Author's personal copy Residues in Brandt’s voles (Microtus brandti) exposed to bromadiolone-impregnated baits in Mongolia Ann M. Winters a,n , Wilson K. Rumbeiha b , Scott R. Winterstein a , Amanda E. Fine c , B. Munkhtsog d , Graham J. Hickling e a Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, USA b Diagnostic Center for Population and Animal Health, Michigan State University, East Lansing, MI, USA c Wildlife Conservation Society, Mongolia Country Program, Ulaanbaatar, Mongolia d IRBIS Enterprises & Mongolian Academy of Sciences, Ulaanbaatar, Mongolia e The Center for Wildlife Health, University of Tennessee, Knoxville, TN, USA article info Article history: Received 14 June 2009 Received in revised form 19 February 2010 Accepted 20 February 2010 Available online 15 March 2010 Keywords: Bromadiolone Secondary poisoning Mongolia Brandt’s vole Microtus brandti Second generation anticoagulant rodenticide SGAR abstract In 2002, hundreds of non-target wildlife deaths occurred in Mongolia following aerial applications of bromadiolone, an anticoagulant rodenticide, to control eruptive Brandt’s vole (Microtus brandti) populations. To clarify whether secondary poisoning could have contributed to these deaths, a field study was undertaken in Mongolia to measure bromadiolone residues in voles following exposure to two concentrations (50 and 500 mg/kg) of bromadiolone-treated wheat. The two treatments produced different total burdens (2.65 mg 70.53SE and 13.70 mg 73.82SE, respectively) and liver burdens (1.74 mg 70.33SE and 8.81 mg 72.33SE, respectively) of bromadiolone in voles (both p o0.05). Total burdens of bromadiolone in voles found dead above ground were higher than those of live- trapped voles (32.35 mg 717.98SE versus 5.18 mg 71.40SE, respectively; p o0.05). These results are valuable for future assessments of secondary poisoning risk to scavengers and predators from large- scale bromadiolone poisoning operations of the type undertaken in Mongolia. & 2010 Elsevier Inc. All rights reserved. 1. Introduction Non-target wildlife deaths can occur when chemicals are used to control outbreaks of rodent pests in agricultural areas or wild lands. Such deaths may result either from direct consumption of toxic bait, or through ‘secondary poisoning’ whereby a predator or scavenger consumes tissues of poisoned target species. There is growing concern about the risk of secondary poisoning to valued wildlife populations (Poche ´, 1988; Shore et al., 1996; Stone et al.,1999; Fournier-Chambrillon et al., 2004). Reports of non- target wildlife contamination and toxicosis following the use of second-generation anticoagulant rodenticides (SGARs) have in- creased worldwide (Eason et al., 2002). This collateral risk must be considered when weighing the benefits of SGAR use. Numerous instances of non-target poisoning were reported in Mongolia in 2002 after bromadiolone-treated wheat grain was spread by aircraft over large areas of steppe grassland to control outbreaks of Brandt’s voles (Microtus brandti), a rodent pest. Bromadiolone is an anticoagulant (AC) compound that acts in the liver to inhibit normal activation of vitamin K-dependent clotting factors, eventually leading to lethal hemorrhage in the animal (Osweiler et al., 1985; WHO/FAO, 1996). Carcasses of non-target birds and mammals found dead or dying in the treated areas showed evidence of hemorrhaging in the neck and mouth (Tseveenmyadag and Nyambayar, 2002), indicating likely anticoagulant poisoning. Among the dead predators and scavengers were two Saker falcons (Falco cherrug), an endangered species throughout its range; two Corsac foxes (Vulpes corsac); and two Pallas’ cats (Otocolobus manul), a near- threatened species (IUCN, 2009). As it was considered unlikely that these species directly ingested treated wheat grain, it was suspected that these deaths were instances of secondary poison- ing resulting from consumption of tissues of poisoned prey. These concerns about possible secondary poisoning impacts of large-scale bromadiolone applications to wildlife in Mongolia prompted the field study reported here. Our objective was to quantify the amount of bromadiolone in live voles and vole carcasses after they were exposed to two different concen- trations of bromadiolone-treated wheat in a field setting in Mongolia. These data contribute to the overall understanding of ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety 0147-6513/$ - see front matter & 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2010.02.021 n Correspondence to: 4800 Progressive Rd., Wapato, WA 98951, USA. E-mail address: annmwinters@gmail.com (A.M. Winters). Ecotoxicology and Environmental Safety 73 (2010) 1071–1077