A fat-tailed dwarf lemur (Image courtesy of Kathrin Dausmann)
In the 18th century Carl Linnaeus named them lemurs, after the Latin lemures—spirits of the dead, wandering ghosts. He knew the primates roamed Madagascar’s forests at night, their large eyes brimming with moonlight, their shrill cries crashing through the treetops. One of the smallest lemurs on the island, the fat-tailed dwarf lemur, resembled a phantom in another way: it completely vanished for seven months each year.
For a long time, no one understood where the fat-tailed dwarf lemur went—a remote part of the island? the spirit world?—or what it was doing all that time, but scientists had a hunch. Perhaps the lemur was hibernating. If so, it would be the only primate in the world—and one of the only tropical mammals—to do so. Given Madagascar’s climate, however, it made sense that a lemur might hibernate to survive annual periods of drought.
In general, Madagascar has two seasons: the hot, wet season from November to April, and the cooler, dry season from April through October. The deciduous forests on the west coast, where many fat-tailed dwarf lemurs live, offer no open sources of water during the dry season and only fibrous fruits bereft of sugar. Perhaps, scientists reasoned, the fat-tailed dwarf lemur hunkered down and waited for the rains to return, slowing its metabolism and dropping its body temperature. It could survive off of nutrients stored in its tail, which always grew plumper as the dry season drew closer.
In 1993 Kathrin Dausmann of the University of Hamburg and her colleagues finally put the hibernation hypothesis to the test. Between 1993 and 2003, the researchers regularly traveled to the forest of Kirindy on the west coast of Madagascar, where they captured 53 fat-tailed dwarf lemurs (Cheirogaleus medius). They tagged all the lemurs with radio transmitters to track their location and implanted six of the primates with small temperature sensors.
A fat-tailed dwarf lemur on the west coast of Madagascar (Credit: Frank Vassen, via Wikimedia Commons)