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Öğe A 21-year recovery trend in green turtle nesting activity: 2002-2022(John Wiley and Sons Inc, 2023) Sönmez, Bektaş; Mestav, Burcu; Yalçın Özdilek, ŞükranLong-term monitoring and conservation are crucial for effective protection, since sea turtles migrate cyclically every 2-3 years and lay multiple nests during a breeding season. Therefore, this study aimed to investigate the long-term trend of nesting activities of green turtles over a 21-year period (2002-2022) on Samandag beach.An early morning survey was conducted every year during both nesting and hatching seasons. The trend analyses in nesting activities were performed using Mann-Kendall and Sen's slope tests together with the augmented Dickey-Fuller stationarity test.The nest count and female abundance increased significantly, whereas clutch size, fecundity, and hatching success tended to decrease insignificantly. The percentage change between the most recent and oldest 3-year mean nest count and mean female abundance, which is performed to comply with the Red List assessment method used by the International Union for Conservation of Nature Marine Turtle Specialist Group, was 769% and 764% respectively.Samandag nesting population accounts for one-third of the Mediterranean's total nest count and one-fourth of its total female abundance. The decrease in clutch size and fecundity may be due to the recruitment of individuals with smaller body sizes or malnutrition as a result of population growth. There was an increase in the number of dead embryos and a decline in hatching success. This may be explained by density-dependent population regulation as a result of an increase in the number of nests.It may be argued that adherence to a uniform strategy and the maintenance of continuous protection through collaboration with governmental and non-governmental organizations with scientifically rigorous methodology are significant factors contributing to the high recovery.This study emphasizes the necessity of adopting a comprehensive conservation approach encompassing both foraging habitats and the significant role played by the population in Samandag in the proliferation of Mediterranean green turtles.Öğe A two-headed green sea turtle (Chelonia mydas) hatchling on samandağ beach, Turkey(Folium Ltd, 2017) Sönmez, Bektaş; Sert, Mehmet; Kayikçi, Senem; Bedirci, Özay; Özdilek, Şükran YalçinA two headed green sea turtle (Chelonia mydas) was found on Samanda? Beach, Turkey in 2015 nesting season. The two heads were anatomically similar with independent reaction to external stimuli. The carapace scutes showed anomalies. Radiography was performed and the spinal column was seen to bifurcate in the area close to the caudal region. In the post mortem examination, esophagus, stomach, liver, lung, heart and trachea were duplicated. The two headed green turtle was subclassified as teratodidymus. Dicephalism rarely occurs in sea turtle and perhaps genetic factors may play a significant role for this two headed green sea turtle. © 2017 Folium Publishing Company.Öğe Body size-related polymorphic foraging strategy in adult green turtles(Elsevier Ltd, 2023) Yalçın Özdilek, Şükran; Sönmez, Bektaş; Mestav, BurcuGreen turtles (Chelonia mydas) are among the prominent migratory and conservation-needing animals. Missing data on the foraging strategy of green turtles limits effective conservation actions in the Eastern Mediterranean. We applied the stable δ13C and δ15N isotope signatures together with body size to evaluate the foraging ecology of green turtles. Five tissue samples were utilized, including keratin, epidermis, red blood cells, plasma, and whole blood. The samples were retrieved from five major breeding areas in Turkey. Significant correlations were observed between curved carapace length and the δ13C and δ15N values of the green turtles in all the breeding populations except for Alata. The bimodal distribution of δ13C and two clusters based on the δ13C and δ15N values indicated a dichotomy concerning the foraging habitats of the green turtles nesting on the Eastern Mediterranean. The body sizes of the females in the first cluster (with depleted values) were significantly larger than the second cluster (with enriched values). The total niche area of the females in the first cluster was larger than that in the second cluster, which may correspond to the generalist/specialist feeding strategy. The present study gives some novel results about the foraging ecology of green turtles in the Mediterranean. For effective and viable conservation actions, further studies are needed to identify the foraging areas of green turtles in the Mediterranean.