Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2023
Höfundar / Authors: Ester Rut Unnsteinsdóttir
Starfsvettvangur / Affiliations: Náttúrufræðistofnun Íslands
Kynnir / Presenter: Ester Rut Unnsteinsdóttir
In northern areas, seasonal dispersal of birds migrating between south and north cause annual fluctuation in resources for local predators who prey upon these birds. Lemmings, however, are small circumpolar mammals that are capable of breeding in all seasons and therefore fluctuate annually instead of seasonally. These lemming cycles are drivers of many arctic predator populations both numerically and functionally. In those areas, Arctic foxes show numerical responses to lemming fluctuations with changes via litter size and number of litters but fail to breed in low lemming years. no lemmings exist in Iceland and migrating birds are the most common diet of Arctic foxes. The Icelandic Arctic fox population has varied between 1300 and at least 9000 individuals during the past 60 years. The rise and fall have been related to changes in some bird populations that foxes are known to prey upon. Numerical responses result in variation in breeding effort via litter size, as is known for the Arctic fox. In contrast to other countries, the fertility of Icelandic Arctic fox vixens has been stable, most likely during the past 100 years and thus population fluctuations cannot be explained by variation in litter size. Indeed, it has turned out that the Icelandic Arctic fox has responded to variation in prey populations with plasticity in the number of litters instead. This long-term stability in litter size is not known in any other areas of the species' distributional range.