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It's just about dark.
The sun is fading behind the thick brush along the Arizona Canal west of 40th Street in the East Phoenix neighborhood of Arcadia. Shouts from soccer players at a nearby park carry, but as the sun sinks deeper, they're drowned out by the buzz of cicadas.
It's a trickle at first. Then, with increasing regularity, bats begin to emerge from a large tunnel. The droning bugs serve as a dinner bell as the light fades, and the bats fly quickly, swooping out of the concrete tunnel to begin an evening of feasting on insects.
It's not quite like the scene in Batman Begins in which a young Bruce Wayne stumbles into a neglected cave on the Wayne family estate and is enveloped by a terrifying swarm of bats, but if you are patient, the canal's colony is still impressive. The Mexican free-tailed bats perform what looks like an aerial dance, looping in rapid circles, in and out of the cave before shooting off eastbound. You can hear them chattering and squeaking, and you can smell them: A thick, musky aroma that smells almost like Taco Bell's crunchy taco shells wafts from the tunnel.
Over the next hour, thousands of bats will emerge from their cave. Experts can't say exactly how many bats live in the tunnel, a Maricopa Country Flood Control ditch that opens on one end at 40th Street just north of the Arizona Canal, and on the other end at 24th Street west of the Biltmore. However, a plaque marking the 40th Street opening proclaims that more than 5,000 bats make the tunnel their summer home. Angela McIntire of the Arizona Game and Fish Department estimates there may be more than that.
"I believe we were first told about this colony in the late '90s," says McIntire, who's served as head of Fish and Game's bat department since 2003. "I always estimate maybe 20,000, but it's kind of hard to tell."
The "Bat Cave" is the area's most prominent bat landmark, but even if you don't happen to notice them, bats are everywhere in metro Phoenix. Each night, when the sun goes down, they emerge from their roosts — from man-made tunnels, bridges, and caves in metro Phoenix's undeveloped and protected desert areas — and fly through the night in search of insects. May through October, thousands of Mexican free-taileds migrate from south of the border to Phoenix and other metropolitan areas, making the town their own, like reverse snowbirds in search of a place to spend the summer.
From the patio of Crescent Ballroom you might spot a few fluttering around streetlights as they devour moths. They're just above you as you ride your bike to a light-rail stop in downtown Mesa. As you nurse a beer at Casey Moore's in the Maple Ash district of Tempe, there are hundreds of bats at work in the neighborhood, flying through the darkness.
Along with the bats come biologists keen to study them. Arizona's Game and Fish Department received heritage funding from state lotteries to create an entire bat department in 1991, and since then, they've employed at least one biologist to study bats. Currently, there are a number of biologists studying bats in the state, including Joel Diamond, a Ph.D. in Tucson who's worked in bat ecology for over a decade. Other experts, like researchers Shawn F. Lowery and Michael Ingraldi, devote time to studying specific bat-related fields of study, like the nocturnal creatures taking up in abandoned mines that dot the outskirts of Phoenix and all over the state.
"Bats are so cool," McIntire says. She initially began working with black-footed ferrets but was drawn to bat study. "Most people have never seen a bat up close, and Arizona has 28 different species. They're all so very different."
Arizona works well for bats.
"Bats like it relatively hot," McIntire says, "but Phoenix, that's too hot," so they choose cooler places in the city. Phoenix's bridges work well, she says, as do abandoned mines. "The number of abandoned mines has influenced the species in the West," she says. With its varied terrain — mountain ranges, wide desert, and urban areas near water — Phoenix has what bats are looking for.
"When you look at the diversity in the environment, you can predict there's going to be a diversity in the species. We have rocky mountain crevices; bats roost in all kinds of different environments. We've got water. Without the canals, it might be much harder for bats to adapt to. People comment on bats drinking out of their swimming pools."
Despite their population density, the bats don't likely want much to do with you.
"They're not attracted to big hair. They don't get stuck in '80s hairdos," Diamond says. Quick to crack jokes and a self-described "bat geek," Diamond has simple advice for someone looking to spot a bat in Phoenix.
"Look up at night. Look up at streetlights downtown, and if you pay attention, you're going to see diversity."
The stigma and popular bat-related myths — Dracula, vampiric fears, and concerns about rabies — don't work in bats' favor. But Game and Fish researchers are quick to dispel rumors: Fewer than 1 percent of the bat population has rabies, and the benefits of having the flying mammals around far outweigh any trouble they may cause when sick or accidentally flying into an attic or garage.
"Large colonies of Mexican free-tailed bats (Tadarida brasiliensis) eat hundreds of tons of moths each week, especially the moths that prey on cotton crops," the Game and Fish website notes, and though they play a key role in keeping local insect populations in check, bats are "North America's most rapidly declining land mammals."
As for the popular idea that bats are pests akin to flying rodents? Diamond objects.
"They're actually more related to primates than rodents," he says. "I just think of them as flying monkeys from the Wizard of Oz. They're fairly intelligent little beasts."
