In an ongoing study in Costa Rica, wildlife biologists are exploring the ecology of two species of sloths in a rapidly changing environment.
Three-toed-sloth, picture taken in the Cahuita National Park in the southeast of Costa Rica (Christian Mehlführer / CC BY 2.5)
“We know a lot about sloth physiology,” said Dr Jonathan Pauli, an assistant professor of wildlife ecology at the University of Wisconsin-Madison, who with colleague Dr Zach Peery has established a sloth study on a private cacao farm in rural Costa Rica. “But when it comes to sloth ecology and behavior, we know almost nothing. It’s a giant black box.”
But some of that mystery is now being peeled away as studies by the team of both the brown-throated three-toed sloth, Bradypus variegatus, and Hoffmann’s two-toed sloth, Choloepus hoffmanni, two fairly common species, are yielding new insights into their mating habits and how the animals transit the landscape.
“The fact that sloths require forested habitat and are sedentary makes them vulnerable to the deforestation common to many parts of Central and South America,” Dr Peery said, also an assistant professor of wildlife ecology at the University of Wisconsin-Madison. “Once a tract of tropical forest has been cleared, sloths have relatively little capacity to seek out new habitats.”
The setting Dr Pauli and Dr Peery are using to study sloths is increasingly representative of the Central American landscape. It is a mix of tropical forest, pasture, banana and pineapple plantations with a large organic cacao operation as a hub. “As far as sloths go, the fields where bananas and pineapples are grown may as well be deserts,” Dr Pauli explained. “Sloths don’t go there. They just don’t move through it.”
But the shade-grown cacao plantation, with its tall trees and network of cables for moving the pods that ultimately become chocolate, seems to be a de facto refuge and transit hub for the two- and three-toed sloths.
“Because of the diverse overstory of native trees, the cacao farm appears to provide excellent habitat for both species of sloths,” Dr Peery said.
Sloths also turn up in the few relic trees in pastures adjacent to the cacao farm, and the researchers hope to find out if the animals are using that habitat as spillover. “And then, of course, we want to compare sloth populations in cacao to populations in intact tropical forests to see if cacao provides habitat that is of as high of a quality as their natural forests,” Dr Peery said.
To flesh out sloth ecological parameters, however, requires a better basic understanding of sloth behavior, knowledge the group is now beginning to accumulate.
For example, in a paper published in the journal Animal Behavior, the biologists describe the mating system of Hoffmann’s two-toed sloth and show that, unlike many other animals, the females tend to disperse from their home range and that the breeding territories of males can slightly overlap, with males tolerating competitors on the fringes but excluding them, sometimes violently, from the core. And Hoffmann’s two-toed sloths of both sexes seem to have multiple partners as well.
“They’re more promiscuous than previously thought,” Dr Pauli said. “We see a much more flexible system of multiple matings.”
In addition to contributing to the store of basic sloth knowledge, the work of the Wisconsin researchers should help wildlife and land managers in the Neotropics make sound decisions to better balance development and conservation.
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Bibliographic information: M. Zachariah Peery, Jonathan N. Pauli. 2012. The mating system of a ‘lazy’ mammal, Hoffmann’s two-toed sloth. Animal Behaviour. Available online 12 July 2012; doi: 10.1016/j.anbehav.2012.06.007
