D e s e r t E x p o s u r e
April
2008
Going Batty
Misunderstood and often maligned, bats count on the work of a few good scientists — and the cooperation of all of us — to survive in the Southwest.
By Donna Clayton Lawder
As the sun sinks in a red blaze below the Guadalupe Mountains, a range jutting across western Texas and southeastern New Mexico, a swarm of Mexican Free-Tail bats streams out of their limestone caves into the darkening sky. Numbering in the millions, the bats show up as storm clouds on weather radar systems.
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USFS bat expert Marikay Ramsey |
"Oh, it's something to see," Marikay Ramsey says of this nightly show — called a "fly-out" — that occurs every warmish evening in Southwest bat havens. "They just go on and on, streaming out at you, over your head. People can't believe it the first time they witness it. It really gives you a sense of awe."
Once clear of the caves where they roost, the bats swarm down into canyons, across fields, swooping after their dinner. From sundown to sunup, sometimes traveling 40 miles for its nightly meal, the half-ounce Mexican Free-Tail bat — whose name comes from the way its tail is formed by a membrane between the bat's hind legs rather than growing directly from its body — will eat half its body weight in insects each day. Multiplied by millions of bats, that adds up to nearly four tons of potential pests to crops and humans devoured every 12 hours.
One of the more common bats in forest service biologist Ramsey's southwestern territory, the species is estimated to number many millions. A colony of Mexican Free-Tails living in the lava tubes on Ted Turner's Armendaris Ranch, for example, is the second-largest in North America and is estimated at several million.
Ramsey currently is transitioning into a new position within the US Forest Service. She has worked as the Bat Conservation Coordinator in Truth or Consequences for the past four years and in Silver City for the six years prior to that, making her the region's USFS bat expert for the past decade.
That experience leads her to caution that not all of the West's 35 species of bats are as numerous as the Mexican Free-Tails. Many area breeds of bat, in fact, are on the federal endangered-species list, designated as sensitive or threatened with extinction.
Locally, Ramsey notes, there is concern over the endangered listing for the Lesser Long-Nosed bat and the Mexican Long-Nosed bat. Four others — the Western Red bat, the Spotted bat, Allen's Lappet-Browned bat and Townsend's Big-Eared bat — are listed as "sensitive" species, according to the forest service. Of the Townsend's Big-Eared species, Ramsey says, "Large numbers would be captured in an average night of netting. Now it's getting much harder to find them, so we can surmise that they are in trouble."
It's not a good time to be a bat. Nearly 40 percent of all bat species in North America are included on state or federal threatened, endangered or sensitive species lists or are candidates for listing. Gray bats, which were among America's most abundant bats in the early part of the 20th century, are now endangered. Indiana bats declined by 55 percent in less than 10 years and also are listed as endangered. In the early 1960s, Eagle Creek Cave in Arizona housed the world's largest known bat colony, approximately 30 million Mexican Free-Tail bats. Yet that population declined over 99 percent in only six years.
While that's bad news for bats, it's equally bad news for humans, Ramsey says. Their extinction — the bats, that is — would have a devastating ripple effect on crops and the economy.
"One of the major things that people can relate to is that bats are the primary predators of nighttime flying insects," she explains. Depending on the species, bats eat up to several thousand insects apiece per night, about one-third to half their body weight. While the biggest Eastern US bat weighs only as much as 17 dimes, that's still a lot of mosquitoes you won't have to swat or deter by slathering yourself in Deet.
But bugs chomp on more than human flesh. Crop damage is the much more serious problem, Ramsey says. "In Bosque del Apache, for example, there are millions of bats swooping around eating flies, mosquitoes, grasshoppers and more. There are millions of bats that eat the Corn-Borer moth. We cannot even imagine the damage our crops would incur if we didn't have those bats alone."
