Use of Space and Movement Patterns of Reproductive Female Green Turtles (Chelonia mydas) From Akyatan Rookery in the Eastern Mediterranean Sea

Verifying habitats, including the foraging and nesting areas for sea turtles, enables an understanding of their spatial ecology and successful planning of their conservation and management strategies. Recently, the observation frequency and bycatch of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles have increased in the northern limit of their distribution range, in the northern part of the East China Sea and East (Japan) Sea. We conducted satellite tracking to investigate the habitat use of seven loggerhead and eight green turtles from June 2016 to August 2022 in this area, where little is known about their spatial ecology. We applied a 50 percent volume contour method to determine their main foraging areas and analyzed 6 environmental variables to characterize their habitats. Loggerhead turtles mainly stayed in and used the East China Sea as a foraging area during the tracking period, while two individuals among them also used the East Sea as a seasonal foraging area. Most green turtles also used the East China Sea as a foraging area, near South Korea and Japan, with one individual among them using the lower area of the East Sea as a seasonal foraging area. Notably, one green turtle traveled to Hainan Island in the South China Sea, a historical nesting area. Our results showed that the two sea turtle species included the East Sea as a seasonal foraging area, possibly owing to the abundance of food sources available, despite its relatively lower sea temperature. Considering that loggerhead and green sea turtles were observed using the northern part of the East China Sea and East Sea more frequently than previously known and that the sea temperature gradually increases due to climate change, conservation and management activities are required for sea turtles in these areas.

The United Kingdom Overseas Territory of Montserrat supports modest but regionally important nesting populations of green and hawksbill turtles. However, knowledge of the spatial ecology and regional connectivity of these populations is limited. Here, we provide the first detailed description of the spatial distribution, migratory connectivity, and habitat use of 9 adult female green turtles Chelonia mydas and 1 adult female hawksbill turtle Eretmochelys imbricata tagged with satellite transmitters at 4 nesting beaches in Montserrat. Two critical aggregation areas for inter-nesting green turtles were identified along the western coast of Montserrat which could act as focal points for spatial protection. Nine individuals, including the hawksbill turtle, performed transboundary post-nesting migrations, covering distances from 45 to 1013 km, and crossing 10 different national jurisdictions. Green turtles migrated to foraging grounds in Antigua and Barbuda (n = 4), United States Virgin Islands (n = 2), Puerto Rico (n = 1), and Dominican Republic (n = 1), whereas the hawksbill turtle migrated to a foraging ground in Guadeloupe. One green turtle remained resident in Montserrat. Within foraging grounds, green turtles primarily occupied sand, seagrass, and hardbottom algal habitats located in shallow (<25 m) coastal waters. On average, turtles spent 22 and 24% of their time within Marine Protected Areas during migration and foraging periods, respectively. Our results provide novel insights into the ecology of individuals nesting at a previously understudied rookery that can be used to inform local and regional management.

We investigated the size distribution, sex ratio, and proportion of sexually mature green (Chelonia mydas) and loggerhead (Caretta caretta) turtles in Lake Bardawil, a large coastal lagoon. During the study 30 green turtles (8 males, 4 females, and 18 juveniles / sub-adults) and 14 loggerheads (1 male, 8 females, and 5 sub-adults) were captured. Forty percent of the green and 64 % of loggerhead turtles were believed to be sexually mature. The green turtles had a mean curved carapace length of 65.23 cm (15 – 100 cm range) and the loggerhead turtles 68.79 cm but with a much narrow range (60 - 80 cm) reflecting the absence of juveniles. This study provides evidence that Lake Bardawil is an important feeding and development area for green turtles and feeding area for loggerhead turtles and expands our knowledge of such important sites in the Mediterranean basin.

