The life cycle of loggerhead sea turtles (C. caretta) is complex and includes neritic and oceanic stages. In the North Atlantic, most loggerheads hatch along the south-eastern coast of the USA and then enter the Gulf Stream and disperse into the open ocean. Following this oceanic stage, that lasts 7-14 years and is often referred to as the “lost years”, they return to neritic foraging grounds in the western North Atlantic. The oceanic juvenile stages are particularly relevant for the conservation of this species, but there is a lack of information about their habitat use during this period of their life. To better understand the habitat use of juvenile loggerheads in the North Atlantic, we gathered tracking data from multiple research teams working in the basin. We assembled a unique and extensive dataset with tracking data collected from 105 individuals (after filtering), tagged from 1994 to 2012. The individuals were captured and released in the Azores (42), in the Canary Islands (24), in Madeira (10) and in the Central North Atlantic (29). The size of the individuals ranged from 32.4 to 74.0 cm CCL (51.9 ± 8.3 cm). Most of the individuals (76) were equipped with Argos PTTs (Wildlife Computers), while the remainder (29) were equipped with archival tags (MiniPAT, Wildlife Computers) that transmitted light-levels and Argos locations. Tracking duration ranged from 5 to 760 days (183 ± 164 days). Tracks were filtered, interpolated at a 24h interval (R package “AniMotum”), and used to generate pseudo- absence tracks (correlated random walks). For all the locations obtained (both presence and pseudo-absence) we extracted several environmental variables, such as sea surface temperature, productivity, ocean currents and eddies proximity. We found a possible correlation of turtle presence to sea surface temperature, proximity to anticyclonic eddies, and an avoidance of shallow waters (<20 m). Boosted regression trees (BRTs) were used in an iterative process to build a basin-scale habitat model for loggerheads in the North Atlantic. This habitat model is important to understand the ecology and space use of juvenile loggerhead sea turtles in the North Atlantic. The model is also a key tool to evaluate and address the impact of anthropogenic pressures, such as incidental bycatch in oceanic fisheries and marine traffic, in support of their conservation.

Understanding the coastal habits of endangered species and the extent of connectivity across various spatial and temporal scales is important in identifying critical habitats that can enhance conservation efforts in other regions of their distribution. In this study, we documented daily and seasonal locations of 15 juvenile yellow morphotype green turtles (Chelonia mydas) (49 – 83 cm curved carapace length; CCL) in Santa Elena Bay and Matapalito Bay in North Costa Rica for 19 – 629 days, determined their site fidelity and assessed their habitat use. We collected location data by employing 11 acoustic receivers placed within 5 main habitat types: muddy areas, reef patches, macroalgae, rocky reefs, and mangroves. Large juveniles (≥ 65 CCL) had their most detections in the macroalgae area during the upwelling season (43.9%) from December – April, and in the reef patch area during the non-upwelling season (36.0%) from May to November. Small juveniles (< 65 cm CCL) had the most detections in the reef patch area during both seasons (dry: 35.4%, rainy: 45.4%). Significantly, 10 out of the 15 juvenile yellow turtles displayed remarkable site fidelity ranging from 68.9% to 100%. Our findings indicated that juvenile yellow morphotype green turtles preferred reef patches, rocky reefs, and macroalgae habitats, with turtles demonstrating a shifting preference towards expected adult habitats (reef patches and microalgae areas) as they grew. Our finding suggested that by protecting similar habitat areas along the Central American coast we can help rebuild the Eastern Pacific Ocean green turtle population.

