River otters, like other social animals, have to carefully weigh the costs and benefits of hanging out in large groups. A big group makes it easier to catch fish, which seems like a good deal, but there's a downside to social life too. More otters means more chances for disease transmission, for example, or for aggressive conflict. So they balance these pressures by living in what researchers call a "fission-fusion society."

"There's this constant dynamic of splitting and joining into larger groups." 

University of Wyoming ecologist Adi Barocas. To understand the factors that drive these social dynamics, Barocas's team, from the University of Wyoming and the Alaska Department of Fish & Game, has spent decades spying on the coastal river otters of Alaska near Prince William Sound. To do it, they use motion-activated camera traps as well as implanted radio trackers.

"The latrines, which are pretty much communal toilets that the river otters use, they seem to have an important function in the life of river otters."

That's right: river otter society is organized around the bathroom. It makes good sense. By investigating a latrine, an otter can sniff out just how many otters there are in the area, and who they might be.

The researchers found that the otters performed more signaling behaviors like sniffing, body rubbing, or urinating, than social behaviors, like grooming or play, at what they called crossover latrines, which were located at the junctions of water bodies. 

Thanks to all that communicative signaling, these crossover latrines were also more likely to host fusion events, resulting in large aggregations of up to eighteen otters. In other words, the otters see latrines as a place to exchange information, a sort of central marketplace.

Because the location of crossover latrines was determined by the physical landscape, this suggests that the complexity of the physical environment plays an important role in determining their social behavior. 

Next, the researchers want to see just how and what the otters communicate at latrines. 

"We often see the river otters sniffing at the latrines and also defecating, and before defecating they do a little ritualized behavior that we termed 'the poop dance.'"

What scents are they trying to sniff out? Which olfactory compounds are at play? Can the otters control the scents they leave behind? Who's watching the poop dance?

And most importantly, why doesn't anybody ever remember to flush?

—Jason G. Goldman 

[The above text is a transcript of this podcast.]

[Adi Barocas et al., Coastal latrine sites as social information hubs and drivers of river otter fission–fusion dynamics.]