Aspects of the Reproductive Biology of the Northern Diamondback Terrapin Malaclemys terrapin terrapin

Abstract

The characteristics, interrelationships and seasonal variation of the nests, eggs, clutches and plastron sizes of a population of northern diamondback terrapins (Malaclemys terrapin terrapin) nesting on a barrier beach island in southern New Jersey were studied during the 1973 breeding season. Positive correlations were obtained between (a) egg length and egg breadth; (b) clutch size and clutch weight; (c) plastron length and clutch size, and (d) plastron length and clutch weight. No significant correlations were found between (a) clutch size and any egg dimension (length, breadth, weight); (b) plastron length and any egg dimension; (c) plastron length and any nest dimension (depth, egg compartment depth, egg compartment width). The mean, median and modal clutch size of 10 eggs suggested that clutch size of northern populations may be larger than those of more southerly situated populations and subspecies. Mean egg size (length, breadth, weight) tended to decrease as the laying season advanced. Comparisons with findings from avian biology concerning eggs and egg-related phenomena were made.