Sea turtles present complex life cycles ranging in entire ocean basins and requiring equivalent complex management and conservation measures. All seven species show feeding reproductive and nesting site fidelity to some extent, although this does not mean that all population individuals use the same non-breeding areas. Different habitat use and use of foraging areas in a population will impact demographic variables and implicate focus prioritization of conservation efforts.
Five of the planet's seven species of sea turtles are distributed in the Eastern Pacific (EP) Ocean. Chelonia mydas, known in this region as the black turtle, is defined as a Distinct Population Segment (DPS) of the Chelonia mydas species and, according to the Endangered Species Act: ESA, is listed as threatened. Likewise, in Mexico is considered under the category of danger of extinction by the official Mexican standard NOM-059 - SEMARNAT- 2010.
Four important nesting areas are known for this DPS: Revillagigedo Islands, Galapagos Islands, Costa Rica, and Colola Beach, Michoacán on the Mexican Pacific coast, while their distribution ranges from Southern California in the US UU to Chile and the Galapagos Islands. The Colola nesting population represents this DPS's most significant, registering more than 15,000 females annually. Colola Beach also provides a contingency habitat for this DPS and the Chelonia mydas species globally, taking climate change and sea level rise into account.
The present study aims to understand the spatial ecology of the eastern Pacific DPS nesting population in Colola, Michoacán, Mexico. Furthermore, it was designed to reach the following objectives:
1. Identify migration routes, strategies, and feeding areas of the Colola nesting population using satellite tracking of 23 nesting females during 2018-2021 nesting seasons.
2. Identify potential areas of overlap of 23 tracked nesting females with fisheries in the EPO during 2018-2021 nesting seasons.
3. Assign pre-nesting habitat to 130 Colola nesting females through stable isotope analysis (δ13C y δ15N) calibrated from the satellite telemetry of a subset of individuals.

Twenty-three turtles were tagged with PTTs (Platform Transponder Transmitters) [Wildlife Computers SPOT6, n = 3 (Redmond, WA, USA); Lotek 376D, n = 20 (Havelock North, Hawkes Bay, New Zealand)] after nesting, at Colola Beach, Michoacán, (n=10) during the 2018-2019 season; (n=13) and the 2020-2021 season. Turtles were tracked using the Argos satellite system. Skin samples were taken from 130 nesting females and analyzed for δ13C and δ15N.
Turtles' transmission averaged 58 ± 27.29 days (range: 24-160 days); distance traveled: average 914.8 ± 433 km (range: 1 a 2121 km). Statistical analysis indicates a significant correlation between size, Migration straightness index, nitrogen isotope ratio, and latitude. Isotopic values of the skin simples ranged between -22.97 a -14.40‰ y de 13.22 a 21.97‰ para δ13C y δ15N respectively.
The data provided by this study will contribute to the effective conservation of the eastern Pacific green turtle DPS, the preservation of its habitat, and other associated species.

Endangered green turtles (Chelonia mydas) and critically endangered hawksbill turtles (Eretmochelys imbricata) are under anthropogenic threats exacerbated by their long-distance migrations. The lack of in-water studies, especially at sea turtle foraging habitats in Malaysia, largely limits the understanding of their population dynamics for the management of the species. Semporna, Sabah, is a major foraging ground for green turtles, yet little is known about the aggregations and thus, the viability of the populations with increasing in-water threats. Therefore, I conducted an in-water mark-recapture study at six sites of northeast Semporna islands between November 2018 and September 2020. Photo-identification was used to recognize individuals within aggregations using their stable facial scute patterns, while straight carapace length (SCL) measurements were obtained through laser photogrammetry. These non-contact, thus minimally invasive techniques were successful in characterizing sea turtle aggregation demographics in Semporna. Results from 90 field surveys, within a depth range of 1-20 m, yielded 822 sightings of 400 green turtles and 30 sightings of 25 hawksbill turtles. A highly disproportionate ratio of hawksbill to green turtles illustrates the lack of hawksbill turtles in Semporna, which is a concern for the species' viability. The highest (24.2 inds/hr) and lowest (2.6 inds/hr) green turtle encounter rates were observed at Timba Timba Island and Baturua, respectively. No inter-island movement was recorded, as sea turtles displayed high site fidelity to their neritic habitat. This is reflected by the high recapture percentage of green turtles (63.2%) at Pom Pom Island, corresponding to a higher sampling effort at this site. SCL measurements of green turtles ranged between 39 cm – 96 cm; however, the adult size class (SCL > 80 cm) was significantly underrepresented in this study at only 16%. My findings suggest that green turtles utilize Semporna foraging grounds as their permanent neritic habitat, a key area for replenishing regional sub-populations. Body condition assessments of these aggregations show that they are visually healthy; however, there is evidence of human-induced threats that should be managed through stakeholder engagement. This research highlights the feasibility of using non-contact research methods to fill knowledge gaps in in-water sea turtle aggregations for species management and conservation.

