Wild Things

Bats Are the Most Fascinating, Bizarre, Generous, Sexy Beasts

I. plyllotis fly
Allen’s big-eared bat (Idionycteris phyllotis) is one of several species of bats listed as of special concern in the United States.

Photo courtesy J. Scott Altenbach

For much of recorded human history, bats have gotten a bad rap as witches, vampires, and agents of the devil. Most people have been led to believe they are blind, blood-sucking mice-with-wings that only want to get tangled in your hair or pass on the rabies virus. Most of which is total baloney.

And it’s really quite a shame, for these creatures ought to be among the darlings of the Internet. Bats are merciless predators, loyal neighbors, tender mothers, and generous lovers with strange and intimidating tongues. Bats give us tequila and were conscripted during World War II. And because breaking into animal celebrity today is a lot like Boogie Nights, I’ll point out that at least one bat species possesses a penis of great and terrifying adaptation.

Now then, what do you say we start with vampires?

Bats make up an amazing one-fifth of all mammal species. A vast majority eat bugs—70 percent of species worldwide—but there are a few curious exceptions. The vampire bats of Central and South America possess dagger-sharp incisors, which they use to open the veins of mammals and birds. They typically choose furless or featherless areas like ears, nipples, legs, and anuses. Now, you might think a chicken would be bothered by a bat biting into its anus, but bat teeth are so sharp that most victims don’t seem to notice. (Don’t worry. Vampires bats live only as far north as Mexico.)

These beasts might sound like they come straight out of hell’s lowest ring, but vampire bats are some of the best neighbors around. A vampire will starve after just two nights without feeding, which happens regularly because juicy mammals are harder to feed on than a sky full of bugs. So the bats help one another out by regurgitating blood meals and sharing them with a comrade. This isn’t quite the right visual to win over the masses, but even grisly altruism is pretty cool.

A. pallidus with centipede
A few bats in the United States and Canada, such as this pallid bat (Antrozous pallidus), land on the ground and forage for insects, other small invertebrates, and even small mammals.

Photo courtesy J. Scott Altenbach

I should also say that vampire bats aren’t technically blood suckers. Mick Harvey, author of Bats of the United States and Canada, explains, “Vampire bats do not suck blood. They lap it up with their tongues, like a cat drinks.” So instead of getting freaked out by an animal that goes for the jugular, just imagine vampire bats as kittens gathered around a bowl of milk. You know, if those kittens’ saliva contained an anti-clotting compound called Draculin and their tongues had two specially adapted ducts for gathering blood

Vampire bats aren’t the only ones with specialized lickers. Some bats eschew both blood and bug and go directly for the sweet stuff. Like hummingbirds, these bats can hover and use their long tongues to reach a flower’s nectar.

Trust me, you want nectar-feeding bats to get their fix. The long-nosed bats of the American southwest and Mexico (genus Leptonycteris) are some of the only pollinators of the agave plant—the source of tequila and bad decisions. One study showed that without bat pollination, the agave’s seed production plummets to 1/3,000th of its bat-assisted rate. 

Cally Harper, a graduate student at Brown University, has been studying another nectar feeder, the Pallas’ long-tongued bat (Glossophaga soricina), to understand how they retrieve nectar so efficiently. Scientists already knew some bats had tiny, hair-like structures on their tongues, but Harper and her colleagues discovered something else—something bizarre.  

“When we looked closer, we saw sinuses on the side of the tongue that basically fill up with blood,” Harper told me. “And when those sinuses fill up there are vessels in each hair which cause them to stiffen and become erect.”

In other words, what scientists once thought to be a limp mop turned out to be a blood-activated appendage, not unlike the mechanism of a human penis. It’s the first time such a thing has been observed in mammals. (See the go-go-gadget tongue at work in Harper’s video, below.)  

Of course tongues have, shall we say, other uses. Oral sex is exceptionally rare across the animal kingdom, for though many animals have been seen licking one another’s genitals, little of this fondling or grooming appears to be for the explicit purposes of assisting reproduction. However, both fellatio and cunnilingus have been observed in fruit bats—before, during, and after the main event. Scientists don’t know if oral sex provides stimulation, lubrication, or sanitation. Maybe it just feels good. (OK, we know it may feel good, but who’s to say how much sensitivity bats have in their hoo-has?) All we can say with certainty is that there is a strong relationship between the occurrence of oral sex and the duration of fruit bat coitus. In other words, oral sex seems to give bats more staying power.

