Wildlife whodunnit: forensic identification of predators to inform wildlife management and conservation

Abstract

Genetic evidence at predation sites is rapidly improving predator‐prey interaction studies and can provide information beyond field‐based investigations. However, factors contributing to the retention of genetic evidence have received limited investigation in a field setting, and researchers have yet to leverage genetic evidence to improve traditional field investigations. Using data from 61 mortality investigations of mule deer (Odocoileus hemionus), white‐tailed deer (O. virginianus), and elk (Cervus canadensis), we evaluated factors influencing predator DNA amplification success and misidentification of predators in field investigations. We found that predator DNA was detected more for prey with higher body mass (18.5% increase per standard deviation [23.1 kg] in carcass body mass above the mean [32.8 kg]). Predator DNA was also 27.0% more likely to amplify when collected from kill sites that had not undergone a freeze‐thaw cycle between the mortality and the investigation. The delay between the kill and the investigation, the swabbing surface, and the amount of precipitation did not influence amplification of predator DNA. Misidentifications of the predator based on the field ID were not influenced by the investigation delay or investigator confidence level, suggesting that investigators should collect genetic evidence even when they feel certain about the predator. Errors in identifying the predator during the field investigation increased for prey with smaller body mass, and the predator was actually more likely to be misidentified than correctly identified for fawns and calves < ~21 kg. Black bears (Ursus americanus), bobcats (Lynx rufus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) were equally likely to be missed in a field investigation, but bobcats tended to be falsely assigned more than expected and cougars were falsely assigned as the predator less than expected. Using genetic evidence as validation, we showed how patterns of predation and the field signs left by predators differed for some species depending on the size of the prey. Our findings should help researchers and managers to optimize their use of genetics to enhance field investigations.

Trace DNA from kill sites identifies predating tigers

“…We therefore recommend the collection of more samples in monsoon followed by summer and winter. We endorse previous suggestions to collect samples promptly to prevent degradation and minimise the influence of scavengers (Ganz et al, 2023; Mumma et al, 2014). Additionally, we strongly recommend collecting multiple sources of samples, including predation samples (such as saliva from fatal wounds and shed hair from the point of kill), at all sites, as these samples aid in differentiation between predators and scavengers, ultimately strengthening confidence assignment in identification.…”

“…Genetic methods are more effective in predator identification than field-based methods (Ganz et al, 2023; Mumma et al, 2014). Samples can also be collected from human predation sites where use of conventional methods becomes a challenge and has ethical considerations (Pandey & Sharma, 2016).…”

“…Trace DNA deposited during a predation event (such as saliva from predation wounds and shed hair at kill locations), essentially serves as evidence, whereas camera traps are typically deployed after the event. However, genetic and conventional methods are prone to misidentification, especially when multiple potential predators and scavengers are at the kill site (Ganz et al, 2023; Steffens et al, 2012; Verzuh et al, 2018). It is, therefore, crucial to triangulate information from various sources, including field investigations, camera trapping, genetic data, and data from collared individuals to identify predators reliably.…”

A Genetic Tool to Identify Predators Responsible for Livestock Attacks in South America and Recommendations for Human–Wildlife Conflict Mitigation

“…Identification from the visual examination of livestock wounds can be ambiguous, as overlap between attack characteristics of different predators makes species discrimination prone to observer bias, especially due to delayed response time, insufficient experience, or if a carcass has been visited by several predator and/or scavenger species [ 24 ]. Genetic analysis, supported by detailed field reports and necropsies, is highly preferred for accurate identification [ 10 , 26 , 61 ]. In the present study, we identified DNA saliva from dog and puma in the calf carcass, but we could not deduce the identity of the initial predator versus a scavenger.…”

Impacts of predation by Eurasian otters on Atlantic salmon in two Norwegian rivers

“…A drawback of using radiotelemetry and temperature loggers is the inability to discern among predator species. To estimate the impact of specific predators in an ecosystem with several predators, other methods would be necessary (e.g., Ganz et al, 2023). Several lines of evidence indicated otter activity and predation on salmon in the two rivers (Box 1), supporting the assumption that tags found on land were evidence of otter kills.…”