Non-target Wildlife Species Research Articles

Comparing anticoagulant rodenticide exposure in barn owl (Tyto alba) and common kestrel (Falco tinnunculus): A biomonitoring study in an agricultural region of southeastern Spain

Second-generation anticoagulant rodenticides (SGARs) are commonly used for rodent control, affecting various non-target wildlife species. Here, blood samples from common kestrels (Falco tinnunculus, n = 70 chicks) and barn owls (Tyto alba, n = 54 chicks and 12 adults) from Southeastern Spain were analysed using HPLC-TQ. SGAR prevalence was 68.6% in kestrel chicks, 50% in barn owl chicks and 100% in adult barn owls, with multiple SGARs in both species. Prothrombin time analysis in barn owls revealed a positive correlation with blood ΣSGARs, suggesting a potential adverse effect on coagulation. Analysis of variables potentially influencing SGAR prevalence indicated that, for kestrels, it was only related to the extent of artificial surface, showing no differences across study sites. In owlets, the highest prevalence occurred in the most urbanized study site, with human population density being a key factor. This study highlights species-specific differences in SGAR exposure, likely influenced by ecological traits. Barn owls probably encounter contaminated prey near anthropized areas, with widespread SGAR use and higher presence of target rodents. Conversely, kestrels, hunting a variety of prey often near human settlements, face consistently elevated exposure from multiple sources. Understanding these variations is crucial for effective conservation and minimizing SGAR impact on non-target wildlife.

Road mitigation structures designed for Texas ocelots: Influence of structural characteristics and environmental factors on non-target wildlife usage.

Roads negatively impact wildlife through habitat fragmentation, loss of habitat connectivity, and wildlife-vehicle collisions, thus road mitigation structures, such as wildlife crossing structures (WCS), wildlife guards (WG), and fencing are commonly used to address this issue all over the world, including in the United States. In South Texas, such structures were built or modified along a State Highway in an effort to address road mortality for the endangered ocelot (Leopardus pardalis) and non-target wildlife species. The goal of this study was to examine temporal changes in wildlife interactions with WCS and WG during and after their construction and modification along a South Texas highway and to determine whether environmental factors influenced use of WCS. Using camera traps deployed to monitor the road mitigation structures, we compared crossing rates, repel rates, and species richness of all species that interacted with the structures, and we examined whether differential wildlife use of WCS and WG was affected by one or more structural dimensions, distance to nearby vegetation, and water presence. Crossings through WCS by wildlife decreased following the completion of construction of mitigation structures; however, repel interactions at WG increased. Overall, crossings decreased at WCS that had higher openness ratios and during periods of precipitation and higher daily temperatures, but distance to vegetation had minimal influence. These factors were shown to influence crossings of each of the five most frequently observed species differently. Lastly, the presence of pooled water at one WCS caused a decrease in crossings when the water level was highest but was not a barrier at lower water levels. By examining influences on wildlife interaction with road mitigation structures, we conclude that a variety of structures, including different WCS configurations, can be beneficial in facilitating movement and restricting entry into the right-of-way for a diversity of wildlife species beyond the target species.

A hidden cost of single species management: Habitat-relationships reveal potential negative effects of conifer removal on a non-target species

Land management priorities and decisions may result in population declines for non-target wildlife species. In the western United States, large-scale removal of conifer from sagebrush ecosystems (Artemisia spp.) is occurring to recover greater sage-grouse (Centrocercus urophasianus) populations and may result in pinyon jay (Gymnorhinus cyanocephalus) habitat loss. Jay populations have experienced long-term declines, due to unknown causes, resulting in a recent petition for listing under the Endangered Species Act of 1973. We developed a Bayesian hierarchical model of jay abundance, using 13 years of point count data (2008–2020) collected across the western United States, to estimate regional population trends, model habitat requirements, assess conifer removal effects on jays, and generate hypotheses regarding jay population declines. Our model included climate and landcover covariates and regional trends in pinyon jay density. We applied our modeled habitat relationships to map predicted pinyon jay density, given 2008 and 2020 resource conditions, and map density changes from 2008 to 2020. Our results indicate pinyon jay populations are declining within Bird Conservation Region 16. Jay density was positively associated with sagebrush cover, Palmer Drought Severity Index, and pinyon-juniper cover. Conversely, jay populations were negatively associated with Normalized Difference Vegetation Index (NDVI). We found higher pinyon jay densities within locations possessing both sagebrush and pinyon-juniper cover; conditions characteristic of phase I and II conifer encroachment which are preferentially targeted for conifer removal to restore sagebrush communities. Conifer removal, if conducted at locations with high pinyon jay densities, is therefore likely to negatively affect jay abundance.

