Holy Habitat! Bats’ Bridge Is Saved

A privately owned bridge that has become home and maternity ward to hundreds of bats in Orange County will be spared from the wrecking ball by becoming public property, a county supervisor said Wednesday.

For more than a year, Supervisor Bill Campbell, activists, several agencies and the bridge owner have negotiated to save the structure.

The Irvine Co., which owns the surrounding land, and two water districts need to sign off on the proposal, said Campbell, who said he didn’t see any hurdles in the bridge’s acquisition.

“Keeping the bridge will be a good thing,” said Campbell, whose district includes the Hicks Canyon Haul Road Bridge spanning Santiago Canyon Road in northeast Orange County. It attracts Mexican free-tailed bats year-round.

If all goes well, the bats that have settled in the structure’s dark hollows will continue to roost and use the concrete-and-steel structure as a maternity ward.

Some outdoor enthusiasts favor saving the bridge so it can be a link to a proposed regional trail system in the Irvine-east Orange area.

Cycling groups routinely bike along the picturesque canyon road, but some cyclists are unaccustomed to maneuvering a shoulder next to passing motorists. Last year, a bicyclist was struck and killed by a gravel truck a few miles from the bridge.

“It’s a great trail opportunity,” said Jim Meyer, executive director of Trails4All, a nonprofit advocacy group. “This will fit into the county’s master plan for hiking and biking.”

The bridge was built nine years ago by Alabama-based Vulcan Materials so that its trucks hauling sediment from a dredging project could cross busy Santiago Canyon Road. Part of the firm’s contract was to demolish the bridge when the work was completed.

But when the pregnant bats were discovered last year, plans were thrown off kilter.

“We did some research to determine what the maternity period was and decided to wait,” said Steve Cortner, a vice president of resource development for Vulcan. “That would allow the mother bats to give birth.”

At that time, the plan was to remove the bridge in June, which might have killed hundreds of young bats. Demolition was delayed several times with the help of Campbell and activists.

After months of negotiations, Campbell said, the two water districts and the Irvine Co. have agreed to his plan.

According to the preliminary agreement, Vulcan will sign over the bridge to the county and pay $95,000 for retrofitting costs the county might face. Campbell said he wanted the county to receive a portion of what the contractor saves by not having to demolish the bridge. County road inspectors have recommended strengthening the bridge, but the supervisor said he was confident the bridge was safe for recreational users and could be retrofitted later, if necessary.

The bridge meets Caltrans construction standards for a temporary bridge and has withstood hundreds of loaded gravel trucks, Cortner said.

“We don’t think anything will knock it down,” Campbell said.Bat populations have fallen considerably as development pushes into the former wild lands, destroying their habitat, activists say.Typically, bats have one pup per year. Because bats roost together, damage to one roost site can affect the entire population, said Stephanie Remington, a wildlife biologist who has studied the colony.

A proposal to build a “bat hotel” near the bridge for the more than 1,500 bats in an attempt to move them was considered. But Remington said there was no guarantee the bats would relocate.

Studies show that the bats tend to breed as early as March but with more consistency in June, Remington said.

The free-tailed bats are medium-sized, with ears wide and set apart to help them find prey such as insects by echolocation. Their bodies are 3 1/2 to 4 inches long, and they weigh about half an ounce.

Bat pups are born deaf, blind and without fur. They rely on their mothers for food and lessons on flying and hunting for mosquitoes, flies, moths, midges, cucumber beetles, stink bugs and other insects.

The thought of destroying hundreds of pups by demolishing the bridge alarmed Remington, who said she found support from Campbell, Vulcan, the Irvine Co. and environmentalists.

In the fall, when temperatures drop, Mexican free-tailed bats migrate to Mexico’s northern states for the winter. But Remington said the colony likes Southern California’s weather, “and are pretty active here year-round.”

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Bat maternity ward

Officials will keep in place a temporary bridge near Irvine Lake where more than 1,500 Mexican free-tailed bats are roosting.

Mexican free-tailed bat

Scientific name: Tadarida brasiliensis.

Description: Dark brown or gray fur, with 3 1/2 - to 4-inch-long body; 12-inch wingspan; half an ounce.

Range: Most populous in Texas and Mexico, but common from Western and Southern U.S. to South America.

Habitat: Caves, buildings, culverts, under bridges.

Diet: Adults eat their weight in flying insects daily.

Other: Nocturnal mammals live in large colonies. Females typically give birth to one pup annually.

Sources: Bat Conservation International; Bats of San Diego County; Mammals of Texas