GPS collars have an apparent positive effect on the survival of a large carnivore

• Published in: Biology Letters
• Main Authors: Milleret, Cyril, Bischof, Richard, Dupont, Pierre, Brøseth, Henrik, Odden, John, Mattisson, Jenny
• Other Authors: Naturvårdsverket, Miljødirektoratet, Norges Forskningsråd
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2021
• Subjects: Gulo gulo
• Online Access: http://dx.doi.org/10.1098/rsbl.2021.0128; https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2021.0128; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsbl.2021.0128

Are instrumented animals representative of the population, given the potential bias caused by selective sampling and the influence of capture, handling and wearing bio-loggers? The answer is elusive owing to the challenges of obtaining comparable data from individuals with and without bio-loggers. Using non-invasive genetic data of a large carnivore, the wolverine ( Gulo gulo ) in Scandinavia, and an open-population spatial capture–recapture model, we found a 16 (credible interval: 4–30) percentage points lower mortality probability for GPS-collared individuals compared with individuals without GPS collars. While the risk of dying from legal culling was comparable for collared and non-collared wolverines, the former experienced lower probability of mortality due to causes other than legal culling. The aforementioned effect was pronounced despite a potentially lower age—and therefore likely higher natural mortality—of collared individuals. Reports of positive effects of bio-loggers on the survival of individuals are uncommon and we argue that GPS collars could shield animals from poaching. Our results highlight the challenges of drawing population-level inferences for populations subjected to poaching when using data from instrumented individuals.