SoiiK- insects show siiuctiiral ailaptatioiis for liv- 

 ing in grassland (Hayes 1927). May beetles in for- 

 ested regions commonly feed at night on the foliage 

 of trees and have well developed wings, but closely 

 related species in grassland areas feed on low grow- 

 ing ])lants during the day and are flightless. The de- 

 velopment of pilosity and thick integuments in some 

 insects appears to be an adaptation to prevent evapo- 

 ration. Prairie May beetles pu]»te in the spring 

 rather than autumn, probably in correlation with 

 their change in food habits, and adults appear in mid- 

 summer rather than late spring. 



An insect niicrohabitat of special interest is the 

 dung of the larger mammals. Bison formerly oc- 

 curred in frequency one to 10-20 hectares. Inasmuch 

 as the output of each animal is about 2^ droppings 

 per day. the number of these microhabitats available 

 was considerable. Some 83 species of arthropods have 

 been collected from cow dung, mainly beetles and 

 flies, but including annelids, nematodes, and proto- 

 zoans. There is a regular succession of insect species 

 breeding and maturing. The microsere is completed 

 in about eight days, the length of time required for 

 the droppings to dry. The first species that arrive 

 are the obligatory breeders on dung. They have the 

 shortest life-histories, and remain for the shortest 

 time. Predatious and parasitoid species prey on the 

 coprophagous ones. The greatest variety of species 

 is present at the middle of the microsere. but the 

 composition of species varies with the season. Spe- 

 cies disappear as the dung disintegrates into the gen- 

 eral surroundings (Mohr 1943, Laurence 1954). A 

 comparable niicrohabitat and succession occurs in 

 carcasses of dead animals (Chapman and Sankey 

 1955). 



Verlebrates 



Table 9-3 g'nes a representative sampling of 

 small mammal populations found in grassland, al- 

 though it is to be expected that the species composi- 

 tion and size of populations will vary locally and from 

 year to year. The mores of grassland mammals, 

 which show how they are adjusted in behavior to 

 live in this community, are tabulated in Table 9-4. 



Birds are not numerous in grassland. In north- 

 western Iowa (Kendeigh 1941b), grasshopper spar- 

 rows, western meadowlarks bobolinks, ring-necked 

 pheasants, marsh hawks, and short-eared owls aver- 

 aged less than one pair per hectare (2.5 acres). 

 Prairie chickens and sharp-tailed grouse formerly 

 occurred where now is to be found only the intro- 

 duced pheasant. The eastern meadowlark predomi- 

 nates over the western meadowlark in the wetter and 

 smaller pastures east of the Mississippi River. 

 Vesper sparrows and horned larks occur in short 



grasses, but usually not in climax areas with dense 

 tall grasses. Upland plovers. Henslow sparrows. lark 

 buntings, and longsi)urs are common locally. 



Some fourteen species of snakes are generally dis- 

 tributed over the prairies (Car])enter 1940). To the 

 east, the blue racer, massasauga, bullsnake, and garter 

 snakes are frequently found. The prairie rattle- 

 snake is increasingly common westward. The lizards 

 Cnemidoplwnis sexlineatiis. Sceloporus undulatiis, 

 and Holhrookia maculata. commonly occur in grassy 

 areas at forest-edges. The horned toad is found in 

 arid habitats. 



The most characteristic amphibian of grassy areas 

 is the toad. All species breed in the ephemeral bodies 

 of water resulting from the rains of spring and sum- 

 mer. One species. Bujo cognatiis. will not breed un- 

 less it rains, even though bodies of water are present. 

 During the hot. dry weather of later summer, the 

 toads retreat to burrows in the earth or to other 

 shelter until favorable conditions again return (Bragg 

 and Smith 1943). 



Grazing food coactions 

 and range management 



Since the vegetative productivity of grasses is 

 very high, herbivorous animals, especially large mam- 

 mals, are favored in the grassland community (Ren- 

 ner 1938). Unlike trees and shrubs, the terminal bud 

 on grasses lies close to the ground and is not ordi- 

 narily injured by grazing. Meristematic tissue lies at 

 the base of the leaves so that when the terminal por- 

 tion of the leaf is eaten ofif, the leaf keeps on grow- 

 ing. Actually, lateral branching at the base of the 

 grass stem is stimulated by grazing, and a thicker 

 and more succulent growth with less fiber is pro- 

 duced. Productivity of grass is reduced if the herbage 

 is removed more than two or three times during the 

 growing season. However, total protein production 

 is not diminished, for frequent clipping results in an 

 increased ratio of leaves to stem, and leaves are much 

 richer in protein content. Light to moderate grazing 



TABLE 9-3 Population of small mammals per hectare (2.5 acres) 

 In mixed prairie of western Kansas (after Wooster 1939). 



Mammal species 



Prairie meadow-mouse 

 13-striped ground squirrel 

 Prairie white -footed mouse 

 Harvest mouse 

 Little shrew 

 Short-tailed shrew 

 Black-tailed jackrabbit 

 Cottontail rabbit 



7.6 

 6.8 

 2.8 

 2.4 

 1.3 

 0.7 

 0.1 

 31.3 



Grassland, forests, and forest-edges 125 



