Lemurs are our very distant relatives although you would have to climb a very long way up our family trees before you found our last shared ancestor perhaps about 65 million years ago. That is when the Haplorhini and the Strepsirrhini went their separate ways. You and I, the monkeys and the apes are haplorhine.
Not too long after that the ancestors of today’s Lemurs made their split with the ancestors of the other Strepsirrhini, the Lorises and Galagos, by the not so simple means of migrating to Madagascar. That was somewhere in the vicinity of 60 million years ago. Madagascar was already an island having split from Africa about 100 million years prior and from India about 30 million years prior. (There is, incidentally, a nice animation of the breakup of Gondwana <HERE> . You can drag the pointer through time and take in the break up at your own pace).
Nowadays such a journey would mean swimming, against the current, at least 560 km from Mozambique. 60 million years ago Africa and Madagascar were just as far apart but further south and ocean currents were likely to have been more favourable to animals washed out to sea on a raft of floating vegetation. Representatives of only five orders of terrestrial mammals established populations in Madagascar so it can’t have been too easy. It is considered most likely that the arrival of just one raft load gave rise to all the various lemurs.
The taxonomy is, of course, in a state of utter chaos. In 1994 there were 33 species, by 2008 there were about 100. DNA analysis is finding splits especially in the nocturnal species where the outward appearance is fairly uniform. I filched the version below from Wikipedia and modified it slightly …
The extant Lemurs comprise five families (and there are three extinct families)
- Family:Daubentoniidae: aye-aye
- Genus: Daubentonia (1 extant species, 1 extinct species)
- Genus: Allocebus: hairy-eared dwarf lemur (1 extant species)
- Genus: Cheirogaleus: dwarf lemurs (6 extant species)
- Genus: Microcebus: mouse lemurs (21 extant species)
- Genus: Mirza: giant mouse lemurs (2 extant species)
- Genus: Phaner: fork-marked lemurs (4 extant species)
- Genus: Avahi: woolly lemurs (9 extant species)
- Genus: Indri: indri (1 extant species)
- Genus: Propithecus: sifakas (9 extant species)
- Family: Lemuridae
- Genus: Eulemur: true lemurs (12 extant species)
- Genus: Hapalemur: bamboo lemurs (5 extant species, 3 extant subspecies)
- Genus: Lemur: ring-tailed lemur (1 extant species)
- Genus: †Pachylemur (2 extinct species)
- Genus: Prolemur: greater bamboo lemur (1 extant species)
- Genus: Varecia: ruffed lemurs (2 extant species, 3 extant subspecies)
- Family:Lepilemuridae: sportive lemurs
- Genus: Lepilemur (26 extant species)
I was lucky enough to see and photograph at least one representative of every family except the Daubentoniidae … the Aye-aye is very hard to find in the wild.
Family: Cheirogaleidae represented by a Mouse Lemur
Family: Indriidae represented by the Indri
Family: Lemuridae represented by the Common Brown Lemur
Family: Lepilemuridae represented by the White-footed Sportive Lemur
Lemurs have a low basal metabolic rate, as much as 20% below the values predicted for mammals of similar body mass. This may have been a trait that enabled the founding population to survive their time on the raft. It may also be as much as they can manage on their fairly energy poor diet, the larger lemurs mainly subsist on leaves, the smaller ones mainly on fruit. Various behaviours such as huddling and opening themselves to the morning sun serve to increase their body temperature …
Nonetheless they are extremely agile and athletic. When Sifakas cross open ground they do so by bounding on their hind legs and are likely to finish the journey by bounding well up the trunk of the tree they are heading for.
And if the trees are close together why not fly?
An Australian is inclined to compare a lemur with the Koala, similarly arboreal, similar diet but one a gymnast and the other a couch potato. Why? The quick answer is the Fosa (pronounced Foossa – long O soft S). This is Madagascar’s largest carnivore, it is somewhat catlike but with a longer body. It will climb trees and it does take lemurs. Thus they need the agility to evade predation.
There is a major flaw in this argument. The DNA studies show that the Aye-aye split from the other lemurs early after colonisation. The radiation that brought about the diverse forms seen today occurred between 42 million years ago and 30 million years ago. Madagascar was without mammalian predators until about 20 million years ago. The Fosa may have sharpened their skills but the skill set existed for more than 10 million years before the Fosa arrived.