ECOLOGY AND ZOOGEOGRAPHY 



647 



Large carnivorous mammals 



Large 



herbivorous! 



mammals 



Figure 453. Food web in a forest community. Some of the possible food relationships have 

 been omitted to simplify. The arrows point from animal or plant eaten to the animal that eats it. 

 (Based on a diagram by James C. Braddock, Zoology Department, Michigan State University, 

 and prepared expressly for this book.) 



grasslands, are inhabited by insects, spiders, 

 snakes, lizards, ground-nesting birds (prairie 

 horned larks, vesper sparrows, etc.), mice, 

 rats, antelope, bison, and many others. 

 Deserts present very severe conditions, espe- 

 cially dryness (less than 10 inches of rain- 

 fall), high temperatures during the day and 

 low at night, and a dearth of food plants. 

 Ants, beetles, lizards, mice, rats, ostriches, 

 and camels are characteristic desert inhabit- 

 ants. 



Aerial animals 



Aerial animals may spend a large part of 

 their time in the air, but they depend on 

 the surface for rest and breeding purposes. 

 The principal types of aerial inhabitants are 

 insects, birds, and bats. Flying fish and flying 



reptiles, except the extinct Pterosauria, are 

 not really aerial animals. The adaptations 

 of flying animals are such as to provide a 

 light rigid body, effective wings, acute vi- 

 sion, and in some the ability to capture food 

 while on the wing. Thus in birds the bones 

 are light; those of the forelimbs are modi- 

 fied into wings; the vertebrae of the trunk 

 and the bones of the pelvic girdle are fused 

 together to give rigidity; the sternum bears 

 a large keel for attachment of the breast 

 muscles; and the eyes are well developed 

 and possess remarkable powers of accom- 

 modation. Birds that feed while in the air, 

 such as chimney swifts and night hawks, 

 have large mouths with bristles at each end 

 that aid in capturing flying insects. Bats 

 catch insects by means of their sharp teeth. 