Öğe Dichotomy in morphology of the same genetic lineage of green turtles(British Herpetological Society, 2023) Sönmez, Bektaş; Mestav, Burcu; Kırbeci, Selma; Yalçın Özdilek, ŞükranMorphological studies of marine turtles are important to provide insight into changes in their developmental environment. This study aimed to determine green turtles' Chelonia mydas morphological differences within the same genetic lineage in the eastern Mediterranean MED3 management unit and to find the best conversion equations between carapace size. A total of 106 adult green turtles (curved carapace length [CCL] range 79–105 cm) were measured on the five major nesting beaches of the eastern Mediterranean during 2020 and 2021. Morphological differences were tested with PERMANOVA and the relationship among body sizes was tested by linear regression. In the eastern Mediterranean green turtles, the mean CCL and SCL (straight carapace length) were 88.5 cm and 83.5 cm, respectively. There were no statistically significant differences in any of the examined morphological characteristics of green turtles collected from five nesting beaches. In the clustering analysis, however, it was found that all the turtles fell into two distinct groups: larger (> 95.2 cm) and smaller (< 85.2 cm) turtles. As well, the conversion equations between CCL and SCL showed a high coefficient of determination (R2 = 0.938). We suggest that the conversion equations may be applied to all green turtles belonging to this population and nesting in the eastern Mediterranean.Öğe First Record on Loggerhead Nest in Gökçeada, Türkiye in Northern Aegean(ABADER (Adıyaman Bilimsel Arastırmalar Dernegi), 2023) Sandik, Emre; Dermanci, Pınar; Sönmez, Bektaş; Yalçin Özdilek, ŞükranThis study presents the first report of a loggerhead turtle nest in the northern latitudes in the Aegean Sea of Türkiye, which was found on the Gökçeada Island of Çanakkale Province, Turkey. The nest contains a total of 129 eggs, 103 of which produced hatchlings and 100 of these hatchlings reached to the sea safely. This sporadic record may be a result of mechanisms developed to overcome the limitations of philopatry and increase their ability to adapt to the predicted global climate change. © 2023, ABADER (Adıyaman Bilimsel Arastırmalar Dernegi). All rights reserved.Öğe Green turtles (Chelonia mydas) feeding on invasive algae Caulerpa taxifolia in Turkey(Folium Ltd, 2015) Yalçın Özdilek, Şükran; Akdeniz, Burcu; Firat, Ali Rahmi; Balkan, Emine İnci; Gürsoy, Sait; Sönmez, Bektaş; Erduğan, HüseyinAn invasive species is a species that has been introduced to an area outside its natural range and can cause ecological problems such as change the functions of ecosystems. A female green turtle was predated by a jackal on Samanda? beach, in Turkey. Stomach content was sampled and stored for diet analysis. Macroalgae were the dominant food in terms of mass, and Caulerpa taxifolia (M. Vahl) C. Agardh, which is an invasive species, was the most frequent food type. Although this species has not been shown to be a preferred diet item for green turtles, C. taxifolia is dominant species at the area and was consumed by the adult green turtle. © 2015 Folium Publishing Company.Öğe Mother-Hatchling Isotopic Relationship in Green Turtle: Isotopic Niche-based Modelling(Biodiversity Research Center Academia Sinica, 2024) Yalçın Özdilek, Şükran; Sönmez, Bektaş; Mestav, BurcuThe isotopic discrimination between the mother and the hatchlings has been modelled in various vertebrates, including sea turtles. In addition to the linear relation between ?13C and ?15 N isotope values of the mother – hatchling couple, there is missing data on the combined effects of both isotopes, which represent ecological niches of a species. The stable ?13 C and ?15 N isotope signatures of live hatchlings and their mother’s epidermis tissues were used in green turtles. The samples were taken from three main breeding beaches, Akyatan, Sugözü and Samandağ in Türkiye during the 2020 nesting season. It was found that both ?15 N and ?13 C values of hatchlings were not significantly different from those of mothers. Significant relationships were found between hatchlings and their mothers in terms of ?13 C value. Furthermore, when the hatchling isotopic niche size is known, the condition probability of estimating the mother isotopic niche size were 85.16% and 92.88% with the 0.95 and 0.99 alpha levels. In addition to showing a linear relationship between hatchlings and their mother's single isotopic composition, the current study offers a novel insight that proposes a niche overlap concept using two isotopes to comprehend the mother-hatchling relationship of green turtles living in the eastern Mediterranean. © 2024, Biodiversity Research Center Academia Sinica. All rights reserved.