South Africa holds a significant portion of the Southwest Indian Ocean (SWIO) loggerhead and leatherback sea turtle populations underpinned by long-term research and conservation efforts on nesting beaches. However, the in-water biology of these species and non-nesting green turtles and hawksbills in adjacent neritic habitats remains cryptic. This study provides the first in-water estimates of relative abundance, demographics and spatial distribution of sea turtles in two Marine Protected Areas (MPAs); iSimangaliso and Aliwal Shoal, on the east coast of South Africa. Over a two-year period, a total of 1057 sea turtle sightings were recorded from timed research surveys (supplemented by voluntourism), citizen science contributions and opportunistic sightings in the two MPAs, from which 227 individual sea turtles were photo-identified (green turtles: n = 120; hawksbills: n = 46; loggerheads: n = 61). Mean (± SD) sightings per unit effort (SPUE) from timed research surveys was highest for green turtles at all sites (iSimangaliso: 2.2 ± 4.47 turtles/hour, n = 263; Aliwal Shoal: 1.2 ± 1.98 turtles/hour, n = 60). Hawksbills had a higher mean SPUE at Aliwal Shoal (0.8 ± 1.35 turtles/hour, n = 48) than iSimangaliso (0.2 ± 1.20 turtles/hour, n = 32) whilst loggerheads had similar mean SPUEs (iSimangaliso: 0.5 ± 1.54 turtles/hour, n = 65; Aliwal Shoal: 0.5 ± 1.16 turtles/hour, n = 36). Reefs supported aggregations of mixed size classes; green turtles ranged from juvenile- to adult-sized with straight carapace lengths (SCLs, measured using paired-laser photogrammetry) of 44.9–99.2 cm, hawksbills were mostly juveniles or subadults (SCL range: 37.4–73.4 cm) and loggerheads were mostly adult-sized (SCL range: 66.9–81 cm). Based on visual estimates, the sex ratios of adult-sized green turtles and loggerheads were slightly female-biased but not significantly different from 1:1. The longest minimum residence periods recorded to date for individual subadult green and hawksbill turtles (676 and 675 days respectively) and adult-sized loggerheads (621 days) were highly indicative of residency. Green turtles, hawksbills and loggerheads displayed strong site fidelity with individuals resighted up to 19, 10 and 11 times respectively on the same reef over the two-year study period. Citizen science data were particularly useful in revealing a wider distribution of sea turtles along the entire South African coastline than currently recognised. This study highlights the importance of the SWIO rookery output in influencing neritic habitats along the east coast of South Africa and provides novel insights into in-water sea turtle biology for understudied populations. The findings form the foundation on which a long-term in-water monitoring programme may be established to expand research efforts along the southern African coastline that may inform effective species-specific management and conservation strategies.

