Adem Özdemir

Population decline of loggerhead turtles: two potential scenarios for Fethiye beach, Turkey

Based on nesting data over a 12-year period (1993–2004), this study points to a negative population trend of the loggerhead turtle population at Fethiye beach, Turkey. The number of nests fluctuated from a maximum of 186 in 1995 to a minimum of 58 in 2004. Successively smaller peaks at 3-year intervals were followed by successively smaller troughs. Two analyses—one representing a dampened oscillation, the other retaining the period and the amplitudes of the nesting cycles—predict that nest number will drop to about 40–50 by 2015, i.e. to about 22–27% of its highest value. This drop at Fethiye does not correspond with a visible increase at neighboring beaches, leading to the interpretation that the number of nesting turtles here is declining. Moreover, the carapace size of emerging adult females is apparently decreasing, as are clutch sizes. Such a potential negative trend at a key Turkish nesting beach is cause for concern, an incentive for continued study, and a call for more coordinated and effective conservation programs in this region of the Mediterranean.

Impact of some invertebrates on eggs and hatchlings of the Loggerhead Turtle, Caretta caretta, in Turkey

Abstract The damage caused by some invertebrates to the eggs and hatchlings of Loggerhead Turtles, Caretta caretta, was investigated during 1999 and 2000 on Fethiye beach, Turkey. Nematoda, Acarina, Myrmeleonidae, Elateridae, Scarabeidae, Muscidae and Tenebrionidae were recorded as infesting nests of Loggerhead Turtles. Tenebrionidae (Coleoptera) larvae were found to have the heaviest impact on Loggerhead Turtle eggs and hatchlings. A total of 185 randomly selected nests was examined. Of the nests examined in 2000, almost 50% contained tenebrionid larvae. Tenebrionid larval damage was recorded in 8.1% of the eggs that were counted in the nests containing larvae and in 0.6% of the hatchlings. However, it could not be determined whether the larvae destroy viable eggs and hatchlings. In comparison to previous years, a remarkable increase in tenebrionid larval damage was recorded.

An Assessment of Initial Body Size in Loggerhead Sea Turtle (Caretta caretta) Hatchlings in Turkey

Abstract Eggs, hatchlings, and adult loggerhead turtles, and incubation durations of clutches, were measured on three Turkish beaches (Dalyan, Fethiye and Göksu Delta), and some physical features of nests were compared. These features were not statistically different among the beaches, except for nest depth and distance to the high water mark. There was a positive relationship between hatchling mass and egg size. The carapace length of hatchlings was correlated with both egg diameter and incubation duration. The duration of asynchronous emergence of hatchlings on Fethiye beach was slightly longer than on the other two beaches, and the size of hatchlings decreased as asynchronous emergence proceeded. Of the hatchlings that emerged first, those that died were significantly smaller in SCL and mass than those that lived. These results suggest that smaller hatchlings may not be vigorous enough to emerge earlier from nests, and that they may be less fit.

NEST SITE FACTORS AND INVERTEBRATE INFESTATION OF LOGGERHEAD TURTLE NESTS

This paper reports the physical nest parameters of loggerhead turtle (Caretta caretta) nests at Fethiye Beach, Turkey that predispose individual nests to invertebrate infestation. All data were collected between June and September 2001 and were analyzed using logistic regression. Pimelia sp. (Tene-brionidae), Musca sp. (Muscidae), Myrmeleon sp. (Myrmeleontidae), and Cryptositigmata were established as infesting the loggerhead turtle nests on Fethiye Beach in 2001. When all groups were combined as invertebrates, distance to low vegetation (t-test, b = -0.13) and grain size (t-test, b = -1.30) were found to be the best subsets of the model indicating whether invertebrates infested a nest. Both factors were negatively correlated with the presence of invertebrates. The same analysis was applied for each individual group of invertebrates. The implications of these results are discussed.

The effect of the predicted air temperature change on incubation temperature, incubation duration, sex ratio and hatching success of loggerhead turtles

Marine turtles are sensitive to temperature changes and thus are likely to be impacted by the predicted climate change. This study assesses the effect of the predicted air temperature change on incubation temperature, incubation duration, sex ratio and hatching success of the loggerhead turtle Caretta caretta at the Mediterranean nesting sites of Dalyan and Fethiye, Turkey. We recorded sand temperatures and used air temperatures at two nesting sites to estimate the sex ratio of hatchlings. The data showed that hatchling production was 59.1% and 77.7% at Dalyan in 2004 and 2009, respectively, and 72.2% and 72.3% at Fethiye at 2008 and 2009, respectively. Incubation temperature was positively correlated with both air temperature and distance to sea. Sex ratio estimation and incubation duration between the years 1993 and 2009 in Fethiye show polynomic trend lines. The best predictors of hatching success were distance to vegetation and wet depth of nest. We modelled the effects of incremental increases in the future air temperature of up to 10°C. We suggest that clutch death is not likely to begin until 3°C of warming, increasing from 5.3% to 100.0% with warming between 4°C and 10°C.

The effect of nest relocation on embryonic mortality and sex ratio of Loggerhead Turtles, Caretta caretta (Reptilia: Cheloniidae), at Dalyan Beach, Turkey

Abstract Marine turtles are globally endangered and one important conservation technique is nest relocation. This study assesses the relationship between nest site factors (wet nest depth, dry nest depth, total nest depth, nest diameter, distance to sea, moisture, clutch size and incubation duration) and embryonic mortality of natural and relocated nests at Dalyan beach, Turkey. Principal component analyses (PCA) revealed a three-factor structure for the natural nests and a four-factor structure for the relocated nests. The clutches in natural and relocated nests had a total of mortality ratio of 21% and 12%, incubation duration of 52 and 50 days, and estimated female ratio of 80% and 88%, respectively. Thus, mortality was lower and incubation faster in the relocated nests, but the proportion of females was higher. Hatching success in relocated nests (84.4%) was significantly higher than in natural nests (72.7%).