Recently, I ferried out to Vinalhaven for a day of birding and nature observation with my friend, Kirk, a naturalist who works there year-round as a Regional Steward for Maine Coast Heritage Trust. Outings with Kirk are always entertaining, as he knows well the island and its inhabitants, human and otherwise.
Despite the winter chill and intermittent rain, we saw quite a few interesting birds. The highlight for me, however, was being shown an otter latrine, of which Kirk has found at least seven on the island. An otter latrine is exactly what it sounds like: a flat, grassy patch alongside water, covered with otter poop. Otter poop is distinctive because it's generally full of fish scales. Also, the animal makes no attempt to hide its scat, leaving it in the most obvious spots as some sort of message to other otters that frequent the area. Apparently in places that host lots of otters — and we're talking about river otters here, not sea otters, which don't live on the Atlantic coast — these group bathrooms are common and can be quite large. This one was probably 20 feet across, on the smaller side as latrines go.
According to Mark Elbroch and Kurt Rinehart, authors of the excellent Peterson Guide Behavior of North American Mammals: "Otters mark sites of high 'traffic' or use... most of their scent-marking occurs in traditional latrines near foraging areas and dens... [the spot Kirk showed me was across the water from a den]. When they are scent-marking they arch their back and curl and undulate their tail. They paw, scratch, and tread on the spot, and then shoot a jet of feces or urine out onto the ground. Sometimes they create mounds of debris to serve as pedestals for their defecations, which can be several inches high and many inches across."
Defecation gyrations! Poop on a pedestal! An otter latrine sounds like a happening spot. And it's hard to ignore all that physical evidence of a good time had by all.
The otter is a member of the weasel family, a group of animals that is highly scent-oriented and thus makes good use of its scent glands. Elbroch and Rinehart write that in addition to anal musk glands, the otter also has glands on its hind feet—so it literally leaves a trail as it travels around its territory. These latrines thus serve as scratch-and-sniff community bulletin boards, letting other otters know such important information as, perhaps, who's passing through the neighborhood, who's ready to mate, or who's feeling dominant. According to Elbroch and Rinehart, the river otter is not highly social by choice, although individual territories often have a lot of overlap. A communal latrine at a common intersection point therefore must help them stay in touch without having to really deal with one another, like sending an email to someone instead of visiting in person.
When he first came across this popular spot, Kirk set up a game camera low on a tree trunk to track what the otters were up to. One otter actually noticed the camera, came right up to it, and rubbed against it; this was captured on film. Kirk thinks the otter detected the human smell on it and was letting him know he'd been found out. Other otters were photographed defecating and urinating. The night of Dec. 15 -16 was a true latrine-fest, with several otters recorded "leaving their mark" throughout the night; Kirk got shots of separate animals actively doing their thing at 9:23 p.m., 9:26 p.m., 9:26.38 p.m., 5:02 a.m., and 6:33 a.m.. And here's a cool latrine party trick: to tell the difference between a male and female otter, watch how they pee. The male otters squirts his urine stream forward, the female backward.
On the day I was visiting the otter latrine with him, Kirk found a yellow gooey excretion from an otter's intestine. Scientists aren't really sure of the significance of this disgusting-looking matter, which is different from anal gland secretions (which are white) and feces, but its discovery alone meant something to Kirk (who took photos that I won't be sharing here).
An island like Vinalhaven offers ideal habitat for the semiaquatic otter, which moves easily between fresh to salt water and feeds primarily on fish—as evidenced by their scaly scats. The most recent otter I've seen—by which I mean an actual animal and not dozens of piles of otter poop—was not in a river at all, but in Camden Harbor. We came across one frolicking around the windjammers this past summer, much to the delight of my six-year-old niece, who'd never seen an otter in the wild before. Somehow I don't think she'd have been quite as delighted as I was by the otter latrine on Vinalhaven, but you never know. With little kids and their "potty humor," it probably would have been dismissed as really gross and then spoken of incessantly at the most inappropriate moments.
For a taste of both Kirk Gentalen's knowledge of the natural world and his sense of humor, check out his nature sightings update for this Penobscot Bay island.
Kristen Lindquist is an amateur naturalist and published poet who works for Coastal Mountains Land Trust in her hometown of Camden.