Route masters

Simple SummaryDespite the continuous observation and drift of globally endangered sea turtles in Korean waters, relevant research and protection policies are deficient. To restore sea turtle populations near Korea, the Ministry of Oceans and Fisheries, Republic of Korea, has been hatching and rearing sea turtles in captivity and releasing juveniles into the sea. We satellite-tracked juvenile loggerhead and green turtles to confirm their movement patterns and adaptability in the wild. The tracked sea turtles used sea currents for movement, and the tracking duration and movement patterns differed according to their body size. In addition, while the loggerhead turtles moved to the Northeast East Sea, the green turtles tended to move west or southwest from the release point. By considering the release time and location, according to the growth level and species, the adaptability of artificially hatched and reared turtles to natural habitats is expected to be high.With most sea turtle populations declining, activities to conserve their habitat and nesting grounds and restore their populations are being implemented worldwide. To preserve the Northwestern Pacific populations, the National Marine Biodiversity Institute of Korea has been releasing artificially propagated sea turtles, but whether these individuals join the wild population remains unknown. The present study aimed to determine the movement patterns of artificially propagated juvenile loggerhead (Caretta caretta) and green (Chelonia mydas) turtles fitted with satellite transmitters on their carapaces and released in the waters of Jeju or Yeosu, Republic of Korea, between August 2018 and April 2022. Loggerheads traveled northward to the East Sea, whereas green turtles moved west or southwest. Two 36-month-old and two 48-month-old loggerheads moved toward their potential nursery grounds and toward their feeding grounds, respectively. Three green turtles with a curved carapace length (CCL) of <40 cm moved toward their nursery or feeding grounds, while three individuals (CCL > 45 cm) moved toward their inshore foraging areas. The travel paths were closely related to the direction of local sea currents. Our results implied that releasing artificially propagated sea turtles, considering their age and CCL, can positively contribute to the conservation of Northwestern Pacific populations.

Trophic ecology of green sea turtles in a highly urbanized bay: Insights from stable isotopes and mixing models

Adult green sea turtles Chelonia mydas are often the largest-bodied herbivores in their communities and may play an important role in structuring seagrass and macroalgal commu- nities. Recent studies, however, suggest that green turtles might be more omnivorous than previ- ously thought. We used animal-borne video and nitrogen and carbon stable isotopic analysis of skin to elucidate diets of green turtles in the relatively pristine seagrass ecosystem of Shark Bay, Australia. Stable isotope values suggested that despite the presence of abundant seagrass resources, turtles assimilated most of their energy from a combination of macroalgae and gelati- nous macroplankton (cnidarians and ctenophores). Video data suggested that macroplankton might be the most commonly consumed food source. Also surprising was the considerable varia- tion in δ 13 C values, suggesting long-term dietary specialization by individual turtles. Overall, green turtle foraging under natural conditions may be less stereotyped than previously thought, and diets of green turtles inhabiting apparently similar ecosystems (e.g. seagrass-dominated ecosystems) may vary considerably across geographical regions. The apparently high degree of individual specialization in diets suggests that conservation efforts should account not only for the potential importance of non-benthic food sources for green turtle populations, but also for the pos- sibility that subsets of the population may play different ecological roles and may be differentially vulnerable to anthropogenic impacts.

Fibropapillomatosis (FP) can be an important conservation threat to green sea turtles (Chelonia mydas) due to its widespread distribution and complex aetiology. Thus, understanding the impacts of FP in sea turtle populations is a research priority towards conservation efforts. The body condition index (BCI), based on straight carapace length (SCL) and body mass (BM), is an accurate indicator of body-nutritional condition that can be used in routine green turtle health evaluations. This study aimed to compare BCI in FP-free (N = 369) and FP-affected (N = 518) green turtles from Brazilian feeding areas. Body condition indices were evaluated in terms of the South-west Atlantic Fibropapillomatosis Score – FPSSWA(mild, moderate and severe), study sites (five Brazilian states), origin (intentional capture, fishery, stranding and afloat) and sex (when known). Curved and straight carapace lengths, and body mass were recorded in order to calculate BCI. Statistical analysis revealed significant differences in BCI among green turtles from different study areas (P= 0.02), and lower BCI values in FP-free than in FP-positive individuals (P&lt; 0.0001). With regards to origin, the highest BCI was found in the intentional capture group (N = 245; 1.47 ± 0.16), followed by fishery (N = 180; 1.46 ± 0.20). Analysis according to sex revealed a higher mean BCI among females than males (P&lt; 0.017). This study provides relevant data on the health and nutritional status of green turtles along the Brazilian coast, in important feeding areas for this species.

