Publication Date


Date of Final Oral Examination (Defense)


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

Jim Munger, Ph.D.


Wayne Melquist, Ph.D.


Jesse Barber, Ph.D.


To obtain current data on the North American river otter (Lontra canadensis) population in Idaho, licensed trappers were mandated to surrender river otter carcasses through provisions of the Idaho Department of Fish and Game’s mandatory harvest report. Throughout the 2002-2003 and 2003-2004 trapping seasons, 237 river otter carcasses were collected. Necropsies were performed to assess age and sex, general body condition, reproductive rates, and concentrations of environmental contaminants in the livers. Reproductive rates were determined by counting corpora lutea and blastocysts in female river otters. Livers were dissected and concentrations of environmental contaminants were determined for the following toxins: mercury and other heavy metals, organochlorine pesticides, and polychlorinated biphenyls (PCBs). No negative relationships were found between environmental concentrations and female reproductive rates or presence of sperm. The majority of otters had contaminant levels well within what is considered background levels. Data from the present study suggest the river otter population in Idaho is stable to increasing. Based on the results from the present study, I conclude that the Idaho Department of Fish and Game’s current management of river otters, including the existing harvest season and quota, are not a detriment to the population.

Included in

Biology Commons