Date of Award

Summer 2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Robert K. Rose

Committee Member

Deborah Waller

Committee Member

Raymond Dueser

Call Number for Print

Special Collections LD4331.B46 R53 2011

Abstract

Rodents are assumed to live their lives in circumscribed (natal) areas with males being more prone to disperse than females and juveniles more prone to disperse than adults. To test these assumptions we examined the initial captures of geographic populations of hispid cotton rat, meadow vole, prairie vole, and marsh rice rat obtained through capture-mark-recapture methods. Capture records were obtained from Kansas and Illinois from long-term studies, and through live-trapping in Chesapeake, Virginia. I evaluated proportions of residents and transients, adults and juveniles, and males and females for significant differences among seasons, years, and geographic locations. The overall body masses of residents and transients were compared for each species and between populations.

Hispid cotton rats exhibited seasonally significant, density-independent transience, with adults forming the greatest proportions of initial captures, and no difference in body mass between residents and transients. Sex ratios of cotton rats deviated from unity for Kansas but not Virginia populations; both had seasonal variation. Meadow and prairie vole populations had seasonally significant transience, with geographic variation in the density dependence of transience and differences in the body mass between residents and transients. Vole populations also had seasonal differences in sex ratios, and the Illinois population of prairie vole was the only I that differed from overall unity. The marsh rice rat from Virginia had seasonal transience and no detectable difference between body mass of residents and transients. The dominant maturity group of the rice rat changed seasonally and was generally juvenile-biased. Sex ratios of marsh rice rats did not differ from unity overall, but were different only for groups of adults and residents. All populations had seasonally significant transience, and 6 populations had a majority (>50%) of initial captures comprised of transients. Three populations, both Illinois voles and Kansas meadow voles, had residents that were heavier than transients, as well as a negatively correlated relationship between population density and proportion of transients.

No population met the expectations of the prominent paradigms, namely that animals are born and live their lives in a circumscribed area, and those that choose to leave a population are prone to biases towards juveniles and males over adults and females. The lack of fit with these paradigms provides support that generalizations of population structure and behavior of open-habitat rodent populations are erroneous and should be used with caution as these paradigms were not useful models of population sub-structure for the examined populations.

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DOI

10.25777/4vcz-2m54

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