Ernest W. Valdez, a wildlife biologist with the US Geological Survey in Albuquerque and co-chair of the New Mexico Bat Working Group (NMBWG), has studied the diets of local bats in the wild. He's found an interesting link between the flying animals and their local habitat — particularly the conifers now threatened by bark-beetle infestation.
"We have found that bats are very important in consuming forest and agriculture pests in New Mexico, including bark beetles and click beetles (adult forms of wireworms)," Valdez says. With concern growing over the spreading damage of bark beetles through local forests, documenting the bats' appetite for the onerous pests adds to bats' perceived value. "Understanding food habits of bats and their effects on insect pests has been a great way to promote conservation of bats, including protecting known roosts and supporting efforts for bat-house construction near areas with agriculture," Valdez says.
Bats also are pollinators and seed dispersers. Next time you're throwing back a shot of tequila, thank a bat. In the Sonoran Desert of the southwestern US and Mexico, the Long-Nosed bat plays a critical role in the lives of several species of agaves — from which tequila comes — as well as giant cacti.
According to the Western Bat Working Group (WBWG), a coalition of laypersons, scientists and academicians, the loss of plant and animal diversity is one of the most serious long-term global problems humanity faces. Many of the world's most economically important plants rely on bats. Some crops from these plants are valued in the hundreds of millions of dollars each year and are crucial to the economies of cash-poor developing countries.
Beyond economics, the delicate "web of life" between species is at issue. The giant cacti in the Southwest provide food and shelter for countless other animals. The relationships between plants and their animal pollinators and seed dispersers are the result of millions of years of evolutionary interplay. If the bat pollinators disappear, the plants and the wildlife that rely on them could be seriously threatened.
Marikay Ramsey says her work with bats in the Black Range and eastern side of the Gila National Forest has been particularly rich — due to a concentration of resident species and the area's location being key to migrating bats. "We're the most diverse part of the US," she says. "In addition to our resident species, we have tropical and subtropical species passing through as well."
Of the 35 species of bats native to the western US, 28 dwell in the southwest between New Mexico and Arizona. Variety of terrain, Ramsey says, is what makes the southwestern part of New Mexico so attractive to the night-flying mammals.
"We have a lot to offer bats, an extremely diverse range of habitat," Ramsey says. "We have conifer forests, we have open areas, and we have caves. And of course our mines — they love those."
Abandoned underground mines provide significant habitat for bats. More than half the species of bats in North America are known to use mines, and at least 22 of the 35 species in the West use abandoned mines to some extent. Mines provide an alternative roosting option and help offset natural habitat loss and human disturbance of bat colonies in caves. Abandoned mines become bats' winter and summer roosting areas, day-roosting spots, maternity sites for reproducing bats, shelter from predators, and feeding and watering sites.
Ramsey says loss of habitat — the loss of large conifers, closing abandoned mines and removing old bridges under which bat colonies often roost, to name a few — has been the number-one threat to bats.
"A lot of mines are being closed for public safety," she says. "What we (scientists) have to do is to say, 'Wait! We need to make sure it is not a really important roost for bats.' And that's not always an easy thing to determine. Bats use mines in very different ways, maybe only certain times of year or certain parts of the mine that you can't even view.
"There are different ways of going about it. You can determine bat presence by piles of guano — that's their waste," she explains. "There can be significant accumulations of it. Other times, more frequently, you find a mine with just a spattering of guano. Sometimes we find insect parts — like legs and wings — that the bats don't eat. Those are left behind and alert us that bats are eating there. Those are really good clues to determining what kind of species are coming through and how often they occupy the mine or cave."
But absence of insect parts and bat waste doesn't mean bats are not using a mine for their roost.
"A tricky thing is that bats hibernate," Ramsey says. "When they are hibernating, they're also not eating, not defecating, so it gets tricky to know they are there. Then the scientists are just left with their best judgment. I always try to err on the side of caution for the bats, assuming if there is some evidence of their presence that they are there in some quantity."
