SREL Reprint #0816




Variation in Reproductive Characteristics of Aquatic Turtles

J. Whitfield Gibbons, Judith L. Greene and Karen K. Patterson



Clutch size (N=473) and frequency were examined in five species of turtles from South Carolina in an effort to relate reproductive attributes to other life history and environmental characteristics.  In determining the relationship between body size and clutch size, body mass and length were found to be equally satisfactory expressions of body size.  Logarithmic transformations of mass had little effect on the correlation between body size and clutch size.

A linear model of the relationship between body size (plastron length) and clutch size explained 67% of the variation for Pseudemys floridana, 56% for P. scripta and 25% for Sternotherus odoratus.  A linear model was not useful describing the pattern in the other two species (r2=0.5, Kinosternon subrubrum and .08, Deirochelys reticularia).  However, within each of the five species, maximum clutch sizes of the smallest individuals are never as large as the maximum clutch sizes of the largest individuals.

Clutch sizes within a species did not vary significantly among years or populations if the effect of body size was removed.  Clutch size varied among months in all species, with a trend of decreasing clutch size during the egg-laying season apparent for P. scripta, P. floridana and K. subrubrum.

Individuals of four species were recorded laying more than one clutch within a single egg laying season.  The proportion of adult females known to have multiple clutches within a year varied for each species.  Monthly timing of egg laying was not consistent for an individual female from year to year.  No relationship could be identified between clutch frequency and body size in K. subrubrum or P. scripta, the only species for which adequate samples were available for such an analysis.


SREL Reprint #0816

Gibbons, J.W., J.L. Greene, and K.K. Patterson. 1982. Variation in reproductive characteristics of aquatic turtles. Copeia 1982:776-784.

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