Genetic and demographic recovery of an isolated population of brown bearUrsus arctosL., 1758

Abstract

The brown bear Ursus arctos L., 1758 population of the Cantabrian Mountains (northwestern Spain) became isolated from other bear populations in Europe about 500 years ago and has declined due to hunting and habitat degradation. At the beginning of the 20th century, the Cantabrian population split into eastern and western subpopulations, and genetic exchange between them ceased. In the early 1990s, total population size was estimated to be < 100 bears. Subsequently, reduction in human-caused mortality has brought about an increase in numbers, mainly in the western subpopulation, likely promoting male-mediated migration and gene flow from the western nucleus to the eastern. To evaluate the possible genetic recovery of the small and genetically depauperate eastern subpopulation, in 2013 and 2014 we genotyped hair and faeces samples (116 from the eastern subpopulation and 36 from the western) for 18 microsatellite markers. Data from the annual count of females with cubs of the year (COY) during the past twenty-six years was used to analyze demographic changes. The number of females with COY fell to a minimum of seven in the western and three in eastern subpopulations in the biennium 1993–1994 and reached a respective maximum of 54 and 10 individuals in 2013–2014. We also observed increased bear dispersal and gene flow, mainly from the western to the eastern subpopulation. Of the 26 unique genotypes detected in the eastern subpopulation, 14 (54%) presented an admixture composition, and seven (27%) were determined to be migrants from the western subpopulation. Hence, the two separated and clearly structured subpopulations identified in the past currently show some degree of genetic admixture. This research shows the partial demographic recovery and a change in genetic composition due to migration process in a population of bears that has been isolated for several centuries.

Genetic and genomic monitoring with minimally invasive sampling methods

“…Contemporary estimates of effective population size or number of effective breeders are also a critical indication of the genetic resilience of a population (Frankham, Bradshaw, & Brook, ), and have been estimated with MIS for brown bears (De Barba, Waits, Garton, et al., ; Gonzalez et al., ), Hector's dolphin ( Cephalorhynchus hectori ; Hamner, Constantine, Mattlin, Waples, & Baker, ), Māui dolphin (Baker et al., ) and Eurasian otters ( Lutra lutra ; Koelewijn et al., ). For the purpose of genetic management of endangered species, the current or contemporary effective size is more relevant than historical or long‐term effective size (Wang, ).…”

Pax Romana: ‘refuge abandonment’ and spread of fearless behavior in a reconciling world

“…As a result, Europe is witnessing the return of formerly threatened large herbivore and carnivore mammals, a process known as ecological rewilding (Navarro & Pereira, ; Deinet et al ., ; Chapron et al ., ; Pereira & Navarro, ; Milanesi et al ., ). It is important to note that our impact on wildlife nowadays is mostly unintentional, such as in the development of infrastructure (Martínez‐Abraín et al ., , , ; Karamanlidis et al ., ; González et al ., ). This factor works in conjunction with the possibility that living closer to humans may provide animals with large amounts of predictable anthropogenic food subsidies (Oro et al ., ) as well as lower predation risks due to the scarecrow effect (Leighton, Horrocks & Kramer, ).…”

Canine adenovirus type 1 (CAdV-1) in free-ranging European brown bear (Ursus arctos arctos ): A threat for Cantabrian population?

“…As with other remnant ursid populations on the continent, it underwent a dramatic decline in the second half of the twentieth century (Martínez‐Cano, Taboada, Naves, Fernández‐Gil, & Wiegand, ). This decline, together with human‐caused mortality as a key factor (González et al., ; Naves, Wiegand, Fernández, & Stephan, ), reduced the Cantabrian brown bear population to a nadir of less than 100 individuals in the 1990s and divided it into two subpopulations (western and eastern) favoured by geographical barriers, thus putting the species in serious danger of extinction in the Cantabrian region (Wiegand, Naves, Stephan, & Fernández, ). As for other European large carnivore species, the establishing of protective legislation, supportive public opinion and a variety of practices (monitoring and conservation plans) enabling large carnivore–people coexistence (Chapron et al., ), led to a recovery of the Cantabrian brown bear population over the last two decades, with an apparent steady increase in the number of individuals (nowadays estimated in 230–260 individuals, Fundación Oso de Asturias, ), bear dispersal and gene flow (González et al., ).…”