The natural history of a northern turtle, chrysemys picta bellii (gray)

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dc.contributor.authorSt. Clair, Robert Charlesen_US
dc.date.accessioned2024-08-15T18:25:38Z
dc.date.available2024-08-15T18:25:38Z
dc.date.copyright1989en_US
dc.date.issued1989
dc.degree.departmentDepartment of Biology
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractComparisons of life history patterns within a widely distributed species can reveal the ecological factors that control abundance and distribution. The turtle is an example of a long-lived, iteroparous organism that experiences delayed maturity and heavy mortality at early life stages. In this 2-year mark-recapture study, I estimated individual growth, reproductive success, and age-specific survivorship of the western painted turtle near the northern limit of its range. In comparison with southern populations, growth rates were lower and individuals attained larger sizes. The slower growth rate delayed sexual maturity in northern females. Males matured earlier than females. Females produced larger but fewer clutches when compared with.most other parts of the geographical range. In general, females did not produce clutches every year. Reproductive potential for this population, near the northern limit of the range, was therefore reduced. Age-specific survivorship in this population was fairly stable after the turtles left the nest. There were more females than males in the population and recruitment was low in all but one of the six lakes within the study area. Levels of predation on nests were very high during years of high reproductive activity. Predation on adults was also higher in such years; most of those taken were probably nesting females. Level of blood lactate in overwintering turtles was measured as a potential factor limiting northern distribution. Lactate concentrations rose 3 to 24 times normoxic levels after 3 months of ice cover. This was less than levels reported for animals in laboratory simulations of hypoxic hibernation. As the turtles were found on the lake bottom rather than buried in the mud, it is likely that this species overwinters under less hypoxic conditions than previously supposed. Most hatchlings remained in the nest over the winter. While this is a successful behavior in other parts of the geographical range, most hatchlings in this population failed to survive. Distributional limits may therefore be set by hatchling rather than adult overwintering survival. There was indirect evidence that some hatchlings emerged in the fall. When compared with southern populations, this northern population showed the following responses to climate: slower growth, reduced annual reproductive potential, and high overwintering mortality of hatchlings. However, it appears that overwintering in adults is less an obstacle than previously thought.
dc.format.extent104 pages
dc.identifier.urihttps://hdl.handle.net/1828/19778
dc.rightsAvailable to the World Wide Weben_US
dc.titleThe natural history of a northern turtle, chrysemys picta bellii (gray)en_US
dc.typeThesisen_US

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