Spatial Ecology Of River Otters In Southern Illinois

Author

Alexander Hanrahan, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2018

Degree Name

Master of Science

Department

Zoology

First Advisor

Nielsen, Clayton

Second Advisor

Schauber, Eric

Abstract

Social behavior and habitat selection of river otters (Lontra canadensis) are highly variable among populations and there is limited information on how space use of this mustelid changes in human-modified environments. Understanding the spatial ecology of river otters is important for efforts focused on habitat management and preventing human-wildlife conflicts. My objectives were to quantify: (1) home ranges and core areas, (2) second- and third-order habitat selection, and (3) relationships between home-range size and intensity of human development for river otters in southern Illinois. VHF transmitters were used to track river otters during 2014-2016. Home-range and core-area sizes then were compared between males (n = 8) and females (n = 10), as was home-range overlap. I also compared the frequency individuals were located <25 m from a conspecific between sexes. Habitat selection at the second and third orders was analyzed with an eigen-analysis of selection ratios. Male river otters had larger home ranges and core areas than females. Home ranges of males overlapped frequently; lack of core-area overlap among females suggested they may be territorial. Males also were located <25 m from a conspecific more frequently than females (P = 0.023), and male-male dyads shared space more than male-female and female-female dyads (P = 0.002). Herbaceous and wooded wetlands were most strongly selected for at both second- and third-order scales, but streams and ponds also were selected. Regarding terrestrial cover types, river otters selected land with vegetative cover over areas with impervious surface (e.g., parking lots and shopping centers). Forests were selected over crop fields at the third-order, but not second-order, scale. Use of urbanized land was uncommon for river otters, and there was a positive relationship (P = 0.004) between home-range size and the percentage of home range within developed open space (e.g., roads and residential lawns). The habitat selection and sociality of river otters in southern Illinois varied among individuals, as it does among river otter populations throughout North America. By recording sex differences in social behavior and selection of aquatic and upland habitat, my study provides wildlife biologists with a better understanding of river otter space use throughout a rural-urban gradient.