Thursday, August 6, 2009

Hot! Hot! Hot! How do the Lemurs Stay Cool in Duke Forest?

Imagine wearing a full length fur coat on a broiling summer day. Now imagine running through the forest, climbing trees and jumping great distances between trees while wearing said coat. That’s sort of what our forest dwelling lemurs do each and every summer day; but for relatively young, healthy lemurs heat is not a problem, as many parts of Madagascar experience temperatures greater or equal to North Carolina's and lemurs have evolved to deal with it.

If you have never visited the Lemur Center, you might be surprised to learn that none of our diurnal lemurs have access to air-conditioning in their cages. In order to cope with heat without AC, lemurs have strategies that allow them to keep cool. Lemurs housed in traditional cages around the building receive a lot of help in this regard from the Technicians who care for them, and you can read more about how these guys stay cool by viewing Nichol’s blog from June 29th.

But free ranging lemurs living in our forested enclosures are pretty much on their own in the quest to avoid the heat. So, how exactly do they do it?

Like dogs, lemurs are incapable of sweating, but unlike their canine counterparts, they cannot dissipate excess heat through a long panting tongue. So there are actually only a few simple strategies that a forest living lemur can utilize on a brutally hot day to stay cool: keep quiet and minimize activity, find a cool place to sit, lie down, or sprawl and, finally, to lick their hands.

Hand licking? Unlike humans or horses who can sweat profusely to cool down, the only way lemurs can obtain some measure of relief by way of evaporative cooling is to lick their fingers and both sides of their hands (one of the few areas of their bodies not fully furred) over and over again. Although not as effective as cranking the AC, this primitive air conditioning seems to work for the free ranging lemurs.

In the middle of a baking hot, dry forest on a 95 degree day, the options for finding a really cool spot are somewhat limited, but shady spots are available in abundance. Plus, the ground temperature will always be cooler than the ambient temperature this time of year, so it is a common sight to see a lemur laying flat out on its stomach or back, arms and legs splayed off to the side with body pressed as close as possible to the cooler ground.

Amazingly enough, large and even medium sized trees seem to offer some heat relief to our forest dwellers. According to DLC Veterinarian, Cathy Williams, the transpiration and evaporation of water which is always ongoing inside a tree keeps it a bit cooler than the outside air. Hence for lemurs in general, and sifaka especially, the hotter the day, the greater your chances of seeing these arboreal vertical clingers and leapers hugging a tree.

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