped pocket gophers (n=123) both pretreatment and post-treatment. Lack of gopher movement on two consecutive days indicated death, and the carcass was retrieved. Strychnine mortality was based on chemical analyses of carcasses, and it occurred in 0.0%, 66.7%, 96.3%, and 89.7% of gophers from the 0.0%, 0.35%, 0.75% and 1.30% TUs, respectively. Natural mortality was 7% on the placebo TUs. All three strychnine treatments provided significantly increased mortality over the placebo (P\u3c0.0001) using Fisher\u27s exact test for paired comparisons. A difference in gopher mortality occurred between the 0.32% and 0.77% strychnine treatments (P=0.003), but not between the other comparisons (0.32% vs 1.30%, P=0.18 and 0.77% vs. 1.30%, P=0.24). Gopher carcasses recovered post-treatment indicated 68 of 86 (79.1%) had strychnine alkaloid residues. The non-target strychnine hazard (using least squares means) by treatment were 4.85 ppm (0.35%), 8.04 ppm (0.75%), and 9.47 ppm (1.30%). Carcass residue differences were not detected among strychnine treatments (F=2.48, df=2,3, P=0.23). Fortunately, non-target exposure was greatly decreased because all carcasses with strychnine residues were recovered underground at a mean depth of 0.51 m (SE=0.027, range 0.15–1.17 m). Placebo-baited TUs had 27 survivors and 2 deaths from unknown causes. None had detectable strychnine levels. No non-target mortalities were documented during carcass searches and radio-tracking activities

HAZARDS TO WILDLIFE ASSOCIATED WITH UNDERGROUND STRYCHNINE BAITING FOR POCKET GOPHERS

Under an Environmental Protection Agency (EPA) contract, we evaluated the hazards associated with strychnine baiting for pocket gophers (Geomys bursarius) with the burrow-builder. On the Sherburne National Wildlife Refuge, Minnesota, we treated 662 ha (1638 acres) with 0.5 percent strychnine-treated bait. Treated fields were scattered throughout 10 sections. Control was effective--data from pocket gopher activity plots showed 87.5 ± 5.9 percent reductions in activity. Populations of other small rodents (while quite low) significantly declined on the treated area, but significantly increased on the control area. To measure secondary effects we equipped 36 raptors and 36 mammalian predators with radio transmitters. We detected little, if any, effect on radio-equipped raptors and mammalian predators. Red-tailed hawks (Buteo jamaicensis), American kestrels (Falco sparverius), great horned owls (Bubo virginianus), badgers (Taxidea taxus), striped skunks (Mephitis mephitis), red fox (Vulpes fulva) and a coyote (Canis latrans) were intensively radio-tracked during treatment; those that utilized treated fields all survived. Mammalian predator tracks and diggings were frequently observed on the burrow-builder tracks after treatment. Red-winged blackbirds (Agelaius phoeniceus) were selected as a representative of seed-eating birds. We marked 100 territorial males on both the treated and control area and monitored them during the treatment. Even though some treated grain was available on the surface and marked birds were observed feeding in treated fields, we did not detect any detrimental effects. Nevertheless, we found one treatment-killed mourning dove (Zenaida macroura)

METHODS OF CONTROLLING JACKRABBITS

Since 1963, biologists of the Denver Wildlife Research Center have been investigating methods of alleviating agricultural damage by the black-tailed jackrabbit (Lepus californicus). Of the several approaches to control, most biological methods (predation, habitat manipulation, disease and parasites, and chemosterilants) appear impractical with present knowledge. Mechanical control except for fence barriers, usually has limited effectiveness. Currently, the most useful approach is still chemical control. Improved baiting techniques and several chemical control agents, including an experimental toxicant highly selective for jackrabbits, are described

PUBLIC RELATIONS IN ENVIRONMENTAL AND VERTEBRATE PEST RESEARCH

In our efforts to investigate environmental concerns, such as vertebrate pests, we as scientists too often neglect or fail to recognize the importance and value of strong public relations. Most scientists would agree that public relations and public education are honorable components of research, but time is often a precious commodity to be utilized in resolving the ecological problem under investigation. Additionally, in many situations, due either to the personality of the researcher or public sensitivity to the problem area, many scientists shy away from public interaction. In the vertebrate pest field, we often deal with ecological problems that stem from social or economic situations. Since our research and pest control activities are strongly linked to man and his environment, it is exceptionally important that we know how to interact with people in order to achieve public understanding of how research is conducted, why certain control practices are implemented, and acceptance of pest management practices. Since much of our research and control activities are dependent upon information supplied by non·scientists, the efficiency and effectiveness of our efforts are enhanced by an ability to communicate. We must be able to ask the right questions, but we also must be able to provide correct and understandable answers

EFFICACY DATA FOR REGISTRATION OF STRYCHNINE GRAIN BAITS TO CONTROL POCKET GOPHERS (\u3ci\u3eThomomys\u3c/i\u3e spp.)

