A striped skunk (Mephitis mephitis) rabies epizootic in northwestern Wyoming was studied from the Index Case in 1988 to the last case in 1993, and possibly is the first rabies epizootic in a previously rabies-free zone monitored from beginning to end. The 843 km2 study area comprised skunk habitat along 90 km of Shoshone River’s floodplain from Bighorn Lake upstream to Cody. Of 1,015 skunks tested, 215 were rabies-positive. Integrating spatial and temporal data from positive cases, we analyzed the epizootic’s movements and dynamics at 6-month intervals using multivariate movement maps, a new multivariate descriptive methodology presented here to demonstrate the epizootic’s directional flow, while illustrating areas with higher case densities (i.e., wave crests). This approach should help epidemiologists and public health officials to better understand future rabies epizootics.

Studying the lower Shoshone River Basin's (SRB) striped skunk (Mephitis mephitis) rabies 6-year epizootic in northwestern Wyoming has produced four didactic lessons. First, physiographic changes by settlers circa 1900 affected its zoogeography by creating a canal system for irrigating crops originating at Buffalo Bill Reservoir (BBR). The resulting landscape changes increased agricultural lands and skunk habitat eightfold between the valley's steep gravel benches. The valley was historically free of skunk rabies until the epizootic's index case in August 1988. Second, human intervention began when the Bighorn County Predator Board (BCPB) proactively implemented rabies trapping surveillance and depopulation programs in 1989. The epizootic's second case occurred in February 1989. From 1990-1993, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (WS) Wyoming office continued these programs. The epizootic ended in 1993 with over 200 rabid animals diagnosed by the Wyoming State Veterinary Laboratory (WSVL) from about 1,000 skunks tested. Cooperator agreements began in January 1989 and continued throughout the epizootic for trapping and shooting of potential vectors. Third, WS National Wildlife Research Center (NWRC) analyzed the epizootic movements using monthly mean movements and standardized ellipsoids. These analyses demonstrated that rabies dispersed radially from the index case until it reached the Shoshone River. From there, the epizootic spread downstream until stopped by Bighorn Lake (BL) in 1989 and upstream until stopped by BBR in 1992. Fourth, descriptive multivariate movement maps (MMMs) of the epizootic were analogous to fluid wave characteristics describing a swell moving along the surface of a liquid as the "leading edge" and "crest." All rabid animal locations were derived from the first use of global positioning system (GPS) in investigating wildlife disease. These lessons learned should assist others to better understand skunk rabies epizootics.

A rabies epizootic occurred in striped skunks from 1988-1993 in a previously rabies-free area of northwestern Wyoming. US DA APHIS Wildlife Services (WS) cooperated with state and local officials by providing a rabies monitoring and depopulation program starting in 1990. Wyoming WS asked for assistance in 1991 from the National Wildlife Research Center (NWRC) to analyze the epizootic's movements. The goal was to address the public's concerns about their health and safety and that of their domestic animals and livestock. All rabid skunks were diagnosed by the Wyoming State Veterinary Laboratory (WSVL) using standardized fluorescent antibody testing of brain tissues. The "Index Case" was collected on August 15, 1988 near Cowley. The epizootic moved radially out from this location and was limited by skunk habitat that was itself constrained by physiographic barriers. Rabies spread up and down Polecat and Sage Creeks before entering the rest of the lower Shoshone River Basin (SRB). It then moved both downstream to the Bighorn Lake and upstream toward Yellowstone National Park. However, when this epizootic ended in 1993, it had reached only the lower SRB downstream from Buffalo Bill's Reservoir and Canyon. This area has been rabies-free ever since. Over the years various analytical techniques have been utilized by the authors to better understand and describe this epizootic. These have included: traditional county surveillance data (1988); GPS, digitized, and geocoded locations (1991); and GIS databases with and rudimentary landscape epidemiology (1992). Following the epizootic, we used more detailed GIS databases as they were developed for land cover (i.e., habitat), hydrology, and human populations from 1999 - 2006. Subsequent rabies analyses have included: movement of the monthly mean locations (2007); spatial ellipsoid movements indicating "wave fronts" or "crests" (2008); and multivariate movement maps (MMM) (2009). MMM were used to illustrate the rabies front(s) with the instantaneous and spatially described density of cases and directional flow of spreading disease. The advantages and drawbacks of each analysis tool are discussed. The evolution of these different analytical tools and their uses should assist epidemiologists in analyzing and understanding future rabies epizootics.