When non-target wildlife species and alien species both affect negatively to an artisanal fishery: the case of trammel net in the Alboran Sea

In the Northern Alboran Sea, artisanal small-scale fisheries using trammel nets suffer economic losses, and local fishermen see their way-of-life endangered, due to interactions with wildlife species such as alien species and dolphins. On the one hand, the alien seaweed Rugulopteryx okamurae, which was first recorded in the Alboran Sea in 2015, has undergone an intensive expansion in the sub-region, monopolizing the available seabed, causing radical changes in the underwater seascape and clogging the trammel nets. On the other hand, the damage caused to the fishing nets by dolphin fish predation is an ancient problem worldwide, but it is intensifying in the last years. The main objective of this study is to understand the main environmental and technical conditions that favor damages of fishing trammel nets in the Alboran Sea, which entails an important loss of catchability, due to (i) the clogging of the artisanal fishing trammel nets by invasive seaweed, and (ii) the breaking of the nets by dolphin predation. Through close monitoring of fishermen in port, we obtained direct information of 548 sets. Our results indicate that approximately 30% of trammel sets suffered a damage due to unwanted interaction with alien seaweeds and dolphins. As seaweeds invasion is a global problem while dolphin-fishing gear interaction is more local, we concluded that only a large-scale management of exotic algae, together with the involvement of local fishermen, could solve the economic problems of this activity.

Non-Lethal Dose-Response Models Replace Lethal Bioassays for Predicting the Hazard of Para-Aminopropiophenone to Australian Wildlife.

Para-aminopropiophenone (PAPP) is a potent methaemoglobin (MetHb) forming agent used for the lethal control of exotic carnivores and mustelids. To assess the sensitivity of Australian wildlife to PAPP we developed an in vivo assay that did not use death as an endpoint. Sub-lethal dose-response data were modelled to predict PAPP doses required to achieve an endpoint set at 80% MetHb (MetHb80). The comparative sensitivity of non-target mammals referenced to this endpoint was found to be highly variable, with southern brown bandicoots (Isoodon obesulus) the most sensitive species (MetHb80 = 6.3 mg kg-1) and bush rats (Rattus fuscipes) the most tolerant (MetHb80 = 1035 mg kg-1). Published LD50 estimates were highly correlated with PAPP doses modelled to achieve the MetHb80 endpoint (r2 = 0.99, p < 0.001). Most dose-response data for native mammals were collected in the field or in semi-natural enclosures, permitting PAPP and placebo dosed animals to be fitted with tracking transmitters and transponders and released at their point of capture. A protracted morbidity and mortality was observed only in Australian ravens (Corvus coronoides). The combination of sub-lethal dose-response assay and survival data collected in the field provided more relevant information about the actual hazard of pest control agents to non-target wildlife species than laboratory-based lethal-dose bioassays. We discuss the need to replace lethal-dose data with biologically meaningful insights able to define a continuum of toxicological hazards that better serve the needs of conservation and veterinary scientists and wildlife managers.

Dicamba drift alters plant–herbivore interactions at the agro‐ecological interface

AbstractNatural populations evolve in response to biotic and abiotic changes in their environment, which shape species interactions and ecosystem dynamics. Agricultural systems can introduce novel conditions via herbicide exposure to non‐crop habitats in surrounding fields. While herbicide drift is known to produce a variety of toxic effects in plants, little is known about its impact on nontarget wildlife species interactions. In a two‐year study, we investigated the impact of herbicide drift on plant–herbivore interactions with common weed velvetleaf (Abutlion theophrasti) as the focal species. The findings reveal a significant increase in the phloem‐feeding silverleaf whitefly (Bermisia tabaci) abundance on plants exposed to herbicide at drift rates of 0.5% and 1% of the field dose. We also identified a significant phenotypic trade‐off between whitefly resistance and herbicide resistance in addition to whitefly resistance and relative growth rate in the presence of dicamba drift after increasing the populations grown in Year 2. In a follow‐up greenhouse study, we found evidence that dicamba drift at 0.5% of the field dose significantly increased the average chlorophyll content (in milligrams per square centimeter) along with a positive correlation between whitefly abundance and chlorophyll content. Overall, these findings suggest herbicide exposure to nontarget communities can significantly alter herbivore populations, potentially impacting biodiversity and community dynamics of weed populations found at the agro‐ecological interface.

