John D. Eisemann

Acute toxicity, histopathology, and coagulopathy in American kestrels (Falco sparverius) following administration of the rodenticide diphacinone

The acute oral toxicity of the anticoagulant rodenticide diphacinone was found to be over 20 times greater in American kestrels (Falco sparverius; median lethal dose 96.8 mg/kg body weight) compared with Northern bobwhite (Colinus virginianus) and mallards (Anas platyrhynchos). Modest evidence of internal bleeding was observed at necropsy, although histological examination of heart, liver, kidney, lung, intestine, and skeletal muscle revealed hemorrhage over a wide range of doses (35.1-675 mg/kg). Residue analysis suggests that the half-life of diphacinone in the liver of kestrels that survived was relatively short, with the majority of the dose cleared within 7 d of exposure. Several precise and sensitive clotting assays (prothrombin time, Russells viper venom time, thrombin clotting time) were adapted for use in this species, and oral administration of diphacinone at 50 mg/kg increased prothrombin time and Russells viper venom time at 48 and 96 h postdose compared with controls. Prolongation of in vitro clotting time reflects impaired coagulation complex activity, and generally corresponded with the onset of overt signs of toxicity and lethality. In view of the toxicity and risk evaluation data derived from American kestrels, the involvement of diphacinone in some raptor mortality events, and the paucity of threshold effects data following short-term dietary exposure for birds of prey, additional feeding trials with captive raptors are warranted to characterize more fully the risk of secondary poisoning.

A review of existing and potential New World and Australasian vertebrate pesticides with a rationale for linking use patterns to registration requirements

Registration is a necessarily sophisticated evaluation process applied to vertebrate pesticide products. Although conducted to minimise any potential impacts upon public health, the environment and food production, the all-encompassing process of registration can stifle innovation. Vertebrate pesticides are rarely used to control pest animals in food crops. In contrast to agrochemicals, relatively small amounts of vertebrate pesticides are used (<0.1%), usually in solid or paste baits, and generally by discrete application methods rather than by broad-scale spray applications. We present a hierarchy or sliding scale of typical data requirements relative to application techniques, to help clarify an evolving science-based approach which focuses on requiring data to address key scientific questions while allowing waivers where additional data have minor value. Such an approach will facilitate the development and delivery of increasingly humane, species-targeted, low residue pesticides in the New World, along with the phasing out of less desirable chemicals that continue to be used due to a lack of alternatives.

Field test of a single-injection gonadotrophin-releasing hormone immunocontraceptive vaccine in female white-tailed deer

Thedevelopmentanduseofsafe,effectiveandpracticalwildlifecontraceptiveagentscouldreducereproduction inlocally overabundant deer populationsinsituations where traditionalmanagement toolssuch as regulated huntingcannot be employed. GonaCon Immunocontraceptive Vaccine (the commercial name for a particular gonadotrophin-releasing hormone(GnRH)-basedemulsion)wastestedinadultfemalewhite-taileddeerinafencedherdnearSilverSpring,Maryland, USA. Observations of udder condition were used to identify does that had become pregnant. Necropsy observations, histopathology and serum concentrations of anti-GnRH antibodies, luteinising hormone and progesterone were used to comparehealthandreproductivestatusoftreated(n=28)andcontrol(n=15)deer.AfterreceivingoneinjectionofGonaCon, 88% of treated deer did not become pregnant during the first year and 47% did not become pregnant during the second year aftervaccination.NoadversehealtheffectsrelatedtovaccinationwithGonaConweredetected,exceptforlocalisedinjection- site reactions in five (29%) of 17 examined, vaccinated deer. Treatment with GonaCon can be a safe and effective means of inducingtemporaryinfertilityinwildwhite-taileddeer.Ultimately,themanagementvalueofGonaConwillbedeterminedby natural-resource professionals who use it as one of many tools to manage deer populations.

