Henry S. Fitch

“ Cannibalism, involving destruction of the newborn, is probably an important factor in the population dynamics of the prairie vole. Only a small percentage of the young known to have been born on an area ever survived to be live-trapped; this small percentage was indirect evidence of decimating losses in the young. Under unfavorable conditions each of several females killed and ate her own litter, but the degree of provocation varied greatly among individuals. Females that gave birth to young in live-traps occasionally ate one or more of their newborn young, as evidenced by discarded remnants. ”

“ The eastern woodrat exerts important effects on its community associates by its use of the vegetation for food, by providing shelter in its stick houses for many other small animals, and by providing a food supply for certain flesh-eaters. In the course of our observations on this rodent on the University of Kansas Natural History Reservation, extending over an eight-year period, from February, 1948, to February, 1956, these effects have changed greatly as the population of woodrats has constantly changed in density, and in extent of the area occupied. ”

“ In one nest which yielded a total of 191 food items, racer remains occurred 13 times, but no other nest yielded records of more than three racers, and some other species of reptiles, notably the black rat snake (Elaphe obsoleta) comprised much more important components of the food. Since only one meal in 26 contained remains of racers, it seems that a red-tailed [440] hawk would destroy only a few racers in the course of a year on its territory of perhaps half a square mile, and that its predation would not be a major factor in the racer's ecology. ”

“ Ordinarily the ant-eating frog stays beneath the soil surface, in cracks or holes or beneath rocks. Probably it obtains its food in such situations, and rarely wanders on the surface. The occasional individuals found moving about above ground are in most instances flushed from their shelters by the vibrations of the observer's footsteps. On numerous occasions I have noticed individuals, startled by nearby footfalls, dart from cracks or under rocks and scuttle away in search of other shelter. Such behavior suggests that digging predators may be important natural enemies. ”

“ In the region of my study the prairie vole breeds the year round, but the rate of breeding changes continually. There is no regularity in the trend of the breeding season from year to year. It is obvious that the species is responsive to environmental changes and is so well attuned that its breeding is speedily initiated or inhibited by changes to favorable or unfavorable weather. The incidence of breeding is highest when temperature is moderate and both water and foods of preferred sorts are plentiful. ”

“ Several of the largest trees, well over a foot in trunk diameter, grow at the lower limestone outcrop. Ash is most abundant at this level and at the terrace just below it. On the one slope where it is concentrated, ash is one of the most common trees, growing in association with American elm, chestnut oak, black oak, and shagbark hickory. This area is one of the most mesic on the Reservation. The soil is usually damp, with thick leaf litter and rich humus. In hilltop fields, formerly cultivated or pastured, saplings of white ash are among the most prominent invaders. ”

“ Home ranges approximately 90 feet across for adult males and young, and a little more than 30 feet across for females are indicated. Actual area of a home range would amount to only a fraction of an acre—from about one-seventh to less than one-fiftieth. The dash of an alarmed skink to a place of refuge, though involving at most only a few seconds, may traverse a large part of its home range. Through long association the lizard is thoroughly familiar with the terrain, so that it can take full advantage of the peculiar features in escaping, hunting, traveling or resting. ”

“ The habitat was uniform. Home ranges probably overlap somewhat, and the spacing is the expression of the need for an otherwise unoccupied area in which there is sufficient space to live. Because individuals tend to fight whenever they meet, there is probably a psychological [Pg 523] tendency for sequestration which results in spacing of houses and reduces social contact thereby avoiding a depletion of energy that would be detrimental to the population. Whereas condition of the hedge row determines whether or not it will be inhabited by woodrats, length determines the number of occupants. ”

“ Kinds of Prey
Throughout the range of the racer small mammals make up an important portion of the food, and the bulk of those eaten are voles (Microtus sp.) and white-footed mice (Peromyscus sp.) . The voles being diurnal, and having habitat preferences similar to those of the racer, are especially subject to attack, but only large adult racers are capable of swallowing a full grown vole. Probably most of the voles eaten are immature. Of the white-footed mice, P. [404] maniculatus especially prefers a grassland habitat, and is usually found in situations frequented by the racer. ”

“ As many as five adults have been caught in a trap simultaneously at times when the population density was high. At such times, the meadow habitat is crossed by a maze of interconnecting surface runways and one runway may be traced continuously for 100 yards or more. Because each individual vole normally confines its activity to a small area, only a fraction of an acre, it is evident that individuals living at different places overlap in their home ranges, and also in the trailways followed in foraging. ”

“ For some of the many prey species the effect is certainly negligible, but for others its predation may be a major ecological factor. In areas where optimum habitat conditions exist its biomass may exceed that of any other insectivorous animal, and in such situations it assumes a major role as a predator and as a competitor with other insectivorous types. In turn it provides part of the food source of various larger predators, including reptiles, birds and mammals. It is a host and carrier of various parasites, including at least one species that regularly attacks humans—the common chigger. ”

“ Food of the eastern woodrat consists chiefly of vegetation; many kinds of leaves, fruits, and seeds are eaten. For many individuals foliage and seeds of the osage orange are the staple; hedge rows and dense trees of osage orange provide favorable sites for the houses. Woodrats are attracted to meat baits, and have been known to feed on flesh of carcasses, even on one of the pilot black snake which is a predator on the rat. ”

“ Throughout much of the United States the racer is abundant and is one of the snakes best known to man. Its active diurnal habits and its preference for a habitat in meadows, pastures, and hayfields rather than in remote wilderness areas, result in frequent encounters with humans. The racer is a predator on many kinds of small animals, both vertebrates and invertebrates; it takes as food chiefly animals that are agricultural pests but also destroys some beneficial kinds. ”

“ Adult males have never been observed to display paternal solicitude toward young, but some individuals, kept with females and their litters, did not molest the young and were accepted by the females as members of the family group.
[Pg 149] Other things being equal, cannibalism involving the young might be expected to be greater at times of high population density. Then, young left in the nest by a female in the course of her foraging would more often encounter adults and partly grown young, both those that lived in the same burrow system and exploring intruders from other areas. ”

“ Occasional individuals possibly attain much greater age, but certainly few live more than five years. Like most small animals, the five-lined skink has a short life expectancy and a rapid population turnover. As compared with mammals of comparable sizes, the small rodents and insectivores that are this lizard’s community associates and are subject to many of the same hazards, the skink is notably successful, with a much longer life expectancy. For these small mammals the life span is seldom as long as a year. ”