Here we present 38 yrs of nesting data of the loggerhead population in Laganas Bay, Zakynthos, Greece, adding data for 2010–2021 to existing published data for 1984–2009. This rookery, encompassing 6 discrete beaches of 5.5 km total length, features the highest nesting density in the Mediterranean. The annual nest numbers, ranging from 667 to 2018, showed no significant long-term trend. Beach nesting contributions increased on some public-accessed beaches (as did nesting success), but decreased on a remote beach that previously held > 50% of all nests. These changes might be attributed to management actions by the National Marine Park of Zakynthos that improved conditions for sea turtles (e.g., restricting nighttime access to the public), indicating that the previously recorded high nesting density on the remote beach may have been atypical. Although no significant phenological changes were detected with the available data in the 20-yr period 2002–2021, the date of the first hatched nest shifted significantly toward earlier dates in the 38-yr data set. Clutch size and body size of nesting turtles exhibited significantly decreasing trends. Hatching success, hatchling emergence success, and in-nest hatchling mortality showed significantly increasing trends. The number of viable hatchlings decreased over the seasons, albeit not significantly, possibly a result of the decreasing clutch size. Incubation durations were revealed as shortening on all beaches, a potential sign of global warming, with a consequent suggested increase of female primary sex ratio. Continuation of this long-term monitoring program is expected to provide further insights in the reproductive traits of this regionally important loggerhead population.

We describe a new species of small chelid turtle from perennial streams in the Araguaia River subbasin near Serra das Andorinhas State Park, São Geraldo do Araguaia, Pará, Brazil. It is morphologically distinct and the smallest known member of the genus Mesoclemmys, with an average straight-line carapace length (CL) of 144 mm and maximum recorded CL of 170 mm. The species has a moderate head width of approximately 20% of CL. The carapace and dorsal soft parts are blackish, the plastron is light brownish yellow with a blackish brown central plastral figure, and the ventral soft parts are pale yellow. It has the largest femoral scutes of any Mesoclemmys and its plastral contact formula is Intergular > Anal > Humeral > Femoral > Abdominal > Pectoral > Gular. We describe the shell and skull morphology of the new species and performed genetic analysis using mitochondrial DNA (cytochrome c oxidase, subunits I [COI] and 16S) to build a phylogenetic tree for the genus, which placed the new species as sister to M. vanderhaegei.

The eruption of Mount Pinatubo in the Philippines in June 1991 reduced global temperatures over the following 2 yrs. The greatest suppression (apart from Antarctica) was centered in the northern Great Plains of North America, directly over my long-term turtle study site. Temperatures at that site in 1992 and 1993 were the coldest in at least 50 yrs. Normal annual hatchling recruitment of yellow mud turtles (Kinosternon flavescens) in the spring following incubation at that site averaged 375; however, only 3 hatchlings emerged in 1993 (1992 incubation cohort), and none emerged in 1994 (1993 incubation cohort). The depressed temperatures apparently prolonged incubation times to such an extent in 1992 and 1993 that hatching was nearly impossible before winter mortality. The result was a gap in the age class structure that was still evident 26 yrs later. This site is at the northern range limit of this species, and this event suggests that incubation temperatures (i.e., summer season length) may be responsible for that limit.

