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One aspect of nest relocation that has received relatively little attention is anatomical differences of the resultant hatchlings. For example, Mast & Carr (1989) observed that for Kemp’s ridleys, “handling of the eggs after oviposition has a marked effect on carapacial scute variability.” A similar effect was reported for hatchlings from relocated olive ridley eggs in Suriname (Hill 1971) and Sri Lanka (Hewavisenthi & Kotagama 1989), and also for green turtle hatchlings in Japan (Suganuma et al. 1994). Although supernumerary and subnumerary scute counts have been observed for nearly all species of turtles that possess scutes (Gadow 1899; Newman 1906), the causes are less clear. Some authors have suggested that abnormalities of scute patterns arise from accidents or disturbances during ontogenetic development (Parker, 1901; Hildebrend, 1930; Zangerl, 1969). Hildebrend (1938) suggested that scute anomalies in diamondback terrapins (Malaclemys terrapin) result from changes in available oxygen supply during incubation. Temperature variation during incubation may also account for scute abnormalities. Morphogenetic effects can occur in turtles as a result of incubation temperature (e.g. Yntema 1976; Yntema & Mrosovsky 1980).

The implications of scute variation for sea turtle biology are unclear. Interestingly, Gadow (1899) noted over a century ago that for loggerhead sea turtles, carapacial scute variation is greater in hatchlings than adults. We confirmed this in loggerheads in a rookery in Turkey (Türkozan et al. 2001). To explain this difference, Gadow (1899) proposed the idea of “orthogenetic variation,” theorizing that young turtles with more than the normal complement of scutes undergo fusion of scutes during ontogeny such that the adults exhibit the normal scute pattern. Newman (1906) opposed this view and suggested that supernumerary scutes were an atavistic reappearance of scutes that had been lost during phylogeny. Another explanation could be that scute variation is linked to reduced fitness, thereby resulting in fewer adult turtles with observed scute variations.

To further investigate this issue and to contribute to ongoing discussions concerning when to relocate sea turtle eggs, we examined differences in carapacial scute patterns, sizes and weights of hatchlings produced from loggerhead nests that were incubated in situ and from nests that were relocated to a hatchery on Dalyan beach, Turkey. From loggerhead clutches laid 2004 season (June to early August), we examined 734 hatchlings from 34 in situ nests and 1188 hatchlings from 49 hatchery-relocated nests. The nests in the hatchery were relocated for either of the following reasons:

We were not able to protect them with wire mesh cages against fox predation or the nests would have been flooded otherwise. The hatchery site was roughly 30 m away from the water line. The physical conditions of the hatchery site were nearly the same as the original nest site because Dalyan beach has a homogenous profile consisting largely of fine sand. We compared measures of straight carapace length (SCL), straight carapace width (SCW), mass, and scute patterns. Length was measured with a dial caliper with an accuracy of ±0.02 mm. Mass was measured with a digital scale (accuracy ±0.1 g). Comparisons of the scute patterns were evaluated with a chi-square test while the length and mass data were compared with one way analysis of variance (ANOVA). All means are presented with ±SD.

Table 1. Proportion of loggerhead turtle hatchlings from Turkey with different distributions of carapace scutes.

The vertebral, costal and marginal series were the most variable and the supracaudal scutes were extremely stable (Table 1). The most common (normal) scute pattern that we found was 1 nuchal, 5 vertebrals, 5-5 costals, 12-12 marginals, and 2 supracaudals. This is concordant with Türkozan et al (2001) and Reichart (1993). There were variations from the normal pattern in hatchlings from both natural and relocated nests (Table 1), with significant differences between the two groups for all sets of nuchal, vertebral and marginal but not costal scutes (Table 2). When the data on deviations are pooled, there was a higher rate of scute deviation for hatchlings from the relocated nests (Figure 1). However, this difference was not significant (Chi-square test p>0.05).

