As one of Yosemite's interpretive rangers, the time is approaching for my favorite part of the campfire program. The fire has burned to a rich even orange glow It's time to begin my final story of the evening. The South Fork of the Merced River murmurs a short distance away, creating the perfect ambiance at the Wawona campground. The audience sits quietly, absorbed in my campfire yarn.

Suddenly, a faceless voice in the audience calls out, "Hey, look! A bat!"

The spell is broken The quiet reverie of moments before is now replaced by something more akin to pandemonium. Once again, the program I've planned is upstaged by the fanciful flight of the world's only flying mammal the bat. Weighing as little as four or five grams, this flying wonder is a heavyweight in popular appeal.

In order to recapture my audience, I've found it necessary to research some basic information about one of Yosemite's most visible nocturnal creatures. But I would hardly qualify as a bat fan. In fact, at times I would happily classify them as a nocturnal nuisance.

l would little guess that soon I would have an opportunity to learn more about my campfire competitors firsthand. When a team of bat researchers visited Wawona, I quickly volunteered to assist in capturing bats as part of an effort to learn how many different species inhabit the southern portion of the park.

Bat Researchers, Dr. Elizabeth (Dixie) Pierson and Dr. William Rainey, are visiting Yosemite for the third consecutive year. Bat research in the Park has been very limited. As Pierson and Rainey report in their findings of last year, "Although bats comprise a major percentage of the mammalian fauna of Yosemite National Park, bat diversity has not been formally investigated in the park since the work of Joseph Grinnell in 1920."

Traveling to different parts of the park, Pierce and Rainey are looking at the distribution and abundance of bats across the varied habitats and great elevation range of Yosemite. Additionally they seek information on the distribution of two rare cliff dwelling species, the Mastiff Bat (Eumops perotis) and the Spotted Bat (Euderma maculatum). In the summer of 1993, a Spotted bat was caught by Pierson and Rainey near Mirror Lake, examined and released. This was a prize catch, being the first live capture of the spotted bat in California; the only former evidence of their existence was from dead specimens found several decades earlier.

A survey of bat diversity may involve several methods of inventory. Usually, inspection of roosts can reveal information about varieties of bat species that tend to colonize. Acoustic surveys use ultrasound detectors to record the different types of sounds used in echolocation of the bat's prey But the best method of sampling general bat diversity is mist netting, where individual bats are captured, studied and then released.

"Using mist nets for bats is a relatively recent innovation," Bill Rainey explains. "Classical bat inventory work relied heavily on shooting them and making study skins of the dead animals. Mist netting is more analogous to modern catch and release trout fishing."

This year, Wawona is one area of the park in which bat activity will be monitored. Early in the evening, hours before sunset, we arrive at what has been selected as a suitable capture site. Tonight's bat party includes Dixie and Bill; several associates and student assistants; Yosemite's Chief Naturalist, Maureen Loughlin; and a couple of ranger/naturalists. The chosen site is along the river, next to the Wawona golf course.

The first order of business is to set up the mist nets. The mist net is a cleverly designed piece of light nylon strong enough to catch birds... or bats. Running my fingers along its tough, lacy fabric, it reminds me of reinforced hair netting. Mist netting is an important means of surveying the bat population because it provides in-hand observations, but a night's catch is not a representative sample of the bat population. Because of differences in foraging behaviors, some species are simply easier to catch than others and those species have a greater representation in the net

The mist net will be stretched across the river to catch the bats which use the South Fork as a fly way in their nightly pursuit of prey. Bats use a unique method of locating their prey called echolocation. Emitting high frequency pulses and listening for the echo bouncing back, they are able to detect flying insects such as moths and mosquitoes. Bats have a voracious appetite, with some species catching their body weight in insects every night

Five sixty-foot nets are stretched about one foot above the water. Four of the five nets reach two meters above the water. The final one is stretched three meters in hopes of capturing the elusive Eumops perotis, which tends to fly higher than other species. Commonly called the Greater Mastiff Bat, Eumops is the largest bat found in North America. Even a beginning batter like myself soon understands that the Eumops would be a prize catch.

