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Evo­lu­tion


A Col­lec­tion of News by Moos

201314Dec09:36

First evi­dence of pri­mates reg­u­larly sleep­ing in the same caves

pub­lished 14 Decem­ber 2013 | mod­i­fied 03 Novem­ber 2014
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Sci­en­tists have dis­cov­ered that some ring-​tailed lemurs in Mada­gas­car reg­u­larly retire to lime­stone cham­bers for their nightly snoozes, the first evi­dence of the con­sis­tent, daily use of the same caves and crevices for sleep­ing among the world’s wild primates.

Lemur cattaThe ring-​tailed lemurs may be opt­ing to sleep in caves for sev­eral rea­sons, said Uni­ver­sity of Col­orado Boul­der anthro­pol­ogy Asso­ciate Pro­fes­sor Michelle Sauther, who led the study. While the cave-​sleeping behav­iour is likely impor­tant because it pro­vides safety from poten­tial preda­tors, it also can pro­vide the pri­mates with access to water and nutri­ents, help to reg­u­late their body tem­per­a­tures dur­ing cold or hot weather and pro­vide refuge from encroach­ing human activ­i­ties like defor­esta­tion, she said.

“The remark­able thing about our study was that over a six-​year period, the same troops of ring-​tailed lemurs used the same sleep­ing caves on a reg­u­lar, daily basis,” she said. “What we are see­ing is a con­sis­tent, habit­ual use of caves as sleep­ing sites by these pri­mates, a won­der­ful behav­ioural adap­ta­tion we had not known about before.” The study results are pub­lished in the Novem­ber issue of the jour­nal Mada­gas­car Con­ser­va­tion and Devel­op­ment.

We think cave-​sleeping is some­thing ring-​tailed lemurs have been doing for a long time. The behav­iour may be char­ac­ter­is­tic of a deep pri­mate her­itage that goes back mil­lions of years.
Michelle Sauther, anthro­pol­ogy Asso­ciate Pro­fes­sor, Uni­ver­sity of Col­orado Boulder »

Although sleep­ing in caves by ring-​tailed lemurs – which are found only in Mada­gas­car – has likely been going on for mil­len­nia, it is only now being recog­nised as a reg­u­lar behav­iour, said Sauther. The endan­gered Fusui lan­gurs, slen­der, long-​tailed Asian mon­keys roughly 2 feet tall, also have been doc­u­mented sleep­ing in caves but as a direct result of extreme defor­esta­tion, mov­ing from cave to cave every few days. There also have been iso­lated reports of South African baboons sleep­ing in caves.

Ring-​tailed lemurs (Lemur catta) are eas­ily iden­ti­fied by their char­ac­ter­is­tic, black and white ringed tails, which can be twice as long as their bod­ies. They weigh roughly 5 pounds with a head-​body length of up to 18 inches and are highly social, con­gre­gat­ing in groups of up to 30 indi­vid­u­als. Sport­ing fox-​like snouts and slen­der frames, they are unusual among lemurs, spend­ing a con­sid­er­able amount of time on the ground feed­ing on leaves and fruit and social­iz­ing, said Sauther.

In “gallery forests” near rivers, ring-​tailed lemurs reg­u­larly sleep high in the canopies of tall trees. But in “spiny forests,” most of the trees with woody stems are cov­ered in rows of spines, mak­ing them uncom­fort­able as well as dan­ger­ous sleep­ing sites because preda­tors can eas­ily climb them, Sauther said. The new study doc­u­ments their cave sleep­ing behav­iour in the dry spiny for­est habi­tat adja­cent to lime­stone cliffs.

The lemur obser­va­tions were made at the 104,000-acre Tsi­manam­pe­sotse National Park and the Tsin­jo­ri­ake Pro­tected Area in south­west­ern Mada­gas­car between 2006 and this year. The research team used field obser­va­tions and motion-​detector cam­era traps to chart the behav­iour and move­ments of 11 dif­fer­ent troops of ring-​tailed lemurs.

One of the early clues to the cave sleep­ing by the lemurs was their pres­ence on lime­stone cliffs adja­cent to spiny for­est trees or on the ground when Sauther’s research team arrived at the study sites early in the morn­ing. “They seemed to come out of nowhere, and it was not from the trees,” she said. “We were baf­fled. But when we began arriv­ing at the study sites ear­lier and ear­lier in the morn­ings, we observed them climb­ing out of the lime­stone caves.”

Watch the lemurs enter­ing the caves for their nightly nap:

The pri­mary preda­tor of the lemurs is a cat-​like, car­niv­o­rous mam­mal called a fossa native only to Mada­gas­car that is closely related to the mon­goose and may weigh up to 20 pounds. Fos­sil evi­dence shows a cougar-​sized rel­a­tive of the fossa that only became extinct sev­eral thou­sand years ago likely preyed on lemurs as well, she said.

There is evi­dence that some early ances­tors of humans in South Africa may have used caves to pro­tect them­selves from preda­tors, said Sauther. The remains of hominids going back sev­eral mil­lion years have been found inside or near lime­stone caves there, and some fos­sil bones have evi­dence of dam­age con­sis­tent with the bite of saber-​toothed cats.

Unfor­tu­nately, habi­tat destruc­tion, includ­ing defor­esta­tion, is increas­ing in many parts of Mada­gas­car. In south­west­ern Mada­gas­car, trees are being har­vested for cat­tle for­age, con­struc­tion mate­ri­als and fire­wood, and the min­ing of lime­stone there – used for the pro­duc­tion of cement, fer­til­izer and other prod­ucts – is increas­ing. Ring-​tailed lemurs are listed as Near Threat­ened by the Inter­na­tional Union for the Con­ser­va­tion Red List of Threat­ened Species.


(Source: Uni­ver­sity of Col­orado Boul­der news release, 04.12.2013)


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