In Walla Walla, when you mention bats, the fictional superhero Batman may spring to mind, toiling behind the scenes to rid the city of Gotham of bad guys of all descriptions. Though Batman foiled a criminal or two an episode, throughout the United States and in the Walla Walla area, our native bats are busy each night each eating scores of insect pests in urban areas and farms.

Long avoided and sometimes despised, bats provide significant pest control to agriculture. A 2011 report in the magazine Science on the “Economic Importance of Bats in Agriculture” cites estimated numbers of between $3.7 billion a year to $53 billion a year saved in crop damage and pesticide use due to bats predation of insect pests.

Texas bats save cotton farmers $6.4 million yearly in reduced usage of pesticide applications, and in California, to the delight of the neighboring rice farmers, 300,000 Mexican free-tailed bats roosting in the expansion joints under the Yolo Bypass Causeway find a bat buffet over the fields, eliminating the need for pest control of damaging armyworms. The nightly “batnado” has become a tourist attraction. Similarly, huge “batnados” from caverns and bridges in Austin, Texas. and Carlsbad, N.M., are major attractions in themselves.

Nocturnal feeders, bats eat many pest moth species such as coddling moths, tent caterpillars, leafrollers, corn earworms, and cutworms — pests of orchard fruits and field crops in both home gardens and agricultural fields.

Bats also avidly feed on mosquitos, beetles, stinkbugs, leafhoppers, cicadas, crickets, and roaches. Pregnant or nursing females can consume two-thirds of their body weight a night in insects. In the 20 to 30-year lifespan of each bat, this adds up to a lot of insects removed from our fields and gardens. Growers of orchard fruits and walnuts, pecans, almonds as well as corn, rice, and cotton farmers have seen measurable benefit from bats.

Ralph Broetje, at Broetje Orchards (now First Fruits Farms) put up many bat boxes around his 5,700 acres of orchards as he didn’t like to spray pesticides.

Bats in the Walla Walla area migrate south for the winter, some long distance like the hoary bat and the silver-haired bat to Southern California and Mexico, or short-distance like the big brown bat, California myotis, canyon bat, little brown myotis, western small-footed myotis and the Yuma myotis.

Walla Walla County is home to two rare bats, the spotted bat and Townsend’s big-eared bat. In summer and winter, bats roost in old mines, cliffs, freeway overpasses, bridges, barns, and old trees. Roosts provide some temperature stability, safe places to sleep, and places to save energy as bats slow down their metabolism when resting. Autumn roosts are called hibernacula. Bats hibernate in clusters and individually.

Some bats frequent urban areas, others only rural or wild places. Riparian areas, meadows and orchards are preferred foraging areas — though each bat species is adapted to and found in specific environments and feeds on specific insects. The over 200 miles of Walla Walla County river restoration projects with the Conservation Reserve Enhancement Program have greatly benefited local bat populations, according to local biologist Mike Denny. Bat houses attached to barns in fruit and nut orchards, especially those ¼ mile from a river or creek see a doubling of bat activity. Houses are occupied April to October, when bats migrate south.

Issues bats face are the removal of old trees and native and riparian vegetation — affecting bats’ need for daytime roosts and places to forage. Pesticides also harm them. Wind turbines kill migrating bat species (more than birds). Bats only have one young a year, so populations are easily affected by deaths. Denny reports that bats were once common around Walla Walla Valley, and sightings are now scarce since the advent of wind farms.

Alarming discoveries of the white-nose fungus disease near Seattle in 2017 and at Mt. Rainier Park in 2018 have biologists worried. This new bat fungal pathogen from Europe, having first appeared 10 years ago, has decimated hibernating bats in eastern Canada and killed 85% of hibernating bats in 30 states east of the Rockies. Nebraska, Texas and now Washington and California are the only states in the western portion of the country to have reports of the disease. Conditions of high humidity and constant low temperatures found in some caves and places bats hibernate allow this pathogen specific to bats to grow. Bats that migrate rather than hibernate are not affected.