HART 



IRVING: They must be able to take quite a lot, because I 

 caught a live Dicrostonyx in March on one of the sand islands 

 off the coast east of Barrow. It was over a mile from shore; we 

 heard him scratching around during the night and he was still 

 alive in the morning. We then traveled about ten miles off- 

 shore on the ice and found one Dicrostonyx which had died out 

 there, but it was obviously not killed by, or transported by a 

 predator. I saw the tracks of several others around seven or 

 eight miles from the shore, which must take them quite a long 

 time at their rate of travel. 



MORRISON: One of our group tracked a lemming a couple 

 of miles out on the ice off Barter Island. There was no indica- 

 tion of where it was going, but the tracks were in a straight line, 

 not as though it was searching or meandering. 



HANNON; With respect to running ability we have observed 

 that the hamster, which is about the same size as the lemming, 

 can run six to eight miles a day — all of this distance being covered 

 entirely during the hours of darkness. 



FOLK; The white rat can run 21 miles, so they are capable 

 of running distances, for example one ran 28 miles in 24 hours 

 and another ran 32 miles in 24 hours. 



IRVING: But the lemmings were found under conditions where 

 even with their hardiness they were expending metabolic energy 

 at a very rapid rate for maintenance of body temperature. 



JOHANSEN: I may perhaps comment on my work on the 

 muskrats. One project was concerned with the fact that the musk- 

 rat has a very dense fur and a naked tail, which suggested to me 

 that this tail might have a crucial importance as a heat exchanger; 

 and this turned out to be the case. The tail of the muskrat as it 

 was studied by temperature measurements and plethysmography 

 (where Charles Eagan gave expert help) showed that the tail blood 

 flow can change by a factor more than 400 within a very short 



234 



