Wednesday, August 11, 2010

The Better to Hear You With

That passage from “Little Red Riding Hood” could apply as easily to Townsend’s Big-eared Bat, Corynorhinus townsendii, as it does to the Big Bad Wolf. This docile little creature is not nearly as menacing, however, and a true friend to farmers and other folks plagued by insects.

I was fortunate enough to discover this roosting individual inside an abandoned house in Brown Canyon on the Buenos Aires National Wildlife Refuge in southern Arizona. Thanks to Philip Kline who had informed me of another species of bat in the same house. That bit of knowledge prompted me to venture into what had to be Hanta Virus Central to try my own luck. I found the solitary Townsend’s Big-eared Bat as a result.

Townsend’s Big-eared Bat occurs chiefly west of the Rocky Mountains from southern British Columbia through Mexico, but isolated populations in the Ozark Plateau and Appalachian Mountains are not thriving. Like most bats, this species is incredibly sensitive to any disturbance during hibernation in caves, mine shafts, and similar locations.

Those big ears come in very handy when the bat is hunting. Most insect-eating bats use echolocation to pinpoint their prey in flight, homing in on the audible signals bouncing off their moving target. Big-eared bats have raised this hunting style to an art form, and few moths can escape these nimble fliers.

This species roosts singly during the day in the summer months, but individuals cluster together during winter. Mating happens in late autumn or early winter, and each female gives birth to a single offspring in May or June. Maternity colonies can include several dozen to a few hundred females.

Look for this species in desert scrub or dry pine forest habitats for the most part. Note that many references still list it by its older scientific name, Plecotus townsendii. Besides the extra long ears, often folded back as the one ear in the image above shows, this bat is recognized by the pair of glandular bulbs that rise above the nostrils.

Additional sources of information include this great page by Texas Parks & Wildlife, and this page from Pima County government that likely addresses the subspecies imaged above since Brown Canyon is in the Baboquivari Mountains (pronounced Bab-o-KEEV-er-ee).

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