The islands of Madagascar and Galapagos may be home to some of the most distinctive creatures on Earth, but it seems the title of having the world’s greatest concentration of unique species of mammals goes to the island of Luzon in the Philippines.
A 15-year-long project has shown that out of 56 species of non-flying mammals known to live on the island, 52 can be found nowhere else in the world.
They include ‘cloud rats’ and tree-dwelling mice with super long whiskers, with 28 of the species identified during the course of the research.
Nineteen of the species have been formally described in scientific journals, and nine are currently ‘in the works’, according to the team of American and Filipino scientists who combed the island for previously unknown mammals.
‘We started our study on Luzon in 2000 because we knew at the time that most of the native mammal species on the island were unique to the island, and we wanted to understand why that is the case,’ said Lawrence Heaney, the project’s leader, who is the Negaunee Curator of Mammals at The Field Museum in Chicago.
‘We did not expect that we would double the number already known.’
Luzon is the largest island in the Philippines, at about 40,000 square miles (103,000 square km).
It has never been connected to any continental land, like Hawaii. But is at least five times older, so the few species that that arrived from the Asian mainland have evolved and diversified with little external influence over thousands of years.
Scientists are fascinated by island-dwelling native species because they showcase a ‘sped up’ version of evolution.
This is because when animals are closed off from the rest of the world, in places where there are few or no predators or competitors, they are able to branch out into special adaptations, eventually forming new species.
This is the case on Luzon, which also have the advantage of being covered in mountains.
The mountaintops form what scientists call ‘sky islands’ – little pockets of distinctive habitat that the animals further adapt to.
‘The animals are isolated high on the scattered mountains, so they inevitably diverge,’ Dr Heaney said.
‘Given enough time, you begin to see huge biodiversity. In the process of trying to understand how that happens, we doubled the number of known species on Luzon.’
Among the 28 new species discovered by the team are four species of tiny tree-mice with whiskers so long they reach nearly to their ankles and five species of mice that look like shrews and feed primarily on earthworms.
Most of the new species live in tropical cloud forest high in the mountains, where frequent typhoons can drop 12 to 15 feet (four to five metres) of rain every year, according to the study published in the scientific journal Frontiers of Biogeography.
Team member Eric Rickart, who is based at the Natural History Museum of Utah, said: ‘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.
‘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.’
Luzon also supports 57 species of bats, most of which live in the hot, humid lowlands.
These include the golden-crowned flying fox, which is one of the heaviest bats in the world at up to two and a half pounds.
Another, the lesser flat-headed bat, is so tiny that it can roost inside the hollow spaces inside bamboo stems.
Danny Balete, a Research Associate at the Field Museum who is based in the Philippines , said: ‘We also wanted to learn more about the conservation status of these wonderful animals.
‘The Philippines is one of the most heavily deforested countries in the tropics – only about seven per cent of the old-growth tropical forest is left.
‘We learned that quite a few of the species are seriously threatened by habitat loss and over-hunting, but none are yet extinct.’
Luzon has a human population of about 50 million, including about 23 million in greater Manila, the country’s capital.
‘Protecting all of these species from extinction is going to be a big challenge. The good news is that when the native forest is allowed to regenerate, the native mammals move back in, and the pest rats get kicked out,’ he added.
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