Egg size and shape, clutch dynamics, and reproductive effort in European tortoises

A. HAILEY AND N. S. LOUMBOURDIS

Department of Zoology, University of Thessaloniki, Thessaloniki, Greece 540 06

Received September 1, 1987

HAILEY, A., and LOUMBOURDIS, N. S. 1988. Egg size and shape, clutch dynamics, and reproductive effort in European tortoises. Can. J. Zool. 66: 1527-1536.

Energetic aspects of female reproduction are described for the tortoises Testudo graeca, Testudo marginata, and Testudo hermanni (three populations of different body size) from northern Greece. Egg width increased with body size in some populations, but smaller individuals produced more elongate eggs, and egg weight was not related to body size. This method for overcoming the constraint of the width of the pelvic canal means that egg width is a poor measure of egg size. Clutch size, clutch mass, and annual egg production varied with body size between populations. Mean relative clutch mass ranged from 4 to 7%, and was highest in the three populations of T. hermanni. All populations laid two or three clutches per year, based on the total number of eggs and large follicles divided by clutch size. Multiple clutches reflect the morphological constraint of packing shelled eggs within the body, rather than energy accumulation during the nesting period. Material for reproduction was stored in growing follicles rather than fat bodies; follicles reached half of their final weight before the animals entered hibernation. Annual reproductive effort as a proportion of body energy content was about 15% in all populations. This is lower than in other reptiles, partly because the carapace accounts for over half of the total ash-free dry weight of the tortoise body.