Managing non-target wildlife mortality whilst using rodenticides to eradicate invasive rodents on islands

Invasive rodents are one of the greatest threats to island biodiversity. Eradicating these species from islands has become increasingly practicable in recent decades, primarily using anticoagulant rodenticides. However, this approach also poses risks to native wildlife, and there has been corresponding development in the management of risks to non-target wildlife species. Here we review strategies and tactics used in operational management of non-target risk, using examples from rodent eradication projects conducted on 178 islands where non-target risk assessment and mitigation was a component of the rodent eradication campaign. We identified 17 different tactics within a framework of three strategic approaches: avoidance of risk, minimization of risk, and remediation of the impact of non-target wildlife mortality. We summarize these tactics in terms of their applicability, strengths, and weaknesses for rodent eradication projects in general, plus the potential interactions with achieving rodent eradication. There remains great potential for further innovation in reducing non-target wildlife risks from rodenticide used for invasive rodent eradications on islands, supporting advancement of the social acceptability of the toolset and biodiversity conservation.

Aminomethylphosphonic acid alters amphibian embryonic development at environmental concentrations

Despite intense societal and scientific debates regarding glyphosate toxicity, it remains the most widely used herbicide. The primary metabolite of glyphosate, AMPA (aminomethylphosphonic acid), is the main contaminant detected in surface waters worldwide, both because of the extensive use of glyphosate and because of other widespread sources of AMPA (i.e., industrial detergents). Studies on potential effects of glyphosate using environmentally relevant concentrations of AMPA on non-target wildlife species are lacking. We experimentally tested the effects of AMPA on embryonic development in a common European toad at concentrations spanning the range found in natural water bodies (from 0.07 to 3.57 μg l−1). Our experimental concentrations of AMPA were 100–6000 times lower than official Predicted-No-Effect-Concentrations. We found that these low-level concentrations of AMPA decreased embryonic survival, increased development duration and influenced hatchling morphology. Response patterns were more complex than classical linear concentration-response relationships, as concentration responses were nonmonotonic, with greater effects at low-concentrations of AMPA than at high levels. Based on our results we recommend that investigators focus not only on effects of “parent compounds,” but also their metabolites at environmentally relevant concentrations in order to comprehensively assess impacts of anthropogenic contaminants on the environment.

ECOdrug: a database connecting drugs and conservation of their targets across species.

Pharmaceuticals are designed to interact with specific molecular targets in humans and these targets generally have orthologs in other species. This provides opportunities for the drug discovery community to use alternative model species for drug development. It also means, however, there is potential for mode of action related effects in non-target wildlife species as many pharmaceuticals reach the environment through patient use and manufacturing wastes. Acquiring insight in drug target ortholog predictions across species and taxonomic groups has proven difficult because of the lack of an optimal strategy and because necessary information is spread across multiple and diverse sources and platforms. We introduce a new research platform tool, ECOdrug, that reliably connects drugs to their protein targets across divergent species. It harmonizes ortholog predictions from multiple sources via a simple user interface underpinning critical applications for a wide range of studies in pharmacology, ecotoxicology and comparative evolutionary biology. ECOdrug can be used to identify species with drug targets and identify drugs that interact with those targets. As such, it can be applied to support intelligent targeted drug safety testing by ensuring appropriate and relevant species are selected in ecological risk assessments. ECOdrug is freely accessible and available at: http://www.ecodrug.org.

Mechanistic modeling of insecticide risks to breeding birds in North American agroecosystems.