This study presents the first published data on the morphometrics of nesting hawksbill turtles (Eretmochelys imbricata) and their eggs and counts of yolked and yolkless eggs per clutch from Iranian Islands in the northern Persian Gulf. We found significant variation in some variables among 4 main nesting islands (e.g., weight of yolked eggs, p = 0.000; number of yolkless eggs per clutch, p = 0.017), but effect size was moderate or less (r < 0.5 or d < 0.8). The diameter (p = 0.039), weight (p = 0.028), and number of yolked eggs (p = 0.000) per clutch increased significantly with curved carapace length (CCL), but the effect size was only large for the number of yolked eggs (f² = 0.152). The number of yolkless eggs did not vary with CCL (p = 0.453) or with the number of yolked eggs (p = 0.523). A meta-analysis of global hawksbill turtle morphometrics and reproductive output revealed significant variation in CCL (p = 0.000) and number of yolked eggs (p < 0.001), with nesting region having a very large effect size on both variables (g² = 0.880 and 0.616, respectively). Hawksbill turtles from the Gulf were smaller than populations from the Gulf of Oman (p < 0.001), Arabian Sea (p = 0.000), Caribbean (p = 0.000), West Atlantic (p = 0.000), and Southwest Pacific (p = 0.000) but not the Red Sea (p = 0.104), and laid fewer yolked eggs than populations in the Caribbean (p < 0.001) and West Atlantic (p = 0.001) but not the Red Sea (p = 0.636). This may be due to hawksbill turtles nesting in the Gulf remaining within its waters postnesting so adult body size is restricted by the relatively poor foraging habitat and/or success and/or the extreme environments, subsequently limiting clutch size. More information on home range and foraging habitat is required to draw similar conclusions about hawksbill turtles nesting in the Red Sea. Hawksbill turtles nesting in the Gulf, Red Sea, and Arabian Sea also appear to lay larger number of yolkless eggs per clutch than other populations worldwide (mean = 17.6 ± 10.8 SD [range = 0–59]). The functional role of yolkless eggs, potentially in the maintenance of thermal and hydric conditions within tolerable conditions in shallow nests laid in extreme environments, requires further investigation. Similarly, the potential for yolkless eggs to be an adaptation to extreme nest environments in other sea turtle species also nesting in the northern Indian Ocean also warrants examination.

The Rio Grande cooter (Pseudemys gorzugi) is an imperiled freshwater turtle native to the southwestern United States and northeastern Mexico. Previous studies investigating P. gorzugi diet have focused on the population occupying the Black River drainage in southeastern New Mexico, while Texas populations have remained unexamined. During the summer and fall of 2020, we studied the dietary habits of P. gorzugi and the syntopic red-eared slider (Trachemys scripta elegans) at San Felipe Creek, Texas, USA using fecal content and stable isotope analyses. We also compared the isotopic niches of these 2 co-occurring turtle species. Filamentous algae were, volumetrically, the most important food item for male, female, and juvenile P. gorzugi. Stable isotope mixing models indicated that lotic and lentic filamentous algae had the greatest proportional contribution to P. gorzugi and T. s. elegans diets, respectively. Stable isotope dietary mixing models also indicate T. s. elegans had a more carnivorous diet, composed mostly of red-rimmed melania (Melanoides tuberculata) and red swamp crayfish (Procambarus clarkii). Carnivory in this species was further supported by enriched δ¹⁵N values and higher trophic position estimates. Pseudemys gorzugi and T. s. elegans had δ¹³C and δ¹⁵N signatures that significantly differed, and the 2 species showed little overlap in isotopic niche space, suggesting a low likelihood of intense resource competition. Our results demonstrate that the diet of P. gorzugi, and the isotopic niche overlap between P. gorzugi and T. s. elegans at San Felipe Creek differ from that in the Black River drainage of New Mexico. The information provided here contributes toward a more complete understanding of P. gorzugi ecology, is useful for identifying suitable habitat worthy of conservation, and can help guide the development of feeding regimes for captive assurance colonies.

La tortuga de Río Grande (Pseudemys gorzugi) es una tortuga de agua dulce en peligro nativa del suroeste de los Estados Unidos y el noreste de México. Estudios previos que han investigado la dieta de P. gorzugi se han enfocado en la población que ocupa el drenaje del Black River en el sureste de Nuevo México, sin embargo, las poblaciones de Texas no han sido examinadas. Durante el verano y el otoño de 2020, estudiamos los hábitos alimentarios de P. gorzugi y la tortuga de orejas rojas sintópica (Trachemys scripta elegans) en San Felipe Creek, Texas, EE. UU. mediante un análisis de contenidos fecales e isótopos estables. Incluso comparamos los nichos isotópicos de estas dos especies de tortugas en coexistencia. Las algas filamentosas fueron, volumétricamente, el alimento más importante para machos, hembras y juveniles de P. gorzugi. Los modelos de mezcla de isótopos estables indican que las algas filamentosas lóticas y lénticas contribuyen en mayor parte proporcionalmente a las dietas de P. gorzugi y T. s. elegans, respectivamente. Los modelos de mezcla dietética de isótopos estables también indican que T. s. elegans tiene una dieta más carnívora, compuesta en mayor parte de melania de borde rojo (Melanoides tuberculata) y cangrejo de río rojo (Procambarus clarkii). La característica carnívora en esta especie fue respaldada aún más por valores de δ¹⁵N enriquecidos y estimaciones de posición trófica más altas. Pseudemys gorzugi y T. s. elegans tuvieron valores de δ¹³C y δ¹⁵N que diferían significativamente y las dos especies mostraron poca superposición en el espacio del nicho isotópico, lo cual sugiere una baja probabilidad de competencia intensa por los recursos. Nuestros resultados demuestran que la dieta de P. gorzugi y la superposición del nicho isotópico entre P. gorzugi y T. s. elegans en San Felipe Creek difieren de aquellas del drenaje del Black River de Nuevo México. La información proporcionada aquí contribuye a un conocimiento más completo de la ecología de P. gorzugi, es útil para identificar un hábitat adecuado digno de conservación y puede ayudar a guiar el desarrollo de regímenes de alimentación para colonias de seguridad cautivas.

