Colonization History and Noninvasive Monitoring of a Reestablished Wolverine Population

Abstract

The southern Norwegian wolverine (Gulo gulo) population was considered functionally extinct in the 1960s but has partly recovered in recent years. Proper management of this population is highly dependent on reliable estimates of critical population parameters such as population size, sex ratio, immigration rate, and reproductive contribution from immigrants. We report on a large-scale population monitoring project assessing these parameters through genetic tagging of individuals, with feces as the source of DNA. Sixty-eight different individuals were detected among 147 successfully genotyped samples collected in 2000 and 2001. Sixty of these individuals were represented in the 2001 sample, which may be considered a minimum estimate of the population size. Almost 50% of these animals were sampled only once, however, indicating that the true population size may be markedly higher. Accordingly, a capture-recapture estimate based on the observed resampling rates suggested a population size of 89 wolverines (95% confidence interval [CI] = 74-104), which is approximately 35% higher than an estimate of 64 obtained from the number of active natal dens (95% CI = 46-95; p = 0.08). Indirect estimates of dispersal distances inferred from mother-offspring relationships suggested that wolverine males have the ability to disperse up to 500 km, a distance exceeding anything previously reported in the literature. Dispersal distances of more than 100 km were detected for females. Bayesian clustering analysis and subsequent assessment of individual relationships suggest that immigrants from northern Scandinavia have contributed and still contribute to the southern Norwegian gene pool, counteracting genetic erosion and reducing the risk of inbreeding depression. Additional sampling efforts will be undertaken during the coming years to allow for observations of population trends, immigration rate, and reproductive variance among individuals. Such data will provide an important basis for the design of an appropriate conservation plan for this small and vulnerable population. Historia de Colonización y Monitoreo No Invasivo de una Población Reestablecida de Gulo gulo Resumen: La población sureña de Gulo gulo se consideraba funcionalmente extinta en la década de 1960 pero se ha recuperado parcialmente en años recientes. El manejo adecuado de esta población depende, en gran medida, de estimaciones confiables de parámetros poblacionales críticos como por ejemplo el tamaño poblacional, la proporción de sexos, la tasa de inmigración y la contribución reproductiva de inmigrantes. Reportamos un proyecto de monitoreo poblacional a gran escala que evaluó estos parámetros por medio del marcaje genético de individuos, con heces como la fuente de ADN. Se detectaron 68 individuos diferentes entre 147 muestras de genotipos identificados exitosamente y colectadas en 2000 y 2001. Sesenta de estos individuos estuvieron representados en la muestra de 2001, lo que puede considerarse como una estimación §Current Noninvasive Monitoring of Wolverines 677 ...

Unbiased Estimator for Genetic Drift and Effective Population Size

“…Nondestructive sampling is trivial for most plants and may be adopted for a number of animals using, e.g., skin or blood biopsy, fin clipping, or noninvasive sampling of feathers, hairs, or feces. The latter has proved effective in sampling otherwise elusive large mammals such as brown bears (Taberlet et al 1997) and wolverines (Flagstad et al 2004).…”

Genetic monitoring as a promising tool for conservation and management

“…This approach will be most compelling when genotypes of reintroduced animals can be determined before release [18] and the fate of each individual tracked by the presence or absence of its genotype in subsequent, non-invasive samples. These data can also be used for parentage analysis to monitor reproductive output.…”

Female breeding dispersal in wolverines, a solitary carnivore with high territorial fidelity

“…In this study, we use location data from 47 adult wolverines (Gulo gulo) monitored during 20 years in northern Sweden. The wolverine is a solitary carnivore with a polygamous mating system (Hedmark et al 2007), intrasexual territoriality Inman et al 2012a) and male-biased natal dispersal (Vangen et al 2001;Flagstad et al 2004). Wolverines occupy arctic tundra and boreal forest zones of Eurasia and North America (Copeland et al 2010) and are adapted to harsh environmental conditions with low productivity by being an opportunistic generalist predator and scavenger that caches food for later use (Inman et al 2012b;Mattisson et al 2016).…”