| Osa Safari: The Sloth, Mike Boston, Osa Aventura (www.osaaventura.com; mike_boston2000@yahoo.com) |
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High upon people’s lists of ‘must sees’ when visiting Costa Rica is the sloth. The sloth has an intrinsic charm, which people find endearing, rather like the koala bear of Australia. It is benign, odd looking, yet cute, and hangs upside down from branches. But let ‘s face it; the sloth is not the most exciting animal in the Neotropics! Nonetheless, behind its rather boring façade lies a very interesting creature indeed.
If any animal were to symbolize the uniqueness of the Neotropical fauna it would be the sloth. It belongs to the oldest extant order of placental mammals to have originated from South America, the Xenarthra (formerly known as the Edentata) – an ancient group that, incidentally, also include the anteaters and armadillos. This once large and diverse order included giants like the huge armadillo-like glyptodont, and giant ground sloths, weighing in at up to four tons. Incidentally, these giants migrated north from South America—once the Panamanian isthmus formed 2.5 million years ago—and were a conspicuous component of the once impressive mega fauna that roamed the forests and plains of both continents. Their extinction, a mere few thousand years ago,
coincided with the arrival of human beings to the New World.The Xenarthra evolved and radiated in isolation for over 50 million years on the South American continent into ten familial lineages. Today, alas, only four of those familial lineages remain. Curiously though, two of these families are represented by the sloths, while the anteaters and the armadillos represent the remaining two families.
In the forests of Central America live two species of sloth: the Brown-throated Three-toed sloth (Bradypus variegatus) and Hoffmann’s Two-toed Sloth (Choloepus hoffmanni). Although both species look superficially similar, current taxonomic opinion considers them to be sufficiently different to warrant their inclusion in separate families: the former is placed in
Three-toed Sloth