Indian Journal of Geo Marine Sciences Vol. 46 (01), January 2017, pp. 163-169

Loggerhead Turtle Caretta caretta nesting activity in Chebba (Centre ): Assessment, problems and recommendations

Imed Jribi

Department of Life Sciences, Faculty of Sciences, University of Sfax, PO Box 1171, Sfax 3000, Tunisia.

[E-mail: [email protected]]

Received 09 April 2014; revised 12 September 2014

As the presence of loggerhead turtle nests has occasionally been reported in Chebba (Tunisia), we carried out a survey in "Essir" and "Sidi Messaoud" beaches during summer 2013 to assess the actual state of the nesting population. We report ten nesting events by loggerhead sea turtles. In comparison to past records, this number is relatively high and suggests that Chebba may host a much higher nesting activity than previously thought and higher monitoring effort is recommended, especially in certain beaches. Results indicate that beaches monitored so far are suitable for development, resulting in high hatching and emergence success; incubation durations indicate that majority of hatchlings produced are males.

[Keywords: Loggerhead turtle, Caretta caretta, Nesting, Chebba, Tunisia]

Introduction 5-6 Atlantic . Loggerhead turtles mainly nest in Marine turtles are an example of a species the eastern basin, with major nesting areas in that is diminishing in numbers as a result of the Greece, Turkey, Cyprus and Libya 3-7. The degradation of the living and nesting habitats, green turtle has a more restricted distribution, incidental catches, and pollution25. Significant nesting only in the eastern region of the eastern resources are currently devoted to numerous basin, mostly in eastern Turkey and Cyprus3-8. conservation and management projects at In a recent review, Casale and nesting areas. One of the most important and Margaritoulis3 estimated at 7200 and 1500 the costly activities for management projects is the mean annual numbers of nests laid along the monitoring of beaches to protect nests and Mediterranean coasts for loggerhead and green hatchlings from anthropogenic threats, such as turtles respectively. These numbers must be coastal development, sand extraction and considered as the minimum as they did not tourism, in addition to management of natural include data from sites other than monitored predation, to ensure high hatching success2-3. beaches or minor nesting aggregations known Richardson4 stated that a complete study of all elsewhere (Egypt, Lebanon, Syria, Italy, aspects related to nesting biology is essential Tunisia). For example, the number of nests for the selection and application of suitable reported from Libya concern only the surveyed marine turtle population conservation and tracts of coast, while the total number of nests management. remains unknown. Among the world’s seven marine turtle In Tunisia, the only sea turtle species known species, only three species frequent the to nest is the loggerhead turtle. Nesting activity Mediterranean: the leatherback turtle has been brought up many times in the (Dermochelys coriacea), the green turtle literature, but never based on precise (Chelonia mydas) and the loggerhead turtle information9-10- 11. The nesting of the (Caretta caretta). Only the last two breed in the loggerhead turtle was first recorded in 1988 on basin and their Mediterranean populations have the beach situated between Ras Dimas and only a limited gene flow with those of the and on the island Great Kuriat12 which

