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http://news.nationalgeographic.com/news/2004/06/0623_040623_lemurs.html

Lemur Is First Known Hibernating Primate, Study Says

James Owen in England
for National Geographic News
June 23, 2004

Madagascar, a large, tropical island off the east coast of Africa, isn't the 
kind of place you'd expect to find a mammal that hibernates. Yet researchers 
say a small, nocturnal lemur resorts to the same tactic used by bears, 
squirrels, and dormice to survive cold northern winters—spending at least 
seven months of the year hibernating through harsh times brought on by 
drought.

The German-based team say their study is the only report of prolonged 
hibernation in a tropical mammal. Furthermore, writing in this week's 
scientific journal Nature, they claim the study provides the first proof of 
hibernation in any species of primate.

The small, nocturnal lemur known as the fat-tailed dwarf lemur (above), has 
been revealed as the first known tropical mammal to spend long periods in 
hibernation, a new study says.

The study focused on the fat-tailed dwarf lemur (Cheirogaleus medius), one 
of a group of snout-faced primates for which Madagascar is famous. The 
island boasts some 32 lemur species, the highest percentage of indigenous 
primates anywhere on Earth.

The fat-tail dwarf lemur gorges on fruit, flowers, and insects during a 
short rainy season between December and February. As its body weight 
increases by around 40 percent, the lemur's tail swells massively with 
stored fat reserves. The animal, which usually weighs five ounces (150 
grams), then goes into a torpor, marked by reduced activity and appetite.

Scientists previously noted that this cycle of behavior is most pronounced 
in western Madagascar, where the climate veers between extremes. Here the 
"fat-tail" was found to take to holes in tree trunks during prolonged 
periods of drought, when trees shed their leaves and food becomes scarce.

Led by scientists from Phillips University's animal physiology department in 
Marburg, Germany, the team revealed that the fat-tail's body temperature 
varied to an extent previously unknown in mammals. Daily fluctuations ranged 
almost 20 degrees Celsius (nearly 40 degrees Fahrenheit), with temperatures 
recorded from as low as 9.3 degrees Celsius (48.7 degrees Fahrenheit) to 
well over 30 degrees Celsius (86 degrees Fahrenheit).

Tree Holes

Body temperatures were found to correlate closely with how well each tree 
hole was insulated. The researchers say this suggests the lemurs body 
temperatures are regulated by external conditions, as with lizards and other 
reptiles, instead of being maintained internally.

"They follow changes in environmental temperature as if they were a piece of 
stone," said Gerhard Heldmaier, from Phillips University. This, he says, is 
potentially of great benefit, as it helps fat-tails conserve their fat 
reserves.

For reasons not fully understood, most hibernating mammals usually go 
through periods of arousal, when they bring their body temperatures up to 
normal levels. "This costs them a lot of energy," said Heldmaier. He added 
that the lemurs studied experienced body temperatures as high as 35.9 
degrees C (97 degrees F) and didnt need to go through arousal during 
hibernation.

The researchers say the condition of hibernation should no longer be seen as 
synonymous with low body temperatures, as is presently the case.

They also state: "To our knowledge, our findings are the first physiological 
confirmation of prolonged hibernation by a tropical mammal, as well as the 
first proof of hibernation in a primate."

Heldmaier added, "Hibernation has nothing to do with the cold. What animals 
are coping with is a seasonal scarcity of food."

He is confident that future studies will show that other primates also go 
into hibernation. He nominates the potto—a loris from western and central 
Africa—as an example.

Kirindy Forest

Areas where fat-tailed dwarf lemurs resort to hibernation include the 
25,000-acre (10,000-hectare) Kirindy Forest on the west-central coast of 
Madagascar. The focus of studies by the German Primate Center, based in 
Göttingen, Germany, the forest exhibits pronounced seasonal changes, with 
most of the trees dropping their leaves to conserve water during the long, 
dry season.

Other lemurs in the forest respond in similar ways to the fat-tail, 
according to Peter Kappeler, head of ethology and ecology at the center.

Writing in the American Museum of Natural History magazine, Natural History, 
Kappeler says female gray mouse lemurs may also hibernate for months, 
adding, "Like their fat-tailed cousins, [they] go through their complete 
reproductive cycle between late December and early February."

Meanwhile, Verreaux's sifakas— large, long-legged lemurs that leap high in 
the canopy—cope with the dry season through calorie-saving measures such as 
cutting distances traveled and sunbathing in the morning to bring body 
temperatures up.

Kappeler says the leaf-eating red-tailed sportive lemur also saves energy by 
reducing its activity level and metabolic rate.

He adds, "These primates offer scientists an opportunity to study how a 
group of related mammals respond to a range of environmental conditions—in 
this case, along the entire length of the world's fourth largest island."

However, scientists say they may not have long to make the most of this 
opportunity, because hunting and destruction of forests in this desperately 
poor country are putting the lemur's long-term future in jeopardy.