Giant, fruit-eating monitor lizard discovered in the Philippines

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Humans have travelled all over the planet but many uncharted regions of the globe still hide unknown animal species waiting to be discovered. With some exceptions, these new finds are largely small creatures that are hard to spot amid the bustle of a tropical forest. So imagine Luke Welton’s surprise when he came across an entirely new species of giant monitor lizard in the forests of northern Philippines.

At two metres in length, it’s not quite as large as its close relative the Komodo dragon, but it’s hardly inconspicuous either. It’s also brightly and beautifully coloured with intricate golden spots running down its otherwise black back. As is often the case, the lizard may be new to science but the local tribespeople – the Agta and Ilongot – have known about it for centuries. It’s actually one of their main sources of protein. Their name for the monitor, bitatawa, is now part of its official species name – Varanus bitatawa

Rafe Brown, who leads Welton’s group, says, “Clues to its existence had filtered in over the last ten years.” Photos of the mysterious animal had been circulating since 2001, but the clincher came when Welton and another student, Cameron Siler, salvaged a specimen that had been brought to them by a hunter. “They knew it was something special, either a rare colour pattern or a new species,” says Brown.

The dead lizard went on a round-the world trip from the Philippines to Kansas. There, Brown’s team counted its scales, examined its internal organs and sequenced its DNA. Their meticulous examination revealed that the animal was closely related to the Gray’s monitor (Varanus olivaceus), which also lives on the same island. But it was distinct enough to count as a species in its own right. “The team in the field were very celebratory,” says Brown.

V.bitatawa has an unusual habit that separates it from all but two other monitor species – it mostly eats fruit. Even before the animal had been discovered, the field team had suspected that a fruit-eating monitor lizard was prowling the forests, based on scratch marks all over the local fruiting Pandanus trees. The final bit of evidence came when Welton opened up the stomach of the specimen he recovered. Inside, he found Pandanus fruits, figs and pili nut fruit, with no trace of a single insect, rodent or bird. Snail shells were the only sign that the lizard occasionally eats other animals.

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So far, the team have recovered three specimens of the new lizard and it seems that V.bitawawa only lives in a small band of mountainous forests in the Philippine island of Luzon. It shares the island with the Gray’s monitor, but the two animals are separated by over 150km that includes three river valleys. They’re unlikely to mingle.

How could such a large and conspicuous animal have gone unnoticed by the many biologists who have studied the northern Philippines? Welton admits that it’s an “astonishing set of circumstances”. He suggests that few scientists have tried to survey the reptile life of the area. And if the new species is anything like the Gray’s monitor, it is a secretive animal that almost never leaves the forests to cross open areas.

The discovery of such an eye-catching new animal cements the Philippines’ reputation as one of the planet’s most important hotspots of biodiversity. In the past decade, scientists searching the islands have found new species of lobsters, meat-eating pitcher plants, rails, flying foxes, parrots, mice, shrews, snakes, frogs and orchids.

You get the feeling that we’ve only just started scratching the surface of the islands’ wildlife secrets. Indeed, if the northern and southern parts of Luzon could harbour two distinct species of monitors, separated by physical barriers, there will probably be other pairs of sister species waiting to be found.

Sadly, as with many new discoveries, the animal’s future is being called into question just as it is unveiled to the world at large. Luzon Island has a thriving human population who have cut down much of its forests. The Gray’s monitor is classified as vulnerable due to the loss of its habitat, and V.bitawawa may be similarly endangered. Welton hopes that the new animal will be beautiful and charismatic enough to act as a “flagship species” for the local area, promoting the need to conserve this most bountiful of habitats.

Reference: Biology Letters http://dx.doi.org/10.1098/rsbl.2010.0119

Images: by Joseph Brown and Luke Welton

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