Insecticide usage in the United States is ubiquitous in urban, suburban, and rural environments. There is accumulating evidence that insecticides adversely affect non-target wildlife species, including birds, causing mortality, reproductive impairment, and indirect effects through loss of prey base, and the type and magnitude of such effects differs by chemical class, or mode of action. In evaluating data for an insecticide registration application and for registration review, scientists at the United States Environmental Protection Agency (USEPA) assess the fate of the insecticide and the risk the insecticide poses to the environment and non-target wildlife. Current USEPA risk assessments for pesticides generally rely on endpoints from laboratory based toxicity studies focused on groups of individuals and do not directly assess population-level endpoints. In this paper, we present a mechanistic model, which allows risk assessors to estimate the effects of insecticide exposure on the survival and seasonal productivity of birds known to forage in agricultural fields during their breeding season. This model relies on individual-based toxicity data and translates effects into endpoints meaningful at the population level (i.e., magnitude of mortality and reproductive impairment). The model was created from two existing USEPA avian risk assessment models, the Terrestrial Investigation Model (TIM v.3.0) and the Markov Chain Nest Productivity model (MCnest). The integrated TIM/MCnest model was used to assess the relative risk of 12 insecticides applied via aerial spray to control corn pests on a suite of 31 avian species known to forage in cornfields in agroecosystems of the Midwest, USA. We found extensive differences in risk to birds among insecticides, with chlorpyrifos and malathion (organophosphates) generally posing the greatest risk, and bifenthrin and λ-cyhalothrin (pyrethroids) posing the least risk. Comparative sensitivity analysis across the 31 species showed that ecological trait parameters related to the timing of breeding and reproductive output per nest attempt offered the greatest explanatory power for predicting the magnitude of risk. An important advantage of TIM/MCnest is that it allows risk assessors to rationally combine both acute (lethal) and chronic (reproductive) effects into a single unified measure of risk.

Behaviour of European badgers and non-target species towards candidate baits for oral delivery of a tuberculosis vaccine

In the UK and the Republic of Ireland, the European badger (Meles meles) is a maintenance host for Mycobacterium bovis, and may transmit the infection to cattle causing bovine tuberculosis (TB). Vaccination of badgers using an injectable Bacillus Calmette-Guerin (BCG) vaccine is undertaken in some areas of the UK with the intention of interrupting this transmission, and vaccination research is underway in Ireland. An oral badger TB vaccine is also under development. We investigated the behaviour of badgers and non-target wildlife species towards three candidate baits being considered for delivering BCG to badgers orally. Bait preference was investigated by recording removal rates of baits and through the use of video surveillance at 16 badger setts. We found high variation in rates of bait removal by badgers among setts but no significant differences in removal rates among bait types or in preference behaviour from video footage. Variation in bait removal among setts correlated with the number of nights on which badgers were seen at the sett, with most baits being removed where badgers were seen on >50% of nights during the ten-day study period. Relatively few baits were removed at setts with low levels of recorded badger activity. Monitoring badger activity prior to bait deployment may therefore be useful in increasing bait uptake and vaccine coverage. Bait removal by badgers increased over the ten-day study period, suggesting initial neophobic behaviour at some setts and that a period of ‘pre-feeding’ may be required prior to vaccine deployment. Our results indicate that all three candidate baits are attractive to badgers. Removal of baits by non-target wildlife species was generally low, but varied among bait types, with smaller baits in packaging less likely to be removed. Enclosing baits in packaging is likely to deter non-target species, although in some cases non-target species did remove up to 13% of packaged baits.

Land Use as a Driver of Patterns of Rodenticide Exposure in Modeled Kit Fox Populations.

Although rodenticides are increasingly regulated, they nonetheless cause poisonings in many non-target wildlife species. Second-generation anticoagulant rodenticide use is common in agricultural and residential landscapes. Here, we use an individual-based population model to assess potential population-wide effects of rodenticide exposures on the endangered San Joaquin kit fox (Vulpes macrotis mutica). We estimate likelihood of rodenticide exposure across the species range for each land cover type based on a database of reported pesticide use and literature. Using a spatially-explicit population model, we find that 36% of modeled kit foxes are likely exposed, resulting in a 7-18% decline in the range-wide modeled kit fox population that can be linked to rodenticide use. Exposures of kit foxes in low-density developed areas accounted for 70% of the population-wide exposures to rodenticides. We conclude that exposures of non-target kit foxes could be greatly mitigated by reducing the use of second-generation anticoagulant rodenticides in low-density developed areas near vulnerable populations.