164 INDIAN J. MAR. SCI., VOL. 46, NO. 01, JANUARY 2017 is considered as the most important nesting site Chebba is known for its intense fishing in the country13-14-15. Some nests were found on activity as a result of its exceptional location, other beaches along the Tunisian coasts such as since its maritime fishing zone is located at the Chebba, , but nesting is not intersection between the Gulf of Hammamet to regularly observed. Additionally, nesting level the north and the Gulf of Gabes to the south. and distribution in Tunisia is not well studied. The coasts of Chebba are divided into two Only a monitoring program has been types: mainly swampy coast to the south and implemented on great Kuriat since 199714 in sandy with rock intercalations coasts to the order to protect nesting sites, nesting females north forming beautiful beaches very busy and hatchlings and to document the nesting during the summer months. activity. Many potential nesting sites have not During this study, we controlled both "Essir" been adequately monitored such as Chebba and "Sidi Messaoud" beaches (Fig. 1) sheltering where many nests have been reported there by nests during the 2013 summer."Essir" is the local people. Four nests were found in one main beach of Chebba. It has a length of beach of this town in 2007 for example. Only approximately 600m and spreads between the the beach of "Sidi Messaoud" was well two points with GPS coordinates: controlled in 1994 and 1995 when Ellouze16 35°14.386'N/011° 08.557'E and found three nests.Recalling the articles of the 35°14.268'N/011° 08.892'E. With its beautiful SPA protocol and the revised action plan on cliff road, this beach is very busy during the marine turtles in the Mediterranean17, taking summer, day and night. into account the new developments concerning The beach of "Sidi Messaoud" is contrary to conservation measures based on scientific "Essir" less crowded. It is a small beach of groundwork, and considering the positive effect about 200m length located behind the fishing of identification of new nesting areas and port and adjacent to the Roman archaeological restoration of degraded nesting beaches site "Borj Khdija". It spreads between the two (Priorities of the Mediterranean Action Plan) on GPS points: 35°14.108'N/011°09.442' E and Mediterranean marine turtle population, the 35°13.998'N/011°09.604'E. present study aimed to increase available data The study was carried out during summer and have clues on potential nesting sites in two 2013. In accordance with the peak of nests beaches of Chebba located in the centre of deposition observed on Kuriat islands 14, our Tunisia. monitoring ran from mid-June to the end of October corresponding to the hatchlings Materials and Methods emergence of the last nest deposited. In "Essir", Tunisia has 1250 km of coastline. A third is information on sea turtle hatchlings tracks was located on the western basin of the received from people frequenting the beach Mediterranean and is a predominantly rocky during the night or early in the morning. In area dotted with small beaches. The rest extends "Sidi Messaoud", the beach was visited during along the eastern basin with large sandy the summer period at least twice a week in beaches and large muddy areas. Length of order to characterize female turtle tracks, sandy beaches for the entire coast of Tunisia is imprinted on the beach sand, as “nesting” or estimated at more than 400 km12. “no-nesting” emergences and to locate egg Chebba is located off Cape Ras Kaboudia chambers. Date of nesting was conventionally assigned as the day after the night when the which is the most easterly point of the Tunisian 18 coasts (Fig. 1). It has the particularity to spread clutch was laid . All detected nests were like a peninsula and the sea surround it on three continuously monitored during the study sides. It has 29 km of coastline with some islets. period, and hatchling emergence was recorded. Nests were excavated 7–14 days after hatchling emergence19 and the total number of eggs (the number of eggs laid into the nest) and the hatching success were calculated by counting unhatched eggs, dead hatchlings in eggs, dead hatchlings in nests and empty eggshells (>50% complete) which were characterized as successful hatching. The hatching success (%) is calculated as follows: (empty eggshells/ total Fig. 1 − Geographic position of Chebba number of eggs)*10020. We tried to estimate

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sex ratio of hatched loggerhead turtles by This choice is also based on the fact that using two methods. The first used the mean pivotal temperature in marine turtles is a temperature during the middle third of the relatively conservative characteristic22- 24. incubation period21, while the second used the incubation duration22. Unfortunately, the Results temperature data logger buried in the nests to A total of ten sea turtle nests were deposited in measure the temperature failed to operate so we Chebba during the summer of 2013, six in "Sidi resorted to the second method for the estimation Messaoud" and four in "Essir". On "Sidi of this parameter. For the purpose of this study, Messaoud" beach, we found all nests deposited incubation duration is defined as the period in and located all the egg chambers. Only one track days between observation of the newly laid nest with one digging attempt but no egg deposition and the first record of emergence, by either was found. On "Essir", the nests were direct observation of hatchlings or their crawl accidentally found by local people frequenting tracks emerging from nests20. The curve used for the beach who observed the hatchlings on estimation of sex ratio as functions of beach. Only the egg chamber of one nest was incubation duration was that of Mrosovsky et al. located. For the three others, only hatchlings 21 adapted to the field by adding 4 days, which disoriented and attracted by light allowed us to corresponds to the interval between hatching know the presence of nests. Nest search did not and the emergence of hatchlings at the sand succeed in locating egg chambers as a result of surface23 (Fig. 2). Equation of the curve used high anthropogenic beach usage and trampling. (after correction) was calculated and the exact The information on the nests deposited is values of sex ratios were derived as was done by presented in table 1. Jribi et al.20. The choice of the study of21 is The nesting season 2013 in Chebba started at based on the fact that turtles from Greece and the beginning of July and ended at the middle of those of Tunisia are part of the same August with duration of 42 days. Compared with some of the larger nesting sites in the Mediterranean population and have the same 25 geographic range. Mediterranean (83.5 in Fethiye beach, Turkey ; 78.5 in Northern Cyprus26 and 87.7 in Kyparissia Bay, Greece27, the season in Chebba seems to be short. The mean clutch size of the seven nests excavated in Chebba 2013 was 86.43 eggs. This value is similar to those recorded in Kuriat islands (Tunisia), Cyprus, Libya and Turkey (Kruskal- Wallis test, H=5.236, P=0.2639) but less than those recorded in Greece7. Kruskal- wallis test between Greece nesting sites and those of the rest of the Mediterranean show a Fig. 2 − Percentage of females as a function of incubation duration (Derived from Mrosovsky et al. (2002)) and significant difference (Kruskal- Wallis test, adapted to the field (Jribi et al. 2013). H=13.7, P=0.01762).

