Volume 34, Issue 3, Summer 2015

Bats in Paradise

By Alison Gillespie


Island View

For many in the Western world, the necklace of 27,000 islands stretching from the south of Asia eastward across the warm, sunny Pacific is the stuff of fantasy and escape, and the very definition of tropical paradise. Although often very small in size, these islands play a huge role in the realm of bats. Collectively, these islands are home to some of the biggest and most unique bats in the world. But while these bats contribute greatly to the Pacific Islands’ incredible species richness and diversity, their existence there is in jeopardy.

This region, which extends east to the Cook Islands in central Polynesia and north to Ryukyu and Ogasawara in Japan, contains an astonishing 31 percent of the currently recognized bat species on earth and approximately 74 percent of those species commonly called flying foxes. In many places throughout these islands, bats are the only native terrestrial mammal.

Some of the bats in this global region are known to inhabit various locations across a vast stretch of the globe. Other species dwell in only one location. Diversity of bat species in this area is largest on the bigger islands off of mainland Southeast Asia; Indonesia alone is home to 219 bat species, more than any other nation in the world.

 

Geology Meets Evolution

It is also here in the tropical Pacific Islands that some of the newest landmasses on earth are being created, as tectonic plates on the earth’s crust scrape against one another and gradually fold upward, and volcanoes located under the water spew forth lava that eventually builds up into mountainous peaks on the forming masses.

Portrait of Bat

This intense geologic activity plays a special role in the evolution of bats, says Chris Filardi, Director Pacific Programs for the Center for Biodiversity and Conservation at the American Museum of Natural History. The mainland often is just close enough to these relatively new land formations that some mainland species are able to fly over the water and reach the new locations. But once there, the species are just far enough away from the mainland that they either do not seek to return or cannot easily do so; this isolation on these islands then forces the bats to adapt and evolve to fit their new surroundings. Luckily, on most of the islands, there are very few other mammals such as monkeys competing for resources. The process “lends itself to the sort of evolutionary trajectories that tend to become unique,” Filardi adds. 

That same intense geologic activity also causes the formation of mountain peaks, which in turn  provide new niches and habitats within which bats can evolve. For example, bats that move upward toward the peaks to roost follow a different evolutionary pathway than those that stay in the lowland, rainforest coastal areas.

“Many people don’t realize that the colonization of bats in the South Pacific began in the Solomon Islands,” says Patrick Pikacha, who grew up in Papua New Guinea and is now a researcher working with Queensland University in Australia. In this archipelago, the elevation shifts from sea level to just above 8,000 feet. For mountain-dwelling bats, the high end of this elevation makes these islands a rare draw in this region.

“If we pan east across the South Pacific, we won’t reach another high elevation again until we reach the Andes in South America,” Pikacha explains. “If we pan west, we won’t reach another until the mountains of New Guinea.”

Cyclones also likely play a role in moving species through the area over time, picking up some bats and transporting them to new, flatter locations, Pikacha says. This phenomenon can cause further evolutionary twists and turns: Those bats that arrive on more isolated, flat islands may again change into something very different from bats of the same species that remain in the mountains among more densely clustered island chains. But with fewer niches within flat terrain, such islands harbor fewer species than their mountainous neighbors. As a result, the diversity of bats decreases from west to east: The Solomon Islands are home to more than 40 species; in Fiji, there are only six; and Tahiti does not have bats at all.

 

Closing the Research Gap

Information on the bats of this region is still being gathered, and some major taxonomic questions remain unanswered. In some locations, political and economic upheaval has made research difficult. In others, geographically remote roosting locations have proven especially hard to survey.

Island View

In 2005, Kris Helgen gained worldwide attention for discovering a new species of bat from the islands of Bougainville: the greater monkey-faced bat (Pteralopex flanneryi), which was also quickly labeled one of the largest bats on earth. Helgen made his discovery at the Smithsonian Institution, where he works as the curator-in-charge of the division of mammals. He has not yet been able to see the bat in its native habitat.

