Seasonal residents of the Phoenix bat cave take flight each night
Bat experts, fans and Maricopa County Flood Control share interest in the Arizona Canal Diversion Channel where thousands of bats roost every summer.
The buzzing of cicadas gives way to a high-pitched chirping. The sky darkens. A few people settle into folding chairs and turn their heads skyward as tiny black specks shoot out of a storm drain, first one by one, then in a large colony.
On one side of the drain is a sign that says “No Trespassing” and on the other side is a sign with facts about Mexican free-tailed bats. Bats are visitors to Phoenix during the summer, the season when bat babies are born.
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The stormwater tunnel, dubbed “Phoenix Bat Cave” on Google Maps, runs along the Arizona Canal near North 37th Place. The 16.5-mile-long, partially underground stretch of concrete tunnel collects and diverts water away from people and property during storms, particularly during the monsoon. It is also home to thousands of bats. The initial estimate of 10,000 seasonal residents may double in August as each female in the maternal colony gives birth.
The tunnel opens again three miles away, releasing more bats into the city each night.
“I come here with my wife and brother-in-law a couple of times a year to watch the bats come out,” said Bill Hutchison, a spectator who said he has been to the bat cave many times. “The nature is great.”
Arizona has 28 species of bats, more than almost any other state in the United States. They often choose to roost in buildings, attics and other man-made structures, such as bridges and storm tunnels.
The Mexican free-tailed bat is the most common species in the Southwest. They are medium-sized and you could hold one between a few fingers. Their fur is usually reddish or dark brown and their wings are long and narrow. They also have the fastest horizontal speed of any animal.
Mexican free-tailed bats are “wing feeders,” meaning they catch insects in the air while in flight, said Angie McIntire, a bat specialist with the Arizona Game and Fish Department. McIntire explains that free-tailed bats eat moths, flying ants and other insects found in the air.
The species migrates from Mexico and female free-tailed bats form maternity colonies where they give birth to a single offspring. The free-tailed bats make Phoenix Cave their summer home, from which they emerge spectacularly each night to feed.
The cave, officially known as the Arizona Canal Diversion Channel or ACDC, was established by the Maricopa County Flood Control District in 1994.
A tall metal fence runs around the perimeter of the long concrete slope leading to the tunnel where spectators often queue. The smell of bat droppings, or guano, rises from the cave when the breeze is low.
Female Mexican bats began roosting in the cave shortly after it was completed, said Lisa Blyler, public information manager for the Flood Control District. They have been there every summer since.
Hally Cokenias, president of Arizona Bat Rescue, the state’s only bat-only wildlife rescue, said she gets rescues from the Arizona Canal “all the time.” Cokenias frees a rehabilitated mother and baby that end up in her care.
Cokenias and his business partner, Benjamin Largent, keep 15 to 20 bats in a warm, dark room in their Mesa home.
“I had been very interested in bats for a long time and I was looking for a place to volunteer, but there wasn’t one,” Cokenias said. “So we decided we would figure it out and start our own rescue.”
These flying mammals have delicate, translucent wings with flexible bones. They are brought to her with broken fingers, dehydration and damaged membranes, usually on the paws of cats that live outdoors. Many of the bats Cokenias rescued from the canal became trapped in the water while trying to drink mid-flight, she said.
Very few of the bats he rescues have been injured as a result of conflict with humans or human infrastructure.
People can have the wrong idea about bats, Cokenias explains, and there’s a fine line between wanting people to be safe but not wanting them to be afraid of them.
There are also a lot of misconceptions about bats and rabies. Not all bats have rabies, he said, and to get it you have to be bitten by a rabid bat. Most sick bats end up on the ground, so the ones that fly by your head probably won’t do you any harm.
Bats also provide pest control. They feed on agricultural pests and other insects.
“The other thing they get wrong is they think they’re ugly,” she said. “They’re actually incredibly cute.”
A ‘pungent’ smell welcomes visitors to the cave
Erick Arntz, the Flood Control District’s operations and maintenance manager, stops the truck about 1,000 feet into the cave. The voices of Flood Control personnel echo indistinctly from the entrance, a distant square of bright sunlight. In the opposite direction, the tunnel stretches into total darkness. Other parts of the tunnel have been used as sets for zombie apocalypse movies, Arntz says.
As he prepared to lead reporters deeper into the cave, Blyler called the cave’s smell “pungent” and said he had to wash the stench out of his nose with soap and water after his last visit.
Guano covers the concrete. A pair of bats dart overhead, disturbed by the truck. Flood Control deliberately doesn’t venture far into the cave during the summer to avoid disturbing the bat colony. The rest of the year, the department conducts weekly walkthroughs to check the tunnel for disrepair, sediment buildup and debris such as rocks, trees and trash.
The tunnel ceiling is lined with thin horizontal cracks in the concrete. These gaps are perfect for bats to hang from, a “happy accident,” Arntz says.
Technically, the area around the cave is private property, but the Flood Control District encourages people to go and watch the bats take flight.
“It’s a really cool experience,” Eliana House said at ACDC’s west opening. House said her son’s kindergarten teacher taught her class about bats and brought them into the cave. She watched as the flow of bats slowed, like when popcorn finishes popping: Bats kept coming out, but only a few at a time.
‘They are night fairies’
There are at least a few visitors on most summer evenings. Spectators park in a nearby neighborhood, joggers and walkers hop off the canal trail, and parents bring their children and carry them on their shoulders for a better view. They set up chairs, take videos, and talk quietly as the bats begin to emerge, laughing when one of the bats zooms by their heads.
On a Fourth of July eve, the Phoenix bat cave was packed. People lined the fence to watch. Within 24 hours, the sky would be decorated with fireworks, but on July 3, it was filled with bats. They fanned out against the deep blue and danced over the canal in the red and gold light of the setting sun.
“It’s magical,” Cokenias said. “They are fairies of the night.”
Just over a month later, on August 6, the crowd was small. Only a few people clung to the fence to watch. The stream of bats was lighter.
John Gunn, a former wildlife manager for the Arizona Game and Fish Department, was among the spectators. He said the bat cave is unique because it is a completely man-made structure that bats have adapted to. It’s rare that something in his business made of concrete and steel has a benefit for wildlife, he said.
“To see hundreds and hundreds of these bats getting a nice benefit from this structure… it’s nice. As a biologist, as a human being, to see how we’re helping our little wild friends while also taking care of our own needs.”
Translation by Alfredo Garcia
