October 17, 2006

Fossils of new pygmy water buffalo provide evidence that it once roamed Cebu island in the Philipines

bullspeciessm.jpg
Color drawing of newly discovered
species of water buffalo
, a color
reconstruction of what B. cebuensis probably
looked like. This drawing shows the extinct
dwarf water buffalo in proportion to the
tamaraw (a rare dwarf water buffalo that
lives on the Philippine island of Mindoro);
a full-sized water buffalo; and a human
being. B. cebuensis, who once lived on the
Philippine island of Cebu, shrunk due to
"island dwarfing," whereby some large
mammals confined to an island shrink in
response to evolutionary factors, such as
less food and a lack of predators.

Illustration by Velizar Simeonovski,
Courtesy of The Field Museum

The fossils of an unusual pygmy buffalo—shorter than a yardstick at its shoulders but with a weight of a reindeer at 350 pounds—show the first evidence that "island dwarfing" can take place among the cattle family. A group of scientists, led by Darin A. Croft from Case Western Reserve University, report the discovery of this new species in the bovine family—the first new fossil mammal from the Philippines in 50 years—in the October issue of the Journal of Mammalogy.

The ancestors of Bubalus cebuensis roamed the Philippines when natural land bridges were suspected to have formed between many of the 7,000 islands comprising this archipelago. Such land bridges developed when the surrounding water levels dropped as much as 400 feet during a recent ice age between 10,000 to 100,000 years ago.

After the ice melted at the end of Pleistocene, the animal that migrated to the area by swimming across small stretches of ocean or roaming across land bridges became stranded on Cebu Island where it evolved and adapted to its smaller habitat, lack of predators and shrinking food sources, said Croft, a professor of anatomy.

The Case paleontologist studied the fossils with researchers and co-authors Larry Heaney from The Field Museum in Chicago, John J. Flynn from the American Museum of Natural History in New York City and Angel P. Bautista from the National Museum of the Philippines in Manila to determine the animal was a new species of buffalo.

The small size of B. cebuensis is what sets it apart from most other members of the bovine family.

"The small size of the new species is probably the result of where it lived—on an island," said Croft. "Many studies have shown that large mammals tend to become smaller over evolutionary time when confined to an island."

He also added that natural selection can produce dramatic body size changes over a relatively short time of thousands of years.

Nearby Mindoro Island is home to a rare and endangered living relative of the water buffalo called the tamaraw (Bubalus mindorensis), which is endemic to the Philippines—and also is suspected of adapting over time to its smaller land area. It is slightly larger with a three-foot shoulder height and a weight of nearly 500 pounds—probably because Mindoro is larger than Cebu. These smaller members of the Bubalus family are just shadows of the domesticated male Asiatic water buffalo (Bubalus bubalis) with a shoulder height of six feet and weighing more than a ton.

The new species' limbs are less than two-thirds the length of those of the existing Asiatic water buffalo and are about 80 percent the length of the tamaraw's. The Cebu dwarf also is distinctive in its relatively large teeth and feet, which are usually reduced in dwarfs.

The exact date of the water buffalo's demise is unknown—maybe thousands of years ago, said Croft.

The species' existence remained buried until its fossils were unearthed by a mining engineer named Michael Armas. In 1958, he found the remains of left and right upper arm bones, a left foot bone, two vertebrae, two lower teeth and parts of the hooves while excavating a tunnel through soft karst of an old coral reef in search of phosphate. He preserved the fossils for some 40 years until they came to the attention of Dr. Hamilcar Intengan, a physician, in 1995, who then reported the findings to researchers at The Field Museum in Chicago, where scientific casts of the fossils are now housed.

"If Mr. Armas and Dr., Intengan hadn't passed these specimens along, we might never have discovered this species nor had any idea that water buffalo once lived in Cebu Island," said Croft.

While the Philippines are home to 172 species of native mammals, of which 111 are endemic, scientists consider the islands to be "megadiverse" and one of the most important biological spots in the world.

"Documenting past mammal diversity in the Philippines, an area of extremely high conservation priority is vital for understanding the evolutionary development of modern Philippine flora and fauna and how to preserve it," said Heaney, a co-author and curator of mammals at The Field Museum. "The concentration of unique mammal species here is among the very highest in the world, but so is the number of threatened species."

Although a large diversity of modern mammals now occur on the Philippine Islands, relatively few fossils have been discovered there.

"Finding this new species is a great event in the Philippines," Bautista said. "Only a few fossils of elephants, rhinos, pig, and deer have been found here previously. We have wonderful living biodiversity, but we have known very little about our extinct species from long ago. Finding this new fossil species will spur us to new efforts to document the prehistory of our island nation."

"Discovery of the first fossil mammal from Cebu Island documents the potential for uncovering more evidence of ancient diversity and extinction in this tropical region," Flynn said. "The recovery of this new extinct species of dwarf buffalo suggests that evolution on islands during climate and sea level changes contributed to the remarkable biodiversity of the Philippines."

Story by Susan Griffith, 216.368.1004.

Posted by: Heidi Cool, October 17, 2006 10:49 AM | News Topics: Collaborations/Partnerships, College of Arts and Sciences, Provost Initiatives, Research, School of Medicine, Science

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