Simple SummaryFibropapillomatosis is a disease of sea turtles that is likely caused by the virus chelonid alphaherpesvirus-5. Sea turtles, and especially green sea turtles, can develop extensive tumors that impede foraging and swimming and can result in high morbidity and mortality. The presence of the virus has not been assessed in Grenada and fibropapillomatosis has anecdotally not been observed in the island’s sea turtle aggregates. From 2017 to 2019, a total of 167 green, leatherback, and hawksbill turtles were examined for fibropapilllomatosis. Skin and blood samples were examined for the presence of the virus and previous exposure to the virus was assessed by checking for antibodies in the blood. No signs of fibropapillomatosis or active viral infection were found in any turtle examined during the study. Antibody testing showed that 34.6% of green turtles examined had been previously exposed to the virus. In 2020, the first case of fibropapillomatosis occurred in a green turtle in Grenada and the presence of the virus was confirmed in tumor samples. These results indicate that to date, active viral infection is rare in Grenada’s turtles, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time, and further studies examining factors that may influence disease are warranted.Chelonid alphaherpesvirus 5 (ChHV5) is strongly associated with fibropapillomatosis, a neoplastic disease of sea turtles that can result in debilitation and mortality. The objectives of this study were to examine green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) sea turtles in Grenada, West Indies, for fibropapillomatosis and to utilize ChHV5-specific PCR, degenerate herpesvirus PCR, and serology to non-invasively evaluate the prevalence of ChHV5 infection and exposure. One-hundred and sixty-seven turtles examined from 2017 to 2019 demonstrated no external fibropapilloma-like lesions and no amplification of ChHV5 DNA from whole blood or skin biopsies. An ELISA performed on serum detected ChHV5-specific IgY in 18/52 (34.6%) of green turtles tested. In 2020, an adult, female green turtle presented for necropsy from the inshore waters of Grenada with severe emaciation and cutaneous fibropapillomas. Multiple tumors tested positive for ChHV5 by qPCR, providing the first confirmed case of ChHV5-associated fibropapillomatosis in Grenada. These results indicate that active ChHV5 infection is rare, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time and further studies comparing host genetics and immunologic factors, as well as examination into extrinsic factors that may influence disease, are warranted.

Abstract. Tapilatu RF, Wona H, Mofu B, Kolibingso D, Alzair N, Erdmann M, Marunaya B. 2022. Foraging habitat characterization of green sea turtles, Chelonia mydas, in the Cenderawasih Bay, Papua, Indonesia: Insights from satellite tag tracking and seagrass survey. Biodiversitas 23: 2783-2789. The distribution area of green turtles is not yet known in Cenderawasih Bay. On 20 November 2020, two satellite transmitters were attached to two female green turtles (Chelonia mydas Linnaeus, 1758) on Kalilemon, Southwest Cenderawasih Bay, Papua Province, Indonesia. Kalilemon area and Mangga Island as part of Kwatisore waters are the major foraging areas for this species and are under threat of turtle opportunistic poachers. The results show that the two turtles (Mary and Nona) dispersed and used limited but consistent and different foraging grounds during the tracking period through the satellite tags between November 2020-April 2021 at Mangga Island and Kalilemon. The composition of seagrass at both stations consisted of the same five species belonging to the families Cymodoceae and Hydrocharitaceae, with relatively different qualitative abundances. Overall, the mean chlorophyll-a content during the study period from November 2020-April 2021 ranged from 0.25-0.55mg/m3 at both foraging grounds (Mangga Island and Kalilemon). The mean SST during the study period ranged from 30.61-31.77oC in both locations. Before the next tracking attempt, more data on seasonal foraging and nesting activities are required. The result of this research is vital to determine the foraging grounds for green turtles related to the seagrass species with its abundance and key environmental factors in the management and conservation of sea turtles in the Cenderawasih Bay area.

