28 Unique Mammal Species Discovered on a Heavily Deforested Philippine Island

July 15, 2016 | Erica Tennenhouse

An earthworm mouse from the Philippine island of Luzon
Photo credit: Larry Heaney, The Field Museum. This tree-dwelling mouse, which has whiskers that reach all the way to its ankles, is one of the 28 newly discovered species unique to Luzon.

“Cloud rats” and “earthworm mice” are found nowhere else in the world.

Luzon is the largest and most populous island in the Philippines. Amid rapidly shrinking forests — the Philippines is one of the most heavily deforested countries in the tropics — Luzon is home to world's greatest concentration of unique mammal species, according a paper published in Frontiers in Biogeography.

Over a period of 15 years, a team of researchers discovered 28 mammals that are endemic to the island, meaning they live nowhere else in the world. These newly described species bring the total number of endemic mammals known to live on Luzon up to 52.

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"All 28 of the species we discovered during the project are members of two branches on the tree of life that are confined to the Philippines," says Eric Rickart, a team member based at the Natural History Museum of Utah, in a press release. The authors refer to these two distinctive groups of mammals as “cloud rats” and “earthworm mice.”

Phloeomys cumingi, a cloud rat endemic to the Philippine island of Luzon

A cloud rat, endemic to the island of Luzon. Credit:Jaroslav Vogeltanz/wikipedia (CC BY-SA 3.0)

"There are individual mountains on Luzon that have five species of mammals that live nowhere else. That's more unique species on one mountain than live in any country in continental Europe. The concentration of unique biodiversity in the Philippines is really staggering," he says.

When animals first colonize islands they often find themselves with a lack of predators or competitors and new types of habitat and resources to exploit. The situation allows animals to branch out into new adaptations, which can hasten speciation.

The mountaintops of Luzon form what scientists call "sky islands" — little pockets of distinctive habitat. "The animals are isolated high on the scattered mountains, so they inevitably diverge, explains project leader Lawrence Heaney from The Field Museum in Chicago. “Given enough time, you begin to see huge biodiversity."

Philippines, forest on Luzon island

Luzon is home to the greatest concentration of unique mammal species in the world, but the island is heavily deforested. Credit: Larry Heaney, The Field Museum

Once the species were identified, the researchers set out to better understand their conservation status. “We learned that quite a few of the species are seriously threatened by habitat loss and over-hunting, but none are yet extinct," said team member Danny Balete, also from the Field Museum.

Around 50 million people reside on Luzon, while only about 7 percent of its old-growth tropical forest remains. "Protecting all of these species from extinction is going to be a big challenge,” he says.

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