Ecological Responses of Midwestern Snakes to Prescribed Fire

Prescribed burning is a commonly used land management tool to reduce the risk of hazardous wildfires and improve wildlife habitat, especially for grassland ecosystems. However, prescribed fire has widely varying effects on differing wildlife taxa. The effects of prescribed fire on herpetofaunal biodiversity have been examined, but the responses of a common and wide-ranging species, the common garter snake (Thamnophis sirtalis), to fire and subsequent effects on its ecology have not been closely studied. The primary goal of this research was to evaluate differing resource use or movement patterns of common garter snakes in burned and unburned habitats. Our objectives were to evaluate habitat use by garter snakes using mark-recapture methods and compare this use between burned and unburned sites. We also collected tissue samples (blood and shed skins) to determine the diet of snakes using stable isotope analysis and compare diets between burned and unburned sites. We performed vegetation surveys to evaluate the effect of differing habitat variables on trap success. Our results suggest that snakes may select for burned grasslands because we trapped more snakes in burned grids. Large amounts of short grass (\u3c 15 cm) near a trap had a negative effect on trap success. The amount of tall grass or bare ground near a trap was not demonstrated to have any effect on trap success. Stable isotope analysis of blood and prey samples and collection of mark recapture data are still ongoing and will provide more insight on resource use of snakes in burned grasslands

Inter-nesting and post-nesting movements and behavior of East Pacific green turtles (Chelonia mydas agassizii) from Playa Cabuyal, Guanacaste, Costa Rica

The East Pacific green turtle (Chelonia mydas agasizzi) is a sub-population of the widely distributed green turtle (Chelonia mydas). Like all sea turtles, East Pacific green turtles have a type III survivorship curve, which is characterized by long-lived adults that have a low mortality rate and high reproductive output with a low hatchling survival rate. For this to be successful, the adults must live through multiple reproductive seasons, and in the Eastern Pacific, there is high mortality on adult East Pacific green sea turtles. The continued success of this distinct population relies on protection during key in water movements: the nesting season and migrations from foraging grounds to nesting beaches and back. Management techniques need to be developed on a site-specific basis so it is crucial to understand the specific habitat needs for each nesting population as defined by the local oceanography. I used satellite telemetry to map movements of Pacific green turtles nesting on Playa Cabuyal, Costa Rica to understand the temporal and physical distribution of turtles both two and three dimensionally during the inter-nesting period and post-nesting migrations to foraging grounds. I deployed ten satellite transmitters across two nesting seasons, 2012-2014, six SPOT5 transmitters and four MK10 transmitters. The sample size for this study included 11 inter-nesting turtles and four post-nesting migrations (two post-nesting turtles were also tracked during their nesting season), curved carapace length ranged from 82.2 to 91.6 cm (mean ± SD = 85±2.84 cm) while curved carapace width ranged from 76 to 90 cm (mean ± SD = 79.5±3.80 cm). The observed inter-nesting period was between 7 and 17 days (mean ± SD, 13.1±2.5 days), which is comparable to the mean of 15.4 days observed as an average inter-nesting interval for turtles nesting on this beach. Post-nesting turtles moved over a period of 19 to 189 days (107.25±90.77 days) with one resident of the Gulf of Papagayo and three that migrated an average of 500 km away from the nesting beach. During the inter-nesting period turtles spread out across the Gulf of Papagayo and, in some cases, migrated out of the gulf and along the coast before returning to nest. The minimum convex polygon (MCP) with percent area use contours indicates that the highest use areas were close to the beach (within 10 km) and a couple isolated areas off the coast in the southern part of the gulf. Overall, this high use inter-nesting area totals 27 km2 and represents the high density twenty-five percent (75% of all positions received) of recorded location data during their movements between nests. Inter-nesting dive behavior indicated that, on average, fifty-five percent of the dives recorded were in the top 15 m of the water column, and sixty-six percent of inter-nesting dives lasted 30 minutes or less. Overall, ninety percent of the time inter-nesting turtles were within 15 m of the surface even though the ocean floor is generally 25 m or deeper throughout the Gulf of Papagayo. The oceanographic characteristic that limited turtles\u27 dive behavior was the water temperature. The temperatures experienced at varying depths changed as the nesting season progressed showing a significantly shallower thermocline in the spring months when compared to the winter months of this study. In December and January the temperature at the surface temperature was 28 °C and stayed above 25 °C to depths of 25 m. In February and March the surface temperature was 25 °C and at 25 m the temperature had already dropped below 20 °C. Turtle behavior changed to reflect this shift in the water temperature with more time spent in the Surface - 5 m depth bin during February–March as compared to December when the waters at depth were warmer. Post-nesting turtles took up residence in locations along the Costa Rica, Nicaragua, El Salvadoria and Guatemala coasts; a pattern similar to other Pacific green turtles nesting more to the South along the Pacific coast of Costa Rica. During migration, the turtles remained within 50 km of the coastline, which allowed them to stay in shallow warmer coastal waters. Dive behavior of these post-nesting turtles shows a bimodal distribution in depth use not previously described for this sub-population, with peak dive depths of 11 to 15 m and 46 to 50 m. This could be indicative of foraging while migrating. Currents are one of the most important factors in migration routes because they determine hatchling dispersal and locations of primary productivity. Chlorophyll distribution was correlated to the post-nesting movements of one turtle. Conservation efforts should focus on regulating the fishing efforts in the area of inter-nesting habitats and migratory corridors because by-catch mortality pressure on adults is currently the biggest threat to the population. By providing the local fisheries with depth integration levels and dates of passage, the set of nets and long lines could be below these normal behaviors and reduced during migration dates to reduce bycatch and fisheries interactions. Fishing regulations need to be enforced and regulated locally on site-by-site bases, eliciting the help of each country and community. Future work with this inter-nesting and post-nesting data will be to analyze the turtle interaction points with local and international fisheries in hopes of generating a management strategy through cooperation along the Eastern Pacifi

