Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal Volume 5: Issue 2

ABSTRACT

Sea turtle species observed nesting at the US Naval Station at Guantanamo Bay, Cuba (GTMO) include greens (Chelonia mydas) and hawksbills (Eretmochelys imbricata), both of which are classified as endangered by the World Conservation Union (IUCN). As Cuba and its neighbors continue to develop their coasts, all efforts should be made to preserve this important nesting refuge. Habitat suitability index models are one tool with which managers can generate hypotheses and experiment with management options. This study used an observational dataset of nests and measured habitat variables to develop habitat suitability index models in a geographic information system. The first objective was to compare the performance of 3 different habitat model-building approaches in order to determine which technique, if any, provides reliable information on sea turtle nesting habitat preferences. A habitat suitability index score for each beach zone was computed using 1) suitability indices with expert weights, 2) unscaled environmental variables with regression-based weights, and 3) a combination of suitability indices with regression-based weights. The second objective was to use the models to lend insight into important environmental descriptors of suitable sea turtle habitat for GTMO. All models predicted moderately well with 40% prediction rates, even though they assigned different weights to the variables. Moderate model performance may be attributed to low samples sizes and/or nest site fidelity that is unrelated to environmental factors. Overall, differences between empirical and expert model results reflect a shift from a regional (Caribbean) to a local scale of analysis (GTMO). However, in all models, compaction of the substrate was almost twice as influential as the other variables, indicating that the looser the sand, the more suitable the habitat. Conservation implications and suggestions for future research are discussed.

ABSTRACT

Field Island in Kakadu National Park, Northern Territory, Australia, supports a nesting population of flatback turtles (Natator depressus) monitored since 1990. We summarize 9 years of survey data for this location and make recommendations for future research. At least 221 nesting flatbacks were tagged at Field Island between 1990 and 2001. Nightly emergence rates indicate that Field Island is a locally and regionally important rookery for flatbacks with no other species recorded nesting. The mean interseasonal remigration period was 2.82 years. Female flatbacks laid clutches of similar sizes to those reported for other Australian rookeries, but nests tended to be deeper than those on nearby mainland beaches. No evidence of size decline (curved carapace length) occurred over the years, and mean curved carapace length was similar to those observed at other nesting rookeries. The amount of biological information now available for the Field Island rookery and the number of nesting turtles already tagged makes it valuable as an index site for flatback turtles in northern Australia.

ABSTRACT

Reproduction and nesting in the ringed map turtle (Graptemys oculifera) were investigated in the Pearl River of west-central Mississippi in 1995 and 1996. Nesting occurred from mid-May until mid-July but peaked in mid-June. Minimum carapace length of females at sexual maturity was 130 mm, but mean size at maturity was between 130 and 140 mm. Mean and modal CSs were 3.7 and 3. Larger females were gravid earlier than smaller ones and both egg and CS declined as the nesting season progressed. CS was positively correlated with both female carapace length and body mass. Mean egg length, width, and mass were 38.8 mm, 22.7 mm, and 11.8 g, respectively. Hatchlings averaged 35.5 mm carapace length and 8.9 g in mass. Annual clutch frequency may range from 0.96 to 1.42, and a minimum of ca. 60% of females reproduced on an annual basis. Predators destroyed an average of 86% of nests each year. Major vertebrate nest predators were armadillos, raccoons, and fish crows. Invertebrate egg predators destroyed an additional 24% of eggs known to be fertile.

The Third Workshop on the Ecology, Status, and Conservation of Diamondback Terrapins (Malaclemys terrapin) was held in Jacksonville, Florida, on 17–19 September 2004. The workshop was sponsored by the University of North Florida and the Florida Turtle Conservation Trust. Sixty-six individuals from academic, scientific, regulatory, and private institutions/organizations met to discuss recent research findings and conservation concerns related to this ecologically significant coastal wetland species. All 16 states within the range of the species were represented. Eighteen papers were presented in sessions on ecology, conservation concerns, environmental education, and status; 13 posters were presented in a separate session.