Lemurs and Madagascar

Madagascar is a 600.000-km2 island positioned in the tropics of the Southern Hemisphere, about 350 km west of Mozambique. This island has been isolated from other landmasses for 160 million years (Tattersall, 1982) and contains some of the richest biodiversity in the world. Among the numerous endemic plants and animals there exists a group of our relatives. A group of primates known as Lemuroidea Gray, 1873, or lemurs, lives exclusively on Madagascar and on a small group of islands close by. They were the only primates to be found on the Madagascar until the arrival of man approximately 2000 years ago.

Relatively few mammals live on this island and the lemurs comprise a large part of its mammalian biota, which mean they play an important role in the island’s ecosystem. Madagascar lacks so many mammals due to its isolation before mammals became common (Mittermeier et. al., 1994) Indeed as there certainly where no primates a 160 million years ago, lemurs must have come to Madagascar later, presumably by crossing the Mozambique channel on a clump of floating vegetation (Mittermeier et al., 1994). Since then an enormous radiation has taken place. Possibly the fact that there was no competition from other primates was an important factor in this adaptive radiation. Even so, a considerable amount of time would have been needed for the amount of variation seen presently in lemurs to have evolved. It has been calculated that the lemurs must have lived on Madagascar for at least 25 to 30 million years (Petter et al., 1977).

Many lemur taxa have gone extinct over the past 2000 years, i.e. since man arrived on Madagascar. The 15 or so taxa that went extinct all were large, presumably slow moving animals, leaving little doubt over the reason for their extinction (Mittermeier et al., 1994). Today’s living lemurs face threats other than hunting. Although hunting and live capture do occur, and sometimes pose a threat to local populations, these are of small importance compared to the massive destruction of habitat. The destruction of forest on Madagascar is severe and continues for three main reasons. The most dangerous threat is the slash and burn agriculture locally called "tavy." A piece of forest is burned to provide the soil with nutrients for growing crops. The soil loses its nutrients in a couple of seasons, and the farmer moves on to a new patch, leaving the ground barren and depleted of nutrients. Because Madagascar lacks fast-growing trees, it takes long-time before vegetation is re-established (Mittermeier et al., 1994). In the meanwhile even more nutrients and soil are lost due to erosion. The second threat to the forest is fire, deliberately started to promote new grass growth for cattle. The last threat is timber, firewood and charcoal production. All of these leave the ground barren and vulnerable to erosion. The population of Madagascar is still growing, so the pressure on forests will only increase. This poses a threat not only to lemur species, but to all of the unique flora and fauna found on this island.

Madagascar has a long history in nature protection, with the first law against cutting down trees dating from 1881, and the first nature reserve created 1927. Today, Madagascar has 267 forest reserves, covering over 1,000,000 ha. (Mittermeier et al., 1994). Yet the rest of the forest is being destroyed at rapid speed. More protection will be needed if future generations will be able to enjoy lemurs and other Malagasy wildlife. To cover all of the different vegetation types of Madagascar, the protected area should be increased to 4,000,000 ha (Mittermeier et al., 1994). To protect the rare lemur species special protection measures for these species must be taken. Some species may need captive breeding in order to be saved from extinction (Mittermeier et al., 1994). Regardless, it is important to realize that all protection is going to fail unless enough research is done to know and understand these creatures. It is also impossible to protect lemurs without the co-operation of the local people. Even when the local people are aware of the importance of the flora and fauna in Madagascar, their economic situation forces them to use the land destructively. Protection of nature should not be at the expense of local people and culture. It might be possible to make people world-wide more aware of lemurs and their precarious position. Lemurs could be a flagspecies for attracting ecotourists to Madagascar, providing a source of income for the local people with a minimum amount of damage to the environment. This would have the added benefit of giving the Malagasy people a reason for protecting their environment.

