Free lunch, may contain lead: scavenging shot small mammals

Abstract

Scavengers are subsidized by the remains of hunting worldwide. Although most studies focus on carcasses of large mammals, small mammals that have been shot likely provide a significant food subsidy as well, particularly in parts of the western United States. Millions of small mammals are estimated to be shot each year for damage control and recreation, many being left in the field. Despite this prevalence of carrion, and the potential for scavengers to ingest residual lead from bullet fragments, the fate of these carcasses is largely unknown. We deployed remote cameras to observe which scavengers consumed shot ground squirrels (Urocitellus spp.) and black‐tailed prairie dogs (Cynomys ludovicianus) in 8 locations across Montana, USA. At least 5 species of mammals and 9 species of birds scavenged, including burrowing owls (Athene cunicularia). Scavengers fully consumed 66% of carcasses and partially consumed 9%. Carcasses lasted an average of 24.5 hours before the first scavenger arrived. Of carcasses that were scavenged, mammals ate 16% and birds ate 84%, with corvids and raptors consuming an equal number of carcasses. Common ravens (Corvus corax) and black‐billed magpies (Pica hudsonia) visited the most carcasses and often arrived first. Scavengers consumed only 9% of the carcasses that were partially concealed by being inside a burrow. Overall, our results indicate that a diverse scavenger community consumes shot ground squirrels and black‐tailed prairie dogs, and consequently, may be exposed to lead from bullet fragments. © 2019 The Wildlife Society.

The lead (Pb) lining of agriculture‐related subsidies: enhanced Golden Eagle growth rates tempered by Pb exposure

“…, McTee et al. , ), and are the most common crop across the landscape studied (72%). Core subsidy area served as a proxy for potential abundance of agricultural‐associated prey and we assumed that prey abundance and/or availability increased with core subsidy area.…”

“…, McTee et al. , ). Despite the positive benefits from subsidies, they also portend risks to raptors resulting from exposure to anthropogenic contaminants (Walters et al.…”

Illegal killing of nongame wildlife and recreational shooting in conservation areas

“…Within many countries, legal wildlife harvest occurs for many of the reasons noted above—medicine, trophy or food hunting, and predator control—but also for recreational purposes. For example, some nongame wildlife, particularly colonial rodents, are legally shot in large numbers for recreational purposes and their carcasses left in the field where they fall (McTee, Hiller, & Ramsey, 2019). There are poorly understood ecological consequences of this legal killing of wildlife for recreational, nonconsumptive purposes.…”

“…There are poorly understood ecological consequences of this legal killing of wildlife for recreational, nonconsumptive purposes. For example, recreational shooting may result in behavioral changes or demographic consequences for targeted species (Vosburgh & Irby, 1998), and it also provides a food subsidy for scavengers (Golden, Warner, & Coffey, 2016; McTee et al, 2019) whose populations may reduce numbers of other species (Esque et al, 2010). Recreational shooting, in general, also can result in deposition of large quantities of lead on the landscape (Huxoll, 2012).…”

Widespread Lead Exposure in Golden Eagles Captured in Montana

“…and ground squirrels (Urocitellus spp.) during spring and summer (McTee et al 2017(McTee et al , 2019Herring et al 2020). That lead may accumulate in bodily tissues and later reenter the blood, further elevating BLL after subsequent exposures.…”