Koh Tao Sea Turtle Head-Starting and Rehabilitation Project Updates
6 March 2013
For the last 12-15 years the Royal Thai Navy has been conducting an annual sea turtle release program on the island of Koh Tao, alongside the local community. In April of 2012, 24 of the sea turtles which for the annual release where found to be sick and covered in infections. Some of the turtles were in such a bad state of health that they barely moved and did not eat. Under the guidance and recommendations Dr. Nantarika Chansue of the Veterinary Medical Aquatic Animal Research Center at Chulalongkorn University, it was decided that the turtles were too sick to be released, and were in dire need of rehabilitation if they were to survive. By May of 2012, we had constructed large sea turtle holding ponds including a flow through tanks to allow constant water change over, mechanical and biological filtration to maintain water quality, and a macro-algae pond to both remove nutrients in the water (that contribute to disease and bacterial growth) and provide a natural food source for the juvenile turtles. Every effort was made to simulate the natural conditions for the sea turtle’s development and health. Following the success of this program, we are requesting to continue the project into the future for both Hawksbill and Green Sea turtles to work alongside the Royal Thai Navy to help restore local populations of these endangered species in the Gulf of Thailand.
Of the 7 extant species of sea turtles worldwide, all are listed as either “Critically Endangered”,”Endangered”, or “Vulnerable” by the IUCN (Eckertet al. 1999). Five species of Sea Turtles can be found in Thai Waters, with only 3 being in the Thai Gulf (the Hawksbill, Olive Ridley, and Green Sea Turtles), all of which are experiencing rapid declines in population abundance and nesting (Settle 1995). For the last 12-15 years the Royal Thai Navy has been conducting an annual sea turtle release program on the island of Koh Tao, alongside the local community and more recently the Save Koh Tao Community group. For the last decade, the New Heaven Dive School (specifically Maleephan and Devrim Zahir) have been assisting by caring for the turtles for 2-3 days prior to their release. This has included setting up holding tanks, feeding, caring for wounds or infections, and other tasks to ensure their comfort and survival prior to release at the yearly Save Koh Tao community festival.
In 2007, The New Heaven Reef Conservation Program (NHRCP) was started at the New Heaven Dive School to encourage and promote reef research, protection, and restoration. The NHRCP carries out daily projects including monitoring the reefs, maintaining coral nurseries and artificial reefs, installing and maintaining mooring buoys, maintaining a giant clam nursery program, testing water quality, coral rehabilitation, coral larval culturing, and much more. Regarding sea turtles, the NHRCP helps to run a community wide sea turtle database, has protected sea turtle nesting areas, reported to sea turtle deaths or entanglements, cared for sick or injured turtles, and coordinated the Save Koh Tao turtle releases.
In 2008, 6 of the turtles brought for release were determined to be too small and unhealthy for release. Preexisting injuries to the turtles included open wounds, bite marks, and partial amputation of rear or front limbs. The reason for the injuries was determined to be biting or fighting amongst the juveniles, especially towards the smaller individuals. As with most reptiles or birds, this is an instinctual response to resource availability, whereby larger juveniles will kill or consume their smaller siblings to reduce competition for limited resources and increase their own chances of survival. At the time, and it is assumed to be the same at the Sattahip center, the turtles were being kept in a plastic tub with no natural objects or food sources available. Mostly the turtles were fed lettuce, which does not contain high levels of calcium or iodine, essential for sea turtle development (Eckert et al. 1999). When turtles were observed to contact or come in close proximity with a smaller individual they would be seen to bite and in some cases remove tissue from the rear limbs of the smaller sea turtle. That year, it was decided to temporarily rear the juvenile sea turtles in a natural enclosure with the consent of the Royal Thai Navy in the vicinity of Ao Leuk Bay, Koh Tao.
