Interstate 80 Bats

July 27, 2023

Question: Why do bats live under the I-80 Yolo Causeway near Davis instead of a more natural setting?

Answer: It is pretty amazing that around 250,000 Mexican free-tailed bats choose the Yolo Causeway as their home. The re are several reasons why they do so, says Yolo Basin Foundation Program Coordinator Corky Quirk. First, Mexican free-tailed bats like heat and temperatures under the Yolo Causeway are warm and stable. The asphalt and causeway deck provide additional warmth. Second, the bats can keep relatively safe from predators by nestling in the causeway's expansion joints and crevices. However, the causeway isn’t totally protected. Predators sometimes hang out under the causeway to prey on fallen bats, especially during birthing and juveniles’ first flights. Peregrine falcons may also show up to hunt bats in the air. Third, bats choose the Yolo Causeway as their home because of its proximity to food. There are foraging opportunities nearby and the adjacent wetlands and rice fields are a good source for insects. The causeway is also just a short bat flight away from farm fields and orchards in Yolo and Sacramento counties.

Habitat loss may also be a factor as urbanization has reduced natural roosting locations such as hollow trees. In fact, the Yolo Causeway may have attracted bats from other areas by providing a safe, warm roosting place.

For more information on the Yolo Causeway bats visit the Yolo Basin Foundation’s website ( https://www.yolobasin.org/battalkandwalks/).