Tropical forests support the greatest diversity of species in the world, yet we are rapidly destroying them. Most deforestation in the tropics is due to agricultural development and livestock production, the two greatest causes of declines in terrestrial biodiversity. However, one strategy that has been gaining attention for its potential to preserve biodiversity is shade-grown agriculture. Crops such as cocoa (Theobroma cacao), the source of chocolate, are grown beneath overstory trees, conserving part of the original forest habitat.
Although past research has shown that biodiversity is usually higher in shade-grown agro-ecosystems than in monoculture crops, until recently little has been known about whether shade-grown crops could harbor populations of more sensitive and specialized species. To this end, Zach Peery and Jonathan Pauli, wildlife biologists from the University of Wisconsin-Madison, sought to determine if a shade-grown cocoa plantation in Costa Rica could serve as a viable habitat for sloths.
“The development of shade-grown agriculture systems presents both opportunities and challenges for biodiversity protection,” the researchers write in their study in the Journal of Applied Ecology, where they specifically looked at whether shade-grown plantations could fully support sloth populations without relying on immigration by individuals from surrounding, intact forests.
Sloths spend most of their time in the forest canopy. They are arboreal folivores, or leaf-eaters, with low metabolic rates, meaning they require prolonged periods of inactivity, hence their common name. Their slow and infrequent movements also result in a weakened ability to disperse, which, coupled with their arboreal lifestyle, makes them especially sensitive to habitat loss and fragmentation.
Two different sloth species are found in the shade-grown cocoa plantation in Costa Rica. The Hoffman’s two-toed sloth (Choloepus hoffmanni) is considered more of a generalist species, because it inhabits a greater range of habitat types and has a broader diet than the brown-throated three-toed sloth (Bradypus variegates), a specialist species.
Peery and Pauli’s study area comprised a mix of cocoa trees grown beneath an overstory of native trees, together with tropical forest patches, cattle pastures, monocultures of cultivated crops, and some human development. The researchers captured sloths of both species and equipped each individual with a Passive Integrated Transponder tag, as well as color-coded radio collars for the adults.