Anticoagulant rodenticides in urban bobcats: exposure, risk factors and potential effects based on a 16-year study

Abstract

Anticoagulant rodenticides (ARs) are increasingly recognized as a threat to nontarget wildlife. High exposure to ARs has been documented globally in nontarget predatory species and linked to the high prevalence of an ectoparasitic disease, notoedric mange. In southern California, mange associated with AR exposure has been the proximate cause of a bobcat (Lynx rufus) population decline. We measured AR exposure in bobcats from two areas in southern California, examining seasonal, demographic and spatial risk factors across landscapes including natural and urbanized areas. The long-term study included bobcats sampled over a 16-year period (1997-2012) and a wide geographic area. We sampled blood (N = 206) and liver (N = 172) to examine exposure ante- and post-mortem. We detected high exposure prevalence (89 %, liver; 39 %, blood) and for individuals with paired liver and blood data (N = 64), 92 % were exposed. Moreover, the animals with the most complete sampling were exposed most frequently to three or more compounds. Toxicant exposure was associated with commercial, residential, and agricultural development. Bobcats of both sexes and age classes were found to be at high risk of exposure, and we documented fetal transfer of multiple ARs. We found a strong association between certain levels of exposure (ppm), and between multiple AR exposure events, and notoedric mange. AR exposure was prevalent throughout both regions sampled and throughout the 16-year time period in the long-term study. ARs pose a substantial threat to bobcats, and likely other mammalian and avian predators, living at the urban-wildland interface.

A review: poisoning by anticoagulant rodenticides in non-target animals globally

“…Of these, 19 papers report poisoning of raptors. There are six publications from the U.S.A. [9, 42, 45, 48,49,50], three from Canada [1, 18, 55], nine from the U.K. [7, 19, 31, 46, 47, 58,59,60,61], two from France [13, 25], three from Spain [28, 43, 44], two from Denmark [5, 11], one from Norway [26], and four from New Zealand (NZ) [6, 8, 14, 35]. These reports and the proposed exposure pathways are summarized below.…”

“…Altogether, there were 2,694 out of 4,891 individuals (55%) of non-target animals have been reported to have AR residues in their livers between 1981 and 2013 [1, 5,6,7,8,9, 11, 13, 14, 18, 19, 25, 26, 28, 31, 35, 42,43,44,45,46,47,48,49,50, 55, 58,59,60,61](A)FGARsSGARsWarfarinCouma-tetralylDipha-cinoneChloro-phacinoneBrodi-facoumBroma-dioloneDifen-acoumDifeti-aloneFlocou-mafenDetection rate (%)1.04.55.05.631.030.026.05.05.7The number of detection27108991131,4651,3461,048101175The number of analysis2,6392,3911,972…”

“…2–5 to 70–80 µ g/kg for brodifacoum respectively) [1, 5, 11, 13, 18, 25, 55]. On the other hand, the detection limits for brodifacoum were 10–50, 2–20, 5, 1–6, and 1.4–50 µ g/kg of NZ [8, 14, 35], the U.S.A. [9, 42, 45, 48,49,50], Norway [26], Spain [28, 43, 44], and the U.K. [7, 19, 31, 46, 47, 58,59,60], respectively. Therefore, high (or low) sensitivity of detection seemingly not always cause over (or under)-estimation, but in some cases might affect accounting of AR exposure.…”

Poisoning by Anticoagulant Rodenticides in Humans and Animals: Causes and Consequences

“…Wildlife expositions or intoxications to ARs have been reported around the world for many mammals such as minks [70], bobcats [71], stoats and weasels [72], foxes [73,74] and boars [67] and as well for many birds [75][76][77]. Exposition of ish was reported near an island where an eradication of rodent with brodifacoum was performed and the risk for human through the consumption appeared very low [78].…”

The stereoisomerism of second generation anticoagulant rodenticides: a way to improve this class of molecules to meet the requirements of society?

“…Exposure may be primary when non‐target species directly eat the bait . But most often, exposure of wildlife is secondary due to ingestion of poisoned rodents by predators or scavengers . This secondary exposure is due to the long tissue‐persistence of ARs, especially of SGARs, in rodents and wildlife.…”