Tree preference of the red squirrel (Tamiasciurus hudsonicus) regarding tree diameter at breast height and distance to edge.

Abstract

Tree preference of the red squirrel, Tamiasciurus hudsonicus, was studied in regards to tree diameter at breast height (dbh) and distance to edge. It was expected that the squirrels would select for greater diameter-sized trees because I assumed the diameter at breast height correlated with cone productivity. Middens, piles of accumulated pine debris from feeding squirrels, were measured for their depth, radii, and eaten to uneaten cone ratio between August 2nd and August 12th at a Norway Spruce (Picea abies) plantation. The study area was divided into ten by ten meter plots, and the dbh of trees surrounded by the middens were measured. It was found that red squirrels significantly preferred trees with dbhs at least 5 cm above the average dbh of the plantation. Average dbh was highest for edge plots and decreased for each successive plot further from an edge. Average plot dbh was positively correlated with light lux. However, midden quality, in terms of average depth, percent potential storage, and average total cone number was lowest at the edge plots and highest in plots between 10 m-30 m from an edge. Territories may be centered in areas with high average dbhs, but not so near to an edge that wood habitat would be compensated for field habitat within the territorial boundaries. Red squirrels were also believed to prefer norway spruce cones over scot's pine (Pinus sylvestris) cones due to the former's probable higher energy content.