Foraging Ecology and Stress in Sea Turtles

As ectothermic marine megafauna, sea turtle physiology and ecology are tightly intertwined with temperature, seasonality, and oceanography. Identifying how turtles respond when exposed to cold water, how they adapt to cold environments when they need to explore cold environments in order to forage, and what foraging resources are exploited by sea turtles are all components central to their conservation. Cold-stunning is a welldocumented phenomenon that occurs when water induced decreases in sea turtle body temperature cause turtles to become immobilized and wash ashore. While most coldstunned turtles are rescued and rehabilitated, we do not know whether cold-stunning is an acute transient occurrence, or a symptom of a bigger environmental problem. Further, while in some environments avoiding cold water is preferential, in other habitats, sea turtles need to inhabit cold environments in order to forage. Along the Eastern Pacific Rim, discrete upwelling locations are characterized by high primary productivity and unusually cold water. In these environments, avoidance is not possible and sea turtles require physiological adaptions to mitigate body temperature decreases in cold water. Little is known about how turtles handle upwelling environments, despite the fact that sea turtles remain in these habitats regardless of water temperature fluctuations. Because upwelling habitats provide increased nutrient presence, and sea turtles are opportunistic foragers, quantification of diet composition will further our understanding of why sea turtles remain in cold water environments year-round. Diet composition in multiple populations of cohabitating sea turtles revealed partitioning that results in reduced inter-specific competition. Further, flexibility in diets provides a wide range of ecosystem services central to habitat resiliency. Therefore, conservation of endangered sea turtles requires complete ecosystem conservation, and complete understanding of the interconnectivity of sea turtles and their environments is crucial

Migratory corridor linking Atlantic green turtle, Chelonia mydas, nesting site on Bioko Island, Equatorial Guinea to Ghanaian foraging grounds.

This study uses satellite telemetry to track post-nesting movements of endangered green turtles (Chelonia mydas) (n = 6) in the Gulf of Guinea. It identifies a migratory corridor linking breeding grounds of Atlantic green turtles nesting on Bioko Island, Equatorial Guinea, to foraging grounds in the coastal waters of Accra, Ghana. Track lengths of 20-198 days were analyzed, for a total of 536 movement days for the six turtles. Migratory pathways and foraging grounds were identified by applying a switching state space model to locational data, which provides daily position estimates to identify shifts between migrating and foraging behavior. Turtles exhibited a combination of coastal and oceanic migrations pathways that ranged from 957 km to 1,131 km. Of the six turtles, five completed their migration and maintained residency at the same foraging ground near the coastal waters of Accra, Ghana until transmission was lost. These five resident turtles inhabit heavily fished waters and are vulnerable to a variety of anthropogenic threats. The identification of these foraging grounds highlights the importance of these coastal waters for the protection of the endangered Atlantic green turtle

Effect of water temperature on the duration of the internesting interval across sea turtle species

5 pages, 3 figures.-- Data availability: Data will be made available on requestSea turtles generally lay several clutches of eggs in a single nesting season. While a negative correlation between water temperatures and the time required between constitutive nesting events (termed the internesting interval) has been previously reported in loggerhead Caretta caretta and green turtles Chelonia mydas, it is not understood whether this relationship remains constant across other sea turtle species. Here, we expanded upon these previous studies on loggerhead and green turtles by using larger sample sizes and including data from species with a wider range of body-sizes; specifically: hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, and olive ridley turtles Lepidochelys olivacea. In total, we compiled temperature data from biologgers deployed over internesting intervals on 23 loggerhead, 22 green, 7 hawksbill, 26 leatherback and 11 olive ridley turtles from nesting sites in 8 different countries. The relationship between the duration of the internesting interval and water temperatures in green and loggerhead turtles were statistically similar yet it differed between all other turtle species. Specifically, hawksbill turtles had much longer internesting intervals than green or loggerhead turtles even after controlling for temperature. In addition, both olive ridley and leatherback turtles exhibited thermal independence of internesting intervals presumably due to the large body-size of leatherback turtles and the unique capacity of ridley turtles to delay oviposition. The observed interspecific differences in the relationship between the length of the internesting interval and water temperatures indicate the complex and variable responses that each sea turtle species may exhibit due to environmental fluctuations and climate changeNJR was funded by the Spanish government (AEI) through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). PST was funded by the Vicenç Mut program of the Govern de les Illes Balears. JT was funded by project AICO/2021/022 granted by Conselleria d'Innovació, Universitats, Ciència i Societat Digital, Generalitat ValencianaPeer reviewe

Key issues in assessing threats to sea turtles:knowledge gaps and future directions

Sea turtles are an iconic group of marine megafauna that have been exposed to multiple anthropogenic threats across their different life stages, especially in the past decades. This has resulted in population declines, and consequently many sea turtle populations are now classified as threatened or endangered globally. Although some populations of sea turtles worldwide are showing early signs of recovery, many still face fundamental threats. This is problematic since sea turtles have important ecological roles. To encourage informed conservation planning and direct future research, we surveyed experts to identify the key contemporary threats (climate change, direct take, fisheries, pollution, disease, predation, and coastal and marine development) faced by sea turtles. Using the survey results and current literature, we also outline knowledge gaps in our understanding of the impact of these threats and how targeted future research, often involving emerging technologies, could close those gaps.</p