Aspects of interspecific interaction betweenReithrodontomys megalotis andMicrotus montanus in one acre enclosures
Two one acre enclosures were cleared of all resident rodents, and then, one enclosure was seeded with founder populations ofReithrodontomys megalotis (grid M) and the other withReithrodontomys megalotis plusMicrotus montanus (grid I). Founder populations consisted of eight animals for each species introduced and a sex ratio of 1∶1.
Five parameters were measured for a period of one year. Data collection was started in September 1971, and ended in September 1972; enumeration was conducted twice a month for three days.
The five parameters measured were: (1) population density through time and individual growth rates; (2) reproduction; (3) survival of age and sex classes; (4) sex ratio; and (5) sizes of home ranges.
There were no significant differences in three out of the five parameters studied. Density estimates along with individual growth rates were not significantly different between the grids. Reproduction, including breeding season and efficiency of reproductive effort, showed no or very little variation due to interspecific interaction. Home range sizes did not appear to be significantly different between the grids. Survival of juvenile males on grid I seemed lower and juvenile males from grid I were significantly smaller although possibly younger than those of grid M. The sex ratio of grid I was significantly different from the expected 1∶1 ratio.
It is postulated thatReithrodontomys megalotis may regulate their density by alteration of their sex ratios.
KeywordsHome Range Litter Size Home Range Size Interspecific Interaction Juvenile Male
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- Asdell, S. A. (1964)Patterns of mammalian reproduction. 2nd ed. Comstock Publishing Associates, Ithaca, N. Y. 670 p.Google Scholar
- Birkenholz, D. E. (1967) The harvest mouse (R. megalotis) in central Illinois.Ill. State Acad Sci. Trans. 60: 49–53.Google Scholar
- Brummel, C. N. (1961) Some aspects of the life history and ecology of the western harvest mouse in southeastern South Dakota.Proc. S. D. Acad. Sci. 40: 85–92.Google Scholar
- Chitty, D. andH. Chitty (1962) Population trends among the voles at Lake Vyrnwy, 1923–60.Symp. Theriologicum. Brno, 1960. p. 67–76.Google Scholar
- Conley, W. H. (1971) Behavior, demography, and competition inMicrotus longicaudus andM. mexicanus. Ph. D. Thesis, Texas Tech. Univ., Lubbock, Texas, 46 p.Google Scholar
- Fisher, R. A. (1958)The genetical theory of natural selection. 2nd revised ed. Dover, New York. 291 p. (originally published in 1929).Google Scholar
- Fisler, G. F. (1965) Adaptations and speciation in harvestmice of the marshes of San Francisco Bay.Univ. Calif. Publ. Zool. 77: 1–108.Google Scholar
- Hamilton, W. J., Jr. (1941) Reproduction of the field mouseMicrotus pennsylvanicus (Ord.).Cornell Univ. Agr. Exp. Sta. Mem. 237. 23 p.Google Scholar
- Krebs, C. J. (1972)Ecology; the experimental analysis of distribution and abundance. Harper and Row. New York. 694 p.Google Scholar
- Lack, D. (1966) Population studies of birds. Claredon, Press. Oxford. 341 p.Google Scholar
- Packard, R. L. (1963) An ecological study of the fulvous harvest mouse in eastern Texas.Amer. Midl. Nat. 79: 63–88.Google Scholar
- Pitcher, E. J. (1973) Aspects of interspecific, interaction betweenReithrodontomys megalotis andMicrotus montanus in one acre enclosures. MS Thesis, Idaho State University, Pocatello, Idaho. 57 p.Google Scholar
- Sokal, R. R. andF. J. Rohlf (1969)Biometry; the principles and practice of statistics in biological research. W. H. Freeman. San Francisco. 776 p.Google Scholar
- Zukerman, S. (1953) The breeding seasons of mammals in captivity.Proc. Zool. Soc. Lond. 122: 827–950.Google Scholar