Reeves' turtle (Mauremys reevesii) originated in China and was once one of the most widely distributed and abundant hard-shelled turtles in China; however, overharvesting has led to a sharp decline in its wild populations. A survey of Reeves' turtle was conducted from July 2021 to March 2022 in Qichun County, Hubei Province, China. A total of 74 individuals were caught in 26 ponds (1078 trap-days), indicating a catch effort population density of 0.07 individuals/trap-day. The 840 similar ponds in the field-surveyed towns indicate a population number of 2391 individuals and density of 4 individuals/km². Our preliminary results suggest that Reeves' turtle populations face serious threats from human hunting activities, habitat destruction, and artificial release and urgently require an aggressive conservation program to ensure their survival.

Box turtle (Terrapene spp.) reproduction has been relatively well studied in northern populations inhabiting more seasonal climates but is much less understood in the subtropics. We assessed female reproduction of T. bauri in southwestern Florida by quantifying courtship, mating, seasonal timing of nesting, clutch frequency, and clutch size. Box turtles were observed courting or mating in 10 out of 12 mo. Radiographs revealed oviducal eggs from January to August. To our knowledge, this is the earliest recorded detection of eggs in wild box turtles. Individual turtles produced 2–4 clutches of 1–5 eggs in a nesting season. This study provides further evidence that turtle populations at warmer climates exhibit extended reproductive seasons compared with similar populations in cooler climates.

The reproductive lifespans of turtles are consistently long, but reproductive cycles are under environmental control and thus can vary within species, populations, and individuals over time and space. Knowledge of turtle species' reproductive traits and their associated variances over time and space are critical to understanding the dynamics of turtle populations, especially those requiring management or conservation. Deirochelys reticularia is a species being considered for protection by the US Fish and Wildlife Service and contains 3 subspecies with some differences in reproductive characteristics of nesting season, annual nesting frequency, and egg retention. We collected ultrasound and x-radiograph data in Texas to identify the maturation size, nesting season, annual nesting frequency, and clutch size of female D. r. miaria in Texas. We observed no reproductive activity in individuals from 101 to 146 mm in plastron length (PL) and detected either unshelled eggs, shelled eggs, or both in individuals from 150 to 197 mm PL. Maturation sizes were similar to those in other regions and for other subspecies. We observed shelled clutches or nesting events from April to July, confirming a spring–summer nesting season in Texas consistent with other D. r. miaria sites and supporting the paradigm that the western subspecies does not follow the autumn–winter nesting season of the other subspecies. We found no evidence that individuals retain shelled eggs while aestivating or overwintering. Individuals nested up to 3 times/yr in Texas. Individuals laid 7–11 eggs and the mean clutch size was 9.2 eggs, similar to other regions and other subspecies. Nesting phenology is regionally variable, so management plans and policies for the species will need to consider that variation and potentially recognize management differences among D. reticularia subspecies.

