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Small bodies, big histories: Three new species of Philippine forest mice

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<div><img src="https://od2-image-api.abs-cbn.com/prod/editorImage/174980372922220250613090624_Four Species of Apomys.png" style="width:750px" class="fr-fic fr-dib" alt="Drawings of four endemic species of Apomys (Megapomys) from Mindoro, including the three new species of forest mice. A = A. gracilirostris, B = A. veluzi, C = A. crinitus, D = A. minor."/>Drawings of four endemic species of Apomys (Megapomys) from Mindoro, including the three new species of forest mice. A = A. gracilirostris, B = A. veluzi, C = A. crinitus, D = A. minor. </div>Mindoro is home to a unique bounty of mammalian wildlife. Many of these animals – including the famous tamaraw, as well as the Mindoro warty pig, and the humble Mindoro shrew – are endemic to the island, meaning they can be found nowhere else on earth. The sheer amount of biodiversity is astounding for an island of its size; with an approximate land area of 9,735 km2, it’s only a tad smaller than a Caribbean nation like Jamaica.It makes you wonder: how did such a remarkable concentration of life forms come about? We may now be one stop closer to answering that question, thanks to the recent discovery of three new species of Apomys, also known as Philippine forest mice, <a href="https://mapress.com/zt/article/view/zootaxa.5647.1.1#:~:text=Three%20new%20species%20of%20Philippine,endemic%20to%20Mindoro%20Island%20%7C%20Zootaxa">as published in the scientific journal Zootaxa</a>.From 2013 to 2017, the renowned biologist Danilo S. Balete led teams of field researchers on extensive field surveys across the entire breadth of Mindoro.Their objective was to close a critical gap in our understanding of the island’s fauna. Up to that point, most mammal surveys had been restricted to the forests of Mt. Halcon. Other peaks in the area, including Mt. Abra de Ilog, Mt. Iglit-Baco National Park, as well as Mt. Wood and Mt. Alibug, were largely untouched by mammalogists, and remained poorly studied. These places became the scientific focus of Balete and his team.The work quickly bore fruit. Mindoro has a longstanding species of forest mouse, called A. gracilirostris, so named for its slender snout, that was first described last 1995, and which can only be found in Mt. Halcon. Two features help distinguish it from others of its kind: a body thoroughly covered in dark brown fur, as well as strongly curved claws used to help dig for delicious earthworms.For decades this was the only known forest mouse endemic to the island. That is, until recently.Over the course of successive expeditions, and as they surveyed more and more of the island, Balete and company encountered three distinctive kinds of forest mice. The first had a brown back but a cream-colored belly, as well as a mask of dark fur across its face; the second shared a similar color scheme, with the addition of conspicuous white tufts of hair behind the ears; The diminutive third had a pale brown belly instead of cream. None had the strongly curved claws that so characterize A. gracilirostris.What’s more, the three mice seemed to inhabit separate areas. The first was captured only in Mt. Abra de Ilog; the second, in Mt. Iglit-Baco National Park; the third, in Mt. Wood and Mt. Alibug.While these differences may seem minor to a layman, to the expert eyes of a mammalogist, they are striking indeed. The team was confident they had found three new species hitherto unknown to science. However, as always, the bigger the claim, the more evidence must be shown to support it. This is why it took so long for their results to be published.After the last round of field surveys wrapped up in 2017, Filipino and American taxonomists spent the following years working closely together to further analyze the specimens they brought home from Mindoro. They pored over tiny skulls, taking minute cranial measurements through dissecting microscopes. Geneticists untangled the lineage of each mouse, using DNA carefully extracted from tissue samples preserved in concentrated ethanol.Finally, following close to a decade of lab work, and after dealing with the many difficulties imposed by the Covid pandemic, the team accrued multiple lines of evidence – morphological, genetic, biogeographic – which all pointed towards the same conclusion. That Mindoro had not just one endemic species of forest mouse, but four, bumping the total number of endemic mammals found on the island from nine to twelve, a whopping 33% increase.The penultimate step was to think of names for the new species. The tiny creature with a brown belly from Mt. Wood and Mt. Alibug they named A. minor, for its small size; the hairy-eared one from Mt. Iglit-Baco National Park became A. crinitus, from a Latin word meaning long-haired; and the cream-bellied critter from Mt. Abra de Ilog was christened A. veluzi, after the late