Table 1− Information on the studied nests in Chebba (2013) Unhatched Sex Laying Emerg ID Clutch Dead Dead in Fertility Hatch Emerg Nest Beach Eggshellinfertile eggs ratio date date (days) size in eggs nests success success success E L (%♀) A S. Messaoud 05/07 31/08 58 83 77 2 2 1 1 0 96.4 92.8 92.8 8 B S. Messaoud 05/07 01/09 59 126 31 90 5 0 0 0 28.6 24.6 24.6 1 C S. Messaoud 13/07 14/09 64 65 35 6 16 8 0 0 90.8 53.8 53.8 0 D S. Messaoud 18/07 17/09 62 82 66 6 2 5 3 0 89.0 80.5 80.5 0 E S. Messaoud 31/07 06/10 68 78 69 0 4 4 1 0 98.7 88.5 88.5 0 F S. Messaoud 15/08 27/10 74 51 44 3 2 2 0 2 94.1 86.3 82.4 0 G Essir - 17/08 - 120 52 59 5 3 1 0 50 43.3 43.3 - H Essir - 25/08 ------I Essir - 01/09 ------J Essir - 13/09 ------Emerg: Emergence, ID: Incubation duration, Hatch: Hatching, E: Early mortality, L: Late mortality

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The hatching success and hatchling emergence Mediterranean (Fethiye beach, Turkey25; success are about 67.1% and 66.6% Northern Cyprus26 and Kyparissia Bay, respectively. In "Sidi Messaoud", where there Greece27, the shortness of this period may is the maximum of studied nests, these rates simply be due to the small nesting population raise to 71.1% and 70.4%. size. This parameter is crucial for the planning The number of infertile in nest B is very and the implementing conservation and important indicating that it would probably be management practices such as reducing the that of a neophyte (new nesting female)28. anthropogenic disturbance resulting from Disregarding this nest, hatching and emergence beach use. rates amount to 80.4% and 79.6%. The hatching and hatchling emergence For the nest deposited in "Essir", there was a successes are high in Chebba. If we eliminate high proportion of infertile eggs and the the nests suspected to be those of neophytes, hatching and emergence rates were low. these rates rise more. Indeed, neophytes are The incubation duration registered in "Sidi known by a tendency to lay once during the Messaoud" beach is 64.2 days. The two nests first season and hatching rates are usually quite deposited during early July (A and B) low28. These results reveal the suitability of the registered incubation durations less important. beaches of Chebba for nesting. The rest of the nests have their incubation The determination of sex ratio of hatchlings extended till the autumn with high risk of is very significant basic information in marine drops of temperature resulting in long turtle population dynamics29-30. It should incubation duration. therefore be taken into account in any The method used as indirect method for conservation planning of nesting beaches in predicting the sex ratios within the nests is order to conserve the “population’s sexual based on the incubation duration of clutches. structure” and act in an appropriate manner for The equation of sex ratio (% of females) as a the protection of these endangered reptiles, function of incubation duration adopted from especially in the context of current global Mrosovsky et al.21 but adapted to the field was warming31- 32. determined as was done by Jribi et al.20 (Fig. Since the sex of marine turtle hatchlings 2): cannot be assessed from external morphology Y=99.88/(1+Exp(–103.34+1.82*X)) and sacrificing hatchlings was not an option where Y is the sex ratio and X is the incubation for ethical and conservation reasons, this duration. parameter was derived from the incubation All nests were predicted to produce more duration indicating a highly male biased males. Four nests among the six studied were results. It is clear that period of deposition of predicted to produce 100% males. The two nests has a great influence on hatchling sex others produced very low proportion of ratio: Nests deposited at the beginning of the females. Although all nests are predicted to nesting season have a warmer temperature produce males, the analysis of the results of the regime which is reflected by a possible female sex ratio for the nests laid in early July and the production. The nests deposited after mid-July rest of nests showed significant differences have their incubation duration extended till (Kruskal-Wallis test, H=3.429, P=0.0285). autumn with temperature regime less warmer Conversely, nest predation (one of the most and so less chance of female production. important causes of nesting failure at many In the Mediterranean, current knowledge Mediterranean nesting grounds7), was never about sex ratio of hatchlings and juveniles is documented and seems not to be a source of somehow contrasting, with more male danger to loggerhead nesting in Chebba. juveniles than expected from hatchling sex ratio in monitored nesting sites29. In fact, the Discussion common pattern of loggerhead marine turtle In the Mediterranean, loggerhead nesting sex ratios in the Mediterranean region and occurs between beginning of June and early globally, is female-dominated33-34-35. Results of August, with sparse nesting from mid-May to this study show the importance of studying early September7. Nesting season in Chebba minor nesting sites because they can give an seems to be short and July appears to be the appreciable contribution, not only in number most important month for nesting. Compared and in genetic diversity14 but also in sex ratio with some of the larger nesting sites in the because they can counterbalance the female

