Nesting of hawksbill turtles (Eretmochelys imbricata) was monitored in 2013 and 2014 at 20 nesting beaches along the shores of Melaka, Peninsular Malaysia. Total nest numbers found were 481 and 463 in 2013 and 2014, respectively. The mean clutch size in 2013 of 123.5 ± 32.3 (SD) was similar to that in 2014 (118.5 ± 39.7). The distributions of nests were not uniform among the 20 beaches, and a large number of nests were found in Padang Kemunting, Kem Terendak, and Pulau Upeh, where the beaches were not always long. The nest sites indicated that the hawksbill turtle preferred to build its nest within the woody vegetation zone. The preferred vegetation species was Scaevola taccada. The temporal nesting pattern was year-round in both years, but the peak nesting season was between May and August, in the south-west monsoon season, possibly due to the gentle winds during this period. The turtles tended to nest between 22:01 and 24:00 h. This study provides basic information about hawksbill turtle nesting and insights into their spatial and temporal nesting preferences, which will contribute towards the conservation of this endangered species.

This study evaluates how key beach features influence suitability for nesting by Endangered loggerhead marine turtles Caretta caretta at an internationally important rookery on Zakynthos Island, Greece. During 2007–2009 we assimilated information on beach structure (elevation above sea level and width), the distribution of all nesting (turtle tracks that resulted in nests) and non-nesting (turtle tracks that did not result in nests) turtle emergences from the sea along 6 km of beach, nest placement parameters (distance from sea and elevation above sea level), and beach use by visitors. We found that turtles preferentially emerged on steeper sections of beach, with higher nesting densities occurring on the most environmentally stable beaches. Elevation was a more reliable indicator of nest placement (1 m above sea level) than distance to shore. However, because nests on steeper slopes are located closer to shore, the risk of damage by tourism is increased in such areas. We calculated a potential 36% overlap of natural nest locations with use of the beach by tourists; however, the recorded overlap was 7% because of existing management protocols. This overlap could be further reduced by focusing conservation effort (i.e. further restricting use by people) on beach sections with the steepest inclines. For example, slopes of > 22° comprise 1 km of total beach area annually, the closure of which (above the immediate shoreline to allow passage) would completely protect 50% of nests. This study shows the value of evidence-based management as a practical scientific tool to conserve threatened species in dynamic protected areas that are of both environmental and economic importance.

In marine turtles the selection of oviposition habitat is a key determinant of offspring success. I investigated which environmental features influenced the nesting activity and nest distribution of the hawksbill turtle Eretmochelys imbricata by daily monitoring of a rookery on the coast of the Arabian Gulf, in Qatar. I mapped the distribution of turtle nests and unsuccessful nesting attempts and measured key beach features. Data were analysed using autoregressive models, a specific regression technique dealing with spatial autocorrelation. Distribution of nests and unsuccessful nesting attempts were strongly spatially autocorrelated. In some areas almost all the turtles that approached the beach excavated a nest, whereas in other areas nesting was scarce but many unsuccessful attempts were observed. Turtle activity was lower in areas with a steep coastline and high rock cover. Nest density was higher on beaches with a low slope and little rock cover, and with soft soil and high vegetation cover. The density of unsuccessful nesting attempts was higher in areas with hard soil and low vegetation cover. These results are relevant for the management and restoration of nesting areas for this Critically Endangered species.

Sex ratios of the American snapping turtle Chelydra serpentina are female-biased at cool temperatures, male-biased at moderate temperatures, and only females are produced at warm temperatures. The laboratory incubation of eggs at several constant temperatures yields patterns of skewed sex ratios. In this study, incubated eggs represented regional samples of C. serpentina from six different latitudes. The sample from the highest latitude yielded male-biased sex ratios across the broadest range of cool temperatures. This male-biased zone and those of the other five samples collectively contributed to a nested arrangement that is approximately symmetrical around a temperature of 24.5°C. Two indices of temperature-dependent sex determination (TSD) patterns (MF pivotal temperature, width of the male-biased zone) were significantly associated with latitude and with published data on several climatic variables (e.g. sunshine and rainfall). At high latitudes, females nest in exposed locations, locally the warmest places. At low latitudes females place their nests in shaded locations. Such nest site selection renders high latitude nests warmer than low latitude nests, even if only intermittently. Given that constant conditions show faster embryogenesis in high vs low latitude eggs, exposed nest sites seem to be an additional adaptation to hasten embryogenesis in high latitude nests. At low latitudes, shading prevents nests from overheating. We propose that a trade-off between evolution, (1) to balance sex ratio and (2) to maintain male-biased sex ratios in a temperature range that favours male fitness, leads to the observed arrangement of concentric TSD patterns centred around male production at 24.5°C.