Relationship Between Eastern Gray Squirrel
Abundance and Mast in Western North Carolina

Robert R. Glesener Heart of Brevard

Community volunteers from the city of Brevard, North Carolina have conducted an annual fall squirrel count for the past 15 years (1997-2011). Although the primary purpose of the count is to monitor Brevard’s unique white variant, it also records data on abundance of all squirrels which has fluctuated widely over this period. One might expect abundance to be a function of food availability, particularly of hard mast (nuts) which can be cached for the bleak winter months. The North Carolina Wildlife Resources Commission (NCWRC) has been monitoring fall hard mast productivity in Western North Carolina since 1983. I plotted observed squirrels/acre from the annual squirrel count against published NCWRC estimates of hard mast for (1) the same year, and (2) the previous year. The same year hard mast explained less than 5% (R-square=.0498) of the variance in squirrels/acre while that of the previous year explained over 50% (R-square=.524). This makes sense since the amount of energy allocated to reproduction should be a function of how well-nourished squirrels were in the recent past, not how much food is currently available for harvest. If soft mast (fruits, berries, etc.) of the previous two falls is also included, total mast explains over 60% (R-square=.603) of the variance of squirrels/acre. This is particularly impressive since the NCWRC sites are spread out over 12 counties with the closest being >10 air miles from the ~3 square mile Brevard study area. Summer soft mast contributed little, possibly because data was less complete.  NC ACADEMYof SCIENCE 109th Annual Meeting March 23-25 2012, Campbell University: pp 46-47.

white squirrel with paws over his ears

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