Whatever purpose oral plays in the sex lives of bats, we presume it does something to help them get pregnant. Reproduction is evolution’s bread and butter, after all, and bats have evolved a number of other curious tricks to keep the species fruitful.

For instance, little brown bats (Myotis lucifugus) go through two phases of mating: active and passive. The active phase comes first and is sort of like spring break. “It’s just one big bat orgy,” says Harvey. Males mate with multiple females. Females mate with multiple males. Heck, little browns occasionally even respond to the calls of other species. (Let’s not to tell the Girls Gone Wild guy. Bats have enough problems.)

T. brasiliensis me exit
Mexican free-tailed bats (Tadarida brasiliensis mexicana) exiting a cave in Texas. It is difficult to estimate the number of bats exiting a cave when large populations are involved. Photo courtesy Michael J. Harvey

During the active phase, female little brown bats seem to have some choice in selecting a mate, or at least as much as any animal can. However, some males have devised a way to overcome this selective power. “The females go into hibernation shortly after mating,” Harvey says, “but some males hang around and, uh, service the females.” It’s not just zonked-out females getting creeped on—approximately 35 percent of passive-phase mating is homosexual.

I know, this makes it sound like male bats are sex maniacs, but all of this late-season banging comes with a cost. Every hump, pump, and sperm dump burns precious calories. Biologist Paul Cryan sums it up, “Those bats are potentially risking their lives as to whether they’ll have enough fat reserves to survive until spring.”

Cryan works with the U.S. Geological Survey to identify other dangers to bats. He’s been studying why windmills are so deadly to creatures with the flight agility of an electron. Wind turbines kill tens of thousands of bats each year, both from direct impact with the blades and from rapid depressurization of the air around the blades as they swoosh through the sky, which can give bats something akin to the bends. Because most turbine deaths occur in the fall, Cryan thought mating might be involved. To test this hunch, he collected carcasses from hoary bats (Lasiurus cinereus) found beneath turbines and checked them for signs of “mating readiness,” such as follicles on the females’ ovaries or the presence of spines on the males’ penises.

Obviously, we must now take a moment to discuss penile spines, as I have a reputation to maintain.

The glans penises of adult male hoary bats (Lasiurus cinereus) found dead beneath wind turbines, showing variation in the prevalence and length of well-developed keratinized spines that grow from the surface of the glans and can extend out past its distal tip.

Photo courtesy Cryan PM, Jameson JW, Baerwald EF, Willis CKR, et al.

No one actually knew hoary bats had Hellraiser penises until Cryan started poking around down there. The spines are formed from keratin, the main material in our hair and fingernails, and they grow in length as the year draws closer to the fall rut. When the time is right, male hoaries engage the females in midair and then fall toward the ground like mating meteorites. Scientists think stabby penises might help the bats form some sort of aerial copulatory lock—which is just the brand of merciless wonder only nature can pull off.

As with oral sex, we can only guess at the advantages afforded by a cactus-like penis. It’s possible the spines stimulate the female’s hormonal response. Alternately, they could remove obstructions, such as a plug of semen left behind by another male. The only thing I can say with any degree of certainty is that once you’ve seen the penis of a hoary bat, your nightmares will never be the same.

As for Cryan’s study of windmill fatalities, the evidence mounts toward some sort of connection with mating readiness, though more research will be needed before we can hope to save these animals from being unfortunate casualties of cleaner energy.

After mating in the fall, some female bats can store semen in their reproductive tract for up to 10 months before they use it for fertilization, one of the longest delays known. There’s even some evidence to suggest that the sperm dock into the female’s body to receive some sort of nourishment while they wait.   

Speaking of weird nutrients, in Papua New Guinea and Malaysia, there are two species of fruit bats with lactating males. Out of more than 5,700 species of mammals, these bats are the only species we know of in which males produce milk. There are two prevailing theories as to why this ability evolved: Either these bats are monogamous partners and the male investing in resources for the young is some new-age evolutionary strategy or, more simply, the bats like to eat leaves or fruit that contains plant estrogens that have a side effect of stimulating mammary tissue. No one has actually witnessed the males feeding young, but perhaps the secrecy is itself linked to survival. Just think what high school’s going to be like for that Time Magazine cover kid.

