This tree is number one for cloud forest mammals going number two

When a human has a sudden need to take a number two, they might seek out a public bathroom. When mammals in the cloud forests of Costa Rica need to defecate, they do something similar. But porcupines, kinkajous and even sloths don’t search for a convenient porta-potty. Instead, they zero in on a strangler fig.

A survey of 169 trees found 11 latrines—all of them in the major forks of the strangler fig tree (Ficus tuerckheimii). A camera trap at one arboreal potty captured 17 different species visiting the spot. The findings, published March 16 in Ecology and Evolution, suggest that treetop toilets might provide communication hubs across mammal species.

Many mammals set aside a place to poo, says Mike Cove, a mammologist at the North Carolina Museum of Natural Sciences in Raleigh who was not involved in the study. “There’s been a lot of observations of this type of behavior and multispecies latrine use in the tropics,” he says. But those were all on the ground. 

Jeremy Quirós-Navarro found his first canopy commode by accident. The plant taxonomist at the University of Connecticut in Storrs was documenting plant life in the cloud forest of Costa Rica. In a tree, at the junction of several large branches, was a pile of poo. Soon, he found more, “but only in a specific tree,” he says.

That tree is F. tuerckheimii, which scientists consider a keystone species in the tropics. This strangler fig provides plenty of food and holes for shelter, and the wide-spreading branches provide travel routes within the tree canopy, making them hubs for many species.

After finding the first four latrines in fig trees, “we started thinking that this is a pattern,” Quirós-Navarro says. After surveying 169 trees from 29 different species, the scientists found 11 total latrines. All were in F. tuerckheimii, and 73 percent of the fig trees surveyed had at least one.

Researchers aren’t certain why the latrines were only found in one tree species. Quirós-Navarro thinks the tree’s structure is important. “They have a specific and particular structure that forms, like a hand at the crown,” he says. “All the branches grow from that part.” Where they join, there’s a flat platform that can be up to a meter across, filled with soil, small plants and in many cases, poo.

The researchers added a camera trap to one latrine. Over two months, they observed about three mammal visitors per day. The spot saw visits from 17 different mammal species. Mexican hairy dwarf porcupines (Coendou mexicanus) were the most frequent visitors, but kinkajous, opossums, pocket mice, coatis and capuchin monkeys all stopped by. Even margays (Leopardus wiedii), secretive arboreal cats, hit up the latrine (though only to spray urine).

Most surprisingly, the camera caught two visits from Hoffmann’s two-toed sloths (Choloepus hoffmanni), a species thought to come down to the ground to go. Both images captured were of a female with young, so it’s possible that “it’s more [of a] risk for them to go and poop in the ground,” Quirós-Navarro says.

But maybe it’s just convenient, says Erik Hom, who studies symbiosis at the University of Mississippi and was not involved in the study. After all, “coming down is quite a way,” he says. If a flat place covered in dirt is available, it might be groundlike enough.

The multitude of species using the area is especially interesting, Cove says. “You have all of these animals coming together, scent marking, defecating, urinating and then, in some cases, rolling in it, anointing themselves in it.”

Many mammals pooping and peeing in the same spot makes these latrines a potential message board of the canopy, Quirós-Navarro says. In the future, he hopes to find out why the fig trees, specifically, are the toilet of choice. But the bathrooms only add to the importance of the strangler fig tree in the tropical forest. It’s a food source, a highway and now, a la-tree-n.