The fat-tailed dwarf lemur is the only primate in the world known to hibernate for an extended period of time.* Hibernation can last up to seven months and is defined by periods of torpor (severely decreased metabolism, heart rate, and body temperature) interspersed with metabolically active periods of rewarming called interbout arousals (see Faherty et al. 2016). Interbout arousals tend to occur every 6-12 days during hibernation.
During torpor, a fat-tailed dwarf lemur’s heart rate drops from about 180 beats per minute to as low as four beats per minute, and its breathing rate slows to just one breath every 10-15 minutes. Its body temperature drops, too, and becomes driven by the ambient temperature of the environment.
During an interbout arousal, a dwarf lemur’s body temperature rises, its heart rate increases, its breathing becomes more regular, and its brain shows massive bouts of REM sleep. Afterward, the animal drops back into torpor.
Before hibernating, dwarf lemurs begin accumulating fat in their tails by gorging on food during the wet season (when fruits and flowers are more abundant) in preparation for the dry season when these foods are more scarce. During their period of gorging, dwarf lemurs’ tails can reach up to 40% of the lemurs’ total body weight. They then enter a state of hibernation, living off of the fat stored in their tails.
*Mouse lemurs are also capable of torpor, but torpor bouts in these animals are typically shorter than 24 hours (Faherty et al. 2016).
Typically solitary foragers, dwarf lemurs have a diverse diet consisting mostly of fruit and flower nectar. While they are thought to be less carnivorous than mouse lemurs, they too eat insects and small vertebrates.
In preparation for torpor, a fat-tailed dwarf lemur can increase its body weight by 75g (about 40%) at a time. It effectively gorges during times of food abundance, to prepare for Madagascar’s dry season when its diet of fruits and flowers is scarce. In the winter months, most dwarf lemurs enter a state of hibernation. During torpor, dwarf lemurs experience a slow-down in their metabolic rates and show a marked decrease in activity and appetite which may last for up to seven months. During this period, these lemurs live off of fat stored in their tails.
Hibernation begins as early as March in Madagascar, when the dwarf lemurs retreat to shelters such as those offered by hollow tree trunks. They sometimes do not emerge until the beginning of the wet, hot season in November. Up to five animals may be found huddled together during this period.
To prevent obesity in our captive dwarf and mouse lemurs during their torpor period, the DLC has established a “winter diet” and a “summer diet.” The winter diet is initiated in early to mid-September, with a gradual decrease in rations fed to the animals. Starting in mid-March the diet is then increased gradually, reaching the full summer diet amount during the breeding season. Without the reduced rations of the winter months, the dwarf lemurs would continue to consume any and all food provided, which, coupled with a greatly reduced rate of metabolism, could result in extreme obesity!
Have you ever wondered how hibernation works? Or if humans could actually hibernate in real life? Check out this informative and adorably illustrated video by Sheena Faherty, one of DLC Director Anne Yoder’s former graduate students. While pursuing her Ph.D. here at Duke, Sheena studied the only primates capable of hibernation behavior: the fat-tailed dwarf lemurs of Madagascar!
To watch, click the image above or click HERE. Then, if you'd like to learn even more about these amazing hibernating primates, check out the talk Sheena gave at the DLC’s 50th-anniversary scientific symposium: “Gene expression and physiological extremes in primate hibernation”. You can also symbolically adopt Raven, a fat-tailed dwarf lemur, through the DLC’s Adopt a Lemur program. Adopting Raven is a wonderful way to not only learn about this amazing species, but also to support Raven's care here at the DLC.
The strong seasonality of breeding found in mouse and dwarf lemurs depends upon a variable “photoperiod,” or day length.
Dwarf and mouse lemurs breed at the DLC from mid-April through July. Gestation is 58-62 days. Both species commonly have litters of two or more offspring.
All captive dwarf lemurs are provided with a wide variety of nestboxes, ranging from PVC tubes of varying sizes, to wooden boxes, to suspended enrichment boxes, all suitable for sleeping and raising young. Mothers give birth in the nestboxes and generally will keep their infants hidden inside these shelters. If they need to move their offspring, they do so by carrying them in their mouths. Mouse and dwarf lemur offspring of up to three weeks of age are transported by the mother in this fashion, but by the time the infants are two months old they are behaving much like adults and are capable of independent locomotion.
On average, mouse and dwarf lemurs reach sexual maturity at one year of age, although females generally are not capable of giving birth until they are 18 months of age. In the wild, juvenile dwarf lemurs tend to enter their first period of dormancy later than adults, perhaps providing the youngsters with a period of reduced feeding competition in which to put on additional pre-torpor weight.
Dwarf lemurs forage in solitude at night. During the day they congregate, in packs of up to five to a tree hole, while they sleep. The composition of these sleeping groups changes seasonally, and often animals do choose to sleep alone.
Sleeping sites generally consist of hollow trees, whose cavities have been cushioned with leaves. Otherwise, they are spherical nests made of dead leaves concealed in heavy undergrowth.
Click HERE to see dwarf lemurs nesting in a tree hole in Tsihomanaomby, a subhumid forest in northern Madagascar.
Females generally occupy “home ranges” in central areas of a group’s range, while a single male may overlap his home range with those of several females. Female prosimians, in general, are considered dominant to males.
The species of dwarf lemur found at the DLC, Cheirogaleus medius, is native to the dry deciduous forests of western and southern Madagascar. These small lemurs can live in primary forests, established secondary forests as well as the gallery forest of the southern spiny desert.
Dwarf lemurs may be responsible for pollinating some species of baobab trees. In addition, they play an important role in the ecology of the tropical forest by aiding in the dispersal of small seeds. As a part of their normal scent marking routine, dwarf lemurs often smear feces onto branches as they walk along well-traveled arboreal pathways through the forest, thereby providing a perfect microclimate for the germination of parasitic plants common in the forest.
When only two species of dwarf lemurs were recognized -- one throughout the eastern forests, one in the western forests -- both were considered widespread and thus not highly endangered. However now that the genus has been reclassified into several species with more limited distribution, the conservation status of each species needs to be re-evaluated. Their small size, nocturnality, and ability to live in secondary forests may provide them with more protection; but, as with all lemurs of Madagascar, habitat destruction increasingly threatens their survival. Primary threats to dwarf lemurs' habitat include slash-and-burn agriculture, charcoal production, and brushfires.
Duke currently houses 19 fat-tailed dwarf lemurs with 11 males and 8 females. The Lemur Center has seen success recently with singeltons, twins, and triplets born to two different mothers over the last three years.
Order: Primates; Suborder: Prosimii
Previously, only two species of dwarf lemurs were recognized: the greater dwarf lemur (Cheirogaleus major) native to the eastern forests and the fat-tailed dwarf lemur (Cheirogaleus medius) in the west. Now a total of seven species are recognized, based on differences in body size, ear characteristics, tail length, skull shape, dentition and pelage.
Adult size: 0.4 – 0.6 pounds
Social life: solitary forager, strictly nocturnal, sleeps in groups of up to 5 individuals
Habitat: western dry deciduous forests
Diet: fruit, flowers (nectar), and occasional insects and small vertebrates
Lifespan: over 20 years in captivity
Sexual maturity: 1.5 years
Mating: extremely seasonal
Gestation: 61 – 64 days
Number of offspring : one to four infants per litter, one litter each year
DLC naming theme : birds (Woodcock, Waxwing, Hummingbird, etc.)
Malagasy name : Matavirambo, Kely Be-hohy, Tsidihy
Fat-tailed dwarf lemurs survive long periods of food shortage by storing fat in their tails!