Up until now, the little brown myotis was the only bat thought to live in the Yukon. But this past summer, a Yukon biologist recorded not one but two new bat species in the territory, and his discovery has a lot to do with advances in technology.

For the last three summers Brian Slough has been using a small portable bat detector to record bats in the wild. He has recorded numerous calls of the little brown myotis, but it was only last summer that his equipment picked up something different.

In the La Biche area of the southern Yukon, he recorded what he thinks is either a western long-eared, a northern long-eared or a California myotis bat. A few months later, while on a field trip at Morris Lake northeast of Teslin, he recorded what he thinks is either a big brown or a silver-haired bat.

Bats can be difficult to study at the best of times as humans cannot hear their high-pitched sounds. But the new portable bat detectors can translate these high-frequency bat sounds into ones that are audible for humans. The unit transfers this sound to a tape recorder, whose contents can then be downloaded into a computer and analyzed on the screen.

"People started off recording bats with high speed tape recorders and analyzing calls with oscilloscopes, equipment that could cost $20,000, but now you can buy sophisticated equipment at a reasonable price," explains Slough.

On Slough's system, called the Anabat II, the bat call appears on the computer screen as a graph, with frequency on one axis and time on the other. "You can analyze factors such as the length of the call, frequency range, and the time between calls which are diagnostic for some species," says Slough.

Bat detectors will not replace more traditional methods for studying bats because biologists still need positive proof of which species live in a particular area. Slough puts up mist nets -- special nets constructed with very fine strands of nylon -- whenever he is doing fieldwork on bats.

A live bat can also provide more information than a recorded call. When Slough captures a bat, he attaches bands to their forearms so that they can be identified if they are recaptured. He also sends tissue samples from the bats to researchers at the University of Alaska who are using genetic studies to track where bats migrate.

But sometimes not many bats end up in the nets because they use very open habitats in the Yukon. When he set up his mist nets by the La Biche River in June, for example, he did not capture any bats, possibly because not many bats had migrated back to the area yet. Most bats are live-captured near roosts in abandoned buildings.

The bat detector did pick up one lone call which hit a high of 100 kilohertz. Calls emitted by a little brown myotis do not exceed 70 kilohertz. At Morris Lake the bat detector recorded a whole series of calls that were of lower frequency than the little brown myotis, which told him that a larger bat had made the calls.

Slough does not think that the presence of new bat species in the Yukon is very surprising as very little is known about bats here. He is the only person doing bat research in the territory. Bat researchers have identified a number of new species of bats in northern British Columbia in recent years, so it is not surprising that these species should be found in the Yukon as well.

While he is certain that the species he recorded were not little brown myotis, he points out that the use of bat detectors to identify species is still controversial in some circles. Bats emit a range of different calls, and there can be overlap of calls between species.

Bats "echolocate" by sending out signals -- usually through their mouths, but sometimes through their nostrils -- and listening for the faint echoes that return. By comparing the original sounds with the returning echoes, bats can measure the distance to a target and even evaluate its size, texture, and direction and speed of movement.

Bats emit only one echolocation pulse per wing beat when hunting. However, when they detect an insect, their pulse repetition rate skyrockets up to roughly 200 wing beats per second, creating what is known as a "feeding buzz."

There are many more questions to be answered about bats in the Yukon. For example, no one knows where they go in winter, though Slough suspects that they head for thermokarst caves in southeast Alaska.

Slough hopes that his research will help to educate people about bats, which still have a bad reputation in some circles. "There is a general fear about bats which is the result of centuries of myths and misconception about them," he says. "The more we understand about them, the more we realize their value and place in natural ecosystems."

Bats fill a very important niche in the natural world. For example, all northern bats are insect eaters, and a species like the little brown myotis can catch 600 or more insects in an hour.

Bat species are in decline around the world, as these species are very vulnerable to extinction. Most females produce only one pup each year, and in winter bats often form huge colonies where they are very vulnerable to human disturbance.

But a major step in conserving bats and learning more about them is finding out which species live in the territory. "It's the whole question of determining the species and what their important habitats are. You cannot conserve animals if you do not know what is there," says Slough.

For more information or to report unusual observations on bats, contact Brian Slough at 668-3295 or bslough@yknet.yk.ca.