The Malagasy lemurs belong to the order Primates Linnaeus, 1758, the group of eutherian mammals to which humans belong as well. Primates are mostly arboreal creatures, with relatively large brains and grasping hands. Within the primate order lemurs are grouped together with the Lorisiformes, their close African relative, in the suborder Strepsirhini Geoffroy, 1812, formerly called Prosimians. This name, which translates as pre-monkeys, was given because the Strepsirhini are a more "primitive" form of primates (Rowe, 1996). The ancestral primate probably was a small nocturnal animal, relying more on its sense of smell than on its vision, not unlike some present day lemurs. The taxonomy of the lemur groups (e.g. whether the lemur superfamily comprises four, five or even more families, is a much debated subject (for example, see Yoder, 1994)). Even the placement of the lemurs within the primates causes debate. Malagasy lemurs are generally considered to be a monophyletic group, but sometimes the Cheirogaleidae Gray, 1873 are grouped together with the African Lorisiformes because of the similarities in morphology (see Yoder, 1997). DNA data (e.g. Yoder, 1997) suggests the Cheirogaleidae do fall within the other Malagasy lemurs, which is the classification used below.

In 1999, the IUCN reported 34 lemur species on the island, some of which are divided in subspecies, giving rise to 56 discernible taxa. These 34 species were divided into five families:

1-The family Cheirogaleidae Gray, 1873 (9 species, 5 genera, 2 subfamilies), the dwarf and mouse lemurs, are small nocturnal animals. They are the most abundant group of primates on Madagascar (Garbutt, 1999), and probably are the most similar to the ancestral lemur that first arrived on this island, it being small enough to make the journey from Mozambique on floating vegetation (Petter et al., 1977). This family is divided in two subfamilies: the Phanerinae Rumpler, 1974 and the Cheirogaleinae Gregory, 1915. The latter contains the world’s smallest living primate: Microcebus myoxinus Peters, 1852, or pygmy mouse lemur.

2-The family Lemuridae Gray, 1821 (10 species, 3 subfamilies, 4 genera) used to contain all lemurs that could not be placed in any of the other families. At present the genus Lepilemur Geoffroy, 1851 has been placed in its own family in an attempt to create structure within this family, Lepilemuridae Rumpler, 1972. In the Lemuridae family is the nominate species of the whole infraorder: Lemur catta Linnaeus, 1758, or ring-tailed lemur. Originally L. catta grouped in the genus Lemur Linnaeus, 1758 with all the species now called Eulemur Simons and Rumpler, 1988. Simons and Rumpler (1988) however found it to have had more in common with the genus Hapalemur Geoffroy, 1851. This posed a problem for the large genus formerly known as Lemur. With the nominate species gone this group has been given a new name, the genus Eulemur Simons and Rumpler, 1988. Petter and van der Sloot suggest dividing the family Lemuridae in three subfamilies to emphasize that Lemur catta has more in common with the genus Hapalemur than with Eulemur and that Varecia is distinctly different from both of them. Three subfamilies are then be recognized within the Lemuridae: The Eulemurinae nov., containing only the genus Eulemur, the Lemurinae Gray, 1821, containing the genus Hapalemur and the genus Lemur, and the Varecinae Gray, 1863 containing only the species Varecia variegata Kerr, 1792.

3-The family Lepilemuridae Rumpler, 1972, (8 species, 1 genus) or sportive lemurs, is sometimes called Megaladapidae, (e.g. Garbutt, 1999) after an extinct member of this family, which was supposedly as big as a gorilla (Petter et al., 1977). The living nocturnal Lepilemuridae are not as big, being about 1 kg. Lepilemur Geoffroy, 1851 is the only genus in this family.

4-The family Indriidae Burnett, 1828 (6 species, 3 genera) contains three genera, two of which are large and diurnal, Indri Geoffroy, 1796 and Propithecus Bennet, 1832. They are the largest living lemurs, with bodyweights sometimes exceeding 7 kg. The third genus is the smaller nocturnal Avahi Jourdan, 1834. All of these have long legs compared to the rest of their body and can make spectacular leaps, up to 10 meter, from tree to tree (Mittermeier et al., 1994).

5-The family Daubentoniidae Gray, 1863 has only one living representative, Daubentonia madagascariensis (Gmelin, 1788), the aye-aye. It is a nocturnal animal, with black coloring, large ears and long slender digits, the third of which one is especially elongated and used to dig out food from small, hard to reach places (e.g. larvae within trees or the inside of coconuts). Its frightful appearance and its habit of raiding crops mean that the aye-aye is frequently killed by local people, who consider it bad luck (Garbutt, 1999).

Bas Reuvers, (Scriptie by ZMA, 1999)