HERPETOLOGICAL JOURNAL, Vol. 1, pp. 425-434 (1990)

ADRIAN HAILEY AND N. S. LOUMBOURDIS

ABSTRACT

Female Testudo hermanni at Alyki, northern Greece were sexually mature at a mean straight carapace length of 150mm, based on the frequency of finding eggs by X-ray or oxytocin injection during the nesting season. Oxytocin-induced egg laying behaviour is described. Egg width (r = 0.49), shape (r = -0.32) and weight (r = 0.30) were all significantly related to body size. Hatchling wet weight was strongly related to egg weight. Hatchlings of T. hermanni were lighter than those of T. graeca and T. marginata in terms of dry weight/egg weight. This pattern reflects the low energy content of T. hermanni eggs, and is possibly a consequence of the use of more productive habitats by this species. Clutch size and clutch mass were weakly related to body size; reproductive potential declined in the largest females. Simple and stratified calculations gave similar estimates of the total reproductive potential of adult females in two populations at Alyki. There were, in round numbers, 250 adult females on the main heath producing 1,700 eggs per year, and 65 adult females on the salt works heath producing 450 eggs per year. Nest predation was low at Alyki, judging from the rarity of destroyed natural nests. This was confirmed by burying chicken eggs to simulate tortoise nests. About 90 per cent of nests probably remain undisturbed during the incubation period.