Alas, the koala lemur is long gone. Its three species were the giants of the Madagascan forests, each the size of a gorilla, but died out half a millennium ago. Other large lemurs, like the sloth lemur and monkey lemur, have met a similar fate, leaving in their wake a host of orphan tree species that now have no animals to disperse their seeds in droppings.
With more of the island鈥檚 lemurs critically endangered, increasing swathes of Madagascar鈥檚 unique flora are living on borrowed time.
Madagascar is one of the planet鈥檚 great biodiversity hotspots, with numerous species, including lemurs and trees, that are found nowhere else.
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Researchers have warned before about its orphan trees, but of Yale University and her colleagues have now pinpointed the role of lemur extinctions for the first time.
Big seeds, big problem
They found that the disappearance of 17 species of fruit-eating lemurs in the past few centuries has reduced the ability of lemurs to disperse seeds by up to a third. This means many of the island鈥檚 plants have lost their primary means of propagation.
The team discovered this by looking at the teeth and jaws of the extinct lemurs, to work out their diet. It seems they ate large fruit with correspondingly large seeds, which they then excreted widely across the island.
Sizeable fruit may once have conferred an evolutionary advantage for many trees, but it has now become a liability. The larger lemur species have died out and the seeds are too big for surviving lemurs to eat, the team reports.
With the big lemurs gone, some plants are already doomed. Others are in a precarious position 鈥� many trees are now entirely dependent on the two largest surviving lemur species, the black-and-white ruffed lemur (Varecia variegata) and the red-ruffed lemur (Varecia rubra).
Cascade of extinction
These tree include, says Federman, most of the 33 species of Canarium hardwoods that dominate the island鈥檚 forests.
The ruffed lemurs are 鈥渦nique and irreplaceable鈥�, says Federman. Which is bad news, because according to the International Union for the Conservation of Nature (IUCN), both species have lost more than 80 per cent of their population in the last 30 years and are critically endangered.
Their conservation should be an urgent priority, says Federman 鈥� not just to preserve lemur biodiversity, but to protect the remaining forests of Madagascar. She predicts a 鈥渃ascade of extinction鈥� if the surviving lemur species vanish, as the forests would begin to disappear, taking away habitat for other animal species.
鈥淭his study is of utmost importance,鈥� says Christoph Schwitzer of Bristol Zoo, UK, a member of the IUCN specialist group for primates. 鈥淚t shows that protecting lemurs means protecting Madagascar鈥檚 forest ecosystems.鈥�
Journal reference: PNAS, DOI: 10/1073/pnas.1523825113
See below for a video showing a recently discovered underwater giant lemur graveyard:
[youtube]https://www.youtube.com/watch?v=ESDk_uLGc1E[/youtube]