In this study we describe some ecological features of Kinosternon scorpioides scorpioides from a section of the Argentina's Chaco ecoregion encompassing the provinces of Salta, Chaco, and Formosa, including the description of the capture sites and an analysis of the feeding ecology of the species. Six field trips were made during the spring and summer months from 2016 to 2020. We captured 23 turtles: 8 in Salta, 8 in Chaco, and 7 in Formosa; all corresponding to the dry portion of the Chaco ecoregion. They were found in a variety of aquatic environments (including those with considerable waste and human disturbance), and they also seemed to tolerate some fragmentation of the forest matrix. The analysis of 20 stomach contents and 14 fecal samples corroborated that K. s. scorpioides is predominantly an opportunistic omnivore, capable of feeding upon a diverse variety of invertebrates, some small vertebrates, and large volumes of vegetal material. The present study provides some baseline information about habitat requirements and feeding habits of the southernmost known populations of K. s. scorpioides.

Testudines is a reptilian order characterized by low annual recruitment and delayed sexual maturity. One testudine species of conservation concern is the Rio Grande cooter (Pseudemys gorzugi), a taxon native to the southwestern United States and the westernmost species in this genus. A clear understanding of the reproductive biology of turtle species in the wild better informs conservation management options. The reproductive biology of P. gorzugi has been formerly investigated in the Black River of southeastern New Mexico. Because life history strategies of chelonian taxa may vary across geographic gradients, we examined the reproductive biology of this species at 3 sites in west Texas from 2017 to 2019. We detected follicle enlargement beginning in the fall with shelled eggs appearing as early as 7 April and as late as 12 August. We found a significant quadratic relationship between day of year and maximum follicle diameter (r² = 0.22, F_2,100 = 15.61; p < 0.05). A significant relationship between turtle size and clutch size was not detected nor was there a significant relationship between turtle size and egg width. We detected a record clutch size of 17 eggs and a mean ± SD clutch size of 11.4 ± 3.11. We observed a single instance of production of 2 clutches. The smallest gravid female we detected with shelled eggs had a plastron length of 179 mm. We also found that the probability of capturing a female gravid with shelled eggs was highest in early June. Our results suggest geographic variation occurs in the reproductive biology of P. gorzugi and highlight the importance of range-wide, temporally extensive sampling. Data presented herein can be included in population viability assessments and inform conservation recovery plans.

Testudines es un orden de reptiles caracterizado por un bajo reclutamiento anual y una madurez sexual tardía. Una especie testudina de interés para la conservación es la tortuga del Río Grande (Pseudemys gorzugi), un taxón nativo del suroeste de los Estados Unidos y la especie más occidental de este género. Una comprensión clara de la biología reproductiva de las especies de tortugas en la naturaleza brinda mejor información a las opciones de manejo y conservación. La biología reproductiva de P. gorzugi se ha investigado anteriormente en el Río Negro del sureste de Nuevo México. Debido a que las estrategias de historia de vida de los taxones de quelonios pueden variar según los gradientes geográficos, examinamos la biología reproductiva de esta especie en tres sitios en el oeste de Texas entre el 2017 y 2019. Detectamos el agrandamiento del folículo a partir del otoño con la aparición de huevos sin cáscara desde el 7 de abril y tan tarde como el 12 de agosto. Encontramos una relación cuadrática significativa entre el día del año y el diámetro máximo del folículo (r² = 0.22, F₂,₁₀₀ = 15.61; p < 0.05). No se detectó una relación significativa entre el tamaño de la tortuga y el tamaño de la nidada ni hubo una relación significativa entre el tamaño de la tortuga y el ancho del huevo. Detectamos un tamaño récord de nidada de 17 huevos y un tamaño medio ± DE de nidada de 11.4 ± 3.11. Observamos un solo caso de producción de dos nidadas. La hembra grávida más pequeña que detectamos con huevos sin cáscara tenía una longitud de plastrón de 179 mm. También encontramos que la probabilidad de capturar una hembra grávida con huevos sin cáscara era más alta a principios de junio. Nuestros resultados sugieren que se produce una variación geográfica en la biología reproductiva de P. gorzugi y resaltan la importancia del muestreo extenso temporal en todo el rango. Los datos presentados en este documento pueden incluirse en las evaluaciones de viabilidad de la población e informar los planes de recuperación y conservación.

