Identifying predators from saliva at kill sites with limited remains

Abstract

ABSTRACT Kill‐site investigations can yield valuable data about elusive predators and predator–prey interactions, provided the predator species can be definitively identified as the one responsible for the predation event. The traditional method of visually analyzing prey remains to identify predators is prone to observer bias and may be particularly challenging when few remains are present or in systems with congeneric predators. Other potential evidence left by predators, such as scat, may be difficult to reliably link to the responsible predator, whereas tracking requires adequate substrate conditions. Swabbing for predator DNA from saliva is an objective yet underutilized alternative that has primarily been applied to larger carcasses. We demonstrate the usefulness of a saliva‐swabbing method for smaller prey with minimal surface area, including kill sites with almost no prey remains or even just a radiocollar left behind. This study is also the first to compare saliva‐swabbing success by sample type (carcass remains vs. radiocollar). From 2010 to 2014, in the Loomis State Forest and Okanogan National Forest, Washington, USA, we employed forensic techniques to increase certainty about predator species identification at snowshoe hare (Lepus americanus) kill sites for the ultimate purpose of elucidating predator–prey interactions. Predator saliva was sampled from remains and radiocollars with foam buccal swabs, stored in lysis buffer for shelf‐stable preservation, and tested for mitochondrial DNA using polymerase chain reaction and species‐specific primers. This saliva‐swabbing protocol yielded definitive and objective predator species identification for a majority (58.5%) of sampled kill sites (nkill sites = 31/53). Not only were minimal remains often able to yield predator DNA, but swabs from radiocollars provided significantly more predator identifications. Saliva swabbing also provided identifications at 65.5% of kill sites lacking identifiable predator sign and contributed significantly more predator identifications throughout the year when compared with snow‐tracking methods. Expanding saliva‐swabbing methods to smaller prey, radiocollars, and limited remains should allow for more definitive predator identifications at kill sites than have been possible with commonly employed methods, thus augmenting the potential to understand and manage for predators and prey. © 2019 The Wildlife Society.

Keywords

• bite mark
• DNA
• forensic analysis
• Lepus americanus
• predation
• radiocollars