Spatial behavior and diet data for discrete-choice analyses: data observed and classified from GPS video camera collars worn by female members of the Fortymile Caribou Herd across Alaska, USA, and Yukon, Canada

Competition for resources and space can drive forage selection of large
herbivores from the bite through the landscape scale. Animal behavior and
foraging patterns are also influenced by abiotic and biotic
factors. Fine-scale mechanisms of density-dependent foraging at
the bite scale are likely consistent with density-dependent behavioral
patterns observed at broader scales, but few studies have directly tested
this assertion. Here, we tested if space use intensity, a proxy of
spatiotemporal density, affects foraging mechanisms at fine spatial scales
similarly to density-dependent effects observed at broader scales in
caribou. We specifically assessed how behavioral choices are affected by
space use intensity and environmental processes using behavioral state and
forage selection data from caribou (<i>Rangifer tarandus
granti</i>) observed from GPS video-camera collars using a
multivariate discrete-choice modeling framework. We found that
the probability of eating shrubs increased with increasing caribou space
use intensity and cover of <i>Salix</i> spp.
shrubs, whereas the probability of eating lichen decreased. Insects also
affected fine-scale foraging behavior by reducing the overall probability
of eating. Strong eastward winds mitigated the negative effects of insects
and resulted in higher probabilities of eating lichen. Lastly, caribou
exhibited foraging functional responses wherein their probability of
selecting each food type increased as the availability (% cover) of that
food increased. Space use intensity signals of fine-scale foraging were
consistent with density-dependent responses observed at larger scales and
with recent evidence suggesting declining reproductive rates in the same
caribou population. Our results highlight the potential risks of
overgrazing on sensitive forage species such as lichen. Remote
investigation of the functional responses of foraging behaviors provides
exciting future applications where spatial models can identify
high-quality habitats for conservation.