THE NOCTULE 83 



The duration of flight is remarkably short, a habit shared 

 with its Irish representative, Leisler's bat. 



Mr. C. Oldham in England, and the late Dr. N. Alcock 

 in Ireland, by careful watching, confirmed the opinion of 

 Dowker that the vesper tinal flight lasts for about an hour 

 and seldom exceeds this limit; two hours away from the 

 roost was exceptional. As Alcock pointed out, " a 

 mammaHhat rests for six months in the year, that only 

 feeds for one hour a day during the other six, spending 

 this hour in rapid and sustained flight as great a con- 

 trast as can be imagined to its previous condition cer- 

 tainly presents a very curious picture of animal economy." 

 Alcock was reckoning it as active from April until Sep- 

 tember, but even allowing for a month or two at either 

 end when the bat comes out occasionally, and for a morn- 

 ing hour of energy, the problem is still acute. During 

 the winter sleep noctules herd together in hollow trees or 

 in the soofs of buildings, but in summer the diurnal 

 resting-place is usually a hollow tree. The species has 

 been included amongst the cave bats, but the evidence 

 is not altogether satisfactory. Regular cave-haunting 

 bats, as I have proved or endeavoured to prove elsewhere, 

 frequently move and feed in the caves themselves, and, 

 in the West of England, at any rate, go abroad to feed in 

 winter. There is much that we have yet to learn about 

 the mystery of hibernation, and one by one our ancient 

 beliefs, founded apparently on the best evidence, are 

 subjected to rude shocks. Yet, so far as we know at 

 present, the noctule sleeps very soundly in winter, all its 

 energies latent during that period when flying insects are 

 difficult to obtain. 



Directly the bats emerge in the evening they fly straight 

 off to the feeding-ground, a glade in the woods, an open 

 field, or some large sheet of water; the situation varies 

 according to the insects which are the object of the chase, 



