Collared lemming

Abstract: The high Arctic has the world’s simplest terrestrial vertebrate predator–prey community, with the collared lemming being the single main prey of four predators, the snowy owl, the Arctic fox, the long-tailed skua, and the stoat. Using a 20-year-long time series of population densities for the five species and a dynamic model that has been previously parameterized for northeast Greenland, we analyzed the population and community level consequences of the ongoing and predicted climate change. Species’ responses to climate change are complex, because in addition to the direct effects of climate change, which vary depending on species’ life histories, species are also affected indirectly due to, e.g., predator–prey interactions. The lemming–predator community exemplifies these complications, yet a robust conclusion emerges from our modeling: in practically all likely scenarios of how climate change may influence the demography of the species, climate change increases the length of the lemming population cycle and decreases the maximum population densities. The latter change in particular is detrimental to the populations of the predators, which are adapted to make use of the years of the greatest prey abundance. Therefore, climate change will indirectly reduce the predators’ reproductive success and population densities, and may ultimately lead to local extinction of some of the predator species. Based on these results, we conclude that the recent anomalous observations about lack of cyclic lemming dynamics in eastern Greenland may well be the first signs of a severe impact of climate change on the lemming–predator communities in Greenland and elsewhere in the high Arctic.

Abstract: The history of lemming research - from the Nordic sagas to "The Biology of Lemmings" lemmings - who are they, where do we find them and where do they come from? population dynamics in lemming - temporal and spatial variation food selection, individual growth and reproduction intra and interspecific relations population biology of wood lemmings with skewed sex ratio the biology of lemmings - where are we and where might it be rewarding to go next? Appendices: how to study the biology of lemmings.

Abstract: Gilg, O., Sittler, B., Sabard, B., Hurstel, A., Sane, R., Delattre, P. and Hanski, I. 2006. Functional and numerical responses of four lemming predators in high arctic Greenland. - Oikos 113: 193-216. The high-arctic tundra ecosystem has the world's simplest vertebrate predator-prey community, with only four predators preying upon one rodent species, the collared lemming {Dicrostonyx groenlandicus). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared lemming with a 4 yr cycle and > 100-fold difference between maximum and minimum densities. All predator species feed mostly ( >90%) on lemmings when lemming density is > 1 ha~ \ but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when lemming densities at snowmelt are >2 ha~ \ giving rise to a step-like numerical response. The long- tailed skua {Stercorarius longicaudus) has a type III functional response and shifts from alternate food (mainly berries and insects) to lemmings with increasing lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus) starts to increase at much lower lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the lemming cycle, but only the stoat has the potential to drive the lemming cycle. Stoat predation is greatly reduced in the winter preceding the lemming peak, and it reaches a maximum in the winter preceding the lowest lemming summer density. Stoat predation appears to maintain low lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles