Food-getting necessarily involves interrelations 

 between organisms and between species ; these inter- 

 relations are among tlie most important coactions in 

 any community. Animals are adapted variously to 

 capture and utilize certain tyjjes of food, and to avoid 

 being captured by other animals. One must under- 

 stand these adaptations and interrelations to appreci- 

 ate projierly the role that food-getting plays in the 

 dynamics of the community. 



FEKDINC BEHAVIOR 



Free-living animals are commonly classi- 

 fied on the basis of normal feeding behavior, thus : 



Herbivores: feed on living plants 

 Carnivores: feed on animals that they kill 

 Omnivores : feed on both plants and animals 

 Saprovores : feed on dead plants and animals, and 

 excreta 



13 



Ecological Processes 



and Community 



Dynamics: 



Food and 

 Feeding Relationships 



These categories are not sharply defined, as few spe- 

 cies are highly restricted in their diet. Plant-feeding 

 forms occasionally eat animal matter, and carnivores 

 sometimes eat fruit or other plant parts, or carrion. 

 The classification is useful, however, and applies to 

 both terrestrial and aquatic forms, and to any taxo- 

 nomic group. 



The various categories are capable of further sub- 

 division. Thus, herbivores include large cursorial 

 grazers, such as bison, antelope, the muskox, caribou, 

 sheep ; small surface-living grazers, such as rabbits, 

 mice, grasshoppers : subterranean-living grazers, 

 such as woodchucks, prairie dogs, kangaroo rats, 

 ground squirrels : browsers, which feed on buds and 

 twigs of trees and shrubs rather than strictly on grass 

 or ground herbs, such as wapiti, deer, moose, grouse, 

 and defoliating types of insects such as the hemlock 

 looper, spruce bud worm, and larch sawfly ; seed-, 

 nut-, and fruit-eaters, such as squirrels, chipmunks, 

 gallinaceous birds, sparrows ; plant-juice suckers, 

 such as aphids, leafhoppers, mosquitoes, chinch bugs ; 

 and cambium feeders, such as bark beetles, gall flies, 

 cynipids (Clements and Shelford 1939). 



Carnivores are also called predators. Carnivores 

 restricting their food chiefly to insects are called in- 

 sectivores : those limiting themselves largely to fish 

 are called piscivores : and so on. Parasitoids eventu- 

 ally consume their hosts, and hence are a special type 

 of carnivore. Some plants are carnivorous. The 

 pitcher-plant, Venus' fly-trap, and sundew, that grow 

 in bogs or wet places, and bladderwort, that occurs 

 in ponds, depend for their nitrogen supply largely on 

 animals that they capture and consume. Perhaps the 

 bacteria, fungi, and viruses that cause disease in ani- 

 mals also belong to this classification. 



187 



