Tuesday, June 16, 2009

Costa Rica 2009: Doesn't this Forest have any Sloths?

Sloths are a medium sized mammal that inhabit the rainforests of Central and South America. These famously slow animals are members of the Order Pilosa, a group that also includes the anteaters and the armadillos. Like most other members of the Order, sloths possess a fused spine, small brains, and small peg-like teeth. The characteristically slow movement and prolonged sleep patterns is an adaptation to the sloth’s uniquely low metabolic rate. Canopy leaves are the primary food that sloths consume. While sloths are technically omnivores due to the occasional consumption of insects and lizards, the mostly leafy diet takes time to digest and is generally nutrient poor. To compensate for the low energy diet, sloths expend little energy throughout the day and are thus a model for energy conservation. 

There are six extant (living) species of sloths that can be divided into two families according to the number of digits on their forelimbs. Commonly known as two-toed and three-toed sloths, these families apparently diverged from each other 35-40 million years ago. DNA and anatomical evidence now suggests that the two-toed sloth is more closely related to a now extinct ground sloth than to its contemporary three-toed arboreal “cousins.”  

Two species of sloths can be found throughout the rainforests of Costa Rica. The Brown-throated Three-toed Sloth (see above) and Hoffman’s Two-toed Sloth (see below) often overlap in their habitat and can be found surprisingly close to each other. The sloths at Hacienda Baru have been found in at least 40 different tree species and are likely to be consumers of the leaves in each of the host tree. The sloths in this region have been observed sleeping (or not moving) for 10 to 17 hours each day. However when they do move, the sloths have been observed moving vertically through the canopy as a way to regulate their body temperature. As a result, the sloths are often found in the mid-canopy at noon to avoid the heat of the midday sun or nestled towards the top of the canopy at night. 

I like to think of myself as a fairly competent naturalist who is capable of finding my own wildlife subjects to photograph. Relying on my prior Costa Rican experiences and finely tuned wildlife-seeking skills, we set out each morning and afternoon in search of a sloth. We knew the sloths were near, but they are crafty little creatures. Sloths have keen skills that include inactivity, sleep and camouflage. Fortunately for us, Jack Ewing, the manager and owner at Hacienda Baru recognized our dilemma and found a guide who would be able to find the elusive sloth. It took Carlos, less than ten minutes to find the first sloth, a sleepy two-toed ball of moss crammed into the fork of a tree. By the end of our sixty minute hike through a transitional forest we were able to observe four different individuals. 

The images pictured below are examples of a two-toed and three-toed sloth. To capture these images we had to shoot at a steep angle into the forest canopy. This type of photography is particularly challenging because it is difficult to expose for details in the animal while preventing a over exposed (white) sky.

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