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School of Environment and Natural Resources


TWEL Sara Adamczak Thesis

Population Demographics and Diet Variation of the North American River Otter (Lontra canadensis) in Ohio, USA

Sara A. Adamczak, MS

Advisor: Stanley D. Gehrt


Estimates of population demographics and reproductive parameters of the North American river otter (Lontra canadensis) are poorly documented in the eastern United States. In the present study, I examined the current population status of river otters in Ohio, reintroduced in 1986, by deriving demographic and reproductive characteristics from necropsies of river otter carcasses collected during harvest from 2016-2018. Results were compared to those of the 2005- 2008 harvest season when river otter trapping was first reinstated. I derived age distribution, sex ratio, pregnancy rate, and litter size of river otters in Ohio. Data indicated 50% of female river otters in the yearling age class showed evidence of reproductive activity. The reproductive rate  of the most current harvest seasons (0.92) and average litter size [3.18 ± 1.00 (SD)] of adult females was compared with the 2005-2008 harvest seasons and values reported for established populations of river otters elsewhere in eastern North American; consistent with an expanding and successfully recolonizing population. The population age distribution was skewed toward younger age classes, with yearling river otters being the most prominent age class in the 2016- 2018 harvest season. The sex ratio (136:100) was male biased, similar to the 2005-2008 harvest season (107:100) and other river otter populations in the eastern United States. My data support an increasing river otter population with acceptable harvest limits in Ohio.