Unexpected rediscovery: The eruption of the Pinatubo volcano in 1991 on the Philippine island of Luzon destroyed the landscape and with it the habitat of many native mammals. But today about 20 species live on the volcano again, including a volcanic mouse believed to be extinct. Contrary to previous assumptions, it seems to have adapted well to the changed habitat.
In June 1991 the Pinatubo volcano erupted on the Philippine island of Luzon. As the second strongest volcanic eruption of the 20th century, it had devastating effects: Lava and ash poured into the area and deposited in the valleys in layers over a hundred meters thick. Later, heavy rains triggered landslides and ash flows that lasted for many months. 800 people lost their lives and the once lush forests in the Zambales Mountains were badly damaged or completely destroyed.
Manhunt in a devastated landscape
In 2011 and 2012, scientists working with Eric Rickart from the Natural History Museum of Utah investigated whether mammals have still lived on the Pinatubo volcano since the landscape was destroyed. Over a period of several months, they searched for mammals at six different locations at the foot of the Feuerberg and up to around 1000 meters in the formerly forested regions at the summit of the volcano. There was hardly any data on the mammal fauna previously living on the island. “Most of these early records described native bat species collected in the 1950s,” says Lawrence Heaney of the Field Museum in Chicago. “But one specimen was particularly fascinating: a small rodent, the only specimen of a new species that was described in 1962 as Apomys sacobianus, the Pinatubo volcanic mouse.”
However, the researchers believed that finding this endemic rodent again 20 years after the volcanic eruption was unlikely. Because in previous research in other regions of Luzon, they had mainly discovered non-native rodent species in the heavily damaged forests. “After the eruption of Pinatubo, we looked for this mouse on other peaks in the Zambales Mountains, but couldn’t find it,” says Heaney. “This suggests a very limited geographical distribution of the species.” Therefore, the team suspected that the species, also known as the long-nosed Luzon wood mouse, may have become extinct across the island.
Well adapted to disturbances
The investigations showed: The landscape around the volcano and on the summit was still very unstable due to the constantly eroding ash and rubble deposits, so that only sparse vegetation grew. The astonishing thing, however: When searching the rough landscape, the scientists actually documented several hundred mammals and were able to assign them to a total of 17 species. Contrary to their expectations, they also discovered the long-nosed Luzon wood mouse, which was thought to be extinct – they even found around 200 specimens of it. They also counted four other indigenous and two non-indigenous rodent species at all altitudes. In addition, Rickart and his colleagues found eight species of bats, most of which (around 150 animals) were common short-nosed bat (Cynopterus brachyotis), as well as wild boars and deer.
“Perhaps the most remarkable aspect of our work on Pinatubo was the rediscovery of Apomys sacobianus,” the scientists sum up. “Of all the species that we have documented, it was the species that coped best with extreme disturbances and under the harsh conditions.” The scientists attribute the high tolerance of the discovered animal species to the severely damaged landscape to the fact that these species are regular Experiencing volcanic eruptions and having adapted to them. “Among the Filipino mammals, Apomys sacobianus is perhaps the most extreme example of such a ‘disorder specialist’”, emphasizes the research team. In the future, Pinatubo will continue to research how natural disasters influence the evolution of the Philippine fauna in order to gain knowledge about the conservation of species.
Source: Field Museum, Article: Philippine Journal of Science, Vol. 150 (S1): 121-133