Effectiveness and target-specificity of a novel design of food dispenser to deliver a toxin to feral swine in the United States

There are no registered toxins available for use on Feral Swine (Sus scrofa, Linnaeus) in the United States. HOGGONE® is a proprietary bait matrix under development in Australia that delivers toxic levels of sodium nitrite to feral swine. However, one challenge is to develop a species-specific oral delivery system to deliver toxins to feral swine in the USA while minimizing non-target wildlife exposure. The HOGHOPPER™ is a lightweight and portable bait delivery system that could overcome this problem. Our objective was to compare non-toxic HOGGONE removal by wildlife that visited HOGHOPPERS during acclimation periods (doors open; free-feeding stage) and activation periods (doors closed; simulated toxic stage) at sites throughout the United States. We conducted 38 HOGHOPPER trials on private and public land in Alabama, Florida, Oklahoma, and Texas, and determined species-specific visitation and HOGGONE removal rates using motion-sensing digital camera systems. We found activated HOGHOPPERS to successfully exclude all wildlife except feral swine and Raccoon (Procyon lotor, Linnaeus). For raccoons the number of baits removed per 24h was reduced by 92% during the HOGHOPPER activation period. No other wildlife removed HOGGONE from HOGHOPPERS. During trials in which raccoon breaches occurred, an extended acclimation period was used. To minimize raccoon exposure risks, an abbreviated acclimation period of ≤ 14d should be used with the HOGHOPPER. This will decrease the likelihood that raccoons learn how to access HOGGONE from the HOGHOPPER. Further experimentation is needed to demonstrate the efficacy of toxic HOGGONE at controlling feral swine populations.

Diverse examples from managing invasive vertebrate species on inhabited islands of the United States

ABSTRACT A wide array of sizes, ecosystems, cultures, and invasive wildlife are represented among inhabited islands. Here, six cases from the United States of America (US) are selected to illustrate the high diversity of invasive animal management issues and objectives. We outline the background, define the problems and management objectives. We identify the management approaches and discuss the results and influences as they specifically relate to inhabited islands. The examples are: (1) Gambian giant pouched rats on Grassy Key, Florida; (2) coqui frogs on Kaua’i, Hawai’i; (3) feral swine on Cayo Costa Island, Florida; (4) rodents and monitor lizards on Cocos Island, Guam; (5) black spiny-tailed iguanas (ctenosaurs) on Gasparilla Island, Florida; and (6) mongooses on Puerto Rico. The outcomes of the programs are discussed, particularly in relation to the impact of human habitation on success.

STATE-LEVEL APPROACHES TO MANAGING THE USE OF CONTRACEPTIVES IN WILDLIFE IN THE UNITED STATES

Abstract:  Several fertility control agents have recently been registered with the U.S. Environmental Protection Agency for management of wildlife or other free-ranging animals. The registration of GonaCon™ Immunocontraceptive Vaccine for use in white-tailed deer (Odocoileus virginianus) and OvoControl for use in Canada geese (Branta canadensis) and pigeons (Columba livia) has caused state wildlife and land management agencies to review their regulatory authority over the use of contraceptives in wildlife. As a result, many states are taking steps to ensure legislation or policies are current with emerging technologies. This article examines the various approaches states are taking to regulate the use of contraceptives. Regardless of the final regulatory approach, biological, social, economic, and political implications must all be discussed as this new tool is introduced into the field of wildlife management. Thoughtful consideration of all aspects of wildlife contraceptive use will lead to the development of sound, best management practices for current and future products.

Nesting and foraging behavior of red-winged blackbirds in stormwater wetlands

Stormwater wetlands are a common part of urban and suburban landscapes. These constructed wetlands provide first-order treatment of effluent from roads, parking lots, lawns and other surfaces. They also provide habitat for wetland-associated birds. Thus, there is a concern that birds may be attracted to potentially toxic habitats. This study assesses nesting success and forging behavior of Red-winged Blackbirds (Agelaius phoeniceus) in retention stormwater wetlands based on drainage type. Drainage categories included residential, commercial, and highway sites. Commercial sites had the lowest nesting success and the lowest diversity of invertebrate foods. Mean nest success values for all three types of wetlands, especially for highway drainages, were comparable to published values from natural wetlands. Over two years of study highway ponds collectively served as source populations whereas residential and commercial sites were population sinks in one year and sources in the other. Red-wings using highway sites had the highest foraging efficiency as determined by the frequency and duration of forays. Residential sites had the greatest human disturbance and generally had intermediate-quality habitat and nesting success. We conclude that while stormwater wetlands collect run off and accompanying pollutants, they can still be valuable habitats for nesting birds in urban and suburban areas. We recommend a few management strategies that can increase avian use of these habitats.