20 INTRODUCTION 



The truth is that every undoubtedly British species, except 

 the little-known Bechstein's, and, perhaps, the Barbastelle, 

 is now known to be somewhere common. In some of the 

 southern English counties the numbers occurring in a single 

 locality and even in the same sleeping place, although not usually 

 in the same crevice, are surprising. In the artificial caverns at 

 Henley-on-Thames at least four^ species congregate, while ten 

 have been taken within the limits of the surrounding demesne. 

 Again, in Normandy MM. Paul Noel and H. Gadeau de 

 Kerville found no less than seven species — the two Horseshoes, 

 Daubenton's, Natterer's, with the Notch-eared, Whiskered, and 

 Mouse-eared — resorting to a single cavern.^ 



Neglect of bats is a grave error in studying geographical 

 distribution, since, inasmuch as these creatures are possessed of 

 the power of surmounting obstacles which to other mammals 

 must be insuperable, their permanent restriction to definite 

 regions must be due to causes of fundamental importance. 

 And, whereas the wings of bats should have enabled them 

 to occupy with uniformity the entire extent of the British 

 Islands, we find in fact that their distribution therein is not less 

 restricted than that of other mammals. 



In considering the distribution of bats, it must be re- 

 membered that physical features, such as woods, water, and 

 caves, have a very distinct influence on their abundance. 

 Probably no species are less particular about their haunts than 

 the Long-eared and Pipistrelle, and they accordingly may be met 

 with in almost every part of the kingdom, one or the other 

 having found its way to the Shetlands and to remote western 

 Irish islets. Some, especially the Noctule and Leisler's, and 

 perhaps the Whiskered, are probably dependent for their 

 existence on woods, while caves, at least in winter, are no 

 doubt essential for the complete comfort of the two Horse- 

 shoes. Daubenton's, on the other hand, restricts itself to the 

 neighbourhood of sheltered streams or stretches of water. 



The most striking fact in the distribution of British bats is 

 the progressive westward decrease in species, from Normandy 

 with fifteen, through Great Britain with twelve, to Ireland with 



* Daubenton's, Natterer's, Bechstein's (once), and Lesser Horseshoe (once). 

 2 Bull. Soc. Amis. Set. Nat. (Rouen), 4th April 1901, reprint, 2. 