Nest site selection is an important aspect of reproductive behavior in sea turtles, and it is influenced by biotic and abiotic beach characteristics. To date, the association between nesting beach characteristics and nest site selection has been explored manually at small scales; yet, hawksbill turtles (Eretmochelys imbricata) nest on a variety of beaches, with knowledge remaining limited on preferred habitat. Here, unmanned aerial vehicles were used to assess all available beaches, identify common characteristics, and determine the preferred nesting sites for hawksbill turtles in the Persian Gulf. High resolution photographs were taken of 236 nests with unmanned aerial vehicles on 7 main islands supporting 10 nesting beaches. The physical characteristics of these nests were photographed (e.g., elevation, slope, vegetation cover, and nest distance from vegetation and the high tide line). Slope was the most important factor regulating nesting activity. Most turtles nested on shallow-sloped beaches with 5° slopes or less (61.4%), at a distance of ≤ 15 m from the high tide line (71.8%), and generally ranged from 1 to 3 m (83.9%) above sea level. Most nests (87.7%) were laid close to the vegetation line (≤ 5 m) in sandy zones. Although there was high geomorphological diversity in landform among the islands, nesting habitat characteristics of hawksbills were consistent. Unmanned aerial vehicles provide a useful approach for identifying the nesting habitat preferences of sea turtles in a time- and cost-efficient manner, covering more surface while minimally disturbing fragile habitat.

Predation of nests and hatchlings can significantly reduce sea turtle reproductive output. On Cavalos island, João Vieira and Poilão Marine National Park, Bijagos archipelago, Guinea-Bissau, one of the primary threats to green turtle nests is predation by Nile monitors (Varanus niloticus). In this study, we tested 3 different nest protection techniques—disguising scent cues, disguising visual cues, and placing a metal net over the nest—to reduce predation on green turtle (Chelonia mydas) nests by Nile monitors. Nests were monitored for 10 d after they were laid, and we found that using metal nets and disguising scent cues led to a significant increase of the number of days it took for Nile monitors to find and predate the nests. Overall reduction in predation rates also approached significance when metal nets or disguising scent cues were used. We used the Risk Reduction metric to compare the effectiveness of our experiment with other nest protection techniques; our results corresponded to a > 50% decrease in the risk of predation, a value comparable to or better than other techniques used elsewhere. We suggest that camouflaging a nest's scent may be the most cost-efficient management option to reduce predation rates by Nile monitors in sensitive areas without damaging the local ecosystem.

Diamondback terrapins (Malaclemys terrapin) are a species of turtle that occupy coastal tidal marshes and nest on sandy areas above the high-tide line. Within the Grand Bay National Estuarine Research Reserve, Mississippi diamondback terrapin (M. t. pileata) shoreline nesting habitat at Grand Battures (also known as South Rigolets Island) has decreased from a 2.34-km length of surveyable shoreline in 2014 to a 1.45-km length of shoreline in 2021. Depredated nest surveys in 2021 detected the lowest number of nests to date at this location, with increased search effort, and this is likely due to the high rates of erosion described for this area.

The southwestern pond turtle (Actinemys pallida), a chelonian species declining in California, depends on aquatic habitats for its survival. This study examined the extent to which the southwestern pond turtle used livestock ponds in rangeland habitat in eastern Santa Clara County, California, and the importance of key habitat features as factors in the presence of turtles in livestock ponds. We found that 12 of the 16 ponds (75%) previously documented to have southwestern pond turtles within the last 15 yrs still supported individuals, while only 1 of 62 ponds (2%) not previously documented as occupied, had turtles, indicating that livestock ponds, especially those known to be occupied, provide important, long-term habitat for this species.

In marine turtles it is well established that the shorter light wavelengths in the visible and near-ultraviolet spectrum provide more potent, and preferred, cues for nocturnal seafinding orientation than the longer light wavelengths. In this study, we simultaneously presented leatherback hatchlings (Dermochelys coriacea) with a short near-ultraviolet (380 nm) and a longer visible (500 nm) light stimulus to determine whether that preference was based upon differences in light intensity, light wavelength, or a combination of both variables. We found that under light conditions mimicking those at the nesting beach on the darkest evenings, the behavioral preference for the shorter light wavelengths was based upon intensity cues, although we speculate that under brighter illumination, wavelength cues might also be utilized.