“A completely clear picture of how all this works across Southeast Asia and the Pacific is still emerging, and that’s maybe one of the most exciting things to realize,” Helgen says. “If we are still naming the biggest bats out there, then there’s a lot of the picture that hasn’t taken shape yet.”

As travel has increased across the globe, so have the opportunities for researchers like Helgen to do their work. Islands that were once very remote and very sparsely inhabited are also becoming easier to reach for field research. He also notes that development has brought an improvement in training and access to education and resources.

“Many people in these countries that have this biodiversity are now the ones able to study it,” Helgen continues. “That’s a source of great optimism for me. The techniques are getting better, and the playing field is being leveled in terms of scientists from the developing world doing this work.” 

Yet such optimism, whether it’s attributed to research or other advances, remains tempered by many considerable conservation concerns regarding bats living in the tropical islands of the Pacific. 

 

The Conservation Challenge

The numbers are stark: Experts say that 70 of the region’s bat species are threatened at some level—11 species are considered critically endangered, 22 endangered, and 37 vulnerable.

 Habitat is disappearing for many of the region’s bat species due to development, logging, increased agriculture and fire. Statistics are not available for every island and vary widely from nation to nation, but where numbers are available, the amount of change is dramatic. In the Philippines, for example, more than 90 percent of the country’s primary forest has been removed.

In some tropical island countries of the Pacific, forest coverage has remained healthy, but many of the places with tree cover are filled with both secondary forests that have been highly disturbed and exotic species, which results in a degraded habitat for bats.

“Bats are a good bellwether species,” says BCI Executive Director Andrew Walker. “If there’s one thing these islands are suffering from, it is acute deforestation.” Walker says he’s been shocked to find that many of the forests he has known during decades of travel to Fiji, for example, have been dramatically transformed and now look more like the grasslands of Wyoming. 

Conservation

Increased travel and economic opportunities, which are helping some of the nations in this part of the world develop rapidly, can improve the standard of living for people, Helgen notes. But they also bring an increase in urbanization and the spread of agriculture, causing change at a speed that is “sobering.”

“There has been a massive transformation of the original native forests into these other types of uses,” Helgen says. “Of course, many types of bats can use those habitats that are replaced. But in many cases or most, they can’t.”

Although bat hunting is illegal in many of the tropical islands of the Pacific, it remains popular and is also a huge conservation challenge.

“There are a lot of people-bat interactions in Southeast Asia,” says Tammy Mildenstein, an assistant professor and Old World fruit bat researcher from Cornell College. Mythical stories and oral histories about bats and their spiritual powers abound, but at the same time, many communities also consider bat meat a very healthy food choice. 

Flying foxes seem to be particularly vulnerable. Despite their name, flying foxes are not closely related to their namesake canines, but they often have facial features that are remarkably similar to European foxes—pointy muzzles, large eyes and triangular ears. Like other megabats, most flying foxes are fruit-eaters that do not use echolocation but instead depend heavily on their sense of smell.

Flying foxes are also very large and roost hanging upside down from trees in groups that can include thousands of individuals. This has made them incredibly vulnerable to hunters in recent decades, says Mildenstein.

Most bats, like the endangered golden-crowned flying fox, (Acerodon jubatus), only have one pup per year during a synchronized breeding season. If hunters attack bats who are pregnant or holding their pups close to their bodies as they sleep during the day, it can potentially wipe out an entire year’s worth of reproduction at a single site.

Even disturbances during the breeding season can be a problem, Mildenstein notes, because they can cause a panic in the mothers, who sometimes drop their babies to the forest floor as they flee gunshots and the smell of hunters’ cigarettes.

Even so, Mildenstein says she finds that the hunters often care very deeply about the bats in Southeast Asia. “They want to eat them, but they don’t want them to go away permanently as a result of hunting,” she says. 

“There’s no way around the fact that Pacific Islanders themselves are the greatest hope for conservation in these local environments,” says Filardi. “Where they have sovereignty, the future is in their hands. And really there are no better hands to hold the future of the islands than the people and cultural histories that have been birthed by these places. If science has a role, then it is in strengthening the curiosity, the commitment and the vision that exists in the Pacific Island communities.” 

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