The most important reservoir of wildlife rabies on the American Great Plains is the striped skunk. A rabid striped skunk taken in August 1988 near Deaver, WY became the index case for a subsequent epizootic in a previously skunk rabies free area. In 1989, more rabid skunks occurred and the epizootic was moving throughout Sage Creek and in later years (1990-1993) through the entire Shoshone River basin. Federal, state, and local officials cooperated in a rabies program with the goal of addressing the health and safety of the region’s citizens, domestic animals, and livestock. Three areas of focus in the program were: 1) immunization of pets and livestock, 2) public education, and 3) skunk population monitoring and control. Rabies immunizations were re-emphasized by the local veterinarians and public health officials for pets to decrease potential rabies spillover to other species. Public education emphasized the dangers of rabies and the behavior of rabid animals using local news media and assemblies at area schools. This paper provides a synoptic overview of the third component – skunk population monitoring and control provided by USDA/APHIS’s Wyoming Wildlife Services (WS). WS provided trapping expertise starting in 1990 with rabid specimens identified by the Wyoming State Veterinary Laboratory. Starting in 1990, WS’s National Wildlife Research Center provided data analysis of rabid locations for the entire epizootic (i.e., 1988-1993). These analyses demonstrated the epizootic’s movements through the novel first use of a Geographic Information System that merged a wildlife disease (i.e., rabies) case/capture locations and dates with additional GIS data layers including hydrology, human population density, and land use. The epizootic ended in 1994 with striped skunks, bats, cats, and one horse affected. Studying this epizootic should benefit officials in planning future surveillance and/or depopulation programs. This study demonstrated the need for a skunk rabies vaccine and effective delivery system, and if the latter had been available maybe this epizootic would have been more limited in its scope and duration.

The efficacy of using 0.01% chlorophacinone on steam-rolled oat (SRO) groats applied in CA alfalfa by spot-baiting/hand baiting around burrow entrances (~11.5 g) to control free-ranging Belding's ground squirrels (Spermophilus beldingi) were compared in 6 randomly assigned square treatment units (TUs). Four TUs were given the rodenticide and 2 treated with placebo bait. Each TU was a 0.4 ha square surrounded by a similarly treated 5.5 ha square buffer zone. Baits were applied on May 13 and re-applied, on May 20 and May 22, after 7 days of un-forecasted cool wet weather greatly reduced their above ground activity. Pesticide (EPA SLN CA-890024) efficacy was calculated as % reduction (PR) of ground squirrels on each TUs measured directly by visual counts (VCs) and indirectly by active burrow counts (ABCs). VCs and ABCs provided mean PRs that met US EPA's 70% minimum standard efficacy threshold for field rodenticides (x = 73.5%, SD + 13.3; x = 80%, SD + 6.2, respectively). ANOVA results of the PRs were highly significant (F = 29.72, df 1/4, p = 0.0055 and F = 72.92, df 1/4, P = 0.001, respectively). All carcasses (38) located above ground were analyzed for pesticide and 80% had detectable levels in whole animals (x = 0.1131 ppm, SD + 0.0928). Suggestions to improve the pesticide’s efficacy and lessen its potential nontarget hazards were discussed.

Striped skunks (Mephitis mephitis) are one of the most important reservoirs of wildlife rabies on the Great Plains of North America. During a skunk rabies epizootic in a previously rabiesfree area of northwestern Wyoming, we studied the spread of rabies from the index case occurring in 1988 until the Shoshone River epizootic ended in 1993. All specimens were sent to the Wyoming State Veterinary Laboratory for Fluorescent Antibody Testing for rabies. The goal of federal, state, county, and local agencies was to address the public's fear about the health and safety of humans and animals. Following several rabid skunk attacks reported to authorities and recounted in local newspapers, a more proactive and responsive approach was sought by the public. As a result, the United States Department of Agriculture’s Wyoming Wildlife Services program began, in cooperation with other state and local offices, a rabies monitoring and control program in 1990. A scientist from the National Wildlife Research Center (NWRC) in 1991 was the first to employ global positioning satellites (GPS) for identifying rabid skunk capture locations. In 1992, an epidemiologist from NWRC was the first to utilize a “geographic information system” (GIS) using geographic hydrology to analyze the spread of skunk rabies. This paper presents an overview of this first use of GPS/GIS that combined rabid skunk locations, geographic hydrology, and time to better understand the epizootic’s movements along the Shoshone River.

