Primitive Primates

Prosimians are “primitive” primates that once ranged the world over—at least in the tropical rain forests—until monkeys and apes came along and out-competed them. Now most prosimians, in the form of lemurs, live on Madagascar. Scientists tell us that the this huge island off the southeastern coast of Africa once had no primates at all. Then a few species of lemurs got there somehow, probably by riding floating mats of vegetation that had drifted from the mainland. No monkeys ever made that journey, and after lemurs went extinct everywhere else they still thrived on Madagascar, where they evolved into more than 100 species to fill various environmental niches around the island.

Over 90 species of lemurs still exist, but many are listed as Critically Endangered, Endangered or Threatened, and all are gravely imperiled due to the near-total and ongoing destruction of their rainforest habitat. In fact, about 90 percent of Madagascar’s rainforest has been cut down for timber and to burn in order to make charcoal.

Existing species range in size from the tiny 1-ounce (30 gram) Madame Barthe’s mouse lemur (Microcebus berthae) to the 22-pound (10kg) indri (Indri indri). The greater bamboo lemur currently is the most critically endangered of all the lemur species, with only around 100 left in the wild. (See a video of the greater bamboo lemur.)

Some truly huge lemur species—some the size of gorillas—used to roam the island, but these began to go extinct after the first human settlers arrived about 2,000 years ago.

Most lemurs live in social groups that are dominated by females. Most live in the rainforest canopy and travel by springing from tree to tree, propelled by their powerful hind legs. Their diet consists mostly of fruits, flowers and leaves, although some species also eat insects, spiders and small vertebrates. Larger lemur species tend to be active during the day, while smaller lemurs generally prefer to feed and move about after dark. All lemurs are known for their large, light-gathering eyes.

While all lemurs are prosimians, all prosimians are not lemurs. And while very few prosimians have survived outside of Madagascar, a handful of species still exist in the rainforests of Asia and mainland Africa. Perhaps the most well-known non-lemur prosimians are the African bush babies, or galagos. There are around 20 species of these small, large-eyed nocturnal animals, which apparently get their name by the cries they make at night. The eat insects and tree gum, and are known for their leaping ability.

Male and female bush babies generally live separately, with groups of females living together and defending a territory against other females, and males living a solitary life in a territory that overlaps that of one or more female groups. Males without territories to defend may form groups of their own.

Indonesia and the Philippines are home to about 9 species of prosimians known as tarsiers. This is another group of small, big-eyed—in this case, huge eyed—nocturnal primates. Interestingly, science tells us that tarsiers are genetically closer to monkeys and apes than are the other prosimians, including lemurs. This indicates that tarsiers split from their common ancestor with the monkeys only after the other prosimians had already done so.