Did You Know: Newfound Shrew Lives on a Single Remote Mountain “How the Heck Did It Get There?”
A new species of shrew has been discovered living high on a single peak in the Philippines, and no one knows how it got there. The shrew, a tiny gray creature with big front feet and an unusually fuzzy tail, probably split evolutionarily from its last relative about 10 million years ago.
The mountain it lives on, Mount Mantalingahan on Palawan Island, is no more than 5 million years old. That means the shrew traveled far to land in its current location, but wait — the new species’ closet relatives (which aren’t all that close) are found in Africa.
“The one mountain is the only place that we know of them occurring,” said Lawrence Heaney, one of the authors of a new paper describing the shrew and the Negaunee Curator of Mammals at The Field Museum in Chicago.
“So one of the questions is, ‘Well, how did it get there?'”
A weird little shrew
Scientists first discovered the shrew in 2007 on an expedition to survey Mount Mantalingahan for biological diversity. Researchers caught multiple specimens of the animals in traps baited with earthworms or fried coconut coated in peanut butter. The shrew, now dubbed Palawanosorex muscorum, or the Palawan moss shrew, immediately piqued the interest of Danilo Balete, the leader of field surveys for the Philippine Mammal Project and a research associate at The Field Museum.
“I started getting messages saying, ‘Oh, we’re getting this weird little shrew. We don’t know what it is,'” Heaney said. The researchers found the shrew living in forests between 5,085 feet and 6,398 feet (1,550 to 1,950 meters) up on the 6,844-foot-tall (2,086 m) mountain. It dwells in the leaf litter among low trees studded with orchids and ferns, and it’s active entirely at night, Heaney said.
The animal measures about 3.5 inches (90 millimeters) long on average and weighs about 0.7 ounces (20 grams) when fully grown.
What makes the shrew weird are its strong front feet and the dark fur covering its tail. Most shrews have tails covered with scaly skin, Heaney said. The shrew is one of three mammal species endemic to Mount Mantalingahan, meaning they live exclusively in that small geographic region. The other two are the Palawan montane squirrel (Sundasciurus rabori) and the Palawan soft-furred mountain rat (Palawanomys furvus). “The Philippines, we have gradually come to realize, has the greatest concentration of unique mammalian diversity — the technical term we use is ‘endemic diversity’ — of any country,” Heaney said.
New shrew species discovered on ‘sky island’ in Philippines
Mountain-dwelling shrew’s habitat gives insights into biodiversity, flood prevention
May 9, 2018
Summary: A team of scientists recently identified Palawanosorex muscorum, a new species of shrew known more informally as the Palawan moss shrew. This shrew, found on what Heaney calls a ‘sky island,’ may help explain why the Philippines is such a hotbed for mammalian biodiversity.
The Philippines teems with biodiversity: 657 bird species roam and fly throughout the country’s 7,641 islands, and over 2,000 fish species swim in the surrounding seas. But beyond these beaked and scaly creatures, the Philippines is also home to the world’s greatest concentration per square mile of unique mammal species.
One of these species — a shrew found around 5,000 feet above sea level — may give us some clues as to what makes the Philippines an ideal environment for mammals.
Palawanosorex muscorum, known more informally as the Palawan moss shrew, was recently identified by a team of researchers, including Larry Heaney, Negaunee Curator of Mammals at the Field Museum in Chicago, in a Journal of Mammalogy paper.
First spotted in 2007 by the late Danilo “Danny” Balete, field survey leader and research associate at the Field Museum, the Palawan moss shrew has a slender, pointed snout and dark coat. Unlike other shrews, its tail is covered in dense fur rather than visible scales. With broad forefeet and long claws, the Palawan moss shrew digs through humus in search of its favorite snack: earthworms. Rainer Hutterer, the paper’s lead author, analyzed these anatomical traits to determine that the Palawan moss shrew was a distinct species.
Heaney emphasizes that the Philippines is such a hotbed for mammalian biodiversity that finding the Palawan moss shrew didn’t exactly shock him and his team: “In many ways, finding this species was exactly what we had expected.”
Co-author Jacob Esselstyn from the LSU Museum of Natural Science adds, “It provides some clues about how small mammals have evolved and moved between Asia and Africa.” In other words, the Palawan moss shrew might help us figure out how the Philippines’ many mammal species got there in the first place.
Another clue: The Palawan moss shrew’s home is a hotbed within a hotbed. Mt. Mantalingahan, a mountain on Palawan Island in the Philippines, is habitat to three unique mammal species, including the shrew.
“There are entire countries that don’t have three unique mammal species — so for there to be three species on one mountain, on one island, in one country is really something,” Heaney emphasizes.
What accounts for this species richness? Mt. Mantalingahan, Heaney explains, is a “sky island.”
While that might sound like something straight out of a sci-fi novel, “sky islands” are real ecological phenomena — isolated mountaintops home to distinct habitats separate from the lowlands and neighboring mountains. These “sky islands” create hubs of biodiversity, allowing for multiple ecosystems — and, by extension, a wider range of species — to coexist within a single geographic area.
These “sky islands” might help explain why mammalian biodiversity thrives in the Philippines specifically. “There could be many new species on these high mountainous regions in the Philippines, but because they are so high, and hard to get to, knowledge of their existence is awfully limited,” Heaney says.
Learning what species dwell in these mountains, Heaney notes, isn’t only helpful for zoologists and ecologists. For those who live and work in Palawan, which constitutes the Philippines’ largest province, protecting the Palawan moss shrew and Mt. Mantalingahan hits even closer to home — it’s a matter of personal and economic safety.
Mt. Mantalingahan, in addition to being a “sky island”, functions as a crucial watershed, regulating the flow of water in Palawan through natural processes. In Mt. Mantalingahan’s case, humus — the low-density mountainous soil the Palawan moss shrew digs through — acts as a sponge, holding water from the frequent rainfall high-elevation places tend to experience.
Deforesting these “sky islands” bears grave repercussions. “That’s where most of the water comes from that people in the lowlands depend on,” Heaney warns. “In deforested areas, when a typhoon hits, it kills thousands of people and animals, and destroys buildings. And if water isn’t being released slowly from the mountains, you’ll have less of it in the dry season, causing drought. If you want to protect your watersheds, you’ve got to protect your habitats.”
Built on agriculture, fishing, and tourism, Palawan’s economy depends greatly on the steady flow of water — from where the Palawan moss shrew lives, to where nearly three-quarters of a million people live.
Today, much of the Palawan moss shrew’s habitat remains undisturbed by human activity. And both it — and we — stand to benefit from keeping it that way.
“Sometimes it’s presented that environmental concerns and economic development are at odds with each other. That’s false,” Heaney asserts. “Smart economic development means not creating situations that cause mass damage as a result.”
Beyond the economic implications of the shrew’s discovery, Heaney says he hopes the new species sparks excitement among the Filipino and international scientific communities, which in turn can help encourage research, conservation, and advocacy efforts.
“People in the world get excited about the cool things that live in their country,” Heaney says. “The fact that the Philippines is such a unique hotspot for mammalian diversity is something people should be aware of, something that people can take pride in.”