ON THK nE'rKJ?]\IINATl()N OF AGE IN BATS. 



BY 



Km'd Andkksen, f.z.s. 



The (.jues^tion was out-e put to me hy a fellow zoologist: " What 

 is the possible age of one of our small insectivorous bats, supposing 

 it is allowed to live its normal span of years without accidents of 

 any kind ?" 1 had to confess that we knew practically nothing 

 about it. Insectivorous bats, any species, are extremely difficult to 

 keep alive in captivity, and Horseshoe-Bats are among the most 

 intractable of all ; 1 am not aware that any species of these latter 

 has been kept in confinement for moi-e than a few weeks. But 

 even if this were otherwise, the length of its life in captivity would 

 of course, give us no reliable information of the age the indi\ddual 

 might reach under the totall}^ different conditi^nsof Nature, though 

 it might in the most favourable cases give us an idea of the lowest 

 possible age of the individual under natural conditions. There is 

 another way to approach the problem, so long as we have no better 

 facts to judge from. The length of the period of immaturity will, 

 as a general rule, in some \'ague sort of way enable us to form an 

 opinion of the normal age the individual is destined to obtain ; a 

 mammal which quickly becomes full grown will probably have a 

 rather short series of years to live as adult, and vice versa. There 

 raiij be hundreds of exceptions from this rule among lower verte- 

 brates, but I doubt that there are many among mammals. In- 

 sectivorous bats have only a short period of immaturity, species of 

 the size of the Rufous Horseshoe-Bat of India (lihinolophus rovxi) 

 hardly more than about six months (I am speaking of the period of 

 growth, not of the time required for sexual maturity, of which we 

 know but little in the case of most bats), and their life-time may 

 therefore be supposed not to be very long. A more definite answer 

 it has, to my knowledge, till now not been possible to give. 



Although I do not deny that it might be interesting to be able 

 to answer the question just referred to, there is another problem, 

 closely connected with this, and which in ni)^ opinion is of more 

 practical importance. It is this. If an insectivorous bat is placed 

 in our hands, have we then anv means by which to determine its 

 age y The question may be answered both ways. It is easy 

 enough to decide whether it is innnature or adult (by examining 

 the epiphyses at the distal ends of the metacarpals, which can be 

 done by simple exterior inspection, without injuring the individual). 

 Supposing it to be adult, it is again easy enough to tell, by the 

 degree of wear of its teeth, whether it is a youngish adult, a middle 

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