The Scandinavian wolverine (Gulo gulo) population is being monitored annually using non-invasive genetic sampling (NGS) and recovery of dead individuals. DNA extracted from faeces, urine, hair, and tissue is used to identify the species, sex, and individual from which each sample originated. These data have been compiled in the Scandinavian large carnivore database Rovbase 3.0 (www.rovbase.se, ... [Show full abstract] www.rovbase.no).
Using the Bayesian spatial capture-recapture (SCR) models developed by RovQuant (Bischof et al., 2019b, 2020b), we estimated annual density and vital rates of the Scandinavian wolverine population for nine seasons from 2013 to 2021. We used single-season SCR models to estimate abundance, except for Norrbotten (Sweden) where we used open-population SCR (OPSCR) models because sampling was not conducted comprehensively before 2017 and after 2019. The use of single-season SCR models was motivated by the fact that they make less assumptions compared to OPSCR models, and that their abundance estimates are relatively robust to model misspecifications. However, OPSCR models remain useful, as they allow estimation of vital rates and yield abundance estimates when there are gaps in monitoring.
Using single-season SCR and OPSCR models, we generated annual density maps and both total and jurisdiction-specific population sizes for wolverine from 2013 to 2021. Based on the spatial capture-recapture modelling approach, the Scandinavian wolverine population was likely (95% credible interval) between 1013 and 1126 individuals in 2021, with 639 to 724 individuals attributed to Sweden and 358 to 418 to Norway. In addition to annual density and jurisdiction-specific abundance estimates, we report annual estimates of survival, recruitment, and detection probabilities.