Abstract:
To quantify the ecological effects of predator populations, it is important to evaluate how population-level specializations
are dictated by intra- versus inter-individual dietary variation. Coastal habitats contain prey from the terrestrial biome, the
marine biome and prey confined to the coastal region. Such habitats have therefore been suggested to better support
predator populations compared to habitats without coastal access. We used stable isotope data on a small generalist
predator, the arctic fox, to infer dietary strategies between adult and juvenile individuals with and without coastal access on
Iceland. Our results suggest that foxes in coastal habitats exhibited a broader isotope niche breadth compared to foxes in
inland habitats. This broader niche was related to a greater diversity of individual strategies rather than to a uniform
increase in individual niche breadth or by individuals retaining their specialization but increasing their niche differentiation.
Juveniles in coastal habitats exhibited a narrower isotope niche breadth compared to both adults and juveniles in inland
habitats, and juveniles in inland habitats inhabited a lower proportion of their total isotope niche compared to adults and
juveniles from coastal habitats. Juveniles in both habitats exhibited lower intra-individual variation compared to adults.
Based on these results, we suggest that foxes in both habitats were highly selective with respect to the resources they used
to feed offspring, but that foxes in coastal habitats preferentially utilized marine resources for this purpose. We stress that
coastal habitats should be regarded as high priority areas for conservation of generalist predators as they appear to offer a
wide variety of dietary options that allow for greater flexibility in dietary strategies.