The residence, home range, and habitat use of juvenile (42.0–63.5 cm midline curved carapace length, CCL), subadult (68.6–84.6 cm CCL), and adult (81.9–104.2 cm CCL) green turtles (Chelonia mydas) was investigated using passive acoustic telemetry in Ningaloo Marine Park, north‐western Australia. Eighty‐one turtles ranging in size from 42 to 104 cm CCL were captured on their foraging grounds and tagged with acoustic tags. Individuals were monitored for up to 913 days (range 48–913 days, median 367 days). Turtles of all sizes demonstrated very high fidelity to their foraging area. Residence declined with turtle body size and home range increased with turtle body size, with an average 50% kernel utilization distribution (KUD) area of 0.29, 0.47, and 0.57 km2 for juveniles, subadults, and adults, respectively. Juveniles occurred only in shallow inshore habitat dominated by seagrass and macroalgae‐covered pavement. Subadults and adults selected macroalgae‐covered pavement, sandy areas of the lagoon, and macroalgae‐dominated patch reefs within the lagoon. At high tide, juveniles were approximately 200 m closer to the shore than at low tide, but there was no tidal pattern of space use in subadult and adult turtles. Less than 5% of turtles departed the array within 6 months and there was no evidence of developmental migrations in subadults. The results highlight the conservation potential for go‐slow areas to minimize boat strike in areas of high turtle density, given the small and stable home ranges. Furthermore, the spatial segregation of juveniles, subadults, and adults will result in variability in the susceptibility of individuals to boat strike. The influencing factors that drive the developmental migrations of turtles to consecutive habitats as they grow, as well as movement away from foraging grounds in response to changes in habitat quality, are complex. The ability of acoustic telemetry to provide long‐term data on all size classes of turtles within foraging areas provides a tool to enable the long‐term monitoring of turtle populations, which is required for at‐risk populations and/or habitats.

In the Mediterranean, the green sea turtle (Chelonia mydas) has exhibited increase in the number of nests over the past two decades. While the Eastern Mediterranean is recognized as a high use area, scarce observations of green turtles in Adriatic Sea suggested only low-level utilization of this area. This study presents new findings of green sea turtles in the Adriatic Sea and analyses the importance of the region for the species. In combination with published records, we present 75 findings of the species in the Adriatic including eight new records. The number of records is generally low but shows an intriguing ten-fold increase since 2000. This may be a result of three confounding factors: (i) positive population trend at main nesting sites in Mediterranean; (ii) increased institutional capacity for sea turtle research and conservation in the past two decades, and (iii) raising sea temperatures. Documented increases in the sea surface temperatures may have established suitable and recurring thermal corridors along Ionian-Adriatic developmental pathway and provided environmental cues for immigration of juvenile green turtles into the Adriatic. As the abundance of the species will likely increase in the future, research and conservation efforts will be needed to avoid the Adriatic Sea becoming a sink habitat for the Mediterranean green turtle population.

An animal’s home range is driven by a range of factors including top-down (predation risk) and bottom-up (habitat quality) processes, which often vary in both space and time. We assessed the role of these processes in driving spatiotemporal patterns in the home range of the green turtle (Chelonia mydas), an important marine megaherbivore. We satellite tracked adult green turtles using Fastloc-GPS telemetry in the Chagos Archipelago and tracked their fine-scale movement in different foraging areas in the Indian Ocean. Using this extensive data set (5081 locations over 1675 tracking days for 8 individuals), we showed that green turtles exhibit both diel and seasonal patterns in activity and home range size. At night, turtles had smaller home ranges and lower activity levels, suggesting they were resting. In the daytime, home ranges were larger and activity levels higher, indicating that turtles were actively feeding. The transit distance between diurnal and nocturnal sites varied considerably between individuals. Further, some turtles changed resting and foraging sites seasonally. These structured movements indicate that turtles had a good understanding of their foraging grounds in regard to suitable areas for foraging and sheltered areas for resting. The clear diel patterns and the restricted size of nocturnal sites could be caused by spatiotemporal variations in predation risk, although other factors (e.g. depth, tides and currents) could also be important. The diurnal and seasonal pattern in home range sizes could similarly be driven by spatiotemporal variations in habitat (e.g. seagrass or algae) quality, although this could not be confirmed.

