On June 15, 1991, after 500 years dormant, Mount Pinatubo exploded in a cataclysmic eruption – the second most powerful terrestrial volcanic eruption of the 20th century. Despite evacuations in the days before, 847 people reportedly lost their lives. The volcano, located on the island of Luzon in the Philippines, spewed lava and ash into the surrounding Zambales mountains, which in places formed pools up to 183 meters (600 feet) thick. The eruption was so powerful that it reduced the height of Mount Pinatubo by 250 meters (820 feet), leaving a hollow in place of the summit. The formerly lush, old forests surrounding the volcano were either severely damaged, or destroyed completely.
Twenty years after this event, Field museum researcher Danilo Balete ventured to Mount Pinatubo to survey the mammals in the area. There were no surveys of the area prior to the eruption, but specimens in the US National Museum of Natural History housed some records for the lower regions. One species was of specific interest: Apomys sacobianus, or the Pinatubo volcano mouse. This species was only known from a single specimen, captured on the lower slopes of the volcano along the Sacobia River in 1956. It was feared that due to living only on this volcano, the massive eruption had wiped the species from the face of the Earth. However, this survey found that against all odds, the volcano mouse was thriving.
After Balete passed away in 2017, the paper was completed by Larry Heaney, Negaunee Curator of Mammals at Chicago's Field Museum, and Eric Rickart, Curator of Vertebrates at the Natural History Museum of Utah. It was published this year in the Philippine Journal of Science. “Danny couldn't pass up an opportunity to see how mammals were faring on Mt. Pinatubo," said Rickart in a statement. "Knowing that a species once thought to be vulnerable, even feared to be extinct, is actually thriving is the finest tribute to Danny that we can imagine," added Heaney.
The locations surveyed were on the eastern slope of the mountain, between 200 and 1,100 meters (656 and 3,609 feet) elevation. The locations were selected with the help of the indigenous Aeta people, as this area is their ancestral domain. The researchers documented 17 mammal species in the area. They found eight species of bat, (three insectivorous and five fruit bats), seven small flightless mammals (five native and two non-native rodents), and two native large mammals (wild pigs and deer).
The Pinatubo volcano mouse was actually the most abundant of the native small mammals found, with 226 captured. The mouse appeared to be lured more successfully with earthworms than coconut bait. “After the eruption of Pinatubo, we looked for this mouse on other peaks in the Zambales Mountains but failed to find it, suggesting a very limited geographic distribution for the species. We thought the volcano might be the only place this mouse lived,” said Heaney. The authors of the paper think that this species is a “disturbance specialist”, thriving in a habitat that is severely disturbed.
In fact, many of the native species seem to have fared miraculously well in the face of calamity. "For some time, we've known that many of the small mammals of the Philippines can tolerate habitat disturbance, both natural and human-caused, but most of them are geographically widespread, not locally endemic species, which usually are viewed by conservation biologists as highly vulnerable," explained Rickart. "Mt. Pinatubo could be a wonderful place to establish a long-term project to monitor habitat recovery and community re-assembly following the eruption, such information would be helpful in efforts to regenerate the many areas that have been deforested by people."