"No one told me that capturing bats is an aquatic sport," I think to myself as I plunge into the South Fork wearing my boots and jeans. The more experienced bat hunters casually pull on their waders and wet suits. Fortunately, in early August the water level is only about thigh depth and the temperature is quite comfortable. Still, I can easily imagine myself a few hours later, stumbling across mossy rocks and floundering in the darkness trying to reach the mist nets that stretch across the river Fortunately, stealth is not an important factor once bats are in the net.

By dusk the nets are opened (it's poor form to open the nets early and possibly catch a bird on its way to its roost). The experienced batters stand by a net, eating a bit of dinner before our anticipated visitors arrive.

Several research assistants are above the river bed, tracking the flight of different species with audio detectors that can identify species whose voices are too high a frequency to be heard by the unaided ear. The ultrasound bat detectors allow the researchers to record the bats' silent symphony which will late be transposed into a visual sonogram. Some, but not all, species have a distinctive call and can be identified through sonograms.

Within minutes of opening the nets, four tiny Myotis yumanensis entangle themselves while hunting insects near the water's surface. On this scientific expedition the Yuma bat is casually referred to as the "Yum-Yum" or by the plural, "yummies".

Although I am excited as I wade out to assist in untangling the creatures, I can tell by the reaction of the experienced bat-catchers that these early arrivals were clearly expected. "Just like human teenagers out with the keys to the car for the first time," Dixie explains to me as her fingers nimbly extract our tangled visitor, "the young Myotis get careless."

I am content to watch the previously immunized biologists handle the bats, since rabies is present in bats and is not a disease to be taken lightly. But research reveals that less than a half of 1% of bats contract rabies (about the same frequency as other animals). Of course all wild animals, including bats, should never be handled if encountered by hikers or campers.

In the middle of the river, I receive my first lesson in bat anatomy as Dixie spreads the wing of the bat to show the fine membranes that stretch across the hand of the bat. The "hand" is indeed similar to our own, with thumb and fingers. In fact, the biological name for bats is chiroptera meaning "hand-wing". The wing is made up of a membrane stretching between the fingers, similar in thickness and strength to a sandwich bag. The translucent membrane is permeated with blood vessels. This vascular membrane not only provides enough blood and oxygen to the wing during flight but also helps in cooling the bat while air-borne. Some bats have even been observed using their wings during aerial assaults to capture prey The bats will use their wings like baseball gloves, snagging insects and swatting them into their mouth. Sometimes they will trap months in the pocket of skin between the rear feet, then in a swift somersault motion, the bats duck their heads into the pocket for a quick in-flight snack.

The Myotis is carefully placed in a small cloth sack ...Bat-in-the-bag. Once on shore the bag holding the bat is placed in a wash-tub sized plastic box filled with strings of clothes pins keeping the bat-in-the-bag secure and warm until it's time for data collection .The tub is dubbed the Bat Hotel. This bat is the first patron of the night for the Bat Motel, but business is brisk: soon there is a line of small cloth bags clipped neatly in a row.

By the end of the night (after three hours of netting) we will have caught and released fifty-four bats --an impressive batting average. I think of the many fishermen who have walked these same shores for hours without even a nibble. The South Fork, I decide, has much better batting than fishing.

"I'll definitely need a glove to untangle this one," Dixie comments as she identifies the struggling bat as Eptesicus fuscus, the Big Brown Bat. Although the Big Brown Bat is definitely brown, it doesn't look very big. To my untrained eye, the big brown bat looks about the same size as all the others. Our first bats, the Myotis, were about the size of a small flying cotton ball. The Big Brown Bat looks to be the size of a big cotton ball. In comparison, the body of the largest of the bats we will catch, a Eumops (Greater Mastiff), using nonmetric measurements, is about the size of a winged-croissant.

Holding the Big Brown Bat in the gloved hand and working with the net with her free hand, Dixie comments, "These guys are feisty" She pauses briefly. "I respect that."

I am also developing an increasing respect for them, as I learn more about these nocturnal creatures.

As the night progresses, so does the number of specimens in our temporary collection. The catch is quite successful - at this rate the bat hotel will have to post a "No Vacancy" sign before midnight. I am now in the river less often. It's not that I've grown blase, just more discriminating. I still wade into the water to examine new species which I have yet to see, which happens frequently Before the night is through, we will have trapped eleven species. But as of 10:30 no mastiff. The nets will be taken down in less than thirty minutes. The mastiff's call is heard overhead, but it is flying too high to be caught.

