Population persistence in a landscape context: the case of endangered arctic fox populations in Fennoscandia

Abstract

Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub‐populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within‐fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine‐scale Allee or Allee‐like effects, as well as environmental influences related to increased competition and exclusion by red foxes.

Shifts in Fox Den Occupancy in the Greater Prudhoe Bay Area, Alaska

“…Extensive studies in Fennoscandia, where the Arctic fox population is now considered to be at critically low levels (IUCN, 2013), have identified interference competition with red foxes as a primary mechanism preventing population recovery (Dalerum et al, 2002;Elmhagen et al, 2002;Tannerfeldt et al, 2002;Frafjord, 2003;Selås and Vik, 2006;Killengreen et al, 2007;Shirley et al, 2009;Herfindal et al, 2010;Angerbjörn et al, 2013;Hamel et al, 2013). Responses of Arctic foxes to red foxes include avoidance (Rudzinski et al, 1982;Schamel and Tracy, 1986;Frafjord et al, 1989;Selås et al, 2010) and den abandonment (Rodnikova et al, 2011).…”

“…There is limited information about when the contraction began in different regions, although MacPherson (1964) reported red foxes on Baffin Island in Canada in 1918. However, within the last 30 years, the contraction of the Arctic fox's range has been extensive enough in the subarctic alpine tundra in Fennoscandia to prompt concern (Hersteinsson et al, 1989;Frafjord, 2003;Herfindal et al, 2010) and to instigate an analysis of the geographical changes across Arctic Canada (Hersteinsson and Macdonald, 1992;Gallant et al, 2012). In both regions, the shifts in distribution of the two fox species have since been considered as part of a suite of physical and biological alterations related to both climate change and increased human activity (Hersteinsson and Macdonald, 1992;Walther et al, 2002;Fuglei and Ims, 2008;Post et al, 2009).…”

Carnivore conservation in practice: replicated management actions on a large spatial scale

“…Dark grey areas represent the known distribution of arctic fox dens in F ennoscandia, from Herfindal et al . . Light grey shows the mountain tundra and thus historically suitable arctic fox habitat.…”

The taxonomy, life cycle and pathology of Sarcoptes scabiei and Notoedres cati (Acarina, Sarcoptidae): A review in a Fennoscandian wildlife perspective

“…Conservation measures include a captive breeding program (Landa et al 2011;Anonymous 2012), supplemental feeding (Angerbjörn et al 2008) and culling of red foxes. The red fox has been identified as a major threat to the arctic fox, as it has been expanding its range into the mountains and is both a strong competitor and predator for the arctic fox (Rodnikova et al 2011;Herfindal et al 2010;Tannerfeldt et al 2002;Linnell & Strand 1999;Elmhagen et al 2002;Frafjord et al 1989;Pamperin et al 2006). The red fox may also act as a transmission vector for S. scabiei to the arctic fox, with potentially devastating effects.…”