Tuesday, April 26, 2016

Nesting activity of sea turtles, Caretta caretta and Chelonia mydas, at Patara Beach over four nesting seasons

The loggerhead turtle known as Caretta caretta is the most common sea turtle that exists in the Mediterranean. Some of the major nesting areas for these turtles are in Greece, Turkey, Libya, Egypt, Israel, Italy, etc. The green turtle, which is known as Chelonia mydas, is well known in the Mediterranean. But this turtle is densest in Turkey, Cyprus and Syria.

Caretta caretta

Chelonia mydas

 Based on the first research of the Turkish coast of turtle nesting areas there are seventeen important nesting beaches on the Turkish Mediterranean coast, this number was then again upgraded in 2003 to 20 important nesting beaches and then to 22 in 2004. In a study the number of C. caretta females are annually nesting on the coast varies between 2280 to 2787 another study estimates in 2010 that C. caretta is 7200 and about 1500 for C. mydas.

The first detailed research that shows nesting activity on Patara Beach in Turkey started in 1989. The highest number of nests was shown in 2006 and it had 127 nests and the lowest number of nests was 33 in 1994. The goal of this study was to show information on nesting activity and show distributions of nests, etc.

In this study about 556 loggerhead emergences were recorded per year over a four year period. About 32 percent of this number resulted in nests and about 180 nests were made per year. On the Patara beach there were 113 nests in 2010, 138 in 2012, 207 in 2013 and 195 in 2014. In the Kumluova beach there were 3 in 2010, 31 in 2012, and 32 in 2013. Kumluova has some wetlands that exist within the beach area and there is more predation which is why there is a higher amount of nests in  Patara. There are also the green turtle emergences, which only had 17 in the 4 year period which were all in Patara. There were only 3 nests that were resulted out of these turtles 1 in 2010 and 2 in 2012.

Figure 1

Figure 1 shows that the nesting season starts in May but the amount of nesting that occurs in may is low. Figure 1 also shows an incline of nesting activity towards the end of June but the peak nesting time take place in July and then dies off again in August which is the end of the nesting period. In May nesting success what at approximately 4.03%, in June it was about 44.93% in July it was 45.62% and in August it was 5.42%.

Table 2

Shown in Table 2 the researchers excavated loggerhead nests. In 2010 they excavated 115 nests, 162 in 2012, 224 in 2013 and 190 in 2014. The overall total of eggs counted was 47,129 eggs and 676 nests. One of the key parts of this study was the amount of hatchlings that were produced from each nest. And they found that 17,929 of the 47,129 eggs were able to make it to sea (38.04% of eggs). There were also 218 green turtle eggs counted and 121 of those eggs produced hatchlings and 94 were able to make it to sea (43.12% of eggs).

Predation affected the nests over the four-year period. 142 of the loggerhead nests were partially predated on and 256 were completely predated on. 55.36% of the nests were affected by predation. Some of the predators include Fox (Vulpes vulpes), dogs (Canis lupus), badgers (Meles meles), and wild pigs (Sus scrofa). There was also some predation by crabs. Some of the nests were provided with metal grates to help with survival. The hatchlings with the protection had a higher survival rate than those that were in natural settings because the predation was lower.

OLGUN, K., BOZKURT, E., CEYLAN, S., TURAL, M., ÖZCAN, S., KARASÜLEYMANOĞLU, K. Ş., & GEROĞLU, Y. (2016). Nesting activity of sea turtles, Caretta caretta (Linnaeus, 1758) and Chelonia mydas (Linnaeus, 1758) (Reptilia, Cheloniidae), at Patara Beach (Antalya, Turkey) over four nesting seasons. Turkish Journal Of Zoology, 40(2), 215-222. doi:10.3906/zoo-1505-8

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