Seeking efficiency with carnivore survey methods: A case study with elusive martens

Abstract

ABSTRACTObtaining reliable information on species distributions is often the first step in conservation. Distribution information can be used to focus survey efforts to estimate population size and examine drivers of occupancy or other population parameters. We compared detection rates and survey costs for 2 techniques (remote cameras and scent detection teams) used to evaluate distribution of a rare carnivore, Humboldt subspecies of Pacific marten (Martes caurina humboldtensis). We used remote cameras at randomly placed sites in coastal Oregon, USA, to compare camera set type (baited, unbaited), bait height (<0.5 m, 1.37 m), and bait types (chicken and lure, cat food) for a 21‐day survey period during winter (27 Jan–12 Apr) and summer (04 Jul–14 Oct) 2015. When a marten was detected, we completed an additional survey within 25 m. Scent detection teams (human handler and dog) performed area‐constrained searches for scat deposited. We used a Bayesian occupancy model to compare detection probabilities for baited camera treatments. We detected martens at 26 sites, and offset stations detected martens at 15 of 24 sites (62.5%). Survey‐level detection probability for martens (the probability of detecting ≥1 marten during a survey) was high for the camera survey during summer and winter (estimates ranged from 60% to 99% and 33% to 82%, respectively), and similar for all treatments. We surveyed 50 sites with both remote cameras and scent detection teams 25 April–25 May 2015. Of 33 sites with ≥1 marten detection, 36.4% of units had a marten detected only by scent detection teams, 30.3% only by remote camera, and 33.3% by both techniques. When the objective was marten detection, survey costs were less for scent detection teams. For identifying individual martens and their sex, cameras paired with hair snares were more cost‐efficient. Scent detection teams provided a complementary method to baited remote cameras for assessing distribution. Using multiple techniques provided an opportunity to quantify limitations of survey methods. © 2018 The Wildlife Society.