In the absence of large mammalian predators such as wolves and bears, river otters are top predators in some of the ecosystems where they occur, including the Indian River Lagoon. Though often blamed for damaging or depleting commercial fish stocks, the bulk of the diet consists of slow moving or schooling non-game fish species (Chapman 1982). Common prey types include: cyprinids, suckers (Catostomus spp.), chubs (Semotilus spp.), shiners (Notropis spp.), catfish (Ictalurus spp.), and perch (Perca spp.) (Banfield 1974; Chapman 1982).Besides non-game fish, river otters also consume crustaceans (primarily crayfish), amphibians, insects, small birds and waterfowl, mammals and plants (Meehan 1974; Chapman 1982; Davis et al. 1992).Competitors: River otters practice mutual avoidance behaviors in order to reduce intraspecific competition. Melquist and Hornocker (1983) observed otters to practice "personal space dispersion" whereby individuals defended territories based on their current location, rather than upon fixed environmental parameters. They postulated that this behavior probably had the effect of reducing direct competition for resources. Mutual avoidance is practiced primarily through vocalization and scent marking rather than by direct confrontation.Predators: River otters have few natural predators other than man; however, young otters are placed at risk for predation from foxes, bobcats, wolves, coyotes and snapping turtles when they leave water to traverse land areas.Habitats: River otters have somewhat large home ranges of approximately 8-78 square km. They utilize a wide variety of riparian communities including cattails (Typha spp), sedges (Carex spp.) and grasslands (Chabreck 1971; Dronkert-Egnew 1991; Waller 1992).Lontra canadensis is well adapted to aquatic habitats from marine to fresh water. Optimum otter habitat, according to Chapman (1982) is in highly vegetated areas having slow moving waters with deep pools, and abundant fish. Otters tend to be most abundant in coastal areas, or in the lower portions of rivers and estuaries. The total habitat area must provide otters with escape cover, den sites, and resting sites.Otters do not dig their own dens; rather, they rely on those dug by other animals, or on natural shelters such as the hollows of trees, tall marsh grasses, or riverbank thickets (Banfield 1974; Chapman 1982).Activity Time: Lontra canadensis is primarily nocturnal. However, it is also highly active in the early morning and in late afternoon (Banfield 1974).