ISTS Symposium43 Program/Agenda

Monitoring environmental changes in sand, soil, and air is important to many research activities geared to understanding their implications on animal growth, metabolism, life cycles, and for oviparous species, in situ embryonic development. Monitoring environmental conditions in sea turtle nests is vital for understanding the impacts of temperature on hatchling sex determination and the influence of global climate change on nesting beaches, and resultant hatchling sex ratio dynamics globally. Numerous communication protocols provide reliable capability to wirelessly transmit real-time soil sensor data, facilitating remote monitoring of measured parameters. Nevertheless, cables are required between sensors installed below the soil surface and receivers above ground, potentially affecting measured parameters. Network receivers that integrate Long Range (LoRa), Radio Frequency Identification (RFID), Bluetooth (BLE), and Global System Mobile Communications (GSM) tend to lose data transmissivity when buried below 15 cm. The current experiments conducted between July 2023 and May 2024 tested the applicability of Nesting Safe’s proprietary Tetherless Underground Surface Communication (TUSC) technology to transmit on-demand temperature and relative humidity; data required to monitor and model sea turtle nest parameters through the incubation period, without disruption to nests. Field experiments were conducted in air to test transmission from a sensor placed 1 m above ground in Quebec. We tested transmission reliability from 2 sensors over a 41 hr period at 0 and 10 cm depth exposed to watering within 2 diurnal cycles in California. To test transmission of Temp/Rh data over distance between the hand-held receiver and sensor, we buried the sensor at 50, 103 and 125 cm depths in a sand quarry. To mimic Hawksbill nests, the sensor was buried and covered at 60 cm depth on a beach site in Thailand. To test data transmission within turtle clutches, the sensor was buried 8 m above waterline at 60 cm depth, surrounded by 90 live chicken eggs and covered with sand. For each test, we collected 12 - 15 readings, then moved to the next distance interval to confirm transmission at that position. Results from transmitting Temp/Rh data 1 m above ground showed data acquisition to at least 700 m until obstructed by thick vegetation. We demonstrated reliable transmission and high sensitivity for 2 sensors exposed to watering. Results from monitoring beach conditions in a sand quarry demonstrated quality transmissions up to 200 m from the sensor. When the sensor was positioned at comparable depths to turtle nests (60 cm), transmission reached 200 m from the buried sensor. When mimicking a clutch of turtle eggs, data transmission was 25 m at 5 radial angles (along the beach, up a 2 m slope through a dirt road, roots, and buildings). Results demonstrate the applicability of Nesting Safe tetherless sensors to monitor Temp/Rh data on beaches within egg clutches. The TUSC technology demonstrates that tetherless sensors provide reliable environmental data at greater depths and distances than prior technologies, validating the potential to access real-time in situ environmental data for turtle nesting beaches, exponentially expanding our understanding of environmental conditions, hatching predictability, and hatchling success.

Sea turtle hatchlings must escape their sand-buried nests to begin their journey to the ocean, a process influenced by clutch size and critical for survival. This study investigates the effects of clutch size on the morphology, physiology, and digging behavior of Chelonia mydas hatchlings. Eggs were split into large (45–60 eggs) and small (15–20 eggs) groups, with experimental setups mimicking natural nest conditions. Morphological measurements, glucose levels, and self-righting performance were evaluated alongside digging behavior using acoustic monitoring at different nest depths. Hatchlings from small groups exhibited larger body and flipper sizes, higher blood glucose levels, and shorter self-righting times, indicating higher energy expenditure but enhanced locomotor performance. In contrast, large-group hatchlings demonstrated energy-saving benefits, shorter total nest escape durations, and lower glucose levels. Digging duration analysis revealed significant depth and group size effects, with larger groups achieving more efficient synchronization, especially near the sand surface. However, small groups displayed prolonged digging at middle depths, potentially due to reduced coordination and denser sand. These findings suggest that large clutch sizes facilitate energy-efficient nest escape, while small group hatchlings compensate with improved post-emergence performance. The study highlights the trade-offs between group size, energy use, and locomotor capabilities, emphasizing the need for careful management when splitting clutches for conservation purposes. Future research should explore long-term effects on hatchling survival and swimming performance to refine conservation strategies.

Monitoring the nesting success of sea turtles and the survival of their hatchlings is vital for understanding population dynamics. A 20-year monitoring program for flatback turtles on Barrow Island in Western Australia has so far relied on tagging data and track counts to determine nesting abundance, but a richer dataset was collected over the 2023-24 nesting season using videography. Arrays of solar-powered cameras were attached to masts on movable trailers, and approximately 90,000 hours of continuous video of adult and hatchling turtles was captured between December 2023 and March 2024 across two index beaches. Over approximately 300 metres of beach, 608 nesting events were documented, and 1126 hatchlings were observed. Nesting success was estimated at 34.2%, meaning that most females that emerged were not observed laying eggs, and 95.2% of emergences occurred between 17:00 and 02:00 hours. Nesting success was negatively associated with luminosity, with the likelihood of success increasing as luminosity decreased. Nearly 80% of hatchlings that could be viewed clearly on camera avoided on-shore predation and reached the relative safety of the surf zone. Of those hatchlings that were predated, golden bandicoots (11.6%) and gulls (8.2%) were the main predators, and to a lesser extent water rats (2%) and brushtail possums (1%). On-shore mortality also decreased as hatchling group size increased (R²=0.47, p<0.001). While there were technical challenges maintaining continuous videography for an entire nesting season (i.e., first nester to last hatchling), video quality was sufficiently high to observe nesting behaviours and predator-prey interactions in detail. Further, determining nesting success via videography now allows estimation of the number of flatback turtle nests laid annually on Barrow Island based on track count data.

