Perianal scent glands, are used for identification, defense, marking territory, and trail marking. During a dive, pulse slows to a tenth of the normal rate of 170 beats a minute, thereby conserving oxygen. Both diurnal and nocturnal. Otter droppings are called spraints. In California the river otter is fully protected under law and may not be taken at any time.
Population densities are low, even in the best habitat.
Over 30,000 pelts are sold annually in the United States and Canada. Animal Life Encyclopedia, Vol. 12, Van Nostrand Reinhold Co, New York. Leopold, A. Starker, Ralph Gutierrez and Michael Bronson. North American Game Birds and Mammals.