“Myotis mytis with White-Nose Syndrome” by Tamás Görföl, via Wikimedia Commons
At first glance, the Ann W. Richards Congress Avenue Bridge in Austin, Texas looks unexceptional, a gray concrete structure. But it doesn’t only transport cars across the lake, it also houses 1.5 million bats – it’s the world’s largest urban bat colony, according to Bat Conservation International. At dusk, all these creatures emerge from underneath the bridge to embark on their hunt. As incredible the sight of this may be, it’s also a sign of just how much we’ve intruded onto the home of these animals.
The polar bears, the pandas, the tigers share the spotlight for species endangered by human activities. But hidden backstage: bats. They fly at night, and especially to the public, they’re overlooked. The important services they provide are also not well-known; they’re the stage crew that helps control insects, the very same agricultural pests that burden farmers. They’re also the bees’ coworkers; they feed on nectar and fruit, and in the process, they pollinate. Which is why it’s all the more important that we focus our conservation attention on them too.
White-nose Syndrome, wind turbines, and habitat loss are a few of the threats that bats in North America face, as stated by a study published in the journal Biological Conservation by Dr. G.A. Hammerson of NatureServe and his colleagues. They discovered that almost half of these species are at risk, and most of them are concentrated on the East Coast. The biggest threat is White-nose Syndrome (WNS), which affects hibernating bat species. It’s characterized by a white fungus that sprouts on the diseased bat’s muzzle, and it’s estimated to have killed several million individuals over the past decade. In some caves, populations have been almost, or completely, wiped out.
The second largest threat is wind energy, in particular to migrating species; bats die from collisions with wind turbines. They’re also threatened by disturbances to their roosting sites, such as mining, vandalism, and flooding to create reservoirs.
However, the effects of pollution and climate change on North American bats are still largely unknown. Chemicals have been found in their body tissue, and pesticides cut down on their food source – insects. Droughts and warming induced by climate change are also predicted to have a negative impact, but all this speculation calls for research to answer these questions.
Dr. Hammerson’s study assessed the conservation status of North American bat species, and data shows that the situation is worse than the separate International Union for Conservation of Nature (IUCN) and U.S. Fish and Wildlife Service (USFWS) report. According to their study, 31% of the 45 species are at risk, grossly more than 9% (IUCN) and 13% (USFWS). For comparison, this proportion is higher than birds (15%), mammals (19%), and scaled reptiles (16%). The bats’ future isn’t bright; this statistic will probably increase as WNS spreads west and wind energy expands.
Dr. Hammerson and his team discovered that geography had the strongest association with conservation status. Even though more bat species call the Southwest home, more at-risk species are actually located in the East. This indicates the East is where caves for cave-roosting bats might not be available, where forests for tree-roosting bats might be lost. Bat populations may number in the thousands, and their ranges may be large, but their numbers are sharply dropping, meaning threats are serious, though the exact rates of decline are still unclear.
It’s not all bad news though. A conservation success story: the gray myotis went from being “Imperiled” to “Apparently Secure” as a result of the push to protect the caves they inhabit. Because of cave protection, Townsend’s big-eared bat and the Indiana myotis improved as well.
That doesn’t mean that they’re wholly safe though – there’re still the impending threats of WNS and wind energy. Dr. Bruce Young, one of the paper’s coauthors, says that we can “prevent the spread of WNS by closing caves where bats roost to human entrance. Wind farms [can] stop and feather turbine blades during seasons and wind conditions when bats migrate.” Clearly though, as the vulnerable bat populations in the East have already illuminated, bats are in a precarious position, and conservation efforts, and research of, should be directed towards the safeguard of their homes, lest we lose the earth’s natural pollinators and pest exterminators.
Hammerson, G. A., Kling, M., Harkness, M., Ormes, M., and Young, B.E., (2017). Strong geographic and temporal patterns in conservation status of North American bats, Biological Conservation, 212: 144-152. https://doi.org/10.1016/j.biocon.2017.05.025