The safety of ONRAB® in select non-target wildlife

ONRAB® is a recombinant human adenovirus type 5 (HAd5) with the rabies glycoprotein gene incorporated into its genome. ONRAB® has been used in Canada as an oral rabies vaccine in target wildlife species such as: red fox (Vulpes vulpes), raccoon (Procyon lotor), and striped skunk (Mepthis mephitis). We evaluated the safety of ONRAB® in non-target wildlife species likely to contact the vaccine baits during oral rabies vaccine campaigns in the United States. We investigated the effects of oral inoculation of high titer ONRAB®, approximately ten times the dose given to target species, in wood rats (Neotoma spp.), eastern cottontail rabbits (Sylvilagus floridanus), Virginia opossums (Didelphis virginiana), eastern wild turkeys (Meleagris gallopavo silvestri), and fox squirrels (Sciurus niger). We performed real-time polymerase chain reaction (PCR) on fecal swabs, oral swabs, and tissues, including lung, liver, kidney, small intestine, large intestine, and when appropriate nasal turbinates, to detect ONRAB® DNA from inoculated animals. By seven days post-inoculation, turkeys, opossums, and cottontails had all stopped shedding ONRAB® DNA. One wood rat and one fox squirrel still had detectable levels of ONRAB® DNA in fecal swabs 14 days post-inoculation. Real-time PCR analysis of the tissues revealed some ONRAB® DNA persisting in certain tissues; however, there were no significant gross or histologic lesions associated with ONRAB® in any of the species studied. Our results suggest that many non-target species are not likely to be impacted by the distribution of ONRAB® as part of oral rabies vaccination programs in the United States.

Primary and secondary poisoning by anticoagulant rodenticides of non-target animals in Spain

Anticoagulant rodenticide (AR) levels were studied in liver of 401 wild and domestic animals found dead in Spain with evidences of AR poisoning, including 2 species of reptiles (n=2), 42 species of birds (n=271) and 18 species of mammals (n=128). Baits (n=32) were also analyzed to detect the potential use of ARs in their intentional preparation to kill predators. AR residues were detected in 155 (38.7%) of the studied animals and 140 (34.9%) may have died by AR poisoning according to the clinical information, necropsy findings, residue levels and results of other toxicological analysis. Animals considered with sublethal AR exposure had total AR residues (geometric mean with 95% CI) in liver of 0.005 (0.003–0.007)μg/g wet weight (w.w.) and animals diagnosed as dead by AR poisoning had 0.706 (0.473–1.054)μg/g w.w. ARs were detected in 19% of baits illegally prepared to kill predators. In terms of the total incidents studied in our laboratory between 2005 and 2010 (n=1792 animals), confirmed poisonings represented 40.9% of the cases, and 21.1% of these were due to ARs (8.6% of the total sample). Nocturnal raptors (62%) and carnivorous mammals (38%) were amongst the secondary consumers with highest prevalence of AR exposure, especially to second generation ARs (SGARs). On the other hand, granivorous birds showed the highest prevalence of AR exposure (51%), especially to chlorophacinone in a region treated against a vole population peak in 2007. The presence of hemorrhages was significantly associated with AR levels in liver, but some animals (7.2%) with elevated residue levels (>0.2μg/g w.w.) showed no evidence of macroscopic bleeding. The use of accumulative SGARs and the application of baits on surface (i.e. treated grain by spreader machines) should be discontinued in future EU regulations on the use of rodenticides to prevent the poisoning of non-target wildlife species.

Endocrine disruption of male mating signals: ecological and evolutionary implications

Summary 1. Endocrine disrupting chemicals (EDCs) are chemicals that interfere with proper hormonal functioning in exposed animals. They enter the natural environment through multiple sources, and many non-target wildlife species are exposed to them via several modes. Exposure causes altered hormone levels, importantly gonadal hormones, resulting in changed reproductive characteristics. 2. Vertebrate male mating signals convey important mate quality information to females. These signals are dependent on androgens for their production and maintenance. Female responses to signals depend on oestrogens. Disrupting these pathways jeopardizes signal production and reception, which has implications for mating system ecology. 3. Besides affecting various aspects of the vertebrate physiology, EDCs can impair hormonal functioning by binding to or blocking hormone receptors, or by altering production and function of hormones or hormone receptors. 4. We consider the ecological implications of multi-generational signal disruption by EDCs. Altered signals can influence population dynamics and sex ratios; local extinctions are possible. Community-level dynamics may be affected via interspecific dependence on signals or population fluctuations. 5. We then address the evolutionary effects of EDC-altered male mating signals in vertebrates and discuss how females may respond to altered signals over evolutionary time. Trans-generational reduction in signal reliability can lead to reduced preference and eventual loss of the signal trait and to the evolution of new traits as signals of mate quality. Genetic divergence between endocrine disrupted and undisrupted populations may result, perhaps giving rise to speciation. 6. Finally, we recommend areas of research to further explore some of the issues addressed in this review. We suggest field surveys to document existing alterations in mating systems and genetic divergence in endocrine disrupted populations. Long-term mesocosm studies and mathematical models would be useful to predict the fate of mating signals and female responses as a result of prolonged endocrine disruption. EDCs have been the focus of ecotoxicology for some time now, and we feel that this analysis should now enter the realm of evolutionary biology to determine the subtle, yet far-reaching effects on exposed non-target wildlife.

