Fat-Tailed Dwarf Lemur
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Back we go to Madagascar, one of my favourite places in the world, even though I've never been there! I do hope I get my chance of paying this awesome island a visit, some day. This is a Fat-Tailed Dwarf Lemur, Cheirogaleus medius. It reaches a body length of about 20 cm/8" and a tail of about 16 cm/ just over 6", and a weight of 160g/about 6 oz. It is one of the smallest of primates. Just from looking at its face, you can tell it is closely related to the bushbabies and the pottos of Africa, as well as the Lorises of Asia, a group I'll hopefully cover soon. The dwarf lemurs are fairly unspecialized, but unique in some ways: they are the only known primates that truly hibernate!
A Tail full of Food for those Long, Dry Months
Madagascar lies mostly in the tropics; only the high-lying, mountainous interior ever experiences cold weather. The dwarf lemurs don't live there; they inhabit the low-lying forests, this species in particular favouring the drier, thorny forests along the west and south of the island. These forests experience distinct wet and dry seasons. The wet season is the growing season for the trees, and the season in which they make leaves, flowers and fruits. Dwarf lemurs are mainly herbivores, primarily eating fruits and flowers. They do help the trees, assisting in pollinating the flowers. They also eat some insects and other small animals. These are more abundant in the spring and summer too. Over the course of the season of abundance, the dwarf lemurs eat as much as they can and purposely accumulate fat! They store this fat mostly in their tails. (It is the same strategy as employed by camels with their humps.) Then, when the food sources dry up, they retreat to their nest holes, curl up and overwinter in a state of deep torpor. They were the first tropical mammals known to do this; now we also know that some Tenrecs, those other unique Madagascar critters, do it too. The fat of course reduces over the course of the hibernation, and when they emerge from their holes at the start of the wet seasons, their tails are thin and sleek!
But this is so far the only primate species known to hibernate. It is a true hibernation. The little lemur spends the whole time, up to seven months, apparently asleep, though for much of this time it may actually not be sleeping, aware but resting. It stops regulating its body temperature; this therefore goes up and down as the temperature around it does – even though, snuggled up and insulated in its tree nest, this variation is not much. The little lemur may even dream! They've been recorded as going into REM ('rapid eye movement') sleep especially when the temperature goes over 27 degrees Celsius (the temperature of a comfortably warm room). REM sleep, in humans, is when we actively dream, so maybe this is so in the case of this little primate also! What might they be dreaming about?
Another interesting aspect, connected to this hibernation, is the dwarf lemur's lifespan. Smaller primates tend to live shorter lives than larger ones; humans have the longest lifespan of all primates, gorillas and chimpanzees coming close, while small monkeys may only live a few years. Dwarf lemurs, however, can live for thirty years! The long periods of inactivity may mean that they don't run themselves down as fast as other similar-sized monkeys or lemurs, allowing them to last longer.
Dwarf lemurs are active at night. This is one reason why, outwardly, they look similar to bushbabies, pottos and lorises, all of which are also nocturnal. They have a 'general small, primitive primate' look. Nocturnal primates are less visually-focused than ones active by day. Thus, visual signals are less important to them. They have not evolved as many visual differences in outward appearance, as other lemurs and monkeys; what they have, are mostly focused on their faces. Dwarf lemurs, like mouse lemurs, lorises and bushbabies, have large eyes that are dark-rimmed, with contrasting white regions around the dark 'spectacles', and a white line going down the snout. This visual embellishment of their faces, seems to be enough for them, acting as a signal especially for sexual partners when they are close. (Like most nocturnal primates, they are monogamous, couples usually sharing a territory.) The rest of their bodies are covered in short, dense fur, greyish on the back and white on the belly. The soles of their hands and feet are bare, and when their tails are fully plumped up, pink skin may be showing through the fur.
This general 'primitive nocturnal primate' exterior appearance has been a very confusing factor for primatologists trying to uncover primate relationships and diversity. This has been true of bushbabies here in Africa: the many, many species all look very similar. In the case of the bushbabies, their calls have helped us to separate them. Each species has a unique call, and this auditory factor is much more important to the nocturnal bushbabies than their appearance is. Consequently, the way to find 'new species' of bushbabies, even though they look exactly like other bushbabies, has been to record their calls and compare these with those of others.
However, dwarf lemurs don't have such distinct calls. To them, factors like smell might be more important, and that's an area where we are notoriously behind other animals. But we have finally been able to start really distinguishing these nocturnal lemurs, by very careful studies of their morphology, and even their genes. We've found that in them, as in their close relatives the mouse lemurs, there are many species hiding in plain sight. At present, science recognizes seven species of dwarf lemur, all looking quite similar. There are even more species of the smaller mouse lemurs. Among these have counted many of the recent 'new species' discovered by science. We've actually known of these dwarf and mouse lemurs, we just didn't know that there were so many different but similar-looking species of them. While we have difficulty distinguishing them from each other, they can do it quite easily!
This lemur is one of the least threatened species in Madagascar, with a very large range. Still, it cannot be called entirely safe, for so long as humans keep destroying wild habitats on that island. Along with the other proper dwarf lemurs, and the fork-marked dwarf lemurs, the hairy-eared dwarf lemurs, and the mouse lemurs, it is classified in the Cheirogaleidae, the dwarf lemur family. This, like all the other lemur families, is endemic to Madagascar.