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Aspects of interspecific interaction between Reithrodontomys megalotis and Microtus montanus in one acre enclosures
Author(s) -
Pitcher Edward J.,
Keller Barry L.
Publication year - 1979
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/bf02512640
Subject(s) - biology , microtus , sex ratio , interspecific competition , juvenile , population , zoology , ecology , demography , sociology
Summary Two one acre enclosures were cleared of all resident rodents, and then, one enclosure was seeded with founder populations of Reithrodontomys megalotis (grid M) and the other with Reithrodontomys megalotis plus Microtus 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 that Reithrodontomys megalotis may regulate their density by alteration of their sex ratios.