Safety studies on an adenovirus recombinant vaccine for rabies (AdRG1.3-ONRAB ®) in target and non-target species

A replication-competent human adenovirus vector in which the rabies virus glycoprotein gene was inserted (AdRG1.3-ONRAB ®) was given by direct instillation into the oral cavity to representatives of three wildlife vector species of concern in Ontario (red fox, raccoon and striped skunk) and to a variety of non-target wildlife species, domestic and laboratory species. Despite use of a relatively high dose of vaccine, no untoward clinical signs were observed. Subsequent to vaccine exposure, detection of vaccine virus in lung, spleen, intestine, liver, kidney and brain of each animal was attempted using an ONRAB ®-specific assay combining PCR with Southern blotting (PCR–SB). Of the 1280 tissue samples obtained from vaccinates or contact animals, 18 (1.4%) were found to be PCR–SB positive. Virus isolation attempts were performed utilizing cell culture for all PCR–SB positive tissues and a selection of PCR–SB negative tissues. Histological examination performed on all PCR–SB positive tissues failed to identify lesions attributed to the vaccine. A quantitative real-time PCR was used to determine the excretion of the vaccine in feces and in the oral cavity with 0.8% of oral swabs and 6.8% of fecal specimens found to be positive. The low rates of recovery of vaccine virus from tissues, feces and the oral cavity suggest that the likelihood of ONRAB ® causing a negative impact on wildlife species is unlikely.

Toxicology and wildlife conservation in Europe: The inadequacy of current EU regulations

Anticoagulant rodenticide (AR) levels were studied in liver of 401 wild and domestic animals found dead in Spain with evidences of AR poisoning, including 2 species of reptiles (n = 2), 42 species of birds (n = 271) and 18 species of mammals (n = 128). Baits (n = 32) were also analyzed to detect the potential use of ARs in their intentional preparation to kill predators. AR residues were detected in 155 (38.7%) of the studied animals and 140 (34.9%) may have died by AR poisoning according to the clinical information, necropsy findings, residue levels and results of other toxicological analysis. Animals considered with sublethal AR exposure had total AR residues (geometric mean with 95% CI) in liver of 0.005 (0.003–0.007) μg/g wet weight (w.w.) and animals diagnosed as dead by AR poisoning had 0.706 (0.473–1.054) μg/g w.w. ARs were detected in 19% of baits illegally prepared to kill predators. In terms of the total incidents studied in our laboratory between 2005 and 2010 (n = 1792 animals), confirmed poisonings represented 40.9% of the cases, and 21.1% of these were due to ARs (8.6% of the total sample). Nocturnal raptors (62%) and carnivorous mammals (38%) were amongst the secondary consumers with highest prevalence of AR exposure, especially to second generation ARs (SGARs). On the other hand, granivorous birds showed the highest prevalence of AR exposure (51%), especially to chlorophacinone in a region treated against a vole population peak in 2007. The presence of hemorrhages was significantly associated with AR levels in liver, but some animals (7.2%) with elevated residue levels (> 0.2 μg/g w.w.) showed no evidence of macroscopic bleeding. The use of accumulative SGARs and the application of baits on surface (i.e. treated grain by spreader machines) should be discontinued in future EU regulations on the use of rodenticides to prevent the poisoning of non-target wildlife species.

