SEED AND FRUIT COACTIONS 125 



are not abundant. Grasshoppers, the army worm, and a few other 

 insects when epidemic remove foliage of all kinds as completely as 

 the large grazers and browsers with which they may compete. 



Importance of the Browsing-grazing Coaction. Browsing by do- 

 mestic animals (and also by wild ones) has exerted considerable 

 influence upon grassland where this contains certain shrubs or is in 

 contact with them. Species with edible fruits but protected seeds, such 

 as the mesquite (Prosopis) and juniper, are widely scattered by cattle 

 and goats in particular, and frequently increase to a point where the 

 grass dominants are more or less completely replaced by them, espe- 

 cially where fire is a regular process. In addition to such changes 

 of composition, there is usually a striking effect upon the form and 

 branching of species that are regularly browsed, by which they assume 

 more or less globular shapes, though these effects are not frequently 

 due to native species. 



Recently Vorhies and Taylor (1933) have given a comprehensive 

 account of the food coactions of Lepus alleni and L. calijornicus, as 

 an outcome of the researches on the Santa Rita Range Reserve in 

 Arizona. This deals not only with the quantity of forage consumed, 

 but also with stomach contents, and the utilization of browse, cacti, 

 grass, and forbs. Most of the plants present are eaten to some extent. 

 The percentages for the respective species were as follows, grass, 45 

 and 24; mesquite, 36 and 56; cacti, 7.8 and 3.3; forbs, 12 and 17. 

 Nevertheless, the authors state that jack rabbits are more abundant 

 where forbs are prevalent than they are in stretches of climax grasses 

 (pages 541, 563), a fact that is more in accord with the food habits 

 of the larger rodents generally. 



In the Old "World, the common rabbit under agricultural conditions 

 has spread from its original home in the Mediterranean region and is 

 often the most serious of rodent pests (Tansley, 1922; Farrow, 1925). 

 In Australia and New Zealand it is paramount, tens of millions being 

 destroyed in a single year in New South Wales alone (Vorhies and 

 Taylor, 1933:571, 567). 



SEED AND FRUIT COACTIONS 



To this group belong the squirrels of the western mountains of 

 North America (except the tassel-eared group), some chipmunks, 

 antelope squirrels, some kangaroo rats, and many wood rats. Outside 

 the tropics this type of coaction is not common among the larger ani- 

 mals; usually some animal food is taken also. The animals belonging 

 strictly to this coaction type are chiefly insects. For example, Kor- 

 stian (1927) found that insects may destroy about 10 per cent of the 