And like primates, they tend to live comparatively long lives. "Some species can live into their mid-40s, so a lot of the bats you're seeing flying around the bars downtown are probably drinking age," Diamond says.
Though they're long-lived, they have slow reproductive rates. The "bat cave" is a maternity colony for the bats, which have only one baby a year.
"So, if you kill a bat, it takes a long time to replace that bat," Diamond says.
Mostly, we humans have been good for bats. Our adaptations to the desert help make the place their summer home, drawn to town by water, spaces to cool off during the day, and plenty of food. Bats mirror the daily lives of Phoenicians in many ways — even using our highways to travel.
"Bats use highway bridges a lot like we do as commuters," Diamond says. Highways offer the same things to bats that they do to traveling motorists: places to eat and refuel and quick, easy lodging. When thousands of Mexican free-taileds cross the border and head toward Phoenix in the summer, they use our freeway system to travel at night.
"They'll use them as a stopover and they use them as a migratory corridor. They'll use I-17 and the 1-10 all the way through town moving north, and when they migrate south, they'll do the same thing," Diamond says.
Though "fantastic bat variety" isn't the first thing would-be tourists might think of when considering a trip to the state, Arizona is home to a wide variety of bat species, 28 in total. But in urban areas like downtown Phoenix, experts estimate that anywhere from seven to 15 unique bat species can be found on a summer night.
"For an urban corridor, it's not like birds, where we have a real decreased diversity," Diamond says. "You actually have a fairly high diversity because we've built up so much synthetic habitat."
Beyond the Mexican free-taileds, Diamond says, there are a few other common species likely to be spotted, like the Western Pippistrele, which shares space with the Mexican free-taileds in the 40th Street tunnel. More commonly known as the "canyon bat," it is striking — with a winged "tribble" reminiscent of the Star Trek creature, augmented with large ears and a small, pug-like face. They're crepuscular, which means they'll sneak out of their caves while it's still bright enough to notice them.
"So it comes out right at sunset, goes out, has some snacks, drinks a couple of beers, and goes back home, and it does the same thing at dawn," Diamond says. "They're cosmopolitan. They're everywhere, but you'll see them in low numbers."
Though you might miss a canyon bat flying by, if you ever come in contact with Eptesicus fuscus (more commonly known by its "really complicated name" the big brown bat, Diamond jokes), you'll know it.
"It's kind of the house bat. If you have a bat in your house, it's probably him. They're generalists. They kind of just fly around and eat whatever they want, from beetles to mosquitos and stuff." Bats tend to have varying "base personalities," he says, and refers to these bats — with their angry demeanor and wingspan of up of to a foot — as the "punk rocker of the bat world." "They're one of those species you'll know when you capture them because they're pissed off," Diamond says.
Some species have found unique desert conditions in Phoenix that have enabled them to take root here.
Lasiurus xanthinus, the Western yellow bat, with its bright blond fur, found its way to Phoenix because of non-native Mexican fan palms.
"The kicker is, they only use palm trees that are unkempt, so you tend to find them close to trailer parks or unkempt condos," Diamond says. "It's usually in the nastier parts of town, where people aren't taking care of their palms. They need those dead palm fronds to roost under."
Another species unique to the desert is Antrozous pallidus, the pallid bat. Wide-eared and pig-nosed, the pallid bat could almost be considered cute — but it's tough, landing on the ground to stalk scorpions and millipedes in parks and along the outskirts of Phoenix.
And, it turns out, they are stinky. "They smell skunky," Diamond says.
Not all bats go for bugs. Mexican long-tongued bats feed on nectar, in particular going after desert plants like saguaros, organ pipe cacti, and agave for their nectar, fruit, and pollen.
As Phoenix has grown and human activity has drawn more bats to town, researchers have noticed something surprising: Some bats are sticking around, defying classic reasoning that they'd leave during the winter.
"It appears as though we have some resident population of [previously migratory Mexican free-taileds] in Tucson," Diamond says. "That's kind of a new thing. With the change in climatic trends, we're seeing some stick around. They decided it no longer gets cold enough to kill them in the winter."
"Their environment is always changing, in subtle ways," McIntire suggests. "Wildlife helps us to detect those changes."
McIntire says researchers in Phoenix have noticed similar patterns, and though she isn't ready to directly tie the bat's year-round residence to climate change, it nonetheless gives researchers even more time with the bats to study their movements and the unique ways they've adapted to life in Phoenix. The department has an outreach program, and other educational outlets study bats, too: The Desert Botanical Garden offers family classes with Tempe-based bat expert Beth Hagen. Despite everything researchers know about them, bats still present mysteries.
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"They're super-difficult to study," McIntire says. "We can find them, put transmitters on them . . . but some of the nuanced sorts of things about their behavior is kind of difficult to parse out."
And though bats maintain a low profile, they're in Phoenix in abundance.
"Think of bat density like you think of bird density," Diamond says. "In the day, you see a bird every 20 to 30 feet. Same thing happens every night. These animals are flying around. You just don't see them."
That is, unless you know what you're looking for.