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Animals that hatch within a subterranean nest, such as turtle hatchlings, expend some of their limited energy reserves digging out through sand or soil to reach the surface. In sea turtles, this emergence process can take the hatchlings 3–7 days. However, we have a poor understanding of this process as it is difficult to observe what is occurring underground. Here, we utilize a novel method to characterize digging-out behaviour: affixing an accelerometer directly to newly hatched green turtles (Chelonia mydas) to record movement until nest emergence. Our data revealed that buried hatchlings maintained a head-up orientation but did not move in the expected left and right swaying motion associated with alternating limb crawling. Rather, they moved using dorsal–ventral heaving and pitching as if swimming vertically through the sand to the surface. Movement activity was irregular and brief, interspersed by many short periods of inactivity, mostly lasting less than 10 min. The first 24 h of head-up activity displayed no diel patterns, but the last 24 h prior to emergence involved more intense movement during night-time hours compared with daytime hours. Thus, our results add valuable new insight, and in some cases change previous assumptions, regarding the digging behaviours during the egg-to-emergence life stage in sea turtles. [ABSTRACT FROM AUTHOR]

Projection models are being increasingly used to manage threatened taxa by estimating their responses to climate change. Sea turtles are particularly susceptible to climate change as they have temperature‐dependent sex determination and increased sand temperatures on nesting beaches could result in the 'feminisation' of hatchling sex ratios for some populations. This study modelled likely long‐term trends in sand temperatures and hatchling sex ratios at an equatorial nesting site for endangered green turtles (Chelonia mydas) and critically endangered hawksbill turtles (Eretmochelys imbricata). A total of 1078 days of sand temperature data were collected from 28 logger deployments at nest depth between 2018 and 2022 in Papua New Guinea (PNG). Long‐term trends in sand temperature were generated from a model using air temperature as an environmental proxy. The influence of rainfall and seasonal variation on sand temperature was also investigated. Between 1960 and 2019, we estimated that sand temperature increased by ~0.6°C and the average hatchling sex ratio was relatively balanced (46.2% female, SD = 10.7). No trends were observed in historical rainfall anomalies and projections indicated no further changes to rainfall until 2100. Therefore, the sex ratio models were unlikely to be influenced by changing rainfall patterns. A relatively balanced sex ratio such as this is starkly different to the extremely female‐skewed hatchling sex ratio (>99% female) reported for another Coral Sea nesting site, Raine Island (~850 km West). This PNG nesting site is likely rare in the global context, as it is less threatened by climate‐induced feminisation. Although there is no current need for 'cooling' interventions, the mean projected sex ratios for 2020–2100 were estimated 76%–87% female, so future interventions may be required to increase male production. Our use of long‐term sand temperature and rainfall trends has advanced our understanding of climate change impacts on sea turtles. [ABSTRACT FROM AUTHOR]

In the past two decades, stable isotope analysis (SIA) has been increasingly used to infer dietary ecology and habitat use in sea turtles. Tissue samples for SIA are often collected from adult females during a nesting event because turtles are easily accessible then. However, this sampling opportunity can be easily missed, or the female may be disturbed during the nesting event and abandon nest construction. The current research assessed the relationships of carbon and nitrogen stable isotope values between mothers, and their eggs and hatchlings of loggerhead turtles Caretta caretta to evaluate the accuracy of using eggs or hatchlings in inferring the mothers' stable isotope values. Whole blood and epidermis from mothers (n = 5), yolk, albumen and shell in their eggs (n = 5 per female) and epidermis, whole blood, liver, muscle and residual yolks in their hatchlings (n = 5 for 3 females) were collected from loggerhead turtles in the 2012/2013 nesting season at Mon Repos sea turtle rookery (24°47'46'S; 152°26'26'E), in South East Queensland, Australia. The effect of lipid extraction on isotopic values in sampled tissues was also evaluated. Lipid extraction had a significant effect on [delta].sup.13C values for egg yolk, residual yolk and liver, but also altered [delta].sup.15N values for these tissues. Significant correlations were found between adult tissues and both their egg-yolk and hatchling tissues. Isotopic values of fresh egg yolk sampled straight after oviposition and residual yolk internalized by hatchlings at hatching were similar, implying that the stable isotope values of yolk remains unchanged throughout embryonic development. Stable isotope values were distinct between different tissues sampled from the same hatchling. With the caution that our results are based on a small sample size (n = 3), they support the method of sampling hatchlings, or eggs, rather than nesting females, to infer information about the feeding habits and migratory patterns of nesting turtle populations., Author(s): Alice S. Carpentier[sup.1] , David T. Booth[sup.1] , Karen E. Arthur[sup.2] , Colin J. Limpus[sup.3] Author Affiliations: (1) School of Biological Sciences, The University of Queensland, 4072, Brisbane, Queensland, [...]

Raine Island, the world's largest green turtle nesting location, has low nest hatching success. The main causes of this low hatching success are thought to be nest destruction by subsequent nesting females, and inundation of nests during high tides and storm surges. But even nests that are protected from nest destruction and inundation appear to have relatively low hatching success, with most of the embryo mortality occurring early in incubation. Here, I compare hatching success and developmental phase of embryo death of protected 'dry' nests from Raine Island (RI) with similar nests from Heron Island (HI), a nesting location previously reported as having high hatching success. Nests at both sites were sampled close to the peak time of nesting (December). Twenty-eight nests were sampled at RI and 14 nests at HI. Nest temperatures were cooler during the first week of incubation at HI (median 26.9°C) than at RI (median 30.1°C), but three-days-in-a-row maximum nest temperatures were higher at HI (median 36.0°C) than at RI (median 33.5°C). I found the hatching success of sampled nests at both locations was similar, ~70%, but most embryo death occurred early in incubation at RI (median 16.5%) compared to HI (median 3.8%), but late in incubation at HI (median 4.9%) compared to RI (median 0.2%). Undisturbed, 'dry' green turtle nests on Raine Island and Heron Island have similar hatching success ~70%; however, most embryo mortality occurs early during incubation at Raine Island but late during incubation at Heron Island. A nest on Heron Island has been excavated to assess hatching success. Photograph by David Booth. [ABSTRACT FROM AUTHOR]

In numerous laboratory experiments involving the incubation of reptile eggs, both the maternal origin of eggs and the incubating environment (nest effect) have been demonstrated to influence hatchling phenotype. Although different hatchling phenotypes have been reported from natural nests, the separate effects of maternal origin and nest on hatchling phenotype in natural nests have not been demonstrated because in natural nests the two effects are confounded with each other. Here, we use a split clutch design to experimentally separate nest effects from maternal origin effects in field nests of green turtles (Chelonia mydas). We found both maternal origin and nest to influence hatchling morphology and locomotor performance in some but not all field nests. By using egg mass (maternal origin effect) and nest temperature (nest effect) in multiple regression analysis, we found maternal origin had a greater influence than nest temperature on the morphological attributes of hatchling mass and carapace size, but nest temperature had a greater influence than maternal origin on the performance attributes of self-righting time, self-righting propensity, swim thrust during the first 30 min of swimming, and power stroke rate during the first 30 min of swimming., Introduction Female sea turtles are large reptiles that typically produce multiple clutches of 50-150 eggs per clutch in a single breeding season (Spotila 2004). Each clutch is buried in sand [...]