The effects of global change on biodiversity become notably conspicuous when examining species engaged in extensive migrations. Their significant mobility allows these species to exploit various areas with suitable characteristics for different phases of their life cycle, including reproduction, migration, and foraging. While it is widely acknowledged that climate change has the potential to modify the distribution of sea turtles, there is a limited number of studies that investigate whether and how climate change projections might impact the distribution of potential foraging habitats on a broader scale. Traditionally, abiotic factors are typically regarded as the main drivers, while biotic factors receive limited attention. Moreover, the few studies that consider biotic factors often rely on proxies for trophic resources. Here, we used a combination of state-space models and habitat suitability models to show how climate change will influence the distribution of foraging habitats for loggerhead turtles in the Mediterranean basin. We sampled a total of 80 adults from satellite telemetry data collection from 2000 to 2022. We calibrated and projected to the future scenarios three habitat suitability models (HSMs): one considering both biotic and abiotic variables (biomass-HSM), one with a proxy for trophic resources (sea chlorophyll concentration) (chl-HSM), and the last one with abiotic variables only (climate-HSM). All models gave AUC > 0.9, with higher values in biomass-HSM compared to the other ones. Turtles are likely to choose calm waters with lower pollution levels, lower salinity, and temperatures around 18-20°C, along with a high benthic biomass. The neritic zone of the foraging grounds was found to cover 80% of the suitability, increasing in future scenarios. We get significant spatial discrepancy among all models, mainly in the Adriatic Sea, Tunisian Plateau, Aegean Sea, and along the French and Spanish coasts. Prey availability is a major biotic factor determining the actual use of a potential climatically suitable area. We highlighted the importance of including both climatic factors and species-specific trophic ecology to assess the potential impacts of global change more thoroughly on feeding grounds and implement targeted conservation measures.

Caribbean green turtles (Chelonia mydas) spend most of their lives foraging in seagrass meadows. The impact of green turtle grazing in St. John, US Virgin Islands, was well-documented in 1986 by Susan Williams (1988). Williams’ study estimated the abundance of green turtles, measured seagrass productivity, and documented the impacts of anchor scarring on seagrass meadows in Maho Bay and Francis Bay. At the time, Thalassia testudinum was the dominant species in both bays. Williams found very low productivity of T. testudinum in Maho and Francis Bays due to the combined effects of intensive grazing by green turtles and extensive anchor damage. The green turtle aggregation was found to be at carrying capacity for the available seagrass meadows in both bays, and turtles were observed foraging consistently for nine hours per day in these degraded environments. Our study evaluates the current interactions between seagrasses and the green turtle foraging aggregation in Maho Bay and Francis Bay. Building on Williams’ study, we reevaluate the same seagrass study sites and assess how the ecosystem has changed over the past three decades. Our team observed the green turtle aggregation in Maho and Francis Bays using methods adapted from Gulick (et al. 2021) for a comprehensive analysis of T. testudinum in the same sites Williams (1988) used. Thalassia testudinum productivity and morphology, grazing intensity, and anchor scars were evaluated at each of Williams’ sites. This data has allowed for a direct comparison between the seagrass meadows in 1986 to 2023. Furthermore, the number of hours per day spent foraging and seagrass species being consumed by the green turtle aggregation was documented to estimate the current grazing pressure. Meadows of T. testudinum are still present in Maho and Francis Bays and support the local green turtle foraging aggregation. Grazing patterns have shifted from consistently foraging for nine hours per day to a traditional bimodal pattern, foraging at peak times in the morning and afternoon. However, T. testudinum parameters measured in 2023 did not behave as predicted for fully grazed or ungrazed sites, suggesting that meadows are now in various stages of transition due to changes in grazing patterns by green turtles. As hypothesized, most sites throughout the bays have higher productivity in 2023 than 1986, likely due to reduced grazing pressure and reduction in anchor damage to the meadows. The National Park Service banned anchoring throughout the Virgin Islands National Park in 2013, protecting the seagrass meadows. In 2023, there were no observed anchor scars throughout Maho and Francis Bays and T. testudinum meadows have rebounded, demonstrating the importance of effective management strategies. This is a rare opportunity to gauge how seagrass meadows have sustained consistent grazing pressure over 35 years. This study will provide a framework to collectively assess how the seagrass meadows have responded to anchor scarring and continuous grazing pressure.