The efficacy of using 0.01% chlorophacinone on steam-rolled oat (SRO) groats applied in CA alfalfa by spot-baiting/hand baiting around burrow entrances (~11.5 g) to control free-ranging Belding's ground squirrels (Spermophilus beldingi) were compared in 6 randomly assigned square treatment units (TUs). Four TUs were given the rodenticide and 2 treated with placebo bait. Each TU was a 0.4 ha square surrounded by a similarly treated 5.5 ha square buffer zone. Baits were applied on May 13 and re-applied, on May 20 and May 22, after 7 days of un-forecasted cool wet weather greatly reduced their above ground activity. Pesticide (EPA SLN CA-890024) efficacy was calculated as % reduction (PR) of ground squirrels on each TUs measured directly by visual counts (VCs) and indirectly by active burrow counts (ABCs). VCs and ABCs provided mean PRs that met US EPA's 70% minimum standard efficacy threshold for field rodenticides (¯x = 73.5%, SD + 13.3; ¯x = 80%, SD + 6.2, respectively). ANOVA results of the PRs were highly significant (F = 29.72, df 1/4, p = 0.0055 and F = 72.92, df 1/4, P = 0.001, respectively). All carcasses (38) located above ground were analyzed for pesticide and 80% had detectable levels in whole animals (¯x = 0.1131 ppm, SD + 0.0928). Suggestions to improve the pesticide's efficacy and lessen its potential non- target hazards were discussed.

Seventy-one Chinese ring-necked pheasants were radio-tracked in mixed crops in Sutter County, CA. Weekly survival of 39 wild (4 native and 35 translocated) versus 32 pen-reared birds were compared at 2 sites (~2,000 ha each) during the fall 1996 agricultural harvests. Pheasant survival after 1 week was wild 74% and 79% versus pen-reared 61% and 57% at the Meridian and Nicolaus sites, respectively. Thereafter, pooled sites survival was ~linear with ~1 wild bird dying every 2.8 weeks for 7 weeks and ~1 pen-reared bird death occurred every 4.7 days for 3 weeks. Several relocated and pen-reared pheasants joined wild flocks, and their survival improved with one of each harvested during the 1997 hunting season. Both survived >400 days. All affected pheasants changed their habitat utilization and movement ecology following the harvest of their primary cover and forage crop(s). Chi square analysis of habitat use by 30 wild and 19 pen-reared pheasants demonstrated habitat preferences were greater than its availability (P < 0.01) for milo (planted only in Meridian), weeds, and corn. Their preferences for alfalfa, beets, and safflower were equal to their availability. Rice was preferred when the fields were dry, but overall it was not preferred (P < 0.01). Also, orchards (cleared of ground vegetation for nut harvests) and fallow habitats were not preferred. Movement ecology data were separated by study site because of significant habitat differences. Home ranges (95% utilization areas) using the minimum convex polygon method to compare wild versus pen-reared pheasants averaged 74 and 67 ha at Meridian and 73 and 140 ha at Nicolaus. Daily rooster and hen movements averaged 295 m and 276 m for wild birds and 335 m and 382 m for pen-reared birds at the Meridian and Nicolaus sites, respectively. Results from the first fall pheasant study in California crops demonstrated they preferred the dynamic juxtaposition of grains and weeds for cover, shelter and forage with water. Twenty-nine pheasants (58%) demonstrated habitat preferences for grains– milo, rice, and corn. Pheasant survival was related to post-harvest habitat changes. Their home range, survival, and movements were very similar at both sites although the crop mosaic and habitat relationships were very different. These new results should be included in both public and private pheasant management practices.

