Aspects of interspecific interaction betweenReithrodontomys megalotis andMicrotus montanus in one acre enclosures
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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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