Does caching strategy vary with microclimate in endangered Mt. Graham red squirrels?

Food hoarding is a common behavior used by a variety of animals to cope with periods of
low food availability. At the retreating edge of species’ distribution, the stressful environment
and unfavourable climate conditions may impose severe costs on hoarding behavior. Since
relict populations are hotspots for evolution and adaptation, and considering that food hoarding
behavior has a strong evolutionary basis, we decided to evaluate the occurrence of
behavioral variability in the amount of food cached by the endangered Mount Graham red
squirrel (Tamiasciurus fremonti grahamensis). We tested the variation in cache size in
response to microclimate, soil relief, vegetation, food availability and squirrel sex. The number
of pits excavated by squirrels to cache cones was used as a proxy of cache size and
was affected by mountain slope aspect and density of trees. More pits were excavated in
the northeast facing slopes. The density of trees negatively affects the cache volume on
southwest slopes, but not on northeast slopes. The sex of the resident squirrel also affects
the number of pits in the squirrel midden, with males excavating 47% more pits than
females. Males and females also presented different responses to the mountain slope
aspect, with females excavating more pits on northeastern slopes than on southwestern
slopes, whereas male cache size did not vary with the slope aspect. Finally, the squirrel’s
caching behavior did not vary in response to midden microclimate variation, a result with
possible implications for the survival of the Mt Graham red squirrels, given the predicted
temperature increases in the region due to climate change.