While investigating the American badger (Taxidea taxus) in eastern Colorado's wheatlands, we studied 3 badgers which were affected by a 2.1 km2 man-made fire and compared them to 2 adjacent badgers unaffected by the fire. All badgers were equipped with radio-telemetry collars and generally located day and night for approximately 1 month pre-fire and 3 weeks post-fire. Three point triangulation locations were converted into a global information system database. Adaptive kernel analyses compared pre- and post-fire horizontal: home ranges (i.e. 95% utilization areas, UAs), core activity areas (50% UAs), movements, den and habitat use patterns. Mean (¯x) locations pre-fire (43.7) and post-fire (32.0) provided home ranges for affected badgers that averaged 8.3 km2 and 9.2 km2, respectively. While 2 badgers maintained one core area which was outside the burn, the third used 2 core activity areas, one remained the same after the fire and second changed. Diurnal to nocturnal movements (measured in 24 hrs cycles) were pre-firex = 1.2 km and post-firex = 1.3 km. Den use remained approximately 5, but some locations changed after the fire. Mean home ranges included 74% winter wheat or wheat stubble. Habitat use for all 5 badgers averaged: 81.4% wheat, 8% riparian, 7.2% sagebrush, and 3.4% burned. Unaffected badgers averaged 7.7 km2 home ranges, 1 core area, 1.0 km diurnal-nocturnal movements, 4 dens, and 93% wheat crops and 7% riparian habitats. After the fire burned 10% of badger 4's home range, 1 of 3 core areas, and 3 of 5 dens, it moved > 3km northwest into another tributary and established 1 new den. However, it frequently revisited the northern portion of its home range and associated core area. After approximately1 month, it consolidated this UA into a new core area 1.7 km northwest and maintained 1 of 3 pre-fire core areas. The fire consumed 6% of Badger 2 home range, and post-fire it moved into the unoccupied southern portion of badger 4's pre-fire home range. It also moved slowly west into sagebrush probably in partial response to the tilling of approximately 1/3 of its home range which was completed on April 16. Only 1.0% of Badger 1's home range and its core area were not affected by the fire. However, it slowly moved its home range southeast approximately 1.0 km into the unoccupied area assumed to have been the home range of an un-collared badger found dead in early April. Its core area moved approximately 0.5 km southwest. In summary the movement ecology of affected badgers illustrated three themes: (1) home ranges and core areas moved initially away from the fire, (2) then adjustments were made by each badger in response to other badgers, the burned area, and habitat requirements, and (3) finally a new equilibrium of home ranges was established among these badgers post fire including the use of the burned areas after a few weeks.

The National Wildlife Research Center (NWRC) conducted a field study to determine hazards to non-target gallinaceous birds following the use of 2.0% zinc phosphide (Zn,P2) baits for vole control in fall alfalfa. Consultation among the NWRC, USDA Wildlife Services, California Department of Food and Agriculture (CDFA), U. S. Environmental Protection Agency (EPA), and the California Department of Fish and Game produced a 3-phased study. Free-ranging ring-necked pheasants and California quail were studied in alfalfa during the concurrent harvest of other agricultural crops. These data would be used by CDFA to support the re registration of their label "Rodent Bait Zinc Phosphide Treated Grain (?.00%)", EPA Reg. No. CA890027. Phase 1 was a pilot study to determine whether the two test species could he maintained in walled enclosures. Phase 2 was a worst-case scenario using the test species in alfalfa enclosures during vole control (i.e., simulated field study). Information from the 14-day post-baiting period led to a better understanding of some variables, including the sub-lethal effects that could impact the design of the final phase. During Phase 3 the actual non-target field study was conducted. Results from Phase 1 showed that these species could be maintained in outdoor enclosures using only wing clipping, 1 m-high metal walls, and no covering nets. Phase 2 proved that in outdoor alfalfa enclosures, baiting for vole control was not hazardous to quail but might be to pheasants. Phase 3 concluded that 2.0% Zn, P, bait when applied per label directions was not hazardous to either wild or pen-reared free-ranging pheasants in fall agricultural areas. This article summarizes the 3-phased study, the resulting data, and conclusions.

The National Wildlife Research Center (NWRC), based in Fort Collins, CO, is the research arm for the Animal Plant and Health Inspection Service’s Wildlife Services Program. Its mission is to resolve conflicts between wildlife and humans. The NWRC established a GIS (Geographic Information System) function in 1996. The relevance of GIS to two projects are featured in this poster. Project 1 was conducted in 1996 and was a joint effort between the NWRC and the California Department of Food and Agriculture (CDFA). In this project, 60 Chinese ring-necked pheasants were radio-instrumented and their movements studied. The main goal of the project was to determine if there were primary hazards to pheasants as a result of the application of the rodenticide zinc phosphide in dormant alfalfa for vole management in the northern Sacramento Valley. Through the use of telemetry and GIS, pheasant habitat preferences emerged, and the absence of these birds in dormant alfalfa contributed to the reregistration of zinc phosphide to control voles in this crop. Project 2 was conducted in 2000 under a contract with the Anchorage International Airport Authority. The NWRC was asked to determine bird strike risks to commercial aircraft from waterfowl moving within the Anchorage Basin. Preferred habitats were selected, along with the flight paths of commercial aircraft, to create an area matrix of possible waterfowl-aircraft intersections within which conflict could occur. The potential rehydration of Klatt Bog was a key focus. If the bog was rehydrated, would the airspace around Klatt Bog create a greater risk to aircraft? GIS was used to build a model that represented the conflicted three dimensional airspace at risk, with and without Klatt Bog rehydrated. Boeing 737 and 747 aircraft were selected to represent the upper and lower altitude boundaries during take-off and landing of commercial aircraft. These aircraft were selected after discussion with flight engineers because most other fixed wing commercial and general aviation aircraft fall between the climb characteristics of these two aircraft. Assuming the rehydration of Klatt Bog would increase its suitability as a bird habitat, the conflicted airspace between 5013090 feet in elevation was calculated at 27,972.1 x 10 m without inclusion of Klatt Bog and 31,814.1 x 10 m with the inclusion of Klatt Bog. Thus, the incremental increase in conflicted air space attributable to Klatt Bog was13.73 % (a 0.1 fold increase). Proceedings of the 10 Wildlife Damage Management Conference. (K.A. Fagerstone, G.W. Witmer, Eds). 2003.

