ISTS42 Program/Agenda

Along the Pacific coast of North America, hard-shelled sea turtles using coastal and offshore foraging habitat may disperse into new areas following currents or warm water thermal corridors. As ectothermic marine reptiles, they are susceptible to cold-stunning (hypothermia) when ocean temperatures drop causing them to wash ashore. Thus, their stranding patterns on temperate foraging grounds may reflect real-time shifts in ocean temperature. Previous cold-stunning research has focused primarily on juvenile sea turtles during periodic mass stranding events along the Atlantic and Gulf coasts of the United States; however, little is known about how this phenomenon impacts large immature and adult turtles in eastern Pacific foraging and over-wintering areas where relatively fewer strandings occur. The goals of this study were to develop a working case definition for cold-stunning for this region and document comorbidities present at the time of stranding for the species and stage classes affected. Criteria for case inclusion were hard-shelled sea turtles that stranded alive north of Point Conception (Santa Barbara County, California, USA) from 2009 to 2022 with a corresponding minimum sea surface temperature at stranding and/or cloacal temperature at intake examination ≤15.0℃. This temperature cutoff was selected based upon the observed thermal threshold of inactivity for resident green turtles in southern California and documented conditions associated with live sea turtle sightings in the study region. A total of 53 cases met the inclusion criteria, including 39 Pacific olive ridleys (Lepidochelys olivacea), 10 East Pacific greens (Chelonia mydas), and 4 North Pacific loggerheads (Caretta caretta). In collaboration with partners from the NOAA West Coast Stranding Network and Department of Fisheries and Oceans Canada, all available stranding, clinical, and necropsy data were compiled from the first two weeks in care. Live strandings occurred year-round as far north as British Columbia with the majority of cases between November and January. A mentation scoring system was developed to categorize subjective descriptions of mental alertness and responsiveness at the time of initial assessment; none of the turtles that presented as comatose and unresponsive survived beyond 5 days. On initial physical examination, turtles exhibited signs of malnutrition, mild to moderate epibiota coverage, acute external trauma, dermatitis, corneal ulcers, peripheral edema, and cloacal prolapse. Approximately 25% (13/53) survived to release or remain in care to date. Of the 75% (40/53) that did not survive, 33 died within 2 weeks of stranding with the vast majority surviving less than 3 days in rehabilitation. Of the cases that were necropsed with histopathology (n=25), significant findings included fungal pneumonia, severe fibrinonecrotic gastroenteritis, intestinal impaction, coelomitis, severe fat atrophy, steatitis, myonecrosis, renal granuloma, and yolk embolism. Confirmation of gonad maturity at necropsy revealed misclassification of stage class for 30% of turtles based on mean female nesting size alone. Further analyses will focus on the relationships between temperature, severity of clinical and pathological abnormalities, and survival outcomes to develop prognostic indicators and standardize data collection across the region to improve rehabilitation outcomes for these protected species.

The Karen Beasley Sea Turtle Rescue and Rehabilitation Center (KBSTRRC) is a nonprofit sea turtle conservation organization in North Carolina. Its mission includes rescuing, rehabilitating, and releasing stranded sea turtles. Since its founding in 1997, KBSTRRC has acquired a 25-year data set of sea turtles admitted for rehabilitation. The recent implementation of RaptorMed, a medical records database, is allowing exploration of the organization’s rehabilitation trends over time.

Over the past 25 years, KBSTRRC has treated 1,313 sea turtles, including 591 greens, 430 loggerheads, 290 Kemp’s ridleys, one post-hatchling leatherback, and one known hybrid (green x loggerhead). Most of KBSTRRC’s admitted turtles stranded in North Carolina, although some patients were transferred from organizations in Massachusetts and elsewhere. Between 1997 and 2007, loggerheads represented the highest percent of admissions. After 2007, there are increasing numbers of Kemp’s ridley and green turtle admissions. Sea turtle admissions peak from November through January, with January seeing the highest overall admission numbers. This is primarily due to an annual cold stunning event that occurs during this time. There is a smaller peak from April through June. Many of these strandings involve human interactions such as fish hooks, boat strikes, and entanglements in line. We attribute this peak to the seasonal increase in people on and around the water, coupled with concurrent large numbers of migrating, nesting, and foraging turtles in the area.

