Help On The Way For Big-Eared Bats
About twenty years ago, on my first visit to Lava Beds National Monument, I walked up to one of the park's signature lava tube "caves" hoping to explore. A gate barred my way. A sign on the gate explained: The lava tube had been colonized by a group of Townsend's big-eared bats, a sensitive species that Monument staff hoped to shield from human disturbance.
Things have only gotten worse for the bats in the years since, but now the State of California may finally be about to give the Townsend's big-eared bat a little extra protection.
Middle-sized bats with 12-inch wingspans, these bats can live for as long as 20 years if they're left to their own devices. (They do far less well in captivity.) Graceful fliers that can drink by skimming water from the surface of a pond while in flight, Townsendses often roost in "flocks" with other species of bat, including the far more common pallid and little brown bats. How can you tell a Townsend's from the other bats? By its big ears, of course, which run about an inch or more from tip to base.
Townsend's big-eared have long been the subject of environmentalist concern. Two subspecies, the Virginia and Ozark big-eared bats, have been listed as endangered under the federal Endangered Species Act since 1979. But California's populations of Townsend's big-eareds have had no such protection -- until this week.
Formerly widespread across the western U.S., with populations as far east as the Blue Ridge Mountains, Townsend's big-eared bats -- Corynorhinus townsendii -- are on the decline in recent years. Habitat disruption is the main reason. Simply walking into a cave, an open mineshaft or abandoned building where Townsend's big-eared bats are roosting can cause them significant damage. Townsendses don't crawl as well as other bats do, which limits their choice of roosting habitat to places where they can fly directly to the spot they want. They prefer to use sheltered communal roosts -- biologists call them "hibernacula" -- that are well-ventilated and completely dark, and they're far more sensitive to human presence than most bats. If a person walks into a place the bats have chosen they may abandon that hibernaculum for good, and their choosiness makes it hard to find suitable replacement roosts.
Female Townsendses give birth to only one baby bat per year, and that childrearing is done in those hibernacula, which adds to the effect of disruption: walk into a cave with a flashlight and you may consign an entire year's crop of new baby bats to an unpleasant end.
And all this was true twenty years ago, before the fungal epidemic White Nose Syndrome started devastating bat populations back east. The disease -- more properly called an epizoötic, an epidemic affecting an animal population -- is likely spread on clothing, boots, and other human accessories. The U.S. Fish and Wildlife Service (FWS) recommends keeping humans out of caves and mineshafts in areas where the disease is prevalent, and urges spelunkers to decontaminate their clothing after a bout of exploring.
In other words, White Nose means there's one more downside for the Townsendses with whom we come into contact, and it might be the one that finally does them in. White Nose Syndrome hasn't made it to California yet, but when it does it could be catastrophic.
That's what the Center for Biological Diversity had in mind when it petitioned the California Fish and Wildlife Commission to list the Townsend's big-eared as endangered under the California Endangered Species Act, and this week the Commission added the bat as a candidate for listing. That act started a 12-month period in which the status of the bat is reviewed by the Department of Fish and Wildlife's Habitat Conservation Planning Branch (HCPB), which will eventually offer a recommendation for or against listing. By April 2014, the HCPB will have given that recommendation to Fish and Wildlife's Director, who has another two months to submit his or her own recommendation to the Commission, which will then make a decision whether to list the bat.
It's a cumbersome process, and it's subject to opposition in the form of public comment. There may be people out there who feel the bats' protection would threaten their income or lifestyle. Protection measures would likely involve closing caves and mines, restricting timer harvests in old-growth forests (the bats do sometimes roost in tree cavities) and restricting use of open-pit mines and quarries where the bats have decided to settle in.
In the interim, though, candidate species do enjoy protection under CalESA, so this week's move by the Fish and Game Commission is a welcome boon to the bats.
One profession less likely to object to protecting the bats: farmers. Townsendses eat a whole lot of flying insects that might otherwise damage crops. They seem to prefer moths, though they've been known to eat beetles and flies if they have to.
Throughout the state Townsendses are generally found in sparsely inhabited areas such as forests and desert shrub land, but mainly where those landscapes include caves and other such shelter. Desert Townsendses are paler than their coastal kin, and are considered to belong to the subspecies Corynorhinus townsendii pallescens. Though reports on the species as a whole talk about the bat's tendency to avoid open desert, the California deserts were once fantastic territory for Townsendses, especially where abandoned mine tunnels and shafts offered habitat enhancement.
According to a 1994 report by UC Davis biologists Elizabeth Pierson and William Rainey, large numbers of the bats once inhabited abandoned mines in the desert. The Alice Mine, at the north end of the Riverside Mountains north of Blythe, once held an active colony of more than 1,000 Townsend's big-eared bats, the largest known in California. Other mines up and down the Colorado River hosted populations of bats, as did non-tourist cave areas in the Providence Mountains and mines in what was then Death Valley National Monument. As early as 1994, it was clear that recreational mine exploration was doing the bats harm. According to Pierson and Rainey, conversion of riverbank habitat to farming may have played a role in the decline as well, as may use of agricultural insecticides.
That was two decades ago. The state of California is finally getting around to addressing the issue. That's a good thing, if a bit belated. The desert still offers the state's widest expanse of potential habitat for Townsend's big-eared bats: perhaps, if we don't fill it with industrial development, it could be the part of the state where they start to make their comeback.
