Yolo Basin Foundation showcases the lives of Mexican free-tailed bats under the Yolo Causeway

This summer, the Yolo Basin will not only house one of the nation’s most exciting wetlands, but also hundreds of thousands of bats. The Yolo Basin Foundation is hosting Bat Walks and Talks from late June to early September to showcase the interesting lives of these animals.

Attendees will learn about native species of bats, then caravan out to Yolo Bypass Wildlife Center to see the Mexican free-tailed bats as they fly out from their roost underneath the causeway

“Watching a bat fly-out is a memorable and exciting experience. Backlit by the colors of dusk, the bats stream from under the Yolo Causeway. It’s a local phenomenon not to be missed,” said Michael Herrera, volunteer coordinator for Yolo Basin Foundation, in a press release.

The Yolo Basin Foundation estimates that about 250,000 Mexican free-tailed bats live under the Yolo Causeway, which the bats inhabit every summer.

“It’s actually a maternity roost. In other words, it’s where the bats come to have they’re young, and they generally have one young a year,” said Rachel Long, farm advisor for field crops and pest management.

The young bats, called pups, roost separately from their mothers. Pups roost in the warmest places of the causeway and the is heat essential for rapid growth. This explaining why the bats enjoy Yolo County, since summer temperatures average 92 degrees.

“Each mother gives birth to just one pup and she nurses her pup. Then, when the pup is around six weeks of age or so, it begins to learn to fly and hunt,” said Mary Jean Quirk from the Yolo Basin Foundation.

Many bat species roost in and around the Yolo Basin area, but the bridge, with its largeness and relative inaccessibility for predators, allows large groups of bats to fit easily in the enclosure.

“The expansion joints below the causeway, they are about one inch wide, and they are made of cement. So, they’re very safe little crevices for the bats to get into. They are about 20 feet up, so predators can’t get there. The circuits of the road helps keep it nice and warm,” Quirk said.

Besides the Mexican free-tailed bats, Yolo Basin Foundation estimates there are a number of other species of bats under the causeway. Big brown bats, in particular, also like to roost under the causeway. However, as Long explains, the bats do not generally experience any kind of competition.

“Some of [the bats] do roost together, and maybe there’s a sort of feeling of safety in numbers,” Long said. “Although they may tend to roost in similar areas, they tend to group based on species.”

Tickets to the Bat Walk and Talk are $12 each and can be purchased at the Yolo Basin Foundation website. Admission is free for children 16 and under. Reservations are required.

Written By: Samantha Solomon – city@theaggie.org