The hawksbill sea turtle, Eretmochelys imbricata, has been identified as a species at serious risk of extinction for more than 40 years and is still listed as critically endangered. While nesting beach protection is important for hatchling production, identifying in-water habitats— inter-nesting, migratory, foraging— is crucial for mitigating threats to population recovery. Here, we report the use of satellite telemetry to monitor the in-water movements of 15 hawksbill turtles Western Caribbean. Transmitters were deployed on nesting turtles at Pumpkin Hill Beach, Honduras (2012 n = 2; 2017 n = 3), Tortuguero, Costa Rica (2000 n = 2; 2014 n = 1; 2015 n = 1; 2021 n = 1), Gandoca-Manzanillo National Wildlife Refuge, Costa Rica (2018 n = 4), and Chiriqui Beach, Panama (2017 n = 1). General patterns suggest that hawksbill inter-nesting habitats were adjacent to the nesting beach and ranged between 0.0004 and 0.25 km² (core 50% utilization distribution) for the 15 – 70 tracking days recorded in this study. Subsequently, these turtles engaged in migrations that covered 74.58 – 577.00 km and lasted between 5 – 45 days to reach foraging grounds, with an average speed of 11.51 ± 3.99 km/d. During migrations, turtles regularly altered their direction relative to ocean current direction resulting in an average movement that used with-current movement to counteract against-current movement (cosine similarity: −0.002 ± 0.107). Foraging habitats were not beach specific and hawksbills from multiple beaches congregated in the same foraging habitat, despite nesting in different years. Turtles in this study foraged in previously identified habitats along the coastal and continental shelf of Nicaragua, Honduras, Belize, and Mexico. Foraging ground area use was generally smaller than inter-nesting area use (n = 8), with only 3 turtles having larger foraging area core utilization distributions, indicating that foraging habitats provide necessary resources without requiring the turtles to traverse large areas to find food and resting areas. Alternatively, some inter-nesting habitats were adjacent to a narrow continental shelf with strong ocean currents, and turtles must actively search for suitable habitats. These data help us better understand inter-nesting and foraging habitat locations, core area use within these habitats, and migration routes between the two. Together this provides vital information to mitigate potential in-water threats to critically endangered adult hawksbills along Central Western Caribbean migration corridors.

1 Large Marine Vertebrates Research Institute Philippines Inc., Philippines

2 Alimanguan Saguip Pawikan, Philippines

3 NOAA Fisheries - Pacific Islands Fisheries Science Center, HI, USA

Abstract:

One of the most significant olive ridley turtle (Lepidochelys olivcea) nesting aggregations in Southeast Asia is located on the beaches of Palawan, Philippines, the country's westernmost province. The Municipality of San Vicente municipality along the island's northwest coast hosts some of the longest and most pristine beaches with hundreds of olive ridley nests per season, which are monitored by the San Vicente Marine Turtle Conservation Network composed of communities, NGOs, and government agencies.

Olive ridley nesting biology, migrations, and inter-nesting patterns are particularly understudied in this region. Satellite telemetry studies have been previously conducted in neighboring countries with animals traveling in the Pacific and Indian Ocean, but no information is currently available for individuals moving through the West Philippines Sea and South China Sea.

In response to this lack of information, a study using satellite telemetry to examine olive ridley inter nesting movements, post nesting migratory and foraging movements was initiated in 2023. Currently, this study has outfitted two individuals with platform transmitter terminals (PTTs), with plans to deploy six additional tags in December 2023. Both individuals tracked were deployed with Wildlife Computer's Spot tag, which utilizes the Argos satellite network.

To date, the platform transmitter terminals (PTTs) transmitted across a range of 94 (22/1 - 4/26) to 104 (27/1 - 5/6) days respectively. Preliminary data suggest that tracked individuals traveled 888 and 1128 km to possible foraging grounds. One individual's telemetry data implies that an inter-nesting area located approximately 10 km offshore from its capture site was frequented throughout the nesting season until the migratory period began approximately 27 days after the tag was deployed.

Our data suggest that the turtles migrated to areas located near Northeast Borneo, Malaysia. One individual ceased transmitting off the coast of Brunei, and the other went further west, potentially establishing residency in the coastal waters of Sarawak, Malaysia, before its final transmission. Data further suggests that individuals used a possible migratory corridor, with both females moving southwest along Palawan's nearshore waters and crossing the Balabac Strait that separates the Philippines from Malaysia and Borneo's north coast. Migrations to potential foraging grounds took approximately 51 to 66 days.

The potential inter-nesting habitat identified, lies in an area of intense fishing activity and is a bycatch hotspot. An in-depth understanding of a species temporal and spatial distributions, migrations, and habitat utilization is crucial to its long-term management and protection. There is currently little to no information on at-sea distribution and foraging grounds around Palawan and the Philippines in general and this data together with bycatch and fishery data, nesting data and population genetic data currently under analysis, will set the bases for local and international cooperation for the conservation of the species in the region.

