Serum Chemistry and Hematology of Black Bears: Physiological Indices of Habitat Quality or Seasonal Patterns?

Abstract

We evaluated the use of serum chemistry and hematological variables as indices of habitat quality for adult (≥4 yr) female black bears (Ursus americanus) in northeastern Minnesota. Blood samples (n = 182) collected from 48 adult females during 1970–1976 showed seasonal variation (P < 0.05) for four of five hematologic characters and seven of 13 serum chemistries. Body mass, red-blood-cell count, mean corpuscular-volume, serum-urea nitrogen, uric acid, thyroxine, and Cortisol were different (P < 0.05) among years of differing food availability. Discriminant functions developed from samples from late summer, autumn, and early hibernation provided 75–80% accuracy in classifying observations into year classes of good and poor food production. Our results suggested that blood characteristics can be indicators of nutritional condition and habitat quality after seasonal rhythms are controlled. We recommend use of blood-profile data to empirically test the utility of our discriminant functions.