Table 2. Comparison of distribution of scute patterns observed in natural nests and hatcheries (0 = hatchlings with no deviations; 1 = hatchlings with scute deviations).

For hatchlings from natural nests, the mean SCL was 40.48 ± 1.60 (range= 33.54-43.62) mm, the mean SCW and 31.73±1.38 (range 25.20-36.46) mm, and the mean weight was 14.81±1.76 (range=8.70-18.90) g. For hatchlings produced by relocated nests, the mean SCL was 40.39±1.34 (range=35.60-44.48) mm, the mean SCW was 31.48±1.10 (27.50-34.60) mm, and the mean weight was 14.51±1.41 (range=9.60-18.40) g. Although there was no significant difference in SCL of hatchlings from natural or relocated nests, hatchlings from relocated nests did have smaller SCW (ANOVA F= 19.65, p<0.001) and lower mass (ANOVA F= 16.77, p<0.001) than hatchlings from natural nests. In contrast, when we compared hatchings exhibiting scute deviations with normal hatchlings from in situ nests (Table 3), the turtles with variable scute patterns were longer (ANOVA F=4.56, p<0.05) and heavier (ANOVA F=13,49, p<0.001). For turtles produced from clutches relocated to hatcheries, hatchlings with deviant scute patterns were smaller (ANOVA F=6.09, p<0.05) than normal turtles, although there was no significant difference in weight (ANOVA F=0.008, P>0.05).

Table 3. Mean size and weight (±SD) of hatchlings from natural and relocated nests (0 = hatchlings with no deviations; 1 = hatchlings with scute deviations).

Scute variation in hatchlings is a natural occurrence, although the rate of expression is generally higher in hatchlings from relocated loggerhead nests in Turkey. Interestingly, hatchlings from natural nests were more likely to have variation in the nuchal scutes than hatchlings from relocated nests, although deviations in nuchal scutes were far less frequent than deviations in marginal, costal and vertebral scutes. Hatchlings from relocated nests were also significantly thinner and had less mass, although the absolute differences were small (<0.3mm for SCW, <0.4g for mass). The differences observed in hatchlings from natural and relocated nests were not likely to be due to differences in seasonal changes in weather, as hatchlings from both groups came from nests that were laid throughout the season. Micro-environmental differences in the zones where natural and relocated nests were incubated may be linked to the anatomical differences, particularly if the sand conditions varied in temperature and/or moisture between hatchery and natural nesting beach (cf. Foley et al. 2000; McGehee 1990). The impact of these anatomical differences in hatchlings remains unclear. Adult turtles tend to have fewer scute deviations than hatchlings (Gadow 1899; Türkozan et al. 2001). Could this indicate that hatchlings with scute deviations are less fit and thus less likely to survive to adulthood, relative to hatchlings with normal scute patterns? It may be that the smaller size of hatchlings with scute variations is linked to reduced fitness. For example Janzen et al. (2000) found that larger hatchlings of Cheldra serpentine exhibited significantly greater survivorship than smaller individuals. Perhaps in loggerhead turtles, smaller hatchlings are more susceptible to predation. Therefore, it is possible that as relocated nests are more likely to produce smaller hatchlings (that also have scute variation), these hatchlings tend to be removed from the population before reaching adulthood, making observations of adults with scute variations relatively rare (Gadow 1899; Türkozan et al. 2001). However, it remains the case that not all hatchlings from relocated nests are small and/or exhibit scute anomalies. It is likely that there are trade-offs associated with nest relocation – for example, higher rates of deformities and possibly reduced fitness (current work) vs. population increases due to increased nest protection. More research is needed on the impacts of translocation and artificial incubation of sea turtle eggs.

Figure 1. Occurrence of hatchlings with scute variations (filled bars) and without scute deviations (open bars) in natural nests and hatchery nests.

Acknowledgements: The authors thank Matthew Godfrey for his contributions. This study is a part of a project supported by the Authority for Specially Protected Areas, Ministry of Environment, Turkey

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