Öğe Sex ratio estimations of Cheloniamydas hatchlings at Samandağ Beach, Turkey(2016) Yalçın Özdilek, Şükran; Sönmez, Bektaş; Kaska, YakupSamandağ Beach, an important nesting location for endangered green turtles (Chelonia mydas), is located at the most eastern part of the Mediterranean in Turkey. Hatchling sex ratio can be one of the key factors for green turtle protection, which is under the threat of global climate change. In this study, sex ratios of hatchlings were estimated by histological examination of dead hatchlings (n = 190) and by nest temperatures (n = 14) at Samandağ Beach between the 2003 and 2007 nesting seasons. The histological examination of dead C. mydas hatchlings and temperature-recorded nests indicated a female-biased sex ratio on Samandağ Beach. By histological examination, top and bottom levels of nests were recorded as 94% and 64% of females. Sex ratios during the middle third of the incubation period ranged from 39% to 97% for females with a mean of 74%. Distance from the sea was correlated with the middle third of incubation temperature (r = 0.604, P = 0.022) and female ratio (r = 0.573, P = 0.032). While nest temperatures and nest parameters such as hatching success, clutch size, nest distance from the sea and from vegetation, nest depth, and the day of emergence were not found significantly different among years (P > 0.05), incubation duration was found significantly different among years (P < 0.05). The results showed a female-dominated sex ratio by both histology and nest temperature. The knowledge of hatchling sex ratios provides information on demographic parameters, and coupled with appropriate conservation measures this can make important contributions to studies of climate change effects on green sea turtle populations.Öğe Some properties of new nesting areas of sea turtles in north-eastern Mediterranean situated on the extension of the Samanda? Beach, Turkey(Triveni Enterprises, 2006) Yalçın Özdilek, Şükran; Sönmez, BektaşOne of the most endangered species in tropical seas, Chelonia mydas (green turtles) prefer undisturbed sand beaches to lay their eggs. While Caretta caretta lays their eggs all over the Mediterranean beaches of Turkey, C. mydas nesting locations are limited with north-eastern site (Alata, Kazanli, Akyatan and Samanda?) of the country and some beaches in Cyprus. Until 2003, no nesting place of both species between Akyatan and Samanda? was recorded. From north to south, the beaches examined in 2003 summer are Arsuz, Konacik, Kale, Tr-H-3, Tr-H-2, and Tr-H-1 in addition to well-known and studied nesting beaches of sea turtle species in Hatay Province: Çevlik, Şeyhhizir and Meydan. Since the Hatay Provincial Coast between Çevlik and Arsuz is hilly and no stabilized road is available, these small beaches were not known to have both C. mydas and C. caretta nests. Some physical and chemical sand properties, the number of nests belong to both species and selected nest specifications were investigated in this study. Kale Beach was found to be the most important nesting place in this less populated area. Based on results, Kale, Tr-H-3 and Tr-H-1 beaches were recorded to have high hatchling success. © Triveni Enterprises.Öğe Yeşil Deniz Kaplumbağası (Chelonia mydas) Yavrularının Büyüklüğü için Indikatör Olarak Bazı Yuva Özelliklerinin Kullanılmasıyla İlgili Bir Ön Çalışma(2017) Sönmez, Bektaş; Yalçın Özdilek, ŞükranVücut büyüklüğü, deniz kaplumbağası yavrularının hayatta kalma şansını artırabilir veya azaltabilir. Deniz kaplumbağası yavrusunun hayatta kalabilirliği için vücut büyüklüğünün önemi göz önüne alındığında, indikatör kullanılarak, yavru büyüklüğünün tahmin edilmesi koruma uzmanları için yararlı bir yöntem olacaktır. Türkiye'de Chelonia mydas popülasyonunda, yavru büyüklüğü için indikatör olup olmayacaklarını belirlemek amacıyla, yumurta sayısı, yuvanın denize olan uzaklığı, kuluçka süresi ve yuva derinliği gibi bazı yuva özellikleri yavru büyüklüğü ile korelasyona tabi tutuldu. Bulgularımız, bu yuva özelliklerinden hiçbirinin yavru büyüklüğünü tahmin etmek için uygun olmadığını göstermiştir. Ancak, kuluçka süresi, yavrunun düz karapas boyu ile zayıf bir korelasyon göstermiştir. Kollinear yuva özelliklerinden türetilen ana bileşenlerin (AB), yavru büyüklüğüne en iyi uyan doğrusal modeli oluşturulduğu zaman, model yavru büyüklüğündeki varyansın sadece % 19.75'ini açıkladı. AB2'nin doğru karapas boyu (DKB) üzerinde anlamlı bir etkisi vardı ve AB1 ile AB2 arasındaki etkileşim, tek değişkenli analizde DKB ve eğri karapas boyu (EKB) üzerinde belirgin etkilere sahipti. F-test sonuçları, modellerin belirgin öngörü yeteneğinin olmadığını önermektedir. Belki de, araştırılmayan diğer faktörler indikatör olarak daha uygun olabilir veya yavru büyüklüğü, indikatör olarak kullanılabilir ancak tespiti yapılamayan bir kaç temel faktör gibi çeşitli faktörler arasındaki karmaşık bir etkileşimden etkileniyordur
