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

mmerrick — Thu, 16 Apr 2020 21:43:52 +0000

Authors

Pereira Mendes, Calebe

Koprowski, John

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.

Additional Information

PLoS ONE

Date of publication:

2019

Topics

caching

microclimate

Mt. Graham red squirrel

larderhoard

midden

Research Categories

Behavioral Ecology Sky Islands Threatened and Endangered Species

Zugmeyer, C. A. and J. L. Koprowski. 2009. Habitat selection is unaltered after severe insect infestation: Concerns for forest-dependent species. Journal of Mammalogy 90: 175-182.

thackerk1 — Tue, 30 Jul 2019 22:07:07 +0000

Authors

Claire A. Zugmeyer

John L. Koprowski

Severe disturbance may alter or eliminate important habitat structure that helps preserve food caches of food- hoarding species. Recent recolonization of an insect-damaged forest by the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) provided an opportunity to examine habitat selection for midden (cache) sites following disturbance. From September 2003 to December 2005, we examined surface temperature and physical and vegetative characteristics associated with random locations and midden sites in insect-damaged forests. Red squirrel use of midden sites that are similar in structure to those used before insect infestation indicates that insect infestation did not eliminate midden habitat. However, differences between occupied middens and historical middens that are unoccupied reflect the severity of insect infestation tolerated by red squirrels. Occupied middens had ,64% tree mortality, high basal area of live trees, and cooler surface temperatures during snow-free months. Forest areas with greater tree mortality would likely not represent habitat, threatening the persistence of an isolated population. Although conservation efforts can protect remaining habitat, disturbance events continually represent a threat. Habitat loss and predictions of increased disturbance due to climate change highlight the importance of documenting response to disturbance.