Everything you didn't know about bats in Los Angeles

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Frequency test: Can you hear 20Khz?

A new research tool at the La Brea Tar Pits may soon shed light on one of the ancient animals whose fossils have been pulled from the pools' gooey depths. 

It's not a wooly mammoth that researchers are hoping to better understand, but another Pleistocene Era mammal: bats. 

"A couple of those bat species that were uncovered in the tar pits are still alive today and still live in the Southern California area,” said Miguel Ordeñana, a wildlife biologist at the Natural History Museum of Los Angeles County.  

Ordeñana isn't hoping to learn about the bats from tens of thousands of years ago so much as he is to know whether they're still able to exist within the now-urbanized environment. 

Recently, he was on a ladder installing an ultrasonic bat detector near the bubbling tar lake in front of the Page Museum. The device records the inaudible calls that bats make as they communicate and echolocate for prey. 

“Each species has a very distinctive call, and this microphone basically picks up these ultrasonic calls, it slows down the frequency for us so we can hear it,” Ordeñana said.

A bad rap

Bats are notoriously disturbing to many people, conjuring up images of blood-sucking vermin, and considered flying rodents. 

In reality, bats are not rodents, and they play an important role in the ecosystem. They can act as seed dispersers and pollinators. The majority of bats in Southern California are insectivorous and act as an effective pest control each year. 

“About $24 million dollars would have to be spent on pest control by the agricultural industry if we didn’t have bats," said Paul Stapp, a mammalogist at Cal State Fullerton. "And that’s just in the five counties of Southern California.”

Bats are also indicators of environmental health. Some require proper habitat in which to roost or find food. Ordeñana said that the fact that the hoary bat chooses to stop in Los Angeles during its migration is a sign that enough foliage exists to make it an important waypoint for the species.

"This is one of the most under-studied species in the world, especially in urban areas," Ordeñana said, referring to bats in general. "Knowing about biodiversity over long periods of time and how seasons kind of influence things – temperature, urbanization – will tell us what are the needs."

An inaudible sound is key

Bats are primarily active at night, making it difficult to know which species are frequenting an area. Rather than rely on sight, researchers need to use the calls bats make to help navigate. 

In order to do that, though, researchers must use specialized equipment. Most humans can only detect frequencies that fall between 20 Hz and 20 kHz, and most bats squeak at frequencies well above that range.  

You can listen to the following audio file to get an idea of the frequencies you can hear. Wear headphones and see where you top out: 

0:00 - 0:01 — 1 kHz
0:01 - 0:02 — 10 kHz
0:02 - 0:03 — 15 kHz
0:03 - 0:04 — 16 kHz
0:04 - 0:05 — 17 kHz
0:05 - 0:06 — 18 kHz
0:06 - 0:07 — 19 kHz
0:07 - 0:08 — 20 kHz

Frequency detection test sound

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The Hancock Park detector is the fourth that Ordeñana has installed around Los Angeles since the bat survey project began in 2012. The others are at the Natural History Museum, a private residence in Beverly Hills and at the zoo in Griffith Park.

It’s the first time that permanent bat detectors have been set up around Los Angeles. They’ll be used to establish a baseline that’ll allow scientists to know how different species are faring in the area over time. So far, the project has identified six species of bat in the area: Mexican free-tailed bat, Yuma myotis, big brown bat, canyon bat, hoary bat and Western mastiff bat. 

Canyon bat

Mexican free-tailed bat

Hoary bat

Simply identifying some of those species has given scientists clues as to the importance of different portions of the region. 

The Western mastiff bat, which was recorded by the detector in Griffith Park, is the largest bat in North America. It requires large bodies of water near its habitat in order to survive. Ordeñana said its presence may indicate the importance of the Los Angeles River for bat biodiversity.

“Griffith Park is right on the edge of the L.A. River, and that might tell us that the L.A. River is more valuable than people think, and it may be one of the major reasons why the Western mastiff bat is still here,” Ordeñana said.

Western mastiff bat

Ordeñana said that he'd like to be able to install many more detectors throughout the area, but costs to do so would be prohibitive — each detector setup costs about $2000.

Less expensive detectors are available for bat hobbyists. Ordeñana said he's hoping citizen scientists will eventually be able to contribute information on bats in their areas. 

“Anybody will be able to do this in the near future, because the technology is so advanced and user friendly that anybody can learn about what’s in their backyard,” Ordeñana said.

The study is one of many Ordeñana does on urban biodiversity. He maintains dozens of trail cameras and monitors the nocturnal movements of deer, coyotes and mountain lions. He said his goal is to get citizens to connect with the wildlife they don't recognize around them.

“A lot of people think that LA is this concrete wasteland devoid of wildlife, but in fact, it has tons of species. It’s a biodiversity hotspot, and bats are no exception," Ordeñana said.

This story has been updated.

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