ABSTRACT. Food habits of arctic foxes (Alopex lugopus) on the western coast of Svalbard were studied in the years 1986-89. Faeces (n = 1018) hunting and feeding habits, utilizing a wide variety of available food items. Alcids (mainly little auks and Brünnich's guillemot), gulls (mainly kittiwakes), were collected mostly in summer, and food remains were recorded both at dens and elsewhere in the region. The foxes were opportunistic in their and fulmars were the major foods in summer. The consumption of alcids by fox families was correlated with availability near the den. In winter, fulmars and, in one region, seals were important foods. Some regional differences in food consumption were found. A change in diet was observed when a litter of pups moved from one den to another (2 of 3 cases). Differences in food habits between years also were found at the same den (4 of 5 cases). Foxes frequently cached food by scatter hoarding, placing only a single item in each cache. Key words: arctic fox, Alopex lugopus, food habits, prey species, food caching, Svalbard RkSUMk. On a 6tudit5 les habitudes alimentaires du renard arctique (Alopex lugopus) sur la &te ouest du Svalbard au cours des ann&% allant de 1986 B 1989. On a recueilli les &es (n = 1018) surtout en W , et on a consign6 les d6bris de nourriture B la fois dans les terriers et ailleurs dans la r6gion. Les renards se montraient opportunistes dans leurs façons de chasser et de se nourrir, et faisaient usage d'une vaste gamme d'aliments B leur port&. Les alcidks (surtout le petit pingouin et la marmette de Briinnich), les mouettes (surtout la mouette B trois doigts) et les fulmars 6taient les sources principales de nourriture estivale. La consommation d'alcid6s par les familles de renards 6tait c o d l & avec leur disponibilit6 B proXimit6 du terrier. En hiver, les fulmars et, dans un certain endroit, les phoques constituaient une source importante de nourriture. On a trouv6 certaines diff6rences rbgionales dans la consommation alimentaire. On a observd un changement dans le r6gime lorsqu'une port& de renardeaux se d6plaçait d'un terrier B un autre (dans 2 cas sur 3). On a aussi enregistr6 des differences dans les habitudes alimentaires d'une a n n & B l'autre au m&me terrier (dans 4 cas sur 5). Les renards cachaient m u e n m e n t la nourriture en Nparpillant, ne mettant qu'un &ment dans chaque cache.

No abstract

Arctic fox (Alopex lagopus) populations in Scandinavia are small and restricted to alpine regions, while red foxes (Vulpes vulpes) are common throughout both Norway and Sweden. The two species are similar in behaviour and diet, and thus competition between them is likely. This study provides seven observations of aggressive interactions between the two species. One adult arctic fox and one cub were killed by red foxes, one male arctic fox was chased away from his den, one female arctic fox and a cub fled into the den as a red fox approached, four cubs fled into the den as a red fox walked upon it and once a red fox walked upon the arctic fox den when no arctic foxes could be seen. Only on one occasion did an arctic fox succeed in chasing away a red fox. Red fox predation may prove to be limiting to the small arctic fox population in Scandinavia, and arctic foxes can be displaced from good dens and the most productive regions. Key words: arctic fox (Alopex lagopus), red fox (Vilpes vulpes), interactions, predation, aggression, field observations, Scandinavia RESUME. En Scandinavie, la population des renards polaires (Alopex lagopus) est petite et se limite aux zones alpines, alors que le renard roux (Vulpes vuipes) est commun dans toute la Norvege et la Suede. Les deux especes, qui ont un comportement et une alimentation semblables sont probablement en competition. Cette etude fournit sept observations d'interactions agressives entre les deux especes: un renard polaire adulte et un renardeau tues par des renards roux, un renard polaire mlle chasst de son terrier, un renard polaire femelle et un renardeau s'enfuyant dans le terrier a l'approche d'un renard roux, quatre renardeaux s'enfuyant dans leur terrier alors qu'un renard roux se tenait au-dessus, et un renard roux se tenant sur le terrier d'un renard polaire alors qu'aucun renard polaire n'etait en vue. Une seule fois, un renard polaire a reussi B chasser un renard roux. La predation par le renard roux pourrait bien limiter la petite population de renards polaires en Scandinavie, et les renards polaires peuvent &re chassks des bons terriers et des regions les plus productives. Mots des: renard polaire (Alopex lagopus), renard roux (Vubes vulpes), interactions, predation, agression, observations sur le terrain, Scandinavie Traduit pour le journal par Nesida Loyer.

No 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.