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 (4g) 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 posttreatment. 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<0.0001) using Fisher's 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 posttreatment indicated 68 of 86 (79.1%) had strychnine alkaloid residues. The non-target strychnine hazard (using least-squares means) by treatment were 4.85ppm(0.35%),8.04ppm(0.75%), and 9.47ppm(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 0.51m(SE=0.027, range 0.15–1.17m). 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.

As part of product-performance and wildlife-hazards studies of 2% zinc phosphide (Zn3P2) steam-rolled-oat baits (11.2 kg ha-1) to reduce vole populations (Microtus spp) in alfalfa (Medicago sativa), we used randomly located, brushed-dirt plots (eight approximately 930-cm2 plots per 0.2-ha enclosure) to monitor bait-broadcast and -removal patterns, as well as to index vole and avian sign. Research was conducted in 18 x 0.2-ha enclosures containing 2.5-year-old stands of alfalfa; a 2-day pre-bait (placebo baits broadcast in all enclosures) period followed by a 14-day test-bait period (placebo and 2% Zn3P2 baits in nine enclosures each) characterized the bait exposures. Baits were broadcast manually by two certified pesticide applicators (CPAs) using Spyker Model-75 spreaders. Baits that fell onto plots were counted < 30 min later to assess the uniformity of bait distribution. The main statistical design was a 2 (placebo or Zn3P2 baits) x 3 (vole-only, vole-pheasant, vole-quail exposures) x 14 (days) factorial, with days considered repeated measurements. In the six vole-only enclosures, baits were removed from the brushed-dirt plots and replaced with four 0% or 2% Zn3P2 baits (one per 232.6-cm2 quadrant; 32 per enclosure); these 'placed' baits were then monitored daily for removal, while the surfaces of all plots were monitored daily for the presence:absence of animal/bird sign. Key results were: (a) 3.51 (+/- 2.66) and 3.39 (+/- 3.52) mean (+/- SD) baits were found on plots after pre-bait and test-bait broadcasts, respectively--less than the predicted 4.52 particles per 930-cm2 plot; (b) baits 'placed' on plots in placebo-baited enclosures were removed earlier than those in Zn3P2-baited enclosures--data in agreement with observed vole mortality; and (c) species x bait interactions occurred for both the vole- and pheasant-sign counts, but not quail-sign counts--data also indirectly confirming Zn3P2-induced mortality effects on voles and pheasants. This technique has utility for a variety of wildlife biology and chemical registration studies; although limited to arid conditions, the technique affords useful indices of broadcast calibration, bait pick-up, as well as target and non-target species mortality.