Response of Nontarget Species to Underground Strychnine Baiting for Pocket Gopher in Southwest Oregon

Abstract Pocket gophers (Thomomys spp.) impede reforestation efforts in the Pacific Northwest and strychnine baiting is used to reduce their populations. We conducted a capture and release program in southern Oregon to determine whether strychnine baiting negatively impacted nontarget small mammal species. Two nontarget species dominated the program: golden mantled ground squirrels (Spermophilus lateralis) and yellow pine chipmunks (Tamias amoenus). There was a short-term decline in ground squirrel populations after baiting, but yellow pine chipmunk populations were not adversely affected. We conclude that underground baiting with 0.5% strychnine treated grain is unlikely to cause long-term adverse effects on nontarget wildlife species in southwest Oregon. West. J. Appl. For. 17(1):9–13.

Organophosphate Insecticide (Famphur) Topically Applied to Cattle Kills Magpies and Hawks

A systematic field study of a black-billed magpie (Pica pica) population revealed that magpies and red-tailed hawks (Buteo jamaicensis) were killed by famphur (=famophos, Warbex?) used as a pouron to control cattle warbles (Hypoderma sp.). Magpie mortality began on treatment day and continued for more than 3 months (38 found dead); mortality peaked between Day 5 and Day 13. Estimates of magpie density (based on transects) decreased in both the control and treatment areas, but the decrease was greater in the treatment area. A red-tailed hawk found dead on Day 10 had eaten a famphur-contaminated magpie. Another red-tailed hawk was found alive but immobilized, and a third died outside the study area. Brain cholinesterase (ChE) activity was 70-92% depressed in all dead birds examined; famphur residues were detected in all 17 magpies and the 2 hawks analyzed. The amount of famphur obtained by the dead magpies was estimated at 5.2-6.1 mg/kg (based on residue concentrations in the gizzard), which was above the acute oral LD, for several bird species. The cow hair portion (12%) of the pooled gizzard contents from 13 other dead magpies produced extremely high famphur residues (4,600 ppm). The residues persisted on cattle hair for more than 90 days post-treatment. Magpie populations in the far western states declined between 1968 and 1979, which corresponds with widespread use of famphur, although other factors may be involved. J. WILDL. MANAGE. 49(3):648-658 Organophosphate (OP) insecticides are now used extensively in agriculture. The topical use of famphur (O,O-dimethyl O-[p-(dimethylsulfamoyl)phenyl] phosphorothioate) in the autumn as a systemic insecticide for control of warbles in cattle was recommended in 1970 (Every et al. 1970). Famphur can be administered to livestock dermally as a pour-on (the only method we observed), orally (mixed with feed), or by intramuscular injection (Ivey et al. 1976). The larvae are killed within the animal during the autumn before they develop into grubs the following year. Grubs emerging on the backs of untreated cattle during the spring may be eaten by magpies (Bishopp et al. 1926), but this is not an adequate control. Observations of magpies dying after famphur use on cattle were reported by ranchers as early as 1973 (unpubl. data, Oreg. Dep. Fish and Wildl., La Grande). Magpies and other species of birds were found dead after cattle were treated with famphur in the United Kingdom (Felton et al. 1981). Magpie brain ChE activity was severely depressed and famphur was identified in the gizzard contents. Another organophosphate (fenthion), also used as a pouron to control Hypoderma larvae in cattle, was implicated in magpie mortality in Canada (Hanson and Howell 1981). Despite relatively rapid degradation in the environment and tissues of homeotherms, some OP insecticides are highly toxic to wildlife for varying periods of time after application (Zinkl et al. 1978, White et al. 1979). The degree of exposure of nontarget wildlife species to OP insecticides can be assessed by measuring ChE activity in tissues and blood (Bunyan et al. 1968, Ludke et al. 1975, Hill and Fleming 1982). The depression of brain ChE activity by 20% or a decrease of 2 SD in wild birds (relative to species baseline data or concurrent controls) has been used as a co servative criterion to indicate absorption of OP chemicals. Depression of brain ChE activity by >50% and confirmation of suspected OP residues in tissues or ingesta are criteria for cause-effect diagnosis of death in birds exposed to anti-ChE chemicals. We studied a magpie population that lived on or near seven ranches where 535 cattle were treated with Warbex? (13.2% famphur). Warbex? was poured along the back line of the cattle at the recommended rate of 0.326 ml/kg body weight, not to exceed 118 ml/animal. The field study was prompted by: (1) reported magpie mortality in Oregon and the United Kingdom; (2) a magpie population decline in the far