WINTER POPULATIONS OF DOUGLAS SQUIRRELS IN DIFFERENT-AGED DOUGLAS-FIR FORESTS

Tamiasciurus douglasii were censused along established transects in naturally regenerated old-growth and younger Pseudotsuga menziesii forests in the Cascade Range of S Washington State during 3 consecutive winters. Squirrel populations were generally higher in old-growth forests and varied dramatically from year to year in synchrony with variations in the annual production of conifer cones. Old-growth forests appear to provide higher-quality habitat for Douglas' squirrels than younger forests due to greater and more reliable quantities of conifer seeds. Converting old-growth Douglas-fir forests to even-aged plantations of younger Douglas-fir would probably result in lower Douglas' squirrel populations. Alternative silvicultural strategies designed to provide increased levels of cone production over time may be an effective means of improving the habitat quality of young forests for Douglas' squirrels. -from Authors