Walt Koenig is the research zoologist at Hastings Natural History Reservation in upper Carmel Valley, Monterey County, California. He is internationally known as the expert on Acorn Woodpecker. Hastings NHR, a field research center associated with the Univ. of California, Berkeley, is an excellent study site. It is rolling oak savanna (above) with a riparian stream and nearby chaparral. While chatting with Walt recently, we learned that he had bats in his belfry ... er, an unused garage. Walt sent me this photo (right); Rita and I drove the hour inland on 1 July 2006 to take a closer look at bats that use oak savanna and day-roost in a garage.
The bat roost is impressive. They are mostly rather small bats with 'pug' faces but no leaf-noses, and rather short ears. They are mostly brownish above and paler below. Size, color, ears and face all suggest bats in the genus Myotis. There have been bat research projects at Hastings NHR in the past, and the Hastings website has an excellent key to the bats of central California. Alas, the key is best used with bats in hand;, when one can measure various body parts. Here, we just have photos. Previous research as shown, however, that at least a dozen species of bats have been recorded at Hastings, including 4-5 species of Myotis.
Evidence of prior bat research was apparent during our short mid-day visit: one of the bats was banded with a metal USFWS band [left]. In the mass of bats on the chimney, we never did figure out exactly which bat had the band.
I focus (below) on two bats from the initial photo (above), and have put a yellow dot on the tragus in the right ear (left ear in our view) of each bat. The tragus is a fleshy appendage at the entrance of the ear that may aid in echolocation (Inges 1965). Its size and shape is important in the identification of some bats. I see a quite different shape in the tragus of these two bats. The one on the left has a tragus that extends almost half-way up the ear, and is curved (like half of a boomerang), while the right-hand bat has a shorter, triangle-shaped tragus. The ears also look a bit shorter overall. Do these represent two species of Myotis? Or could the second bat (right-hand bat below) just be a youngster with less than full-grown ears and tragi? Does the latter theory explain the apparently small, blacker bats in the photo above (the one with the banded bat), especially those with "puppylike" faces?

Dave Johnston at U.C. Berkeley provided the answer: this is a maternity roost of Long-legged Myotis Myotis volans, and those with triangular shaped tragus are the youngsters.

Literature cited:
Ingles, L.G. 1965. Mammals of the Pacific States, 3d ed. Stanford Univ. Press, Stanford, CA.
PHOTOS: All photos are © 2006 Don Roberson, except those attributed to other photographers and used with permission; all rights reserved.





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