Wetland Use by River Otters in Massachusetts

Wetland loss and vegetational change in the northeastern United States could affect river otter (Lutra canadensis) populations, but few studies have addressed river otter use of wetlands in this region. We documented wetland types used by river otters during 1988-89 in central Massachusetts by using latrine revisitation rates as an index to habitat use. We determined whether use varied by season or wetland type by comparing revisitation rates of river otters at 86-134 otter latrines located in differenet wetland types. We also characterized shoreline habitats at latrines by comparing habitat features at 132 river otter latrines with nearby, unused shoreline sites, using uni- and multivariate techniques. Wetlands used by river otters included 3 wetland systems and 9 subsystem/class categories: palustrine (open water, aquatic bed, emergent, scrub-shrub, and forested); lacustrine (limnetic open water and littoral); and riverine (lower and upper perennial open water). These wetlands represented sites impounded by humans (artificial) and beavers (Castor canadensis) as well as lotic (unimpounded) wetlands. Latrine revisitation rates did not differ (P ≥ 0.05) seasonally or among wetland types, except during summer when the rate was higher (P \u3c 0.05) at beaver-created wetlands than at artificial impoundments (0.73 vs. 0.60, respectively). Habitat features found more often at latrine sites than at nearby, unused sites included large conifers, points of land, beaver bank dens and lodges, isthmuses, and mouths of permanent streams. Biologists could locate otter latrines more efficiently by concentrating efforts along shorelines with these features