Laboratory tests, field telemetry trials, and actual use field efficacy evaluations showed that a 0.5% strychnine alkaloid steam-rolled oat-groat hand-bait formulation (EPA Reg. No. 56228-20) with molasses, salt, glycerine, and soda was effective in controlling northern pocket gophers (Thomomys talpoides). Baits retaining at least 0.5% strychnine (w/w) were as effective (\u3e95% control) as baits with 0.75% and 1.0% strychnine in field telemetry hand-baiting trials as well as operational hand-baiting and burrow-builder baiting field tests in forest habitat. Data indicated that the 0.5% strychnine hand bait (molasses formulation) should be reregistered and would be a good substitute for the 0.5% strychnine-Rhoplex bait (EPA Reg. No. 56228- 12) currently registered for burrow builder use for pocket gopher control. Both the retention of strychnine on bait, and use of a highly palatable top quality bait carrier were two important factors affecting efficacy of the bait

LOCAL WINTER MOVEMENTS OF FOUR RAPTOR SPECIES IN CENTRAL COLORADO

Although most North American raptors are migrator

EFFICACY OF STRYCHNINE EGGS FOR CONTROLLING FRANKLIN GROUND SQUIRRELS

In February 1985, the Environmental Protection Agency (EPA) established standards for reregistering strychnine for controlling ground squirrels. One standard required efficacy data on strychnine concentrations below those presently registered with the EPA. The 8.0 mg of strychnine per treated egg currently registered in North Dakota (ND820001) for controlling Franklin ground squirrels (Spermophilus franklinii) on waterfowl production areas (WPA\u27s) was included in this standard. The U.S. Fish and Wildlife Service (USFWS) decided to maintain the strychnine egg registration because this is the only method available for controlling this species on WPA\u27s. In 1986, the Denver Wildlife Research Center (DWRC) conducted laboratory tests indicating that no ground squirrel mortality occurred after they fed on 0.5 mg, 1.0 mg, or 2.0 mg strychnine-treated eggs. Ground squirrel mortality was 88%, 89%, and 88% after feeding on 3.0 mg, 4.0 mg, and 5.0 mg strychnine eggs, respectively. All died after feeding on 6.0 mg strychnine eggs (Matschke, unpublished data

Hazards to wildlife associated with underground strychnine baiting for pocket gophers

Under an Environmental Protection Agency (EPA) contract, we evaluated the hazards associated with strychnine baiting for pocket gophers (Geomys bursarius) with the burrowbuilder. On the Sherburne National Wildlife Refuge, Minnesota, we treated 662 ha (1,638 acres) with 0.5 percent strychnine-treated bait. Treated fields were scattered throughout 10 sections. Control was effective--data from pocket gopher activity plots showed 87.5 + 5.9 percent reduction in activity. Populations of other small rodents (while quite low) significantly declined on the treated area, but significantly increased on the control area. To measure secondary effects we equipped 36 raptors and 36 mammalian predators with radio transmitters. We detected little, if any, effect on radio-equipped raptors and mammalian predators. Red-tailed hawks (Buteo jamaicensis) , American kestrels (Falco sparverius), great horned owls (Bubo virginianus), badgers (Taxidea taxus), striped skunks (Mephitis mephitis), red fox (Vulpes fulva) and a coyote (Canis latrans) were intensively radio-tracked during treatment; those that utilized treated fields all survived. Mammalian predator tracks and diggings were frequently observed on the burrow-builder tracks after treatment. Red-winged blackbirds (Agelaius phoeniceus) were selected as a representative of seed-eating birds. We marked 100 territorial males on both the treated and control area and monitored them during the treatment. Even though some treated grain was available on the surface and marked birds were observed feeding in treated fields, we did not detect any detrimental effects. Nevertheless, we found one treatment-killed mourning dove (Zenaida macroura)

Hazards to wildlife associated with 1080 baiting for California ground squirrels

Under an Environmental Protection Agency (EPA) Interagency Agreement, we evaluated the hazards to wildlife associated with aerial 1080 (sodium monofluoroacetate) baiting for California ground squirrels (Spermophilus beecheyi fisheri). We conducted the study in Tulare County, in south-central California, in the eastern foothills of the San Joaquin Valley. Vegetation is annual range grasses and associated forbs, under open stands of oak (Quercus spp.), with cottonwood (Populus spp.), California sycamore (Platanus racemosa), and California buckeye (Aesculus californica) along stream bottoms. The study monitored a large-scale operational baiting program conducted in Tulare County by the Tulare County Agricultural Commissioner. During early June 1977, (in the vicinity of the study area) about 25,000 ha (60,000 acres) were spot-treated with 0.075 percent 1080-treated oat groats at about 6.7 kg/ha (6 lb per swath acre). The actual surface area baited was about 3.4 percent of the range. California ground squirrel populations were reduced about 85 percent following baiting. Primary hazards to seed-eating birds appear minimal as indicated from intensive carcass searching and the results from 31 radio-equipped mourning doves (Zenaida macroura) and 10 radio-equipped California quail (Lophortyx californicus). One of two white-breasted nuthatches (Sitta carolinensis) found dead after treatment contained 1080 residue. One of two samples of dead ants also contained 1080 residue. Twelve cottontail rabbits (Sylvilagus auduboni) were found dead after treatment and four contained 1080 residue, indicating some primary hazard to this species. Secondary hazards to raptors and mammalian predators were evaluated by attaching radio transmitters to 24 raptors (red-tailed hawks, Buteo jamaicensis; turkey vultures, Cathartes aura; a golden eagle, Aquila chrysaetos; great horned owls, Bubo virginianus; barn owls, Tyto alba; a screech owl, Otus asio; common ravens, Corvus corax; a common crow, Corvus brachyrhynchos) and 42 mammalian predators (bobcats, Lynx rufus; coyotes, Canis latrans; gray fox, Urocyon cinereoargenteus; badgers, Taxidea taxus; striped skunks, Mephitis mephitis; raccoons, Procyon lotor; and opossum, Didelphis marsupialis) and monitoring their movements before, during, and after treatment. Five of the six radio-equipped coyotes and three of the 10 radio-equipped bobcats (one bobcat was emaciated, possibly a result of a trap injury) were found dead after treatment. Three dead striped skunks (not radio-equipped) were also found dead after treatment and one contained 1080 residue. No other treatment-related mortalities were indicated among the remaining radio-equipped birds or mammals. Also, monitoring of 58 active raptor nests indicated no treatment-related mortalities