Identifying dispersal pathways and critical habitats is essential to evaluate risks and inform effective management strategies of migratory marine species during all life stages. This is especially true for sea turtles that are conservation-dependent and for which management needs usually precedes comprehensive data collection. The aim of this study was to model dispersal pathways (representative of individual behaviour) and compare potential dispersal corridors (representative of population-level behaviour) of hawksbill, loggerhead, leatherback, and green sea turtles from key rookeries in the Western Indian Ocean (WIO) with different dispersal strategies. We used the Sea Turtle Active Movement Model (STAMM) to simulate post-hatchling dispersal under the combined effects of ocean currents and habitat-driven movements. Simulation results confirmed the high connectivity between hatching sites and developmental areas in the WIO; dispersal is mostly driven by ocean currents but differs among species and years with habitat quality also differing among species. Active swimming appeared to have little influence on their dispersal patterns during the first year. We then analysed simulation results using a movement-based kernel density estimation to identify dispersal corridors for each species. There were three distinct dispersal corridors: among equatorial Indian Ocean Islands (hawksbills); along East Africa (green turtles); and around southern Africa (loggerheads and leatherbacks). These results provide a first estimation of the dispersal pathways used by neonate turtles, that are usually lacking in conservation assessments. The results can also assist to develop more targeted management measures like RMU designation or marine spatial planning for the lost years.

The North Pacific loggerhead sea turtle, Caretta caretta, undergoes one of the greatest of all animal migrations, entering the sea as hatchlings from nesting beaches in Japan and appearing years later along foraging grounds off Baja California Sur, Mexico after spending several years or more living in the Central North Pacific (CNP). The mechanisms that connect these distant habitats have remained poorly understood but are crucial for managing this endangered species. This is especially true given recent spatial shifts associated with warm water events. Our research group analyzed 15 years of data from satellite-tagged juvenile loggerheads released in the Western and Central North Pacific and proposed the Thermal Corridor Hypothesis (TCH) based on observations that turtles in the CNP can transition eastward to the North American coast as a function of unusually warm conditions. To test this hypothesis, we have initiated the first-of-its-kind experimental oceanographic approach for a top marine consumer, deploying satellite tags on cohorts of 25 juvenile loggerheads in the Eastern North Pacific high seas across four years with variable environment conditions (2023-2026). Here, we discuss the hypothesized movements of loggerheads from the 2023 cohort, with the expectation that turtles will move eastward towards the North American coast given the El Niño conditions, which will likely result in the opening of a thermal ‘corridor’ of warm water bridging these two regions. The outcome of this work has critical implications for conservation and management. As the North Pacific continues to undergo unprecedented changes in the Anthropocene, understanding how sentinel species such as sea turtles will respond and adapt to climate variability is imperative to effectively maintaining and managing healthy ecological connections across their entire North Pacific habitat.

This project monitored the post-release movement pattern of 31 sea turtles rehabilitated at the New York Marine Rescue Center (NYMRC). The NYMRC rescues and rehabilitates all sea turtles stranding along the extensive coastline of New York. Sea turtles strand for various reasons including entanglement, vessel interaction, malnourishment, debilitation, and cold stunning. Many of the stranding cases can be linked to human activities in this region which overlap with sea turtle habitat. Between 2019 and 2023, NYMRC attached satellite (Wildlife Computers - SPLASH and SPOT) tags to 31 of the 194 sea turtles that were rehabilitated and released (16%). Three different species of sea turtles were tagged as part of this project: Kemp’s ridley (Lepidochelys kempii, n=10), Atlantic green (Chelonia mydas, n=8) and loggerheads (Caretta caretta, n=13). Data collected from these tags supports the rehabilitation efforts of NYMRC by illustrating the post-release movement patterns and survivorship of successfully rehabilitated sea turtles. Preliminary data shows southern-coastal and offshore movement patterns that have previously been associated with preferable (i.e., “normal”) post-release behavior. Tag duration ranged from 29-606 days, with more than 80% of tags transmitting at least 100 days, with an average tag life of 226 days. Of the 31 released turtles two restranded following release and one turtle was found deceased with evidence of vessel interaction. Data from these turtles provides crucial information on local foraging areas used by these species in New York state and federal waters in the late summer and early fall. On average, released turtles spent about 70 days (6-150 days) within state waters before navigating south or offshore. To further understand sea turtle behavior within state waters, Customized Animal Tracking Solutions (CATS) tags were implemented in 2023. Data obtained from both tags will provide a more complete understanding of New York’s sea turtle population.