Most fish hooks, internal and external, can be removed and the animal released quickly. Many boat strike injuries, on the other hand, are fatal. Natural illnesses seen include cold stunning, nonspecific “debilitated turtle syndrome,” which is often presumed related to past cold stunning events, and shark bite injury.

This preliminary summary presents our first comprehensive review of the data. We hope continued data examination will offer additional insight into sea turtle health, disease, and rehabilitation.

Marine turtles face numerous threats, both natural and anthropogenic. Around the world, care centers take in hundreds of injured or sick turtles each year and through their rehabilitation, contribute to the collective effort of turtle conservation. The temporary stay of turtles provides an opportunity to gather a multitude of data that can be used to improve knowledge and veterinary medicine.

On Reunion Island, located in the southwest Indian Ocean, the Kelonia care center received 4 different species of sea turtle since 2000: Chelonia mydas, Caretta caretta, Eretmochelys imbricata and Lepidochelys olivacea. Each new turtle undergoes a thorough veterinary examination, which also includes blood sampling. Blood tests (i.e., Pack Cell Volume, White Blood Cells, total protein, glucose, calcium, creatinine, albumin, globulin, phosphorus and acid uric) are analysed to help with diagnosis and to guide treatment protocols.

We therefore have the results of hematological and plasma biochemical values for 412 marine turtles since 2007: 312 loggerheads, 51 greens, 30 hawksbills and 19 olive Ridleys. Blood characteristics vary according to certain criteria (i.e., specie, wild versus captive, population...) and are generally limited in our area. The aim of this study, in addition to establishing a hematology baseline for the region, is to compare survival outcomes considering physical examination findings and hematology and plasma biochemistry profiles.

The average PCV per species is 33.9% (+/- 0.3), 31.1% (+/- 1.0), 26.4% (+/- 1.5) and 21.9% (+/- 1.9) respectively for loggerhead, green, hawksbill and olive Ridley turtles, confirming significant differences between each species. As for the fate of the turtles, the hematocrit of turtles that died during rehabilitation was significantly higher for loggerheads and hawksbills and lower for greens. Would this be species-specific (greens seem more prone to anemia) or show clinical signs (dehydration for loggerheads and hawksbills)? Also, the WBC levels for loggerhead turtles that died during rehabilitation were significantly lower than those of successfully rehabilitated turtles, suggesting a poor immune response in those cases.

We are still investigating the results to shed more light on hematological and biochemical values of injured and sick sea turtles brought to Kelonia, to find possible correlations between those values and (i) the fate of the patient, (ii) the turtle size classes, (iii) the pathologies encountered and (iv) how caregivers can adapt treatments.

Although the standards established in Reunion are not always comparable with the literature, partly due to differences in populations and the distinct geographical area, this recently developed baseline is already useful to Kelonia for adapting the rehabilitation process and the animal welfare. In addition, it will support the perpetual need for data acquisition and contribute to improve knowledge of marine turtles in the region by supplementing standards in the southwest Indian Ocean.

Understanding the status of sea turtle populations, and threats that may impact their survival are important for effective conservation. Stranding data represents a valuable opportunity for research by providing knowledge on the occurrence and spatiotemporal trends of different species and life stages, their biological health status, as well as morbidity and mortality caused by both natural and anthropogenic threats. However, the use of stranding data could be limited by biological and oceanographic factors (e.g., carcass decomposition, ocean current), as well as unstructured postmortem investigation protocol, leading to unquantifiable survey effort and inconsistent data collection, forbidding precise health and mortality assessment.