Immediately upon placing the juvenile sea turtles into the natural enclosure, their behavior and health changed dramatically. Limbs of injured sea turtles which had been chronically infected or open, healed in days, and in some individuals, regeneration of lost limb tissues was even observed. Individuals ceased to bite or fight over resources, as in the enclosure natural, nutrient rich food was available in high abundance (including macro algae, biofilm, bivalves, and crustaceans.) In fact, where in the tanks individuals would attack when bumping or resting against another individual, in the natural enclosure they were observed to forage side-by-side, and even sleep against one another. Based on our observations, the sea turtles benefited greatly from being in the natural enclosure instead of being in the plastic or tile tubs. The project however ended abruptly when the wall of the enclosure was destroyed in a storm, and the sea turtles were able to escape to the sea. After a thorough investigation of the shoreline, no dead turtles or shells were found, so it was assumed that the turtles survived the premature release.
In April of 2012, 24 of the sea turtles which arrived with the Royal Thai Navy for the annual release where found to be sick and covered in infections, assumedly due to being raised in close proximity in tubs with poor water quality. Some of the turtles were in such a bad state of health, that they barely moved and did not eat. Under the guidance and recommendations Dr. Nantarika Chansue of the Veterinary Medical Aquatic Animal Research Center at Chulalongkorn University, it was decided again that the turtles were to sick to be released, and were in dire need of rehabilitation if they were to survive. 23 of the sea turtles were not released, but relocated back to the NHRCP for constant monitoring, daily antibiotic and nutrient injections, and wound cleaning and dressing. The daily care of the turtles was carried out by volunteers of the NHRCP, and Dr. Jae Intaraksa of the NOISTAR Animal Clinic donated the necessary medications and vitamins and administered the daily injections.
By May of 2012, we had constructed large sea turtle holding ponds including a flow through tanks to allow constant water change over, mechanical and biological filtration to maintain water quality, and a macro-algae pond to both remove nutrients in the water (that contribute to disease and bacterial growth) and provide a natural food source for the juvenile turtles. Through research of other head-starting programs was carried out (Caillouet 1993, Okuyama 2010, Eckert et al. 1994, and Frazer 1992) and very effort was made to simulate the natural conditions for the sea turtle’s development and health, including:
- Natural substrates such as dead coral and dead giant clam shells were placed into the tanks to allow the turtle’s access to natural habitat to rest under and wedge themselves into to sleep. This natural substrate also allowed for the turtles to practice foraging and feeding skills which are essential for their survival in the wild (Eckert et al. 1999, and Okuyama 2010).
Coconut braches found on the beach or cut and dried in the sun were floated on the surface of the tanks to allow the turtles a place to rest, or to hide from other individuals, as in the wild sea turtles are solitary animals that will often travel through the sea under flotsam and debris (Carr 1987).
- Cleaning shrimp were introduced into the tanks to remove parasites and fouling organisms from the turtles. Within 4 days, the turtles no longer had algae on their shells, nor where they ever observed to have obvious signs of skin or shell parasites.
- Water temperature, pH, and DO levels where maintained by the system, and tended to be very stable due the construction of the flow through and filtration systems and the daily water changes.
- The turtles were fed a diet consisting of macro-algae (Sargassum, Padina, and Halimeda), raw fish, and turtle pellets (purchased from an aquarium store) (Eckert et al. 1999, Okuyama 2010). Also, when doing net and debris removals from reefs around the island, often many crabs, shrimps, and other crustaceans are brought back with the rubbish, these were also fed to the turtles when available, which would induce very frenzied feeding behavior, indicating that this was a preferred food source of the developing juveniles, possibly due to their high calcium content.
The turtles were observed, daily for behavior, as well as relative ability in feeding, swimming, and diving. The turtles were also measured and weighed regularly to monitor growth and calculate the amount of food to be given each day (2-5% of body weight as per Okuyama et al. 2010 and Eckert et al. 1999).
After reaching a shell length of about 24 cm the turtles have been released to the sea in the vicinity of either Ao Leuk or Chalok Ban Kao, by boat. In some cases, released turtles had been observed a week later to still be in the same area, surviving well and displaying natural behaviors (foraging, diving, predator and human avoidance, etc.)
