HOWELL — ^CALIFORNIA BAT ROOSTS 
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time of daily appearance evidently varies considerably in different 
parts of the range of the species. 
Several foreign observers have conducted exhaustive experiments — 
too well known to dwell upon here at much length — which prove that 
all bats are provided with highly developed tactile nerves in the wing 
membrane; but that those with very large ears, in addition to face and 
nose appendages, have these members so extremely sensitive that it 
is beyond human comprehension. They can dodge threads hung in a 
dark room and perform other remarkable feats. It is small wonder 
that these peculiarly endowed creatures should select the darkest hours 
in which to do their hunting, while their less gifted brethren often appear 
at sunset. Certain students have claimed that the sense of sight in 
the large-eared bats is less acute than in those with small ears, and this 
may usually be so, but certainly not in the case of Macrotus, which 
can see better than any other bats with which I am acquainted. In 
some genera, the formation of the nose bones indicates an especially 
keen sense of smell, and such probably often pick insects from leaves 
and other resting places (as Plecotus is known to do) . 
Many bats have the power partially to suspend animation when 
asleep. They then become semi-torpid, with decreased temperature 
and respiration, even on the hottest days; and it takes several moments 
— longer in cold weather — for them fully to regain their normal activity. 
This torpidity evidently can be indulged in by the bats at will, and 
during cooler weather may last for considerable periods. Rain, unless 
accompanied by very low temperature, has little effect upon bats, but 
high winds render them almost helpless, and the partial suspension of 
all bodily functions then stands them in good stead and enables them 
to bide their time with considerable comfort until the climatic conditions 
are more propitious. This phenomenon I have called voluntary hiber- 
nation, as opposed to the true hibernation in which, because of cold, 
failure of food supply, or other external influences, an animal becomes 
completely torpid in spite of itself. The so-called hibernation of most 
bats evidently belongs to the former class, although there are at least 
several foreign species which hibernate in the true sense of the word. 
Among most forms of bats, the sexes are usually found apart, espe- 
cially at the season when the young are born. Of the species most 
typical of the deserts, the males probably spend the entire season in 
the one zone; but with certain others, as G. M. Allen has pointed out, 
the males may seek a higher altitude than do the females during the 
hottest weather. Certain collectors have noted that only females and 
