The northwestern pond turtle (Actinemys marmorata; WPT hereafter) is a semi-aquatic freshwater turtle native to the west coast of North America and is experiencing significant population decline. Identifying predators of WPT females and their eggs can address major gaps in data regarding western pond turtle mortality and population-limiting factors. During the WPT nesting season in 2021, we documented nest predation events by examining trace predator DNA (i.e., saliva) collected from WPT eggshell, carapace, or plastron fragments found at predated nest sites located in Humboldt County, California. We also developed a field protocol to collect WPT eggshell and carapace or plastron fragments that would limit the possibility of contamination. To examine the evidence of potential predators, we conducted forensic molecular analyses and developed a polymerase chain reaction (PCR) protocol to detect mammal species, which focused on amplifying carnivore DNA using carnivore-specific primers. Our results successfully identified the western spotted skunk (Spilogale gracilis) as a local mammalian predator of WPT nests. Our study outlines field and laboratory techniques and methods useful for obtaining and amplifying trace DNA exposed to environmental elements, as well as a deeper investigation into declining WPT populations.