The Spotted Bat -- Washington's Mystery Bat
by Margaret Gaspari
The Spotted Bat (Euderma maculatum) is undoubtedly the easiest American bat to identify with its black back sporting three large white spots and its huge pink ears, the largest ears of any American bat. Often considered America's most beautiful bat, it is also the most elusive. It's been found in arid areas throughout the western United States including Oregon. It's been found in British Columbia. We've even heard them in this state. But no one has ever caught a Spotted Bat in Washington. Yet!1
Actually this bat is somewhat of an enigma throughout its range. It is caught only rarely. Prior to 1958 there were only 16 known specimens. Except for one sixty-year-old record of four found hibernating in a cave in Utah, we have no idea where it goes in the winter. All this makes biologists decidedly uneasy. We don't know enough about this bat to know whether it's in danger of extinction or not.
How can a species hide so effectively from the determined efforts of science? Well, for one thing, the Spotted Bat needs crevices in rock high on cliff faces for day roosts. This requirement means that their population distribution is patchy. It also means that they are hard to find and study. Secondly, they don't leave their day roosts until it is quite dark. Then they tend to hunt fairly high and always alone. Most are caught in nets over the water sources they rely on.
The Spotted Bat does have a few habits that help scientists. One is that its echolocation calls are loud and so low (8-16 kHz) they can be heard without a bat detector. In fact, people often mistake their calls for insect noises. These calls are an excellent adaptation to catching the large, tympanate moths that can hear only higher bat calls. Low calls also travel long distances (700-800 feet) and so they may help the bat advertise its hunting territory and prevent intrusions by other Spotted Bats. Their calls also explain their huge ears. Usually found only on gleaning bats, big ears in this case are useful for picking up echoes long range.
Another interesting habit of the Spotted Bat is its hunting technique. It may fly five to ten miles to its hunting grounds where it will forage high, 30 ft to 45 ft up, catching its prey (mostly moths) on the wing. Amazingly it will continue to fly all night covering the same route it did on previous nights, and with amazing punctuality. With this type of strategy, the females are unable to return to feed their young until the night's hunting is done.
Recently a lot more effort has gone into collecting data on this beautiful bat. It's echolocation call, a high pitched, metallic click, can alert biologists to their locations. So if you're in the Okanagan, or in northeastern Washington, or anywhere east of the Cascades this summer, keep an ear out for our most elusive bat. You may be able to add another piece to the Spotted Bat puzzle.
1. In 2002 a Spotted Bat was finally mist netted in eastern Washington.