Updated: Nov 7, 2021
The squeaking sound of the little Mariana fruit bat, also known as Guam’s flying fox, has long gone silent. The bridled white-eye bird stopped singing long ago.
These two rare species, both endemic to Guam and Rota, are among the 23 species in the United States that have gone the way of the dinosaur, according to the U.S. Fish and Wildlife Service. The list includes 11 birds, eight freshwater mussels, two fish, a bat and a plant.
The bridled white-eye and little Mariana fruit bat were both listed as endangered on August 27, 1984 and were included in a recovery plan that came too late in 1990.
“The little Mariana fruit bat was last observed in 1968,” said Chelsa Muna-Brecht, director of the Guam Department of Agriculture.
“It didn’t have full protection and it was already rare before conservation programs came into existence,” Muna-Brecth said.
Officials and advocates said most of the species in question might have been extinct, or almost so, by the time the Endangered Species Act was enacted in 1973.
Their stories hold lessons about a growing biodiversity crisis and offer a glimpse into the future of the island’s ecosystems. People poach and overfish. Climate change adds new perils. On Guam, invasive species such as the brown tree snake and rhinoceros beetle are emerging as major villains in the island’s ecosystems.
“The bridled white-eye and little Mariana fruit bat don’t appear to exist anymore. There’s nothing to recover, as far as we know,” said George Curt Fiedler, biology professor at the University of Guam’s College of Natural and Applied Sciences.
Rescue may have come too late for these species, but there’s hope for others, Fiedler said. “I think we the public should be more concerned about saving the endangered species that are still around,” he said.
Fiedler leads a study team from the Terrestrial Marine and Freshwater Invertebrate Laboratory at UOG’s Natural Sciences Division. The study focuses on Guam’s native tree snails, of which three of four species were listed as endangered in 2015.
Of the three listed species, one (Partula radiolata - the Guam streaked tree snail) is fairly common, “more so than we realized when they were listed,” Fiedler said.
The other two tree snail species have much smaller numbers and inhabit relatively few locations, he said. One of them (Samoana fragilis), also occurs in a single small population on Rota and has eight populations on Guam.
The humped tree snail, (Partula gibba), is reported on several CNMI islands, but is mostly declining in number and might even be genetically different on other islands. “On Guam, it occurs in one area on the Naval Telecommunications Station. One really bad typhoon could wipe them all out there,” Fiedler said.
The fourth species, Alifan tree snail (Partula salifana), went extinct in the 1950s from its limited range on southern Guam peaks.
“I’m holding out hope that it might still occur in some isolated ravine, but have not been able to locate them,” Fiedler said. “Snails don’t get much attention, along with our eight-spot butterfly and Slevin’s skink - also endangered. They aren’t the charismatic megafauna that Ko’ko birds are, so they get overlooked.”
Native tree snail species were once common sights in Guam’s limestone and strand forests. Their populations started declining due to a combination of habitat destruction and the introduction of predators.
“Although there are natural predators of tree snails, introduced animal predators are now the major source of mortality, including rats and pigs. The careless introduction of two additional snail-specific predators has made the situation worse,” according to a UOG article posted on its website.
The study team also identified the Manokwari flatworm as the biggest threat to the tree snails. “Although this voracious predator eats introduced pests like the giant African snail, its impact on native land snails has been devastating. Empty shells of dead snails litter the ground in many forested areas,” UOG said.
Conservationists have also noted climate change as the biggest ecological threat. “The effects of climate change on even the smallest species can threaten ecosystems and other species across the food chain,” according to the International Union for Conservation of Nature. “Because species lowest in the food chain are often among the first impacted by climate change, the full impact of species loss may not be seen for decades.”
To achieve on-the-ground conservation for species and habitats around the United States, the USFW collaborates with states, tribes, private landowners, non-governmental organizations and federal partners on achieving goals that focus on recovery.