Hatchling sea turtles orient to the ocean based on lowest-lying brightness cues; typically the light of the moon and stars reflecting off the water. Anthropogenically generated lights are often brighter than natural light and may cause hatchlings to misorient towards these artificial lights. Significant efforts have been devoted to discerning possible light wavelength and intensity combinations that do not cause this misorientation in hatchling turtles. These two factors, in concert with the positioning and angling of lights, define turtle-safe lighting. Typically, turtle-safe lights employ Low-Pressure Sodium Vapor (LPS) bulbs, which generate light of 590 nm, or red LEDs (630+ nm). However, these lights were described as turtle-safe for only a small set of turtle species, with limited to no testing in our study species, hawksbills. More recent research has focused on isolating intensity and wavelength to better understand how these two factors influence phototactic responses, finding that in leatherbacks the main driver is intensity. We aimed to discern the main driver of hatchling phototaxis in hawksbill turtles, hypothesizing that, similar to leatherbacks, intensity is the main driver of the phototactic response. We presented hatchling hawksbill turtles with choices of two wavelengths of light in Y-maze choice experiments. In our first set of experiments, hatchlings were presented with different wavelengths at the same intensity relative to threshold; either 1.0 log unit or 0.25 log units above threshold. Hatchlings were presented with 590 nm vs. 660 nm, or 590 nm vs 535 nm. In our second set of experiments, hatchlings were presented with different wavelengths at equal intensity, both above threshold. Comparisons consisted of 590 nm vs. 660 nm, 590 nm vs 535 nm, and 535 nm vs 470 nm. Our first experiment showed that hatchlings oriented towards the light that was brighter, regardless of threshold. Our second experiment showed that hatchlings oriented randomly when lights were equally bright. These results suggest that hatchling hawksbills use intensity as the primary cue for seafinding at low intensities of light. This is in direct contrast to previous studies that suggest that hatchling sea turtles prefer to orient toward shorter wavelengths of light. Our results corroborate more recent findings in leatherbacks; that light intensity is the primary factor for seafinding. With light intensity as the primary cue for seafinding, turtle-safe lighting in the visual spectrum may not actually exist, as even low intensity light has been shown to attract hatchlings. This highlights the importance of turning off beachfront lighting during turtle nesting and hatching seasons as the best way to avoid misorientations.

Current research on egg failure in leatherback turtle nests in Southeast Florida, USA shows that approximately 55% of unhatched eggs have no signs of embryonic development when necropsied. Is the lack of detectable signs of development (e.g., embryonic tissues or blood) the result of infertile eggs that never formed an embryo, or dead early-stage embryos degrading in the nest before excavation and necropsy? To identify how infertility contributes to leatherback egg failure, 30 eggs from each of 19 nests (n=570 eggs) laid in Boca Raton and Juno Beach, Florida, USA were collected after oviposition for ex situ incubation. During incubation, eggs were monitored at least twice daily. To identify if an egg was fertile, two methods were used. The first method was to observe whether a white spot formed (i.e., egg chalking) on the eggshell surface within 14 days of incubation. In eggs that did not form a white spot, the second method was to use fluorescent microscopy to verify the presence or absence of embryonic cells in the perivitelline membrane, a technique that has recently been proven to work in sea turtle eggs. Using white spot formation as an indicator of fertility, we found 97.3% and 93.3% of eggs were fertile in 2023 and 2024, respectively. Employing fluorescent microscopy techniques increased the accuracy of fertility assessments compared to using white spot formation alone as an indicator of fertility. The combination of white spot observation and embryonic cell detection found a fertility rate of 98.3% in 2023. Microscopic analyses of 2024 eggs are ongoing. This experiment is the first to quantify fertility rates in sea turtle eggs using fluorescent microscopy techniques. Additionally, this is the first report of fertility rates of leatherback eggs in Florida, USA and these fertility rates are higher than most reported at nesting beaches globally (~80%). Thus, fertility rates are high in leatherback sea turtle eggs in Southeast Florida, suggesting that infertility is not a major factor contributing to egg failure. Therefore, to understand most of the egg failure in leatherback nests in this region, the causes of early embryonic mortality require investigation.

Sea turtles, in comparison with marine mammals, sea birds, and fishes, are the most affected by microplastics in terms of number of individuals impacted and concentration within each organism. The ubiquitous nature and persistence of microplastics in the environment further compromises sea turtles as all seven species are currently threatened or endangered. Microplastic contamination was quantified in unviable loggerhead sea turtle eggs (Caretta caretta). Eggs were collected from seven locations along the northwest coast of Florida. A total of 70 nests and 350 eggs were examined. Microplastics (n = 510) were found in undeveloped loggerhead sea turtle eggs across all seven sites, suggesting that maternal transference and/or exchange between the internal and external environment were possible. Microplastics were categorized based on color, shape, size, and type of polymer. The predominant color of microplastics was blue/green (n = 236), shape was fibers (n = 369), and length was 10-300 µm (n = 191). Identified fragments, films, beads and one foam (n = 187) had the most common area of 1 - 10 µm² (n = 45). Micro-Fourier Transform Infrared (µ-FTIR) spectroscopy analysis demonstrated that polyethylene (11%) and polystyrene (7%) were the main polymer types. For the first time microplastics have been found in unviable, undeveloped loggerhead sea turtle eggs collected in Northwest Florida.