On the wonder of bats

One of my earliest memories involving bats dates back to when I was five years old. I was outside on the lawn at my grandmother’s house in central Washington State, looking up at the darkening evening sky as winged forms darted in and out of my line of vision. I don’t know which of the fifteen bat species found in Washington I was observing, but it seems likely that they were little brown bats, which are common and most active around dusk. My memory is that I heard their high-pitched chirps–and this may have actually happened, since young children can hear sound frequencies emitted by bats that are inaudible to human adults. Even at five, I knew bats were harmless if left to their own devices, so I was not afraid of the creatures swooping and diving after insects above my head. On the contrary, I felt a sense of wonder toward these mysterious creatures of the night, so unlike any other animal I was familiar with.

Probably no other group of mammals commonly found in close proximity to people elicit as many mixed emotions as bats. Long feared in some cultures, today bats are widely recognized as important keystone species in ecosystems from deserts to tropical rainforests. Yet, it seems safe to say that even most people who appreciate bats have seldom if ever had the opportunity to study them at close range in their natural habitat. Their nocturnal habits, flying ability, and the small size of most temperate species all conspire to make bats exceptionally difficult to observe. As a result, even many nature enthusiasts know very little about their local varieties of bats.

This is especially ironic considering that, with almost 1,400 species known to science, bats constitute the second-largest group of mammals, surpassed in diversity only by rodents. Traditionally, they were divided by scientists into two subgroups. The Microchiroptera contained mainly insect-eating bats who use echolocation to find and hunt their prey–like the species I watched at age five. The Megachiroptera, meanwhile, consisted of the usually larger, fruit-eating bat species found almost entirely in the tropics.

Today, this simplistic division has been discarded thanks to new research showing that some insect-eating bats are actually more closely related to members of the “Megachiroptera” than they are to the other insect hunters. Even so, the old classification system can be a useful framework for thinking about the very different feeding strategies evolved by bats in different parts of the world. The insect-eaters are by far the most numerous and widely distributed, being found on every continent except Antarctica and in a wide range of ecosystems. Still, it is in the tropics that insectivorous as well as frugivorous bats achieve their highest level of diversity. This was driven home for me when I visited the Loreto region of Peru in my early twenties. In this heavily forested region home to the upper waters of the Amazon River, I watched from the river’s bank as uncountable thousands of bats emerged at dusk to chase the even vaster number of mosquitoes and other small insects in the air. Most of these were small bats, similar in size to the ones I knew from home, but occasionally I would glimpse the shape of a much bigger bat vanishing into the trees, tantalizingly near but impossible to make out clearly in the dark.

Bats are famous for employing echolocation–a type of natural radar similar to that used by dolphins underwater–to zero in on flying insect prey in the dark. Fruit-eating bats, however, lack this ability and instead rely largely on a keen sense of smell to find their food. It was once assumed that frugivorous bats simply never evolved to echolocate, but it now seems possible that all modern bats evolved from an ancestor with this adaptation. If this is the case, then fruit-eaters would have gradually lost their ability to echolocate for food as they evolved over millions of years to embrace a plant-based diet.

Less than a year after my experience watching bats in Washington, my family visited the Oregon Zoo for the first time on my sixth birthday. Of the many wonderful animals we saw that day, some of the most fascinating were the bats in the African Rainforest section, where Egyptian fruit bats and Rodriguez flying foxes hung from the wire ceiling and fought over slices of melon left dangling for them to feed on. I was particularly enamored with the Rodriguez fly fox, a species that is small compared to other members of the flying fox family, but still impressive with a wingspan of up to three feet. As the name “flying fox” suggests, their furry face and large snout give them a somewhat dog-like appearance that delighted me as a child. To this day, the smell of rotting fruit like that which permeated the bat exhibit can recall to my mind memories of these strange creatures with shiny eyes and leathery wings, using their thumbs to crawl hand-over-hand upside down across the ceiling.

While most bats eat either insects or fruit, there are some notable exceptions. Certain species feed variously on fish, small mammals, or even scorpions. And of course, there are the infamous vampire bats, denizens of the tropics who drink the blood of large animals. This unusual habit historically contributed to giving all bats a bad name, although the vampires are much more likely to bite livestock or wild animals than humans. This hasn’t stopped exaggerated tales of blood-eating bats from taking hold and turning large parts of the human population in some countries against bats in general.

Today, of course, bats are imperiled by the same suite of threats facing most groups of animals, from climate change to habitat destruction to the indiscriminate use of pesticides that wipe out their insect prey. Bats in North America have also been devastated by white-nose syndrome, a deadly fungal infection likely introduced from Europe. The elusive nature and undeserved ominous reputation of bats have contributed to them receiving less attention from conservationists than many more charismatic animals–and there is still much we simply don’t know about the threats they face. For example, while around a hundred species are listed as endangered or critically endangered, more than 240 others are classified by scientists as “data deficient,” meaning we lack enough information about them to say whether they are in imminent danger of extinction.

Fortunately, bats also benefit from many of the same actions that help other endangered species. Every time you advocate for your elected representatives to support climate action, attend a hearing to stop a proposed fossil fuel project, or speak up in defense of your local woods or wetland, you are helping bats as well as a host of other creatures. Let an appreciation for the wonder and mystery of bats be one more incentive to continue our work on behalf of a livable planet.


Photo credit: US Fish and Wildlife Service, Pacific Region

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