21477201
not annotated - annotated - LINNAEUS only
The importance of marine vs. human-induced subsidies in the maintenance of an expanding mesocarnivore in the arctic tundra.
1. Most studies addressing the causes of the recent increases and expansions of mesopredators in many ecosystems have focused on the top-down, releasing effect of extinctions of large apex predators. However, in the case of the northward expansion of the red fox into the arctic tundra, a bottom-up effect of increased resource availability has been proposed, an effect that can counteract prey shortage in the low phase of the multi-annual rodent cycle. Resource subsidies both with marine and with terrestrial origins could potentially be involved. 2. During different phases of a multi-annual rodent cycle, we investigated the seasonal dynamics and spatial pattern of resource use by red foxes across a coast to inland low arctic tundra gradient, Varanger Peninsula, Norway. We employed two complementary methods of diet analyses: stomach contents and stable isotope analysis. 3. We found that inland red foxes primarily subsisted on reindeer carrions during the low phase of a small rodent population cycle. Lemmings became the most important food item towards the peak phase of the rodent cycle, despite being less abundant than sympatric voles. Isotopic signatures of tissue from both predator and prey also revealed that red foxes near the coast used marine-derived subsidies in the winter, but these allochthonous resources did not spillover to adult foxes living beyond 20-25 km from the coast. 4. Although more needs to be learned about the link between increasing primary productivity due to climatic warming and trophic dynamics in tundra ecosystems, we suggest that changes in reindeer management through a bottom-up effect, at least regionally, may have paved the way towards the establishment of a new mesopredator in the tundra biome.
Ann file
T1 Species 29 34 human
N1 Reference T1 Taxonomy:9606
T2 Species 381 388 red fox
N2 Reference T2 Taxonomy:9627
T3 Species 813 822 red foxes
N3 Reference T3 Taxonomy:9627
T4 Species 1030 1039 red foxes
N4 Reference T4 Taxonomy:9627
T5 Species 1063 1071 reindeer
N5 Reference T5 Taxonomy:9870
T6 Species 1270 1275 voles
N6 Reference T6 Taxonomy:10058
T7 Species 1354 1363 red foxes
N7 Reference T7 Taxonomy:9627
T8 Species 1716 1724 reindeer
N8 Reference T8 Taxonomy:9870