Many animals, including sea turtles, alter their movements and home range in relation to the particular type and quality of the habitat occupied. When sufficient resources are available, individuals may develop affini- ties to specific areas for activities, such as foraging and (or) resting. In the case of green sea turtles (Chelonia mydas L.), after a number of years in the open ocean, juveniles recruit to shallow-water developmental habi- tats where they occupy distinct home ranges as they feed and grow to maturity. Our goal was to study the habitat use and home range movements of juvenile green turtles along a shallow, worm-rock reef tract in Palm Beach, Florida. Six turtles, measuring from 27.9 to 48.1 cm in straight carapace length and from 7.2 to 12.6 kg in mass, were tracked via ultrasonic telemetry from August to November 2003. Upon capture, each turtle's esophagus was flushed via lavage to determine recently ingested foods. In addition, four turtles were recaptured and fit- ted with a time-depth recorder to study dive patterns. Home range areas measured with 100% minimum con- vex polygon and 95% fixed kernel estimators varied from 0.69 to 5.05 km 2 (mean=2.38±1.78 km 2 ) and 0.73 to 4.89 km 2 (mean=2.09±1.80 km 2 ), respectively. Home ranges and core areas of turtles were largely restricted to the reef tract itself, and showed consider- able overlap between food and shelter sites. The mean number of dives during daylight hours (0600- 1800 hours) was 84±5.0 dives, while the mean during night hours (1800-0600 hours) was 39±3.0 dives. Dives during the day were shallower (mean=3.20±1.26 m) than dives at night (mean=5.59±0.09 m). All six turtles were found to have a mixed diet of similar macroalgae and sponge fragments. Our results reveal that juvenile green turtles occupy stable home ranges along the nearshore worm-rock reefs of Southeast Florida, during the summer and fall. Determining which habitats are used by green turtles will assist conservation managers in their global effort to protect this endangered species.

Space use is commonly estimated in animal ecology and has become a cornerstone of evidence‐based conservation planning, with animal tracking increasingly used to underpin the designation of protected areas with high conservation value. However, tracking technologies and analytical methods may introduce biases in home range size estimates. We assessed these potential biases using simulated tracking data and published home range size estimates from empirical animal tracking studies. We first simulated animal movement data and added published location error estimates for different technologies used for tracking sea turtles. Location data were analysed using common space use estimation methods (minimum convex polygon, fixed and autocorrelated kernel density estimation, biased random bridge and dynamic Brownian bridge movement model). Second, we reviewed home range size estimates obtained using different technologies to track hawksbill (Eretmochelys imbricata) and green (Chelonia mydas) turtles to assess the relative impacts on home range estimates due to (i) tracking accuracy and (ii) analytical methods. For both simulated data and empirical values of space use from the literature (n = 90 studies), relatively large home range estimates tended to be generated from lower resolution Argos tracking compared to higher‐resolution Fastloc‐GPS tracking. These findings reflect inaccuracies in location data providing spuriously large movements. For example, Argos and Fastloc‐GPS home range size estimates for adult green turtles averaged 393 and 53 km2 respectively (n = 64 and 39 individuals). For simulated data, biases introduced by tracking accuracy had a far greater impact on home range size estimation than the analytical method used, apart from when using autocorrelated kernel density estimation (AKDE) which compensated for positional error very well. Our results suggest that in many cases, hawksbill and green turtles have relatively small home ranges (&lt;10 km2 and in some cases, &lt;1 km2), with this picture of their limited space use only emerging through high‐accuracy tracking. These general conclusions likely apply broadly across taxa and will impact attempts to assess patterns of home range sizes recorded for individuals across studies in different regions.