Date of Award

Fall 1991

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Robert K. Rose

Committee Member

Gerald Levy

Committee Member

Harold G. Marshall

Call Number for Print

Special Collections LD4331.B46 K73


The population dynamics of two species was studied for one year on Craney Island in Portsmouth, Virginia. This dredge disposal site provided good habitat for the house mouse, Mus musculus, whose opportunistic behaviors can withstand the sudden changes in a dynamic environment. Although the site was not optimal habitat, a population of Microtus pennsylvanicus, the meadow vole, was sustained there. Of the seven species of small mammals captured, 65% were house mice and 28% were meadow voles. Meadow voles were more successful at establishing short periods of residency than were house mice; on average, each meadow vole was captured three times and each house mouse was captured only twice. No significant differences from a 1:1 ratio were found for house mice in the overall sex ratio (total number of captures and total number of animals tagged), and the sex ratio did not deviate from a ratio of unity during any month of the study. Sex ratio in meadow voles deviated from unity in three months of the study and in the total number of captures and tagged individuals. There were more males in all cases. House mice reached a peak density of 104 individuals per ha in the first autumn of the study (1989); meadow voles peaked at 41 individuals per ha in early autumn 1990. Both populations had an even-aged age structure during the year. The breeding seasons of the two species were asynchronous, with the house mice having a shorter breeding season. Lifespans for both species were rather short due to a low recapture rate. The most commonly used habitat type was Phragmites australis (=communis), perhaps because it provided the most cover.


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