After all of this pillow talk, we’ve hardly scratched the surface on bats. You could spend your life studying their ultrasonic calls alone. These pulses of high frequency sound would register well over 130 decibels, or about as loud as a freight train, if only we could hear them. (Imagine a dozen of those ripping through your backyard at dusk.) It’s so intense, Harvey writes that “echolocating bats possess a muscular mechanism that enables them to deafen themselves while they are sending out calls so they will not harm their own sensitive hearing.”

In South America, Spix’s disc-winged bats (Thyroptera tricolor) take this ruckus to another level by roosting in curled up leaves. Like an old fashioned ear horn, the shape of the leaf amplifies incoming calls by an entire order of magnitude, and roost buddies find each other before bed. (Side note: These bats have suction cups on their wings. I am not kidding.)

But bat shrieks are also capable of great nuance. A study of the false vampire bat (Megaderma lyra) suggests bats may be able to recognize the voices of their friends. Males of another species, the Mexican free-tailed bat (Tadarida brasiliensis), appear to sing in order to woo their mates. As a female flies past, the male belts out little ditties to attract her attention, then tries to keep her interested by free-styling combinations of syllables and phrases.

Noctilio leporinus fish
The greater bulldog bat (Noctilio leporinus) of Mexico, Central America, and South America, a fish-eating species, fishes by skimming over water and gaffing fish with its sharp claws. Photo courtesy J. Scott Altenbach

You’re probably familiar with bats using sonar to hunt insects in the air, but the greater bulldog bat of Central America (Noctilio leporinus) has a different trick. Using echolocation, it can detect tiny ripples on the surface of water and then swoop down like a screaming eagle and pluck a minnow clean out of the water with its claws. (That’s right, baby. Bats can fish!) It almost seems unfair that any animal should be gifted with such superpowers, but they are not absolute. Some species of moths have been co-evolving with bats for so long, they now sport supersonic hearing that allows them to hear and react to the calls of bats. Scientists even recently discovered three species of hawkmoths that create clicking noises with their genitals, perhaps as a way to scare off their ancient bat foes or at least jam their radar.  

And then there’s the time we tried to weaponize bats to fight the Japanese. During World War II, the U.S. military’s “Project X-Ray” aimed to attach tiny, timed incendiary devices to bats and release them over Japanese cities, presuming they’d naturally seek shelter in random eaves and shutters. In theory, thousands of simultaneous explosions would set whole cities ablaze and incite panic among the populace. (The plan was eventually scrapped to focus on the A-bomb, but not before a few bats got loose and incinerated a military building and one unlucky general’s car.)

There’s just so much to love about these creatures and so much to learn about them before they’re gone. Bats in the Eastern United States and Canada are being devastated by a plague known as white nose syndrome. They have no earthly desire to get in your hair, and while the creatures do occasionally carry rabies, only one to two people contract the disease from them each year.

Honestly, if you want to see a healthy bat-to-human interaction, take a trip to Austin, Texas. Beneath a bridge downtown lives a colony of 1.5 million Mexican free-tailed bats—the largest urban population of bats in the world, responsible for consuming about 10 tons of insects in a single night. And every day from March to October, you can watch them dive out of their roost en masse and fly toward the horizon in a black cloud that under any other circumstances would call to mind the End of Days—or at the very least a Meatloaf song.  

Of course, in Austin they just call it “dusk.” Tourists flock to the bridge and the nearby riverbanks to witness the spectacle. Some people even rent kayaks and pay admission on riverboats to gaze in awe from below—though umbrellas are recommended, as the bats tend to eject their bowels upon exiting the roost. In fact, the sour-sweet smell of guano in the air will hit you long before a bat ever does.

Everything is as it should be: The bats stream off into the dusk to make a living. And the humans stand jaw-dropped and camera-handed, basking in the glorious diversity of mammalia.

Special thanks to Ann Froschauer at the U.S. Fish and Wildlife Service.