Lemurs, cousins of monkeys, are unique and fascinating mammals found only on the islands of Madagascar and nearby Comoro. There are eight lemur families with 15 genera and 103 + existing species and subspecies as of 2012. They belong to the order Primates, to which man is also a member. Primates are mostly unspecialized tree dwelling mammals with five digits (fingers) with nails instead of claws. Primate eyes are set near the front of the head providing judgment of distances and stereoscopic vision. Aside from man, most primates inhabit tropical or subtropical regions.
To better understand the present variable lemur mammal complex in Madagascar, one needs to understand the natural conditions that were in play over millions of years. This large island is between the size of Texas and California and is about 400 kilometers (about 250 miles) from east Africa, the closest continent. Along the west side of Madagascar runs a steep escarpment which contains most of the island’s remaining tropical lowland forest. To the west of this ridge lies a plateau. In the center of the island are mountain ranges in altitudes from 750 to 1,500 m (2,460 to 4,920 ft) above sea level. To the west of the highlands, the increasingly arid terrain gradually slopes down to the Mozambique Channel and mangrove swamps along the coast. The east coast receives heavy rainfall November through April while a cooler dry season occurs the rest of the year. The central highlands are even drier and cooler while the west and southwest approach even a semi-arid climate. The island thus offers rich geographical and ecological habitat diversity in which fauna and flora have thrived in relative isolation during the past 88 million years when scientists say the island separated from the India continent during the late Cretaceous period. As a result of this long isolation from neighboring continents, numerous plants and animals underwent natural selective processes and are found nowhere else on earth. In fact, up to 90% of all flora and fauna on Madagascar are endemic or unique to the island. The prolonged effect of isolation and natural selection on lemurs thus has resulted in a confounding array of multi-colored and morphologically and behaviorally diverse and yet sometimes somewhat similar qualities that continue to challenge scientists. Zoological taxonomists thrive in study of obvious and the subtle anatomical and behavioral qualities of fauna as they seek to differentiate and show relationships among closely similar characteristics in applying nomenclatoral criteria. Indeed, the fauna (and flora) of Madagascar offer a mecca, even a paradise, for scientific study on many different levels.
Lemurs are the most numerous of Madagascar primates and belong to the families of Lemuridae, Daubentonidae, and Indriidae. They communicate more with scents and vocalizations than with visual signals. Lemurs have a low basal metabolic rate and may exhibit dormancy such as torpor and hibernation. They have seasonal breeding and social dominance by females. Most are herbivores and eat different kinds of fruits and leaves, some are specialists. Due to dietary differences, several species of lemurs may coexist in the same forest without directly outcompeting each other. Lemurs vary in size from mouse-like to over four feet in length, much like a big dog. All (except the Indri) have long bushy tail with pointed faces, nostrils near the tip of the snout. Lower front teeth point forward and form a comb. The outer pair are cheek teeth and the lower tusks really cheek tooth with two roots.
Lemurs may be divided into four groups:* However, much additional taxonomic research work has been performed during and since the 1990’s resulting in controversial classifications depending on which species concept is utilized.
The Aye-Aye is one of the most peculiar and unique of the lemurs. About the size of cats, they have huge bushy tails. Ears are very large and naked. Teeth are so peculiar they were once thought to be rodents, as they have no canine teeth and ever growing four upper and three lowers. Fingers and toes are unusual. They inhabit dense forests and eat insects, eggs, small animals and the pulp and juices of some fruits and plants. Only one young is born at a time.
Small Woolly Lemurs
These lemurs have elongated ankle joints giving the hind legs a four-jointed appearance, finger and toe pads and large eyes. They are all nocturnal and are of very small size. The Lesser Mouse-Lemur is less than four inches long and has a tail of similar length. These live in tall damp forests, open scrub land and even in open reed beds. Curiously, some spend part of the year in an inactive/comatose condition during the hot dry season after storing masses of fat at their tail base and hind legs, while some are active throughout the year. Diets are mostly insects, but they also eat honey and plant saps. Some jump (leap) rather than run. Two young are born at a time.
Large Woolly Lemurs
These lemurs are bulky, agile mammals that move about in large family units or tribes, night and day.
Some eat only leaves and have no upper front teeth. Within this group is great diversity and variety. Some are adapted to marshes, some are arboreal and feed off the tops of forest trees, some sun themselves in the morning, some make nests, some are ground-living and sit on their haunches to eat, holding food in their hands and biting with their back teeth. The Brown Lemur is bewildering as no two are exactly alike. The Mongoose Lemurs vary in a hopeless style. The Red-bellied Lemur is the smallest species and is wholly diurnal and looks like some of the other species. Species differences cause monumental quandries to researchers and others who study them.
These lemurs have short broad muzzles and widely separated eyes, with naked faces. Their movements are more deliberate and slower and precise. Their legs are unusually long and they walk or hop like kangaroos. The big toe is enormous and diverges at more than a right angle from the other toes which are held together with webbing. Silky Lemurs are large animals most with silky coats. Some are diurnal, some nocturnal. They are purely vegetarians and bear only a single young at a time. The Indri is the oddest of all lemurs, having no tail. These have slender hind limbs and enormous hands and feet. They are large, some measuring over two feet in length and often vary from one another in coloration, but the face is usually dark with a lighter topknot and throat collar.
At least 17 lemur species have already gone extinct due to human activity and habitat loss. A number of Lemur species are presently considered endangered. Because of threats from illegal logging, economic privation, and political instability, the International Union for Conservation of Nature (IUCN) considers lemurs to be the world’s most endangered mammals, noting that as of 2013 up to 90% of all lemur species confront possible extinction in the next 20 to 25 years.
Quinn, A. and D. E. Wilson. 2002. Indri indri. Mammalian Species, No. 294, 5 p.
*Sanderson, I. T. 1961. Living Mammals of the World. Doubleday, Garden City, NY., 303 p.
Photo of Lepilemur sp. By Desire Randrianarisata, J. Mammal., vol. 85, no. 3, June 2004.