We examined if Valley pocket gophers (Thomomys bottae) exhibited a seasonal preference for consuming steamed-rolled oat (SRO) groat bait treated with 1.6% Dupont oil blue A (fat-marking dye). Field tests were conducted in California alfalfa fields during winter, summer, and fall, and in walnut orchards during winter and summer. Five treatment units (TUs) were established each with ∼60 burrows for each season and habitat studied during 1997–1999. SRO groat marker bait (4g) was placed inside each active burrow. All bait sites were re-opened about 96h later and examined for the presence (all or some) or absence of bait. The average bait site disturbance after 4 days of baiting was 78.2%. Traps were used to capture gophers up to 5 days after baiting. Valley pocket gophers (n=744) were examined for the presence of blue dye in their cheek pouches, skin/fur, and fat. We expected that if gophers moved the bait, their cheek pouches and fur would be marked; if they consumed bait, their fat would be marked. In alfalfa, 54.2%, 46.8%, and 65.7%, of gophers were marked (trapping on days 5–9) by blue dye in one or more of their cheek pouches, skin, fur, or subcutaneous fat in the winter, summer, or fall, respectively. In orchards, 57.1% of gophers were marked in winter and 53.4% in summer. Of those that were marked, all (100%) had their fat dyed blue, followed by skin/fur (34.4%males:43.7%females) and cheek pouches (5.7%males:10.1%females). ANOVA results indicated no difference in seasonal marking efficacy in either alfalfa or orchards (F=3.59, P=0.0598 and F=0.12, P=0.7384, respectively). The usefulness of 1.6% Dupont oil blue A dye as a marking agent for Valley pocket gophers was not demonstrated overall or for any season in either habitat. Therefore, a better marker for this gopher is needed. Some factors that may have influenced these results were discussed including: (1) baiting methodology (∼66% of the bait sites were devoid of bait at the end of the study), (2) species specific dye properties, (3) bait acceptance (i.e. aversion to the dye), or (4) availability of alternative foods.

Valley pocket gophers (Thomomys bottae) cause considerable damage each year to a variety of crops. In the fall of 1997, efficacy data were collected after the hand placement of anticoagulant grain baits into underground burrows of Valley pocket gophers in northern California. Twenty-four Treatment Units (TUs) were divided into one of four treatment groups: 1) 0.01% diphacinone; 2) 0.005% diphacinone; 3) 0.01% chlorophacinone; and 4) 0.005% chlorophacinone grain baits. Each treatment group contained five treated TUs and one control TU. Active burrow systems were hand baited with the respective baits. Efficacy was determined through use of the open-hole index and radio telemetry. Neither the 0.005% or 0.01% chlorophacinone or diphacinone grain baits met the Environmental Protection Agency’s 70% standard for verifying efficacy of rodenticides. Potential reasons for the low efficacy of less than 10% for the four treatment groups are discussed.

Both wild-caught (32) and pen-reared (29) ring-necked pheasants (Phasianus colchicus) were studied using radio-telemetry in agricultural areas including: milo (sorghum — Sorghum vulgare), rice (Oryza sativa), corn (Zea mays), alfalfa (Medicago sativa), melon (Cucumis melo), and weeds. Following capture, demographic data collection, and radio-collaring, they were released into agricultural habitats near Meridian and Nicolaus, CA. After 7 days of acclimation, habitat use and mortality of radio-collared birds were monitored daily using radio-telemetry with Global Positioning Satellites units to record their locations. Randomly selected Meridian alfalfa fields (≈160 acres) were treated with 2% zinc phosphide (Zn3P2) on steamed rolled oat (SRO) baits for vole control, whereas, Nicolaus alfalfa fields (≈160 acres) were treated with placebo baits. After ≈5 weeks of radio-tracking during September and October 1996, no pheasants were killed as a result of the Zn3P2 baiting. Baits lost substantial potency (>30%) during their exposure to field conditions after 24 h. Most pheasants died from avian or mammalian predation (n=34, 85%) with pen-reared pheasants more vulnerable to predation than wild pheasants. All mortalities were found in habitats other than alfalfa; upon dissection, they did not have SRO baits (either control or treated) in their gastrointestinal tracts.

Investigations of the weatherability of spot-baiting for ground squirrel control in northern CA field studies were conducted with a registered bait consisting of 0.01% chlorophacinone (an anticoagulant rodenticide) on steam-rolled oat groats. For reference purposes, a laboratory test was later conducted in an environmental chamber simulating some of the observed weather conditions. Three weathering plots were established in alfalfa for field tests. Each was baited with rodenticide fortified bait that was handled the same as for a simultaneous control project. Test areas were protected with wire mesh to prevent bait consumption by birds and mammals. Bait samples were collected daily over 7 days, then frozen, and shipped for analysis. Test No. 1 conducted under wet conditions showed a 71% loss of chlorophacinone after 1 week. Test No. 2 demonstrated a 57% loss of chlorophacinone under drier conditions. Test No. 3, a 24 h test under very wet conditions within the alfalfa field irrigated by overhead sprinklers, had a 92% loss of chlorophacinone. Laboratory studies using controlled environmental conditions: light (16 h light:8 h dark), with a mean relative humidity of 98%, and a range of temperature 11.1–27.8°C (52–82°F) showed ≈50% loss of the chlorophacinone. The magnitude was less (37% at 7 days) in the environmental chamber when corrected for water weight gain.