Madagascar is an island like no other. Almost 90% of its native plant and animal species live nowhere else in the world – a truly staggering statistic. Although it is considered part of the African continent, Madagascar feels like an entirely different world from the mainland. There are no large herds of grazers there, nor any big cats or dogs. Instead, evolution has produced a highly imaginative collection of strange and exotic-looking animals. Primates that behave like woodpeckers. Geckos that scream like banshees. Chameleons the size of insects.
Roughly the size of France, Madagascar is the fourth largest island in the world. It’s also the oldest island, having split from the ancient supercontinent of Gondwana around 165 million years ago. At the time, it was still connected to what would later become the Indian subcontinent, but the two diverged around 80 million years later. The inhabitants of this great landmass had it all to themselves and they evolved in relative isolation.
For this reason, although the plants and animals of Madagascar often look vaguely familiar – they resemble monkeys, hedgehogs and civets, for example – they are actually completely different creatures: lemurs, tenrecs and fossas. Evolution on Madagascar has simply come up with similar, but subtly different, solutions to the same problems encountered elsewhere in the world.
Land of the Lemurs
Of all the weird and wacky animals found on Madagascar, it is undoubtedly the lemurs that have become the star of the island, accounting for more than a third of the unique mammal species that live there. Contrary to popular belief, lemurs are not monkeys. They are more primitive primates called prosimians, which comes from the Greek words pro, ‘before’, and simian, ‘ape’.
When the first primates were evolving, around 55 million years ago, Madagascar had already long split away from what is now mainland Africa. A few of the lemur’s ancestors managed to reach the island sometime afterwards, probably by floating on large rafts of vegetation or storm wreckage from the continent. Genetic studies tell us that all modern lemurs stem from that single event. They found what must have been an idyllic prosimian paradise: few mammalian predators and a range of vacant ecological niches to exploit. They were pioneers in this strange land, and it wasn’t long before they spread out to colonise Madagascar’s many different habitats.
On the mainland, more highly developed creatures evolved. These included the bigger-brained monkeys. The prosiminians were unable to compete successfully for food and territories against these more advanced primates. As a result, most of the lemurs’ prosimian relatives on the mainland died out, with only a few managing to survive as small, nocturnal, unobtrusive creatures such as bushbabies and lorises that found protection in thick forests.
But on Madagascar itself, the lemurs were safe. Monkeys never reached the island, and so lemurs continued to proliferate and evolve into a huge variety of forms. Today, we know of at least 110 living species, many of which have only been discovered in the past 20 years or so.
Lord of the Rings
The most well-known species of lemur is undoubtedly the ring-tailed lemur, which lives mainly in the dry forests in the south of the island. Its raccoon-like bandit mask and long, banded black-and-white tail are instantly recognisable to most, for it frequently appears in zoos, nature documentaries, and, more recently, in animated films. However, it is not your typical lemur. Whereas most of its cousins are strict vegetarians, with some of them feeding on very specific plants (bamboo lemurs, for example, eat almost exclusively bamboo), the ring-tailed lemur eats a wide variety of things, including leaves, fruits, insects, spiders and even small vertebrates such as birds and lizards. It is also the most active by day, which makes it relatively easy to observe.
A highly social species, the ring-tailed lemur lives in mixed-sex groups of between six and 30 individuals. Although most lemurs spend much of their time in the trees, the ring-tailed lemur is primarily a ground-dweller. Whole troops of them can often be seen walking along in single file, their tails held like giant question marks above them so that other members of the troop can easily see them in the brush. As with most lemurs, it’s actually the females that are in charge of these troops, and although both males and females have separate hierarchies within a group, all females enjoy dominance over the males – even the lowliest female outranks the most senior male.
Ring-tailed lemurs use scent to convey strategic messages about territory, social rank, and sexual availability. Olfactory communication is far more developed in lemurs than among monkeys and apes, and especially so in this particular species. Both sexes mark their territory with genital scent glands, sometimes even performing handstands to apply their scent higher up on trees and other vegetation. Males also have additional glands on their chests and wrists, the latter of which open through horny spurs. But whereas all lemurs are sensitive to smell and use it socially, ring-tails do so in a spectacular fashion: they fight with it.
During the breeding season, a male will draw his tail several times between his wrist glands so that it becomes anointed with his scent. Then he will face a rival male on all fours and thrash his tail over his back so that the smell is fanned forwards, washing waves of perfume over his opponent. Usually, one of the males finds his rival’s scent so impressive that he retreats (although it should be noted that this smell does not register in human nostrils). Physical violence between males is therefore rare, although the females within a troop can fight so violently with one another that serious injury and expulsion is common.
There is surely no better place in the world to look for evolutionary oddities than Madagascar, and over the coming month, we’ll be looking at just a few of the strange and wonderful creatures that call this huge island home. Next time, we’ll be going from the most terrestrial lemur to the most arboreal (not to mention the largest): the indri.