Virtopsy (virtual necropsy), the application of postmortem imaging techniques, has been applied extensively in veterinary forensic medicine and is proved to be conducive to the ease of operation, enhanced reproducibility, digital storage, and opportunity to seek second opinion. Virtopsy provides initial or complementary evidence on the health status and cause of death of stranded animals, and serves as a guide for veterinary pathologists, improving the accuracy in subsequent diagnosis and facilitating disease surveillance.

Since 2014, a pioneer virtopsy project has been implemented to advance the local cetacean stranding programme in Hong Kong, and since August 2019 the application has been extended to sea turtles (both live and deceased). Computed tomography (CT) and three-dimensional surface scanning (3DSS) have been routinely performed to document the internal and external conditions of each subject whenever possible. To date, 52 live stranded and 42 deceased sea turtle carcasses of 5 different species (Caretta caretta, Chelonia mydas, Dermochelys coriacea, Eretmochelys imbricata, Lepidochelys olivacea) were studied using the virtopsy approach.

The role of virtopsy has become pivotal as veterinarians and stranding response personnel became more aware of its strengths. Previously, necropsy was often omitted for carcasses of advanced decomposition in view of limited findings anticipated. Through virtopsy, biological health conditions can be documented without disrupting the body integrity. This allows the in situ detection of various pathologies, including skeletal dislocation, fluid accumulation, gas embolus, foreign body ingestion, and parasitic infection. These additional findings largely improved the assessment of injuries and deaths caused by anthropogenic threats, especially for decomposed carcasses. The non-invasive approach also minimized the risk of contracting zoonotic diseases for the personnel involved.

Discussions regarding the modification of stranding response workflow to accommodate virtopsy, including concerns over manpower, logistics, equipment, and safety, were followed by the standardisation of protocols and techniques for clinical and postmortem investigation. Pitfalls encountered were addressed with corrective measures to ensure the structural and practical management of the first virtopsy-led sea turtle stranding and salvage programme worldwide. The novel scheme of image data reconstruction methodologies has substantially modernised the characterisation and documentation of external and internal conditions of sea turtles. By advocating the use of virtopsy, we aimed to address knowledge gaps in the biological health and stressors that caused morbidity and mortality that conventional necropsy may not be able to answer, which will inform better veterinary practice, conversation management and policymaking for the protection of sea turtles.

In response to prolonged stressful events, sea turtles produce the hormone corticosterone, which circulates in the bloodstream and contributes to mobilization of energy reserves. When sea turtles strand on beaches in the northeastern U.S. in the late fall and winter due to cold stunning, a process akin to hypothermia, exposure to cold conditions triggers corticosterone production. Release of this hormone is an important physiological component of the cold stunning response. Life stages and species most prone to stranding from cold stunning on New York’s beaches are juvenile Kemp’s ridleys and Atlantic greens, along with subadult loggerheads. This study documented the change in plasma corticosterone that sea turtles experienced following rescue and rehabilitation, aiming to understand how levels change over time, and to correlate plasma levels to successful rehabilitation and release. During 4 cold stun seasons (2020-2023), blood samples were obtained by a senior staff member from the New York Marine Rescue Center (NYMRC) for all live stranded sea turtles. Samples were taken at three intervals: during the intake physical (day 1), after the animal was warmed to optimal body temperature (day 5, approximately 24˚C), and shortly before the individual’s release following rehabilitation (6-9 months post-rescue). Animals that died during rehabilitation were sampled post-mortem. Plasma samples were processed at Manhattanville College with a Corticosterone ELISA kit (Enzo Scientific) optimized for vertebrates. Corticosterone levels were indeed highest following cold stunning and showed a progressive decrease over time. However, trends seen across the three species differed, with Kemp’s ridleys exhibiting higher average corticosterone levels throughout the rehabilitation period. Analysis of this data will allow us to further understand the physiology of recovery from cold stunning, which supports broader conservation efforts of sea turtles along the northeastern US coastline.