“Balete’s mouse”: New genus of “shrew mice” named in honor of Filipino biologist

| Written by UP Media and Public Relations Office

One of the members of the newly discovered genus, “Balete’s mouse, “was caught on camera. Photo by Danilo Balete.

They might not get as much attention as the Amazon Rainforest or the Great Barrier Reef, but the mountains of the Philippines are some of the most biodiverse places on the planet.

Inch for inch, these misty cloud forests are home to more unique species of mammals per square mile than anywhere else on Earth. Finding these mammals, most of which are tiny and hard to spot, is challenging work for even the most seasoned scientists. But the late biologist Danilo “Danny” Balete, University of the Philippines (UP) Los Baños alumnus, lecturer at the UP Diliman Institute of Biology, and former research associate in the Field Museum of Natural History in Chicago, had a special knack for fieldwork. One of the mice he discovered turned out to be not just a new species but a new genus entirely.

“In the past several decades, we’ve learned just how incredibly important the Philippines are in terms of being home to mammals that are found nowhere else, and a lot of that knowledge can be traced back to fieldwork led by Danny Balete,” says Larry Heaney, the curator of mammals at Chicago’s Field Museum and senior author of the paper describing the new mouse in the Journal of Mammalogy.

“Naming a new species after anyone is a big deal, a major honor given to people who make long-term, high-impact contributions to biodiversity science,” says Dakota Rowsey, the study’s first author and the vertebrate collections manager at Arizona State University and research associate at the Field Museum. “Naming a new genus after someone is one of the highest honors biologists can bestow.”

“Sky islands” in the Philippines

The mountainous geography of the Philippines contributes to its biodiversity. Its high mountains are cooler and much wetter than the surrounding lowlands, making it difficult for small mammals to get from one mountain peak to the next. As a result, they tend to stay isolated on their own “sky islands,” evolving separately from each other and forming new species.

“The taller and the bigger the mountain range, the more species of mammals will be living there that don’t live anywhere else in the world,” says Heaney.

Filipino biodiversity scientist

Filipino biologist Danny Balete posing with children. Photo by Larry Heaney, The Field Museum of Natural History, Chicago.

Heaney has been studying the mammals of the Philippines for 40 years, and he first met Danny Balete in the late 1980s. At the time, Balete had completed his Bachelor of Science degree in Zoology from UPLB. He was already making a name for himself with his love of nature and skill at fieldwork.

“I was establishing a research program and asked, ‘Who would be a good, enthusiastic young person to take into the field?’ And several people immediately said, ‘Danny Balete.’ So I invited him to do field work with me, and he did fantastically well,” remembers Heaney. “He was just a superb field biologist. Danny could identify every plant, every frog, every bug, everything that you encountered. It was just astounding.” Balete and Heaney went on to work together for the next 25 years until Balete’s sudden death in 2017.

“Danny contributed hugely to scientific knowledge about biological diversity in the Philippines. His enjoyment of biodiversity was infectious, making him a mentor and inspiration to a generation of researchers and conservationists,” says Mariano Roy Duya, Assistant Professor at the Institute of Biology, UP Diliman, and co-author of the new publication. “By the time of his death at far too young, he was already one of the most prominent biodiversity scientists working in the Philippines.”

Even after his death, Balete continues to shape what scientists know about Philippine mammals. When scientists discover something in the field, it often takes years for their work to be analyzed, written up, and published. That is the case with the newly described shrew mouse.

A new kind of mouse

Danny Balete in the midst of conducting fieldwork deep in the Philippine forests and mountains. Photo by Larry Heaney, The Field Museum of Natural History, Chicago.

In 2007 and 2010, Balete went on expeditions to Mount Kampalili on the island of Mindanao as part of a Field Museum collaboration with the Philippine Eagle Foundation. The museum wanted to know what mammals lived alongside one of the largest and most critically endangered birds, the Philippine eagle (Pithecophaga jefferyi).

While on Mount Kampalili, Balete and the team made a startling discovery: a dark brown mouse with small eyes and a long, tapering nose like a shrew, different from anything he had seen on that island. It looked more like mice he had seen hundreds of miles away on the island of Luzon.

“High up in the mountains, Danny was able to get cell phone service, so he sent me a text message, saying, We just caught this animal that looks a lot like the ones from Luzon, and it should not be here,'” recalls Heaney. “So he immediately recognized that this was something cool.”

Three specimens of the new mouse were shipped to the Field Museum for further analysis to confirm Balete’s hunch. And despite Balete’s death, his colleagues continued to study the specimens from his fieldwork. Rowsey, then a postdoctoral researcher with Heaney, led a DNA analysis of the shrew mouse and found that Balete was right. The rodent was different from any species known to science.

“That DNA study demonstrated that the new mouse was not related to the species up in the northern Philippines but to species from Mindanao. It appears as though this is a remarkable case of what biologists call convergence—distantly related species that have independently evolved to resemble each other in ways that allow them to use habitats and resources in similar ways,” says Rowsey.

“Balete’s mouse”

Animals, plants, fungi, and other organisms, are named scientifically based on what their closest relatives are. Humans, for instance, are Homo sapiens. Sapiens is our species, and we are part of the larger genus Homo, which includes our now extinct closest relatives, such as Neanderthals, Homo neanderthalensis. And since a genus is a higher level group than a species, describing a whole new genus, like this mouse, is a bigger deal than finding a new species.

“New species of mammals are being discovered globally at a considerable clip, maybe 50 to 100 new species per year,” says Heaney. “Finding a brand new genus, a previously unknown-to-science genus like this, only happens a couple of times per year. In our 40 years of intensive study of Philippine mammals, this is one of nearly 50 new species, but just the fourth new genus we discovered.”

The new genus’ scientific name Baletemys means “Balete’s mouse,” in “honor of Balete’s work in discovering it and so many other creatures. “As we began picking up the pieces after his death, it became obvious to us that we had to name this new mouse after him. He deserves this,” says Duya.

Of mice and eagles

In addition to honoring Balete, the researchers say the new genus is essential because it is another puzzle piece in understanding the diversity of life in the Philippines. Demonstrating that Mount Kampalili is home to a mouse found nowhere else on Earth may bolster conservation efforts by indigenous communities, which would help the mouse’s neighbors, including the critically endangered Philippine eagles.

“It’s really important to show that when we protect one species, like the magnificent Philippine eagle, we protect our unique biological wealth and cultural heritage,” says Jayson Ibanez, co-author. Ibanez is a senior lecturer at UP Mindanao, an adjunct professor at the UPLB School of Environmental Science and Management, and Director of Research and Conservation of the Philippine Eagle Foundation.

The Philippine eagle and the new “Balete’s mouse” are neighbors to the indigenous Mandaya Ethnic Tribe of Mt. Kampalili. “Indigenous peoples get very excited whenever they learn that they share their homeland with a unique lifeform. And in this case, when we help protect Mt. Kampalili, we also protect the primary watershed, airsheds, and biocultural sanctuaries for much of southeastern Mindanao, giving huge benefits to all the people who live here. With all the threats from watershed destruction and climate change, we need all the help we can get,” says Ibanez.

A snapshot of the mossy forest in Mt. Kampalili. Photo by Danilo Balete.

Press Release by the Field Museum Public Relations, press@fieldmuseum.org. Sharon A. Jansa of the University of Minnesota and Eric A. Rickart of the Natural History Museum of Utah also contributed to the study.

Download the Journal of Mammalogy paper here.