A Menlo Park resident discovered some unexpected neighbors after a crew hired to power wash her home on Dec. 26 found a colony of Mexican free-tailed bats nesting behind an outdoor mural.

The nocturnal critters couldn't have picked a more apt art piece to make their home: the mural depicts St. Francis, the patron saint of animals.

“The irony of these bats being found behind a mural of the patron saint of animals was not lost on us,” said Peninsula Humane Society/Society for the Prevention of Cruelty to Animals (PHS/SPCA) spokeswoman Buffy Tarbox.

When the mural was removed, some of the bats fell from where they were sleeping, and there were concerns that they had been injured, according to Ms. Tarbox.

So the bats were scooped up and brought to the PHS/SPCA Wildlife Care Center in Burlingame, where they were treated with oxygen and heat for about an hour, she said.

When the wildlife caretakers ascertained that the bats were healthy, they were released back into the wild. Many went right back to the mural.

The resident of the home did not know about the bats before Tuesday, but told the humane society she will continue to let them live there, Ms. Tarbox said. "Bats make great neighbors," she said, noting that they provide insect control by eating moths and mosquitoes, pollinate local flora and are nocturnal, so they aren't active or visible during the day.

The resident of the home has asked that the specific location not be made public so as to protect the bats from being disturbed again, she noted.

Mexican free-tailed bats are not a threatened species, but their population is being monitored because, like many wildlife species throughout California and the western U.S., they are suffering from habitat loss, Ms. Tarbox said.

They like to nest in caves, attics and trees, under conditions like those found behind the mural. On average, they are 3.5 inches long, with tails that span about half of that length, Ms. Tarbox said.

Anyone who comes across a bat colony or accidentally disturbs one should call the PHS/SPCA at (650) 340-7022, she said. Each year, the Wildlife Care Center rehabilitates between 1,200 and 1,400 animals.