Graduation Date
Summer 2025
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Wildlife
Committee Chair Name
Jeff Black
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
Micaela Szykman Gunther
Second Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Third Committee Member Name
Dan Barton
Third Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Keywords
River otter, Kinship, Microsatellite, Sociality, Fission-fusion, Humboldt County, Genetic
Subject Categories
Wildlife
Abstract
Previous studies of river otters (Lontra canadensis) in coastal Humboldt County, California have documented varying social group compositions over the last four decades. It has been assumed that otters travel between coastal wetland sites, but the extent of movement has been unknown. Socially, river otters have been observed alone, in small family groups that consisted of an otter mom and pup(s), in larger helper groups that consisted of an otter mom, pup(s), and at least one additional adult or juvenile (helpers), and in all-adult social groups. Until now it was unknown whether the composition of social groups was made up of related or unrelated otters. By pairing DNA microsatellite analysis with behavioral sampling, we were able to confirm that river otters travel between sites and join and exit social groups in a fission-fusion fashion. Female river otters with pups tended to avoid non-kin. DNA “fingerprints” of helper groups provided evidence that helping behavior was kin-based: all helper otters observed were related to the pups they provisioned. One sampled site hosted a static all-male group that did not intermix with other individuals. Another sampled site hosted all-adult social groups that were typically made up of relatives but were tolerant of non-kin, and males and females regularly intermixed without signs of aggression. These results show that river otters can travel extensively through wetland complexes and that adults are tolerant of conspecifics to a degree. Otter moms raising pups, however, were less tolerant of non-kin. Bonding through affiliative behavior appeared to contribute to group cohesion, and social foraging was prevalent in all social groups. Coastal wetlands and a wastewater treatment plant that also served as wildlife sanctuary hosted a variety of river otter social groups. Protecting semi-intact estuarine habitats and incorporating findings on kinship and sociality into reintroduction planning can support long-term population sustainability. These strategies align with the IUCN Otter Specialist Group’s emphasis on using genetic data from native populations as a critical baseline for conservation and restoration efforts.
Citation Style
JWM
Recommended Citation
Vickers, Whitney E., "Patterns of kinship and sociality in North American river otters" (2025). Cal Poly Humboldt theses and projects. 2333.
https://digitalcommons.humboldt.edu/etd/2333
Included in
Animal Sciences Commons, Biology Commons, Ecology and Evolutionary Biology Commons, Genetics and Genomics Commons