Monday, October 8, 2012

Raising a Stink

River otter scent marking (c) John Ashley
A river otter raises his tail and scent marks a beaver lodge within his territory.
How do you communicate with others like yourself when you are mostly solitary, often nocturnal, and see better underwater than above? If you're a North American river otter (Lontra canadensis), you follow your nose. River otters post visual and olfactory cues at conspicuous locations all along the banks of their aquatic territories.

River otter territories can range from 5 to 48 miles of rivers and streams (male territories longer, female territories shorter). Individual otter territories often overlap. So to keep in touch they select a series of latrine sites to post important information, such as age, sex and breeding condition. They use feces (otter feces are called "spraints") as visual bookmarks, and coat them with a musky spray from special anal scent sacs. The odor can be detected for several weeks, and the secretion's chemical composition varies slightly by individual.

Scent marking appears to serve several purposes, so an experiment was conducted on captive male river otters in Alaska to sort through the stink. Researchers found that male otters paid more attention to male scent than female scent, and dominant male otters spent more time inspecting male scent than did subordinate males. The researchers concluded that musky spray at otter latrine sites is used primarily by male otters to determine the social status of other males in their territory.

Researchers in Maryland also reported seasonal variations in scent marking at river otter latrine sites. Scent marking by otters peaked in fall and spring (September and March). They attributed the fall peak to family groups visiting the latrine sites, and the spring peak to communication between adult otters during the breeding season.

River otters were once common from northern Alaska to southern Florida, but they were greatly reduced across their native range by the early 1900's due to unregulated trapping, habitat loss and water pollution. More recently, habitat improvements and reintroduction projects have reestablished river otters in portions of their former range, and they are now listed as a species of "least concern" on the IUCN Red List.

Learn more about all of the otter species at the International Otter Survival Fund.