Lemurs Lost and Found: New Species Discovered but the Primates Face Extinction

Each new species contributes another piece to the puzzle in understanding how mouse lemurs evolved and spread to different types of habitats on the island.

A group of lemurs at Colchester Zoo, England. Credit: jans canon/Flickr, CC BY 2.0

A group of lemurs at Colchester Zoo, England. Credit: jans canon/Flickr, CC BY 2.0

Of all the animals found in Madagascar, lemurs are the most discernible. Until 25 years ago, there were only two species of mouse lemurs known. These are a kind of lemurs belonging to the genus Microcebus, which translates to ‘small monkey’. The recent discovery of three new species of mouse lemurs, described in a study published in the journal Molecular Ecology on April 20, by a team of researchers from the German Primate Center (GPC), University of Kentucky, the American Duke Lemur Center and the University of Antananarivo, takes their total count to 24.

Each new species contributes another piece to the puzzle in understanding how mouse lemurs evolved and spread to different types of habitats on the island. Peter Kappeler, head of the Behavioural Ecology and Sociobiology Unit, GPC, and a member of the team that has now described 21 other species of mouse lemurs, says “this new information is an element towards understanding how biodiversity on Madagascar arose”.

“By using new, objective methods to access genetic differences between individuals, we are able to find independent evidence that these mouse lemurs represent new species,” adds Kappeler. This has been possible because of a combination of advancements in genetic analysis along with frequent expeditions to remote areas that were previously inaccessible. As the team sampled more areas and generated genetic data from more individuals over the years, they found that there was evidence to suggest description of new species that might have otherwise seemed very similar to each other in appearance. Kappeler explains, “The genetic techniques we used could facilitate species identification, thus also contributing to further new descriptions in other animal groups”.

One of the new species is called Microcebus ganzhorni, after the ecologist Jörg Ganzhorn who first initiated research on the island and has been engaged in the protection of lemurs since 1992. The second, Microcebus manitatra, which means ‘to spread’ in Malagasy, derives its name from the expansion of the range of the previously known species from western Madagascar to its southeastern part. The third species, Microcebus boraha, is named after its place of origin, the island of Nosy Boraha that lies to the northeast of Madagascar.

The mouse lemur as such resembles an elongated mouse 30 cm long at most with thick fur, long tails and big saucer-like hypnotic eyes. They are mostly arboreal; their large eyes enable them to perfectly absorb everything in the complete darkness of heavily wooded forests. They can be lightning quick, reaching speeds of 40 km/hour, but graceful while foraging for food amongst the trees. They can also be feisty creatures capable of making as easy a meal out of a scorpion as quickly as they can devour mistletoe fruits. The grey mouse lemur is the largest, weighing around 65 grams, and the smallest is the Madame Berthe’s mouse lemur at only 30 grams.

Molecular studies suggest lemurs evolved from two major episodes of diversification that took place on Madagascar, one 30-42 million years ago and the other which occurred 8-12 million years ago. Mouse lemurs came into existence during the second episode. During the same period, another genus called Eulemur, commonly known as brown lemurs, evolved along with mouse lemurs. Biologists believe this evolutionary divergence between the two genera may be due to their time-related activity patterns. Brown lemurs evolved to be active during the day while mouse lemurs lead a nocturnal existence.

And as mouse lemurs evolved to be active at night, they forfeited colourful physical appearances to find a mate and distinguish between themselves by olfactory and auditory communication. All mouse lemur species are very similar to one another in appearance but they do not interbreed and are individual species. These features are encompassed by a biological process called cryptic speciation, common to many species in the tropical regions, whereby two genetically distinct species appear physically similar. Another manifestation of cryptic speciation is between forest and savannah elephants: although they closely resemble each other physically, genetic analysis shows they are as evolutionarily distinct as lions and tigers.

There is so much biodiversity that is unique to the island that Madagascar is often referred to as the ‘eighth continent’. Geologists suggest Madagascar first broke away from the main Gondwana block around 160 million years ago. Then, it broke off from India 50 million years later, and life on the island has been evolving in isolation ever since. The bio-geo-historic seclusion laid the foundation for Madagascar to be appraised as a laboratory of evolution, with over 80% of its life-forms found nowhere else on the planet. It not only boasts of huge numbers of endemic species but also demonstrates fascinating examples of adaptive radiation, an evolutionary process exemplified by Darwin’s finches from Galapagos islands. There, a group of finches diversified into a multitude of separate species – each exhibiting a variety of morphological and physiological traits in order to either adapt to eco-geographic changes or fill in ecological niches.

Palaeontologists have found fossilised records to suggest the lemur’s ancestors lived around 60 million years ago. As they diversified across Madagascar in absence of any predation and competition from other mammals, they mostly evolved in pockets, adapting to niche habitats created by physical barriers.

Madagascar is also known for one of the highest recorded rates of deforestation anywhere in the world, with as much as 90% of the lemur’s habitats having been wiped out (2015). Large tracts of barren lands dotted with abandoned saw mills serve haunting reminders of pristine forests that once stood tall just a few decades ago. There is a grave danger that the world may lose lemurs even before we fully comprehend their existence. According to the International Union for Conservation of Nature’s ‘Red List’, more than 100 known species of lemurs make up the world’s most endangered of mammals.

If Madagascar is to preserve its biodiversity, benefits from local conservation and ecological services like tourism should be shared equitably amongst local populations. Making use of scientific tools for conservation and training local scientists and researchers will help disseminate knowledge and importance of preserving plants and animals among local population in the immediate vicinity of protected areas. Improvement in park infrastructure and patrolling will help forest rangers to keep a check on illegal hunting. To preserve old and newly discovered species, the most urgent need is augmenting the expansion of Madagascar’s protected area network to not only study the extent of their distribution and gather estimates of their abundance but also build a safe haven for its last remaining species and offer them a chance at survival.

Vrushal Pendharkar is a writer at IndiaBioScience.