Q&A: Bats on 10th Street downtown feast on pesky insects

Published: Monday, Jul. 1, 2013 - 12:00 am | Page 1B
Last Modified: Wednesday, Jul. 3, 2013 - 10:10 am

The high-pitched chirping escalated with excitement. The first brave bat emerged. Two more followed. Suddenly, a stream of about a hundred bats poured out from a tiny crack between two downtown buildings. They flew out rapidly into the sunset and were out of sight within eight seconds.

Every night – weather permitting – residents and visitors to the east-facing strip of 10th Street between J and K streets witness a spectacular show: hundreds of Mexican free-tailed bats leaving their urban summer home to hunt for insects.

The bats live in an inconspicuous crack between Bud's Buffet and Nails Galore. From about 8:30 p.m. to 9 p.m., the nearly 1,000 bats take flight in waves. The waves are one to three minutes apart, each lasting only a few seconds.

Corky Quirk is the resident bat expert at the Yolo Bypass Wildlife Area. She is an advocate for education about bats, who she says are the farmer's friend as well as ours.

Why are these bats living in downtown Sacramento? Wouldn't they rather live in the country?

They live anywhere that there's insects. Sacramento has big rivers, and there's lots of creeks around. And there are a lot of fields close to the river downtown.

Mexican free-tailed bats live under Spanish tiles, in parking garages – anywhere they can find a crevice that's 1 inch wide.

If you think about expansion crevices under bridges, those are about 1 inch. They're just perfect.

Cement and brick are especially similar to cave walls – they cling quite well to that. We've done a good job building things that they enjoy.

At 10th Street, it looks like that crack has recently opened, and that it reaches quite a bit back. They like humid, they like dark and they like high – that's a safety issue. They're not going to be in crevices close to the ground.

They like the warm side of a building, and the east side usually has good solid morning sun. During the summer, the west side is too hot. But east is popular, and the cement holds that warmth. They like it hot.

Should they be removed from this site?

I don't think there's a reason to. Mexican free-tailed bats eat a tremendous amount of mosquitoes. They also eat other insects including moths. They like attacking the crop pests. They eat the moths whose larvae eat corn and tomatoes.

They're our No. 1 nighttime insect control. Most of our crop damage is done by nighttime insects. I get a lot of kids worried they are eating ladybugs and butterflies – but those aren't flying at night.

Sometimes people wonder if they're eating the fruit in our orchards. No. We have no fruit bats in the United States.

But what about rabies?

Most bats are not sick with rabies. But, a bat on the ground has a 1-in-10 chance.

If you see a bat on the ground, cover it with a box and call us. If we're able to help it, then we do. We bring it back to health so it can go back and eat the insects.

There are lots of other of reasons bats end up on the ground. It's more likely that something happened – maybe it got knocked down by a predator. Or, when it gets really, really hot, they'll try to get close to the opening and knock each other out.

It's difficult for bats to take off from the ground. They're not like birds. They can't jump up and fly – their flight system is different. Generally, bats will drop and catch lift that way.

Describe a day in the life of a Mexican free-tailed bat.

Right now, because they're pregnant or nursing, they wake up a little before sunset. Then they hunt for a couple of hours. They can fly a 50-mile radius of their roost, although they don't need to. They're fast – they fly 50 to 60 miles per hour. They can go very high and catch moths that are migrating, up to two miles high. I think of them as the jet planes of bats.

They eat a lot of insects: 1,000 Mexican free-tailed bats eat about two brown grocery sacks of insects nightly. After eating, they go back and nurse their pup. They rest and groom. Then, two hours before sunrise, they hunt again. When bugs are active, that's when bats are active. It takes a lot of energy to fly, so they're not going to waste their time.

A nursing or pregnant bat's energy needs are especially high. Her baby is a third of her size – I think of it as a human mother giving birth to a kindergartner. At about six weeks it will physically be her size. So she needs to eat about her weight nightly.

How long do bats live?

If it makes it through the first year – which is hard for most wild animals – they can live to be about 20 years old. But not all of them do – due to a variety of things: predators, migration, finding enough food, or if something happens to their roost.

What got you interested in bats?

I've always liked the underdog, and they're definitely the underdog. When I started working at Yolo Basin almost nine years ago, I found out about the colony under the causeway. And the more I learned, the more I wanted to learn.

Humans – just because we're afraid – we kill things. Just because. That's why I think education is really important. The bats are eating the insects that are a problem for us. As long as we use our head and don't touch a down bat, then there's no issue.

Call The Bee's Ellen Le, (916) 321-1031.

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