Functional and numerical responses of four lemming predators in high arctic Greenland

Abstract

I. 2006. Functional and numerical responses of four lemming predators in high arctic Greenland. Á/ Oikos 113: 193 Á/216.The high-arctic tundra ecosystem has the world's simplest vertebrate predator Á/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 (1 , 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 (1 , 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.

Trophic ecology, behaviour and host population dynamics in Echinococcus multilocularis transmission

“…The populations of V. lagopus in arctic ecosystems usually display a numerical response due to the low availability of alternative prey and the high amplitude of its main small mammal prey (e.g. the collared lemming Dicrostonyx groenlandicus) (Gilg et al, 2006). By contrast, there are apparently conflicting results about the ability of V. vulpes to display a numerical response: its density was not related to A. scherman density variations in the grassland plateau of the E. multilocularis endemic area of western Switzerland (Weber et al, 2002), whereas it displayed a numerical response in the Mediterranean scrubland of Spain after the collapse of its main prey, the European rabbit Oryctolagus cuniculus (Ferreras et al, 2011).…”

Ilkka Hanski and Small Mammals: from Shrew Metapopulations to Vole and Lemming Cycles

“…lemmings were live-trapped in several plots throughout the summer snow-free season in order to "calibrate" the long-term relative abundance inferred from the census of winter nests, monitored by Sittler since 1988. Predators' functional responses were closely monitored by mixing an array of specific methods, from radio tracking to detailed diet analysis and behavioural observations made from hides (Gilg 2002, Gilg et al 2006.…”

Will Collared Lemmings and Their Predators be the First Vertebrates to "Fall Over the Cliff" in Greenland Due to Global Climate Changes?

“…The lemmingpredator community exemplifies these complications, yet a robust conclusion emerges: in practically all scenarios and for the ranges of parameter values examined, climate change increases the length of the lemming population cycle and decreases the maximum densities reached during the fluctuations ). The latter change, in particular, is detrimental to populations of their predators, which are adapted to make use of the years of prey abundance (Gilg et al 2006). Indeed, in northeast Greenland, even the Gyrfalcon is strongly dependent on lemmings, for the densities of larger prey, such as Arctic Hare (Lepus arcticus) and ptarmigan are too low in most years.…”