Additionally, having the sea turtles on land has allowed us to increase the awareness and teach the local community about the threats facing sea turtles locally and globally. We have hosted multiple events with local and foreign school children to allow them to see the endangered sea turtles up close, and in some instances assist in the feeding, care, or monitoring of the turtles. Local boat captains have also taken notice of the program we are running, and have been watching for threats to sea turtles and reporting to us when they have seen turtles or problems such as illegal fishing, lost nets and marine debris, or mis-behavior by visitors or tour guides.
By April of 2013, all of the turtles will have been released to the sea, healthy and large. As we already have invested a large amount of money, resources, and time into rehabilitating these turtles and developing improved head-starting techniques, we are requesting to continue the project into the future for both Hawksbill and Green Sea turtles to work alongside the Royal Thai Navy to help restore local populations of these endangered species in the Gulf of Thailand.
Design of the flow through tanks
The flow-through tanks at the New Heaven Dive School are multi-use tanks which have been specially designed to facilitate the rehabilitation and rearing of juvenile sea turtles. Using a stand-pipe system, the water in the tanks flows continuously 24 hours a day to maintain a high level of water quality. Water flow to each tank can be controlled separately, to facilitate the quarantining of sick turtles and to provide any tank to be used as a feeding tank. The basic design of the system can be seen in the photo below.
The tanks are constructed out of concrete, which have been rendered to be water proof. PVC and a sump pump are used for the water system, and air stones have been added to each tank. Before introducing the turtles, the system was run for 2 weeks, with 1 bottle of vinegar added per day to neutralize pH. After pH was stable for 24 hours without adding any vinegar than the system was assumed to be stable, and the turtles were placed in the tanks. After flowing out of the individual tanks, the water is passed through a course and fine mechanical filter, before flowing through a biological filter creating using bio-balls, ceramic rings, and broken clay tiles. After the filtration, the water is circulated through the sump, which is also exposed to the sun to allow for the growth of macro-algae to remove dissolved nutrients from the water and provide food for the turtles. Marine probiotics are added to the system weekly (purchased from an aquarium store) to maintain water quality, reduce harmful bacteria, and increase the effectiveness of the biological filter.
For daily feeding, one of the shallow tanks is isolated and drained halfway. Turtles are placed in the feeding tank in pairs, to reduce competition, and allowed to feed for no more than 15 minutes. After feeding, the water from this tank is emptied to the sea, the tank is cleaned, and then refilled. Each day approximately 20-30% of the water in the system is replaced with clean-sea water, pumped during high tide.
Health and behavior of the turtles is monitored daily through visual observations. Individuals are given a score of 1-5 for the following categories: Feeding, Diving, Mobility. Notes are also made on any health issues or interesting observations. Growth of the turtles is monitored using an electric scale to track weight, and a measurement of the shell length using a flexible tape measure (to the nearest 0.5cm).
Upon arrival in April of 2012, there were 24 turtles; 21 small hawksbills, about 2 months old, and two larger Green Sea Turtles, about 9 months old. All of the 24 turtles were sick, weak, and the two green turtles were covered in open wounds and infected sores. All received a score between 1-2 in all health categories for the first month of care. Hope for survival of all the 23 turtles was low. By April 30th, one of the larger green turtles had died despite daily injections of vitamins, antibiotics, and IV Saline (for rehydration). And by June, nine of the smaller hawksbill turtles had succumbed to their illness.
By June, the one Green Sea Turtle and 10 Hawksbills remained, with 9 of the 10 receiving a score of 5 for all health categories (the last one, number 13, scored a 1 in all categories, and then died on the 8th, of July. For the rest of the year, all of the turtles scored between 4 and 5 on all health categories.
The average starting weight of the Hawksbill turtles was 48 grams (range from 42-52 g). By December of 2012, the average weight of the turtles had increased to 805 g (range from 603-1,000 g) (see Appendix A). The surviving Green Sea Turtle weighed 380 g in April, and had reached a weight of 1,130 g by July 25th. The green sea turtle was released in a very healthy state from a boat on August 12th, 2012 in the vicinity of Ao Leuk Bay.
