AMERICAN BATS — HANDLE Y 213 



Subgenus Plecotus 



Invasion of Eurasia by way of the Bering Strait area by the P. 

 auritus stock probably occurred during the Phocene [much migration 

 in Middle and Upper Pliocene (Simpson, 1947, p. 625)]. This would 

 have required a more northern distribution than any species of Plecotus 

 has today. Changes in habits or habitat could have allowed a more 

 northern range. 



Species of Plecotus now range into the warmer portions of the Cana- 

 dian life zone (and its Eurasian equivalent) . The cooler portions of this 

 zone lie within 1 ,000 miles of Bering Strait. Only a slight amelioration 

 of today's climate would be required to provide similar floral conditions 

 to Bering Strait. The present wide distribution of cool climates seems 

 to be an exception in geological history. Even during the Pleistocene 

 "Ice Age" warm climates and their associated faunas extended farther 

 north during the interglacial periods than they do today. Presumably, 

 during the Pliocene, warmer climates may have extended even farther 

 north. 



If the pre-Pliocene Plecotus-li^Q bats were not cave inhabitants, then 

 a change in habit to include cave roosting would have allowed a more 

 northern dispersal, provided suitable food supplies and adequate caves 

 were available. Resort to caves for hibernation permits habitation of 

 areas with colder winters. It also provides refuge in eras of changing 

 climate, for modification of the climate within the cave may be negli- 

 gible in comparison with the change on the surface. Barhastella and 

 Plecotus auritus frequently roost during the summer under loose bark 

 on tree trunks, in cavities in trees and under the eaves of houses, but 

 usually hibernate in caves or in attics of houses. The most primitive 

 living species of the subgenus Corynorhinus , P. rafinesquii, appears 

 to be primarily a tree rooster, whereas the progressive species P. 

 townsendii seems to roost only in caves and houses. 



The ancestors of Plecotus auritus spread through most of the tem- 

 perate portions of Eurasia, but were blocked from southward expansion 

 into Maylasia and Africa by the hot climates of the equatorial regions. 

 They came eventually to overlap broadly and perhaps partially dis- 

 place the range of their relative, Barhastella, a rather rare bat whose 

 continent-spanning range averages somewhat more southern than the 

 range of P. auritus. 



The Plecotus that now inhabits Eurasia and northern Africa is 

 probably not very different in appearance from the pre-Pleistocene 

 migrant. This may be inferred from its similarity to the primitive 

 New World species P. phyllotis and Pleistocene P. alleganiensis and 

 P. crassidens. If a common origin for these forms and P. auritus be 

 envisioned, and if a pre-Pleistocene dispersal of Plecotus into Eurasia 



