i86 DISCUSSION 



R. M. Laws: One British Company has spent about /;i25,ooo on this 

 technique, but there are still problems to overcome. 



C. W. Hulme: The chief problem has been the development of a 

 conductor which can be incorporated in a nylon fore-runner and withstand 

 the tension and enormous stretching which this is subjected to. This has now 

 been solved, more or less. 



A. JoNSGARD : Norwegian gunners dislike the electric method because it 

 has been liable to errors. 



C. W. Hulme: Superstition (electrophobia) and prejudice also are 

 involved in their objections. 



J. B. Cragg: I think there is no doubt that the electric system as at 

 present constituted is more difficult to use, at least under Antarctic conditions. 

 M. E. Solomon: Turning to McLaren's paper: would it be possible for 

 experimenters or Eskimos to make artificial birth lairs — such as igloo-like 

 shelters over holes made in the ice — and so increase the seal population on 

 a stretch of coast? 



L A. McLaren: This is a nice idea, though it might be difficult to induce 

 a seal to enter a hole smelling strongly of man. 



J. B. Cragg: Are you satisfied with the efficiency of the Eskimo methods 

 for finding lairs ? 



L a. McLaren: The Eskimos certainly do not fmd most of the lairs. 

 The argument has been based on an a priori assumption that a given area has 

 limited sites available, and on an observed correlation between seal numbers 

 and the extent of fast ice. 



G. C. Varley: Obviously suitable areas are a prior requirement. But 

 what controls the seal density within them? The animals must feed while 

 suckling — can food be a limiting factor ? 



L A. McLaren: There may be some element of competition for food. 

 But the 'best' coast-lines (as defined on arbitrary geographical grounds) have 

 the biggest seal populations although these are very crowded and this 

 correlation suggests that trophic factors are not limiting. 

 H. R. Hewer: Do these seals feed during lactation? 

 L a. McLaren: Yes, The ringed seal does, in contrast to the harp seal 

 which breeds on the unstable pack ice and often starves during a short 

 suckling period. The ringed seal has a long suckling period, of up to two 

 and a half months, and so must feed during it. 



H. R. Hewer: This may not be an absolute necessity, for many bull 