Some conservation groups, she notes, like the WBWG and the New Mexico Bat Working Group, fight for legislation to preserve mine habitat for bats. "It's a balance of public safety and bat habitat," she says. "Of course, the companies don't want the liability of having an unsafe open mine, a hazard to humans. But one thing we can do is instead of them just back-filling a mine and shutting it off, we can get a bat gate installed."
| A Face Only A Mother Could Love? Who says bats aren't lovable? You can "Adopt-a-Bat" for just $15 by clicking a link on Bat Conservation International's Web site, www.batcon.org The seven available species pictured offer a fun and friendly introduction to the world of bats. Adoptive "parents" receive:
Adopt a bat for $15 or pay $35 for adoption with a basic level membership in the organization. |
Placing a gate of horizontal bars over a culvert is a popular solution, she says, as it is simple to install, low cost and keeps humans out while allowing bats to pass in and out.
"I've been working with Arizona fish and game, trying to get a particular mine gated for bats," she says. "It gets tricky, as it is a designated wilderness area. It's also a particularly important piece of habitat, as it's geothermally heated, so certain species live there that don't live everywhere else."
Ramsey acknowledges that cost often enters into the picture. "If the mine opening is next to a trail head or something like that, near the public, then there has to be some more sophisticated gate systems. Sometimes that involves concrete and such, and of course, that's more costly. We're mostly talking about abandoned mines, so they are owned by land management agencies and there's not a lot of money for that kind of thing. We (conservation groups) try to get grants. Fish and game and state agencies may help with the grant process."
In 1993, Bat Conservation International (BCI) and the Bureau of Land Management (BLM) founded the Bats and Mines Project, with a goal of reducing the loss of bats during closures of abandoned mines. Many states now are recognizing the importance of mines as bat habitat and are incorporating the abandoned mines issue into their wildlife and bat conservation plans. BCI says that bat-friendly gates are gaining in popularity.
Another threat to bat survival, Ramsey says, is wind energy. "We will be getting some wind energy sites — one in the Burros and one at the southern end of the Black Range. There are lots of bat and bird deaths from those turbines," she says. "We're all yelling for green energy methods, but there's a cost to bats and birds. These issues need to be addressed."
Still another emerging threat is a deadly one about which little yet is known. "Recently, scientists and other people concerned about bats have been talking about White Nose Syndrome," Ramsey says. "No one knows yet what it is, what's going on with that. There were a few thousand deaths from it last year in the Northeast. It's characterized by a ring of fungus around the nose, but that appears to be just a symptom, not a cause. Hibernating bats eat a lot to build up fat reserves, but in the bats with White Nose Syndrome, their fat deposits are inadequate. The first thing that enters scientists' minds, of course, is climate change. Are warmer temperatures causing this? Are bats the canaries in the coal mine, warning us that something bad is happening and it's coming our way?
"We haven't seen any White Nose Syndrome here in the Southwest, but we are looking out for it." Ramsey, also a member of the NMBWG, has made flyers to bring awareness about this disease to spelunkers and cave enthusiasts.
On the bright side, indiscriminant killing of bats is not the threat it once was, Ramsey says. "We do, unfortunately, see some of that. We do occasionally find some bat carcasses. But thankfully, kids these days have less prejudices and fears, and they educate the grown-ups in their families, too."
Art Telles, the US Forest Service wildlife and fish program manager who works out of the Silver City office, echoes the importance of educational outreach, yet also acknowledges that budget cuts have left an unfortunate gap in this regard. "We lost a lot of our information specialists," Telles says. "Locally, we really count on things like the Aldo Leopold High School, because they're environmentally aware, and the GCEC (Gila Conservation Education Center) trunks going out to local science teachers to help fill the gap." (See the November 2006 Desert Exposure.)
"A biologist's job through the forest service is to make sure endangered or sensitive species are not being threatened or negatively impacted," Telles adds. "We make sure that any projects in the forest do not push them into a threatened status." Such projects might include grazing allotments, fuel wood gathering, prescribed burns and putting in power lines.
