LARGE BROWN BAT. Eptesicus fuscus (Peale and Beauvois)

Field character.—Size large, about 3 times that of Little California Bat, and only slightly smaller than Hoary Bat. (See pl. 21d.) Total length 4-1/4—5 inches (110-124 mm.), tail 1-3/4—2 inches (47-52 mm.), hind foot 2/5 inch (10 mm.), ear 1/2 inch (12-13 mm.), spread of wings 13-1/4 inches (337 mm.). Coloration rich brown above, pale brown beneath; flight membranes, ears, and muzzle blackish.

Occurrence.—Common in summer in Transition and Canadian zones on west slope of Sierra Nevada. Recorded from Smith Creek, 6 miles east of Coulterville (3000 feet), eastward to Merced Lake (7500 feet). Forages in open spaces between trees at 20 to 50 feet above ground.

The Large Brown Bat merits its name both as to size and color as it is several times as large as the other 'brown' bats (genus Myotis) of the region, and its coloration is a rich brown. Since it is common in practically all parts of the Yosemite region between altitudes of 3000 and 7500 feet, it is likely to come to the attention of visitors in most of the well-known stopping places on the west slope of the mountains. It has not yet been recorded on the east side of the Sierras in the Yosemite section.

The Large Brown Bat does not come out until some time after the Little California and Merriam bats have begun to fly. In Yosemite during June of 1915 this bat appeared from 7:40 to 7:50 P.M., while toward the end of July the days had shortened so that Eptesicus was abroad at 7:30. In late August, at Merced Lake, it was out at 7:15 P.M.; and on October 2 that same year, in Yosemite Valley, a bat of this species was seen over Sentinel Meadow at 5:46 P.M., when Half Dome was still pink-tinged with direct sunlight.

When foraging, this bat courses about in clear places in the forest or over open cañons; usually it keeps well up, anywhere from 25 to 50 feet above the ground. Each individual seems to have a definite forage route or beat. If the collector misses a shot, he is sure to have another chance at the same bat if he but holds his post until the animal swings around over its course again. The flight is relatively slow, and its course is maintained in a direct line for longer periods than is that of most other bats. These features, together with its larger size, render the Large Brown Bat an easier target for both the eye and the gun than are most other species.

The electric lights in the 'streets' of Yosemite's tent cities serve to attract multitudes of native moths and other night-flying insects and these in turn draw the bats. One evening in July there were fully 20, mostly of the present species, to be seen about the lights in one of the camps, where they seemed to be faring exceedingly well.

Our records for this bat, based upon specimens taken, end with August 28 (1915) at Merced Lake; but bats believed to be of this species were seen until late in October. No Large Brown Bats have been observed in the region during the winter months. The species seems not to have been found anywhere in California during that season; in all probability, like many of the birds, it retires to some more southerly locality to spend the period when flying insects are scarce or wanting in our latitudes.