We investigated occupied squirrel middens and squirrel sightings and vocalizations as indicators of red squirrel (Tamiasciurus hudsonicus) abundance in the high-elevation whitebark pine (Pinus albicaulis) zone. Data were collected 1984–1989 from line transects located on 2 study sites in the Yellowstone ecosystem. We evaluated the performance of each measure on the basis of precision and biological considerations. We concluded that, of the 3 measures, active middens were the best indicator of red squirrel abundance. We also observed that the density of active middens dropped by 48%–66% between 1987 and 1989, following a severe drought and extensive wildfires that burned one of the study sites during 1988.
Mattson, David J. and Reinhart, Daniel P.
"Indicators of red squirrel (Tamiasciurus hudsonicus) abundance in the whitebark pine zone,"
Great Basin Naturalist: Vol. 56
, Article 11.
Available at: http://scholarsarchive.byu.edu/gbn/vol56/iss3/11