By January of 2013, the remaining Hawksbills had all exceeded a weight of 1,000 grams, with an average weight of 1,137g. Shell length of the hawksbills had increased from an average of 6 cm in April 2010, to 22 cm in January 2013 (range of 6.2-7, and 21-23.2, respectively).
Dr. Jae Intaraksa inserted RFID tags into the turtles on January 29th, 2013, and a complete list of the RFID numbers can be found in Appendix B. Subsequent to tagging, the Hawksbill turtles have been slowly released as they reach a shell length of about 22.5 cm. The first two were released by boat in the vicinity of Chalok Ban Kao on February 10th. The turtle was observed to exhibit natural behaviors in the first 30 minutes post-release, diving and exploring the reef, and wedging under corals to rest. One of the turtles was observed surfacing for air about 6 days later, approximately 20 meters from the site of release, indicating that the turtle was surviving well. Two more turtles were released in the same location on February 28th, and were observed for the first hour post-release. Again the turtles exhibited natural behavior and survival instincts and had strong swimming and diving skills.
The initial construction of the Sea turtle rearing ponds was about 170,000 baht. Maintenance, food, and materials cost an additional 54,000 baht in 2012, and 9,000 baht for the first month of 2013. These costs have been covered by the New Heaven Dive School through the sale of marine conservation courses, and have required no additional outside funding.
Future Needs and Requests
As the last 4 of the Hawksbill turtles will be released in March of 2013, we will no longer have any juvenile turtles to rear in the ponds. Based on the success and achievements of our first year of the program we are requesting that the Royal Thai Navy allows us to continue our program with the donation of new juvenile turtles. Having new turtles will not only help us to raise environmental awareness amongst local community members and visitors to Koh Tao, but also allow us to assist the Royal Thai Navy in protecting and increasing the populations of endangered sea turtles in Thai waters.
Additionally we invite the Royal Thai Navy and other researchers to work with us to publish papers and reports on the developments of the program to spread awareness to other Thai communities and to help track the populations of both natural and head-started sea turtles around Thailand.
The Royal Thai Navy, Along with the Department of Marien and Coastal Resources, is one the leading groups helping our community with the conservation of Sea Turtles, and their assistance to our efforts in invaluable. We would also like to thank Dr Jae Intaraksa for all of her time and efforts in caring for the turtles when they were sick, and advising our team members on the proper care for these marine reptiles. We would also like to thank Dr. Nantarika Chansue of the Veterinary Medical Aquatic Animal Research Center at Chulalongkorn University.
- Caillouet C.W., Fontaine C.T. 1993. Captive Rearing of Sea Turtles: Head Starting Kemp’s Ridely, lepidochelyskempii. Proceedings American Association of Zoo Veterinarians. Pp. 8-12.
- Carr A. 1987. New Perspectives on the Pelagic Stage of Sea Turtle Development. Conservation Biology 1:2, pp. 103-121
- Eckert K.L., Scott A., Crouse D., Crowder L.B. Maceina M., Shah A. 1994. . Review of the Kemp’s Ridley Sea Turtle Headstart Program. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-3, 11 p.
- Eckert K.L, Bjorndal K.A., Abreu-Grobois F.A., Donnelly M. 1999. Research and Management Techniques for the Conservation of Sea Turtles. SSC/IUCN Marine Turtle Specialist Group.
- Frazer N.B. 1992. Sea Turtle Conservation and Halfway Technology. Conservation Biology. 6:2 pp. 179-184.
- Okuyama J., Shimizu T., Abe O., Yoseda K., and Arai N. 2010. Wild versus head-started hawksbill turtles Eretmochelys imbricate: post release behavior and feeding adaptation. Endang. Species Re. 10:181-190.
- Settle S. 1995. Status of Nesting Populations of Sea Turtles in Thailand and Their Conservation. Marine Turtle Newsletter 68:8-13.
- Photo credits: Chad Scott, Sirachai Arunrugstichai, and Kaen Zahir