410 



G. O. Batzli et al. 



faster turnover rate of gut contents than an ungulate, it requires less time 

 for foraging. Caribou, on the other hand, being large and mobile, are 

 less vulnerable to predators and can therefore spend more time foraging. 

 During the summer they must make up for the undernutrition they suffer 

 during winter. Their grazing patterns can be interpreted as an attempt to 

 maximize their intake of high quality forage. But on some days harass- 

 ment by mosquitoes and warble flies prevents them from obtaining ade- 

 quate nutrients. 



Owing to their periodic abundance lemmings can strongly affect 

 vegetational composition and production on the coastal tundra at Barrow. 

 There is little evidence of this in the Prudhoe Bay region, however, and 

 the effects of grazing are not conspicuous there. Both lemmings and cari- 

 bou influence soil characteristics by burrowing, trampling and manur- 

 ing. 



A proposed nutrient-transport hypothesis ascribes the uneven distri- 

 bution of soil nutrients and biological activity in polygonized terrain to 

 the redistribution of nutrients by animals. 



