Movement tactics of a mobile predator in a meta‐ecosystem with fluctuating resources: the arctic fox in the High Arctic

Abstract

Animal movement is a fundamental process shaping ecosystems at multiple levels, from the fate of individuals to global patterns of biodiversity. The spatio-temporal dynamic of food resources is a major driver of animal movement and generates patterns ranging from range residency to migration and nomadism. Arctic tundra predators face a strongly fluctuating environment marked by cyclic microtine populations, high seasonality, and the potential availability of sea ice, which gives access to marine resources in winter. This type of relatively poor and highly variable environment can promote longdistance movements and resource tracking in mobile species. Here, we investigated the winter movements of the arctic fox, a major tundra predator often described as a seasonal migrant or nomad. We used six years of Argos satellite telemetry data collected on 66 adults from Bylot Island (Nunavut, Canada) tracked during the sea ice period. We hypothesized that longdistance movements would be influenced by spatio-temporal changes in resource availability and individual characteristics. Despite strong annual and seasonal changes in resource abundance and distribution, we found that a majority of individuals remained resident, especially those located in an area characterized by highly predictable pulse resources (goose nesting colony) and abundant cached food items (eggs). Foxes compensated terrestrial food shortage by commuting to the sea ice rather than using long-distance tracking or moving completely onto the sea ice for winter. Individual characteristics also influenced movement patterns: age positively influenced the propensity to engage in nomadism, suggesting older foxes may be driven out of their territories. Our results show how these mammalian predators can adjust their movement patterns to favor range residency despite strong spatio-temporal fluctuations in food resources. Understanding the movement responses of predators to prey dynamics helps identifying the scales at which they work, which is a critical aspect of the functioning and connectivity among meta-ecosystems.

Predators attract prey through ecosystem engineering in the Arctic

“…Thick snow cover has been suggested to reduce predation rates on lemmings (Gilg et al 2006), but a recent study found that thick snow cover only weakly limited fox predation attempts made by jumping through the snow, did not affect attempts made by digging, and did not provide lemming protection against ermine predation (Bilodeau et al 2013a). These observations suggest in years with high lemming densities, when foxes continue to occupy dens consistently during winter (Lai et al 2017), enhanced snow depth on dens may not protect lemmings from predators and predation risk on dens could be high. In such years, fox dens may act as ecological traps (reviewed in Hale and Swearer 2016), where net fitness is reduced by increased predation risk despite the benefits of enhanced thermal protection and improved quality and quantity of forage.…”

“…These observations suggest in years with high lemming densities, when foxes continue to occupy dens consistently during winter (Lai et al. ), enhanced snow depth on dens may not protect lemmings from predators and predation risk on dens could be high. In such years, fox dens may act as ecological traps (reviewed in Hale and Swearer ), where net fitness is reduced by increased predation risk despite the benefits of enhanced thermal protection and improved quality and quantity of forage.…”

“…In years with low lemming densities, Arctic foxes in coastal areas often leave their dens and venture on to sea ice to feed on ringed seal (Phoca hispida) pups and seal carcasses killed by polar bears (Ursus maritimus; Roth 2002, Lai et al 2017. In such years, predation risk on dens may be lower, allowing dens to become good winter refuges.…”

Use of Supplementary Feeding Dispensers by Arctic Foxes in Norway

“…Juveniles from unrelated litters used the same feeding stations and sometimes at the same time, suggesting that breeding pairs seemed to allow the juveniles from other litters at the dispensers within their territory. Temporal variation in food availability may allow a breeding pair to tolerate additional individuals in its territory at times when food abundance is high, as described in Svalbard (Eide et al 2004), Canada (Lai et al 2017), Sweden, and Iceland (Elmhagen et al 2014). It could also be that these unrelated juveniles were only visiting the feeding dispensers sporadically while dispersing, during a period when adults were less territorial.…”

Long‐distance flights and high‐risk breeding by nomadic waterbirds on desert salt lakes

“…; Lai et al. ). Birds are among the most mobile of all organisms and undertake some of the world's longest migrations, usually in predictable annual cycles (Alerstam et al.…”