ÃÛèÖÖ±²¥

Bats didn’t use the largest of the original houses in the canyon south of ÃÛèÖÖ±²¥. Experts with the Bat Conservation International group suggested the bat boycott might stem from the fact that the large houses were vulnerable to scorching heat and high winds.

The upshot: The “bat mansions� were replaced with smaller houses three years ago, and at least some bats are taking advantage of the more modest digs.

“All the big ones have been changed to smaller houses with better mounts,� said Doug Moore, education director for the Friends of Madera Canyon, the group overseeing the project. “I wouldn’t say there’s an overwhelming number of bats using them, but they do get use — especially in the summertime.�

An added benefit: The four bat-house sites in the canyon, with 15 houses overall and information signs, serve an educational purpose in telling visitors of the role bats play in the ecosystem — from serving as pollinators to preying on insects.

Bat house logic

Many people might wonder why bats, which typically live in caves, trees or under bridges, would need houses perched on 20-foot poles in a national forest woodland.

A sign, posted near four bat houses along the canyon’s Accessible Trail, explains: “Because bat habitat is increasingly threatened by development, deforestation and disturbance of caves, bat houses have become important artificial roosts for numerous species. Depending on design, location and temperatures, bat houses can be used as maternity or bachelor roosts, or as rest stops during migration.�

Too big, too hot

“Some of the older houses were 4 feet by 6 feet and 3 or 4 inches wide,� Moore said. “They were very, very thin, and they had the main face of the house right in the western sun in the summertime. Some were getting up into the 130- to 135-degree range. They were so hot there was no way of getting bats to use them. And those great big ones were like sails on a ship. They would be bent to the ground in a wind.�

The replacement houses — on the order of 2 feet tall and 18 inches wide — have better ventilation and an adjustable mount so sun exposure can be controlled from season to season, Moore said.

“We’re definitely maintaining them and trying to keep the interpretive value up,� he said. “And they definitely are being used by some bats. I’ll sometimes take a folding chair and hang out around the bat houses, and I see them coming in just after sunset. When it gets to be twilight, you can see quite a few bats.