On this final night of the inventory, the group wants to finish early (early this night is 1:30AM), so the nets will be closed at eleven. Meanwhile, Dixie begins to examine each bat and to collect data. The bats that screeched and struggled in the net a few minutes before, seem docile as they are handled for examination.

Sitting at a portable table set up near the river, Dixie peers into a binocular microscope, determining such things as gender, age, and the amount of tooth wear The length of the forearm is measured along with the weight of each animal. For their temporary lodging in the bat hotel, the guests are expected to leave a small deposit.. of guano. The bat scat will be examined later for remains of insect parts to determine the feeding habits of the different species.

During their short stay in the bat hotel, many bats enter a slightly torpid state. Dixie slips a young bat under her jacket, warming it up before releasing it. Ray Miller, a research associate, does likewise.

"Bats have a normal temperature of one hundred and seven degrees," Ray explains. "Even our body heat is barely enough to jump start a sluggish bat."

Ray is in charge of carefully launching the bats back into their aerial habitat. Bats are used to beginning a flight from their elevated roosts in trees and cliffs rather than from near ground level, so precautions are taken to assure them enough height to gain momentum for successful flight. As if someone just let the bat-out-of-the-bag, most eagerly take wing. Coaching the reluctant ones like personal proteges, Ray gently tosses one into the air, following it with a spot light to confirm a successful departure.

As we finish examining the bats, Bill is in the river, taking down the nets. His work is interrupted at regular intervals by thoughtless bats who don't realize we're trying to finish up for the evening. Finally he clambers up the bank of the river bed.

"The last bat of the evening," he says with a triumphant voice. "Guess which one."

"Eumops!" Dixie says Bill gently hands her the bag with the catch of the night. Forgetting the work at hand, Dixie slips the Eumops head out of the bag. Seeing only the head, I can already see that it is by far larger than any of the other species we've captured. Almost reluctantly she slips it into the bag and we continue our bat inventory saving the Eumops as the finale.

Several bats later, it's time to examine the final specimen, the Eumops. The nets are packed up, and the other bats released, so everyone gathers around to admire the large bat With a professional excitement, they examine a large scent sack near the animal's neck. After looking at the gland, Dixie absentmindedly strokes the fur on the back of the quiet creature. "Bats are so gentle," she says softly "You'd never hold any other wild animal like this. Imagine trying to hold a wood rat."

A few photographs are taken of this gentle giant before Dixie climbs to the roof of the van to give the bat greater height for its takeoff Aided by a careful toss, the bat glides silently into the night

It's now early morning, the bags are packed into the van, but Maureen Loughlin, Acting Chief Naturalist, discusses possible future projects with the bat team. If funding is available, perhaps radio telemetry devices can he purchased to track the bats back to their daytime roosts. In the course of a night's hunt, large bats can travel perhaps as much as twenty-five miles in search of enough food. Twenty-five miles...as the bat flies... covers a lot of territory in Yosemite. Bats roosting in Tenaya Canyon or on the face of Half Dome could cover large portions of Yosemite valley every night Research in bat ecology has been limited, so information gained in Yosemite could have much broader implications in the study of forested lands of Western North America

The data has not yet been analyzed for this night's bat inventory. But immediate observations reveal an amazingly rich diversity of bat species living in the park. Juveniles and nursing females prove that the park supports a reproductive population. Yosemite proves not just to be a park playground for people, but also an important habitat for the preservation of yet another variety of animal.

The newly gained information on bats will be helpful in determining appropriate park management strategies. Construction of bridges (an important roosting site for bats) can be designed to provide bat roosting space. Further investigation is needed of abandoned mines around the Park and the role they play in providing roosting habitat. According to last year's survey, the Mastiff and the Spotted Bat (both rare species), are believed to roost and forage in popular recreational use areas (rock faces and meadows). Recreational impact upon these sites warrants further study

How much of tonight's activities will contribute to the scientific body of knowledge about bats, I don't know. But the experience has certainly contributed to my own knowledge as a ranger/naturalist. During future campfires I will never look at bats in the same way. Bats will be considered honored guests, not campfire competitors. As with so many fields of natural history knowledge brings respect. Tonight I've gained admiration, appreciation, and perhaps even a little affection towards the my former campfire competitor -- the bat.