(4) Relation of the individual mammal to the development of the community — 

 mammals as related to the origin of ccmununities and to such processes 

 as migration, invasion or reinvasion, establishment » competition, 

 dominance, extinction; mammals and ecological succession; primary 

 and secondary succession; mammalian "weeds'*; climax assemblages of 

 mammals; factors governing distribution of mammals; effects of extreme 

 or intermittent conditions on mammalian distribution; mammals and 

 climatic cycles; mammalian numbers as affected by variations in 

 forest, forage, wildlife, crop production. 



Mammalian Influences on Environment 



A. On physical surroundings. 



(1) Incorporation in soil of organic animal materials — such as skin, 



hair, bones, antlers, horns, other organic materials, feces, urine. 



(2) Digging— formation of tunnels, holes, hollows, mounds; burial of rocks, 



logs, grass, or other objects by excavated materials; accumulation of 

 materials for nests; storage of food; extent of cultivation of soil, 

 the plowing effect of burrowing mammals; reduction of ditch banks, 

 stream banks, or other topographic features by burrowing; general 

 effects on erosion, beneficial, neutral, harmful; dimensions of tunnels 

 and chambers, volume of earth r^noved. 



(3) Packing of soil by tramping or trail making. 



(4) Dam building and flooding of valleys. 



(5) Collection of materials for nests, with subsequent decay and soil 



building. 



^(6) Effects on the soil of dissemination, planting, or removal of vegetation 

 by mammals and of burying fertilizing materials. 



B, On plant cover. 



(1) Use of miscellaneous plant parts, as stems, roots, leaves, twigs, or 



seeds for food (fig. 5), shelter, or nests — overgrazing; mammal-caused 

 zones of vegetation about burrows, water holes, and other areas of 

 concentration; activities of mammals in gnawing bark and eating 

 cambium, girdling trees, or cutting down plants or trees. 



Figure 5. "Types of feeding often identify the mammal 

 involved. Left: Deer browsing. Right: Rabbit gnawing, 



15 



