Where to See a Quarter Million Bats Take Flight Near Sacramento
If you think the fastest land mammal on Earth is the cheetah, you’d be wrong. That title belongs to the Mexican free-tailed bat, capable of straight, level, powered flight at nearly 100 mph. These tiny speedsters might not seem like much, but each summer, a colony of roughly 250,000 of them fills the skies just outside Sacramento, and the public is invited to watch the show.
Welcome to the Yolo Causeway, home to the largest known urban bat colony in California. On summer and fall evenings, spectators gather beneath the overpass that connects Davis to West Sacramento, part of the Yolo Bypass Wildlife Area, to witness the bats’ nightly emergence. The Yolo Basin Foundation offers weekend “Bat Talk and Walk” tours, where visitors not only witness the spectacle but also learn about the ecological role bats play and meet a few up close.
That’s how we found ourselves under the causeway on a scorching August evening. Marshlands line the trails leading in, bursting with American wild sunflowers. Waiting at the parking area outside of the overpass, Charlie Russell, bat handler, educator, and volunteer with NorCal Bats, greets us with a quiet smile and a soft-spoken enthusiasm.
From a small black carrier, Charlie gently pulls out a Mexican free-tailed bat. It blinks up at us with large, intelligent, berry-bright eyes. The golden light of sunset catches the delicate ridges of its ears. Just before we succumb to the overwhelming cuteness, it opens its tiny mouth to reveal a set of sharp fangs and promptly sinks them into Charlie’s gloved hand.
“These guys bite,” Charlie says calmly. “That’s why we’re all vaccinated for rabies, and always use gloves.” If you see a bat in the wild, it is best to not touch them.
Not all rescue bats are releasable. Some, injured by cats or birds of prey, can no longer fly and become “ambassador bats” for education and outreach. But the goal for any rescue is always release.
“We treat babies and adults the same,” Charlie explains. “If we can get them flying and able to care for themselves, they’re released, ideally back near where they were found. Only the ones who can’t fly well enough to survive stay with us.”
NorCal Bats, the nonprofit that handles these rescues, has seen some strange cases. One particularly odd rescue involved a business replacing a sign. When workers found bats overwintering inside it, they dumped them, still half-hibernating, into a trash can. Some flew off, some were rescued and rehabilitated, and some, sadly, didn’t survive.
“I’ve handled bats knocked out of the sky by Peregrine falcons,” Charlie adds, “Every rescue is different.”
In the documentary The Invisible Mammal, directed by Kristin Tieche and screened last spring at San Rafael’s Doclands Festival, we see this rescue work in action. Baby bats are bottle-fed, weighed, and monitored until they’re ready to return to the wild. The film also addresses the threat of white-nose syndrome, a deadly fungal disease decimating hibernating bat populations in North America. In this documentary we meet Corky Quirk who is the Founder of NorCal bats and works with the Yolo Basin Foundation. Sadly she was not available on the night we went as she was giving a bat talk at Olompali. It was Corky who arranged for us to meet Charlie. Most Saturday nights she is out giving educational talks at the causeway. Her depth of knowledge and love for these tiny mammals makes her talks worth the trip.
The importance of bats to ecosystems and agriculture is often overlooked. Mexican free-tailed bats, for example, consume their weight in insects every night, including moths and beetles that would otherwise wreak havoc on crops.
“They reduce the need for pesticides,” Charlie says. “And yes, they eat some mosquitoes too, which everyone appreciates.”
Here are six favorite facts about Mexican free-tailed bats:
- They’re the fastest mammal in the world, clocked at over 98 mph.
- Scientists discovered that hairs on their hind feet are fluoresce under black light. No one knows why.
- They can reach altitudes of two miles to feed on migrating moths.
- Bracken Cave in Texas holds the world’s largest aggregation of a single mammal species, over 20 million Mexican free-tailed bats.
- Lactating females must eat their body weight in insects nightly to produce milk.
- A newborn pup weighs about one-third of the mother’s body weight, the human equivalent of giving birth to a toddler.
Most bat species in California have just one pup a year, though a few species occasionally have two or more. That low birth rate makes conservation and rehabilitation efforts even more critical.
The Yolo Causeway colony is especially unique for its size but also for its accessibility. Other bridge colonies often require river access by canoe. This one is just off I-80, minutes from Sacramento, and viewable from a flat walking trail. It’s become a hub for families, nature lovers, and bat enthusiasts alike.
As the sun dips below the horizon, a hush falls over the gathered crowd. Rustling and high-pitched squeaks echo from under the overpass. It is the sound of a quarter million bats preparing for a night of hunting. They begin to fly back and forth under the causeway as if gaining speed. Then, suddenly, long ribbons of bats pour from under the bridge, spiraling into the deepening sky. They head off toward nearby orchards, a quarter million strong.
Gasps ripple through the group of spectators. Children cheer. Couples hold hands and smile. The talks will continue through September, so be sure to book a spot before it’s too late.
If you can’t make the trip to Sacramento, The Invisible Mammal which won for audience favorite at DocLands will be shown again at The San Rafael Film Center on September 4th. To get tickets visit their website here https://rafaelfilm.cafilm.org/invisible-mammal/
If you want to help keep your local bat population healthy here’s how you can help:
- Install a bat house: NorCal Bats has recommendations at norcalbats.org/bat-houses
- Keep cats indoors: A leading cause of bat injuries is domestic cat attacks
- Donate or sponsor: NorCal Bats relies heavily on public donations and volunteers. They also maintain an Amazon wish list at norcalbats.org/how-we-are-funded
- Book an educational talk: NorCal Bats offers presentations in classrooms, libraries, and community events for a modest fee. Info at norcalbats.org/bats-in-the-classroom
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