So what can people do to help bats survive? "One of the main things homeowners can do is to create a pond or place of water on their property. That's a big thing in this arid area," Ramsey says. "It needs to be a somewhat open place so the bats can drink on the fly. They don't land at the water's edge to drink; that's not their habit. So for a water source to be attractive to bats, it needs to have enough room around it so they can swoop in, drink and go."
Individuals interested in helping preserve bats can also help out conservation groups, she adds, especially groups concerned with helping to maintain wild habitat, like the WBWG and the NMBWG.
Building and hanging bat houses, something Ramsey says is pushed in city areas, can also provide alternate habitat for threatened bats. Forest service program manager Telles says bat houses not only provide a place for desperate bats to roost, but help to fill that education gap, too.
"It's true that we have a lot of natural habitat for bats," Telles says, noting that many bats roost under the bark of our larger Ponderosa pines. "It's amazing some of the places you'll find them." He puts his hands together and peeks through the tiny sliver of space between them. "I mean, crevices that are just teeny!
"But even with all the trees around, I had bats at my own house, roosting right on the side," he goes on. "So, I put up a bat house. They're great. They're educational, they're fun, and they get people over their misconceptions about bats, too."
Bat Conservation International (www.batcon.org) sells ready-to-hang houses, simple kits and instruction manuals for do-it-yourselfers.
Telles also says there's room for people to help out as volunteers, doing bat surveys, for example. Volunteers are coordinated through the researchers working in the area. Interested parties can contact him, he says, or the local universities — through the biology department at WNMU and the wildlife department at NMSU.
The NMBWG also accepts volunteers and has some opportunities for student employment. Locally, members of the group have worked with New Mexico Department of Transportation (NMDOT) on bat awareness and use of wooden bridges by bats. At the suggestion of NMBWG members, bat houses were placed near colonies located under bridges to serve as an alternate roost during renovation or demolition of those bridges.
But maintaining natural habitat when possible is, of course, the best option, Telles says, pointing to the forest service's ecosystem management goals. "We're trying to get fire back on the landscape," he says. "We are trying to mimic what fire would have done naturally in the past." Smaller, intermittent fires would normally clear out brush and smaller trees, he says, leaving healthier big trees, the kind of trees bats need to roost.
"The best thing is to have a healthy, natural habitat," Telles says. "Of course, that's been compromised, so the next best thing is for people to be aware, to be considerate of the bats. To understand them and to help them."
| Bat Basics According to Bat Conservation International (www.batcon.org): Bats are warm-blooded mammals, but such unique ones that scientists have placed them in a group of their own, Chiroptera, which means "hand-wing." All living bat species fit into one of two major groups, the Microchiroptera or the Megachiroptera. Members of the latter group are commonly referred to as "flying foxes" because of their fox-like faces. Bats have fur and their wings are made of stretched skin, not feathers. Fewer than half of one percent of bats have been found to carry rabies. Like humans, bats give birth to completely dependent young and nurse them from a pair of pectoral breasts. In fact, Linnaeus, the father of modern taxonomy, was so impressed by the similarities between bats and primates (lemurs, monkeys, apes and humans) that he originally put them into the same taxonomic group. Today's scientists generally agree that primates and bats share a common shrew-like ancestor, but belong to separate groups. Bats have been around for a very long time. Bat fossils have been found that date back approximately 50 million years, and those ancient bats closely resemble the bats we know today. Many bats must live in large colonies in order to successfully rear young. Yet most species produce only one young per year. These factors combine to make bats exceptionally vulnerable to extinction. |
US Forest Service, 3005 E. Camino del Bosque, Silver City, NM 88061, 388-8201, www2.srs.fs.fed.us/r3/gila. Western Bat Working Group, PO Box 2153, Rapid City, SD 57709, www.wbwg.org New Mexico Bat Working Group, www.geocities.com/nmbwg