Author: Stephanie Jill Kamel

Publisher:

Published: 2006

Total Pages: 366

ISBN-13: 9780494159668

Maternal behaviours, such as nest-site choice, can be major determinants of offspring phenotype and fitness. In egg-laying species, incubation environment can influence offspring body size, performance, survival and sex. This thesis focuses on variation among females in maternal nest-site choice and the consequences that this variation can have for offspring survival and performance. I investigated nest-site selection in leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles at three levels: (i) in two species of sea turtle nesting in different environments, (ii) within populations of the same species and (iii) within individual females both within and across nesting seasons. In both species, evidence was found for individual-level nest-site preferences. This was an unexpected result for leatherbacks, as it had long been assumed that females placed their nests randomly due to the unpredictability of their environment. Results were more striking in hawksbills, with individuals exhibiting remarkably high repeatability for nest-site microhabitat characteristics, both within and across nesting seasons. Some females preferred nesting in the forest, some in the forest edge and others still in open areas. With a few exceptions, hatching success and sea-finding ability were similar in all beach microhabitats. This raises the question of what, if not differential offspring survival, is maintaining these preferences. Frequency-dependent selection, wherein females gain a fitness advantage by producing the rare sex, is one possibility. This idea gains some support from the finding that beach temperatures varied dramatically by microhabitat: nests laid in the forest were exposed to male-producing temperatures while those in less vegetated areas were warmer and more female producing. A related aspect of this work has been to consider the conservation implications of nest-site choice. Using seasonal beach temperatures and the distribution of hawksbill nests, I estimated a balanced primary sex ratio, a situation that is likely to change if the current rates of island deforestation in the Caribbean continue. It also appears that Guadeloupe hosts one of the largest hawksbill populations in this region, indicating that data from this nesting beach are critical for developing a more robust demographic picture of Caribbean hawksbills.