7/10/02
The Naturalist's Corner
By Don Hendershot
The
largest bat in eastern North America is a loner and seldom seen. Which
is a shame, because the hoary bat (Lasiurus cinereus) is a striking
animal. The fur, or pelage, of the hoary bat is a combination of yellowish-brown and dark brown hairs. The buffy or tawny yellow face and throat stand out from the rest of the body, which is composed of darker brown hairs tipped with white giving the bat a frosted or hoary appearance. The snout, lips and margins of the ears are black. The coloring, while distinctive, is cryptic, and when the bat is roosting on a tree trunk it is quite camouflaged.
The hoary bat can reach a length of six inches with a wingspan of 16 inches. Yet for all this mass, it still weighs about an ounce (28 grams.) Of course all things are relative — 28 grams puts the hoary in the super heavyweight division of eastern bats. Two of the most common eastern bats, eastern pipistrelle and little brown, weigh seven and eight grams, respectively. The closest eastern bat, in size, to the hoary is the big brown, which weighs 18 grams and may reach a total length of five inches and has a wingspan of 14 inches.
Hoaries are incredibly strong and swift flyers, which is probably the reason they have the widest range of any bat in North America. Hoaries range from coast to coast and from the tundra of Canada to the rainforests of Argentina. During migration they have turned up in places like Bermuda, Iceland and the Orkney Islands of Scotland.
In fact, at some point in time hoaries made it to the island of Hawaii. The only terrestrial mammal in Hawaii, ‘ope ‘ape ‘a, the Hawaiian hoary bat (L. C. senotus) is smaller than its mainland cousin. Scientists believe the ‘ope ‘ape ‘a is a descendent of the South American hoary. Some biologists feel that the Hawaiian hoary may have been isolated long enough to have evolved into a distinct species.
Like most bats, the natural history of the hoary is not well documented. Most are migrant but a few hibernate. The ones that do hibernate appear to hibernate much as they roost — exposed on a tree trunk. One was noted hibernating on the trunk of an Apache pine in the Chiricahua Mountains of Arizona during temperatures as cold as seven degrees Fahrenheit.
Migration is the only time these solitary animals gather. Migrating groups can number in the hundreds. They migrate to southern California in the West and to the Gulf Coast states and on to Mexico in the East.
It is believed that mating takes place during migration, but because of delayed implantation the female doesn’t become pregnant until spring. There are usually two pups born in May or June. The babes are born nearly hairless and the mother cradles them beneath her wings while she roosts. On about the third day the pups’ eyes and ears open. By about three weeks, the young resemble adults and by six to seven weeks they are flying.
The hoary’s diet is made up predominately of moths, but other flying insects like beetles, flies, grasshoppers, dragonflies and even occasionally mosquitoes are taken. Hoaries will get territorial if food is scarce, chasing other bats from their favorite feeding sites. The hoary may eat up to 40 percent of its body weight during a single outing.
Hoaries are rarely seen. Not only are they solitary, they are one of the last bats to leave the roost in the evening, often waiting to well after sundown. If you are fortunate enough to spot a hoary slicing through the moonlight it will be an occasion you will remember. That nearly foot-and-a-half wingspan is pretty impressive.
Hoaries, however, do occasionally give clues to their presence. While most bats’ echolocation sounds are emitted at too high a frequency for human ears, hoaries sometimes emit low-frequency chirps that fall into the range of human hearing. These chirps in the dark can turn you on to some amazing night time company.
(Don Hendershot can be reached at don@smokymountainnews.com)