MUSKRAT POPULATIONS IN VIRGINIAS ELIZABETH RIVER - PHYSIOLOGICAL CONDITION AND ACCUMULATION OF ENVIRONMENTAL CONTAMINANTS

This study evaluated the physiological condition and environmental con taminant concentrations in muskrats inhabiting the contaminated lower region of the Elizabeth River, Virginia, (USA). Muskrats trapped in th e lower region of the Elizabeth River weighed less, had lower mean fat indexes, lower relative spleen weights, greater relative adrenal weig hts, and an increased incidence of disease and parasitism compared to muskrats trapped in the less contaminated upper region of the Elizabet h River or Nansemond River. Concentrations of the metals aluminum, cad mium, copper, nickel, and zinc and the number of polyaromatic hydrocar bon compounds were greater in lower Elizabeth River muskrats compared to upper region Elizabeth River or Nansemond River muskrats. These phy siological data indicated that muskrats in the lower region of the Eli zabeth River were in poor health relative to muskrats from the other r egions studied. However, no significant difference in fecundity or den sity was observed among regions studied, suggesting that the level of environmental contaminant exposure was not sufficient to elicit a popu lation level response. Greater population declines following severe na tural environmental stresses (large storms, extreme cold, etc.) would be anticipated in lower region Elizabeth River muskrats; however, the muskrat population in this region does not now appear to be at risk of extirpation.