and great Maria Josefa “Sweepea” Veluz, mammalogist of the National Museum of Natural History of the Philippines, who dedicated her life towards the study and conservation of her country’s rich biodiversity.The discovery of three brand new species would be momentous enough. However, by rigorously analyzing the genes of the three new species as well as the previously known A. gracilirostris, the team also managed to reveal the deeper evolutionary history of forest mice in Mindoro.Approximately 4.7 million years ago, the ancestor of all four forest mice arrived in Mindoro from the neighboring island of Luzon. How exactly these small animals ever survived such a voyage remains a mystery, but there are modern observations of small rodents being swept out to sea on fallen logs or similar floating debris during a storm.Usually the story would end there, as a textbook case of what biologists call colonization. When individuals from one species become separated from the rest of their kind, such as by becoming stranded on an island, over time the isolated populations accumulate enough differences from each other that what was once a single species, becomes two: the original still on Luzon, the other now thriving in Mindoro.But wait – Mindoro has four species of forest mice, not just one. How come? The secret may lie in geography. Mindoro is an ancient oceanic island surrounded by deep-sea channels on all sides. Its topography is rugged and mountainous, a product of its long geological history. Remember that the four species of forest mice are found on separate mountains. Understand that mountains themselves may serve as isolated sky islands for animals, the cool forests at high elevations cut off from neighboring montane habitats by an intervening sea of hot and humid lowland jungle.With that, the picture becomes a little clearer. Around 4.7 million years ago, a population of ancestral forest mice lands in Mindoro. Over eons this tiny band establishes itself, multiplies, and spreads across the island. They colonize the mountains. With the passing millennia, the separate mountain populations themselves become isolated from each other. By around 1.3 million years ago, this long process of within-island speciation yields its modern product, that single ancestral immigrant having subsequently diversified to form A. gracilirostris, A. minor, A. crinitus, and A. veluzi.It&#x27;s worth noting that events described above applies to the rest of the Philippines as well. Luzon has a similarly complex geological history. So does Mindanao. It’s this combination of many islands of different sizes with variously rugged topographies – that special blend of an archipelagic nature with stubbornly mountainous terrain – which makes the country such a hothouse for evolution, such a teeming laboratory for biologists to study and ponder. It’s why the Philippines is one of the most biodiverse countries in the world, why it is home to so many unique forms of flora and fauna, and why so many conservationists dedicate their careers to protecting its spectacular forests.As if all this weren’t enough reason for the people of Mindoro to be proud of their home, here’s another. Remarkably, it seems that Mindoro is currently the smallest known island where within-island mammal speciation has taken place. The next smallest island is, funnily enough, also Filipino: Mindanao, which has a land area of close to 100,000 km2.For the authors of the Apomys paper, however, the sweetest victory of their work may be getting a chance to honor a cherished colleague. As the authors themselves wrote: “We take great pleasure in naming this species in honor of Maria Josefa &quot;Sweepea&quot; Veluz (1968-2022) ... in recognition of her lifetime of contributions to field and museum studies and to public appreciation and enjoyment of the remarkable mammal fauna of the Philippines through [the] development of exhibits at the National Museum.”You may find their work in the pages of the scientific journal Zootaxa, titled “<a href="https://mapress.com/zt/article/view/zootaxa.5647.1.1#:~:text=Three%20new%20species%20of%20Philippine,endemic%20to%20Mindoro%20Island%20%7C%20Zootaxa">Three new species of Philippine forest mice (Apomys, Muridae, Mammalia), members of a clade endemic to Mindoro Island</a>.&quot;

Mindoro doesn't have just one endemic species of forest mouse, but four, bumping the total number of endemic mammals found on the island from nine to 12, a whopping 33% increase.

Mindoro doesn't have just one endemic species of forest mouse, but four, bumping the total number of endemic mammals found on the island from nine to 12, a whopping 33% increase.

Small bodies, big histories: Three new species of Philippine forest mice

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Small bodies, big histories: Three new species of Philippine forest mice

ABS-CBN News,

Rio Constantino

Published Jun 13, 2025 04:36 PM PHT

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