JRIBI: LOGGERHEAD TURTLE CARETTA CARETTA NESTING ACTIVITY IN CHEBBA 167 biased sex ratios registered in the majority of Despite the small number of nesting major nesting sites across the globe. It would females, the increasing knowledge on the therefore be very important to continue the processes of genetic diversification should estimation of sex ratio in Chebba to see if 2013 focus conservationist’s attention to the nesting season was exceptional or if the male protection of small rookeries. Small rookeries biased sex ratio is a character of the site. Male- may play an important role in the maintenance producing areas may contribute to a better of genetic diversity36 because the loss of understanding of the sex ratio patterns and may nesting sites is accompanied by the loss of also represent important areas in future specific genotypes37. scenarios of climate change, with increased Unfortunately, national and regional temperatures and consequently increased strategies of conservation of marine turtles are female production31. focused mostly on the reduction of mortality Despite the encouraging results of this 38-39-40 due to the interaction with fisheries and study, nesting population in Chebba is the protection and monitoring of major nesting seriously endangered by direct threats during sites. Obviously, conservation should try to the terrestrial phase of reproduction protect the maximum with the minimum (deposition of eggs, incubation, hatching and 41 effort , but for wider and more effective emergence and return to the sea). The impact conservation we strongly suggest that besides of degradation of nesting beaches, increase of protection measures for major nesting sites, artificial lights and huge frequenting of more efforts are made to monitor and protect beaches are likely to be the major sources of minor sites as Chebba and Kuriat in Tunisia as danger. In "Sidi Messaoud", the construction well as Calabria and Sicily in Italy. of an aquafarm near the nesting beach represents a danger which must be stopped Concerning Tunisia, the strategy should immediately. In "Essir", destruction of coastal include a preliminary phase to precisely assess dunes behind the beach to give aesthetical nesting beaches mainly in the region extending feature to the cornice had grievous from the gulf of Hammamet to the tunsian- consequences because the beach was eroded Libyan border. Actions implemented should and exposed to light from the road. In fact, all focus on the protection of new nesting beaches, hatchlings emerged were attracted by light in and if not possible for all areas, at least control the opposite direction of the sea and some of urbanization (buildings, artificial lights, etc.) them were crushed on the road. Fortunately and coastal erosion in order to avoid what rebuilding the dunes began last years and the happened in "Essir" beach when there has been results have begun to appear. destruction of dunes. Furthermore, the installation of umbrellas Acknowledgements and night beach attendance must be stopped in order to protect nesting activity on this beach. The author would like to thank the team of the Chebba Fans Association for the awareness Conclusion effort made. All thanks are also addressed to The state of loggerhead turtle nesting in Nadege Zaghdoudi-Allan for the revision of Chebba and in Tunisia generally is far from the English. clear. Apart from the monitoring of the Kuriat References islands beaches, which is considered the most important nesting site in Tunisia, no effort for 1 Lutcavage, M.E., Plotkin, P., Witherington, B. and Lutz, P.L., Human Impacts on sea Turtle Survival. In: research nor conservation of nesting beaches The biology of sea turtles, Edited by Lutz J.A., has been deployed. The long sandy beaches on Musick J.A., CRC Press, Boca Raton, Florida, USA, the Tunisian coast and the occasionally 1997, pp. 387-411. signaling of laying on certain beaches suggest 2 Adam, V., Tur, C., Rees, A.F., Tomas, J., Emergence that the phenomenon is likely to be greater pattern of loggerhead turtle (Caretta caretta) hatchlings from Kyparissia bay, Greece. Mar. Biol., than expected. A survey campaign to assess 151(2007) 1743-1749. national nesting populations is now most 3 Casale, P. and Margaritoulis, D., Sea turtles in the needed, particularly in those areas where Mediterranean: Distribution, threats and nesting was documented such as beaches of the conservation priorities. Gland, Switzerland, IUCN gulf of Hammamet and those in southern Press, 2010, pp. 294. 4 Richardson, J.I., Priorities for studies of reproduction Tunisia (Zarzis, Jerba). and nest biology. In: Research and management

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