'Costa del Sloth'
In February 2024 I took a trip to Costa Rica in search of sloths. Sloths are a group of xenarthran mammals comprising the suborder Folivora. Noted for their slowness of movement, tree sloths spend most of their lives hanging upside down in the trees of the south and Central America. There are six extant sloth species in two genera – Bradypus (three–toed sloths) and Choloepus (two–toed sloths). The two groups are from different, distantly related families, and are thought to have evolved their similar morphology via parallel evolution from terrestrial ancestors.
The first sloths we encountered were living within the campus of the University of Costa Rica, which holds some of the largest patches of forest in the San José Metro Area. Initially we came across 5 individuals of the brown-throated sloth Bradypus variegatus (a mother and baby, two adolescents and a solo male) but also a very active – and surprisingly quick Hoffmann's two-toed sloth (Choloepus hoffmanni). Later we encountered more individuals of both species, though mostly the brown-throated three-toed sloth, in Manuel Antonio National Park on the Pacific coast of Costa Rica.
The ancient Xenarthra included a significantly greater variety of species, with a wider distribution, than those of today. Ancient sloths were mostly terrestrial, and some reached sizes that rival those of elephants, including Megatherium – the giant ground sloth, notably collected by Charles Darwin during his expedition to South America on HMS Beagle.
