Survival rates of juvenile reptiles are critical population parameters but are difficult to obtain through mark-recapture programs because these small, secretive animals are rarely caught. This scarcity has encouraged speculation that survival rates of juveniles are very low, and we test this prediction by estimating juvenile survival rates indirectly. A simple mathematical model calculates the annual juvenile survival rate needed to maintain a stable population size, using published data on adult survival rates, reproductive output, and ages at maturity in 109 reptile populations encompassing 57 species. Counter to prediction, estimated juvenile survival rates were relatively high (on average, only about 13% less than those of conspecific adults) and highly correlated with adult survival rates. Overall, survival rates during both juvenile and adult life were higher in turtles than in snakes, and higher in snakes than in lizards. As predicted from life history theory, rates of juvenile survival were higher in species that produce large offspring, and higher in viviparous squamates than in oviparous species. Our analyses challenge the widely held belief that juvenile reptiles have low rates of annual survival and suggest instead that sampling problems and the elusive biology of juvenile reptiles have misled researchers in this respect.

Rates of growth and reproduction of the pathogens that cause emerging infectious diseases can be affected by local environmental conditions; these conditions can thus influence the strength and nature of disease outbreaks. An understanding of these relationships is important for understanding disease ecology and developing mitigation strategies. Widespread emergence of the fungal disease chytridiomycosis has had devastating effects on amphibian populations. The causative pathogen, Batrachochytriumdendrobatidis (Bd), is sensitive to temperature, but its thermal tolerances are not well studied. We examined the thermal responses of three Bd isolates collected across a latitudinal gradient in eastern Australia. Temperature affected all aspects of Bd growth and reproduction that we measured, in ways that often differed among Bd isolates. Aspects of growth, reproduction, and their relationships to temperature that differed among isolates included upper thermal maxima for growth (26, 27, or 28°C, depending on the isolate), relationships between zoospore production and temperature, and zoospore activity and temperature. Two isolates decreased zoospore production as temperature increased, whereas the third isolate was less fecund overall, but did not show a strong response to temperature until reaching the upper limit of its thermal tolerance. Our results show differentiation in life-history traits among isolates within Australia, suggesting that the pathogen may exhibit local adaptation. An understanding of how environmental temperatures can limit pathogens by constraining fitness will enhance our ability to assess pathogen dynamics in the field, model pathogen spread, and conduct realistic experiments on host susceptibility and disease transmission.

Developing sea turtle embryos only successfully hatch within a relatively narrow temperature range, rendering this immobile life stage vulnerable to the vagaries of climate change. To accurately predict the potential impact of climate change on sea turtle egg mortality, we need to fully understand the thermal tolerance of developing embryos. We reviewed the literature on this topic, and found that published studies interpret the primary literature and subsequent reviews very differently. Based on early literature reviews, the maximum thermal tolerance of sea turtle embryos is frequently cited as either 33 or 35°C. In many sea turtle populations, however, nest temperatures often exceed 35°C by up to several degrees (usually just prior to hatchling emergence) and eggs still hatch successfully. Mean incubation temperatures up to 35°C generally produce hatchlings, although leatherback and olive ridley turtle embryos may be less tolerant of high incubation temperatures than green and loggerhead turtle embryos. Sea turtle embryos are likely to be more sensitive to the duration of time spent at potentially stressful temperatures than to the temperature alone. To complicate matters, developing embryos may change their thermal tolerance as they grow. Overall, we are only beginning to understand how exposure to high temperatures experienced in the field influences embryonic development and hatchling production. This knowledge gap is hampering our ability to predict the impacts of climate change on sea turtle populations, and future work should focus on understanding how temperature and other climatic variables influence embryonic development and, thus, crucial population attributes such as hatchling production.

Aim To understand whether climate limits current sea turtle nesting distributions and shapes the ecological niche of the terrestrial life‐history stage of these wide‐ranging marine vertebrates. Location Coastlines world‐wide. Methods I predicted the spatial distributions of nesting habitat under current climatic conditions for seven sea turtle species using information criteria and maximum entropy modelling. I also compared niche similarity among species using three niche metrics: I, Schoener's D and relative rank. Results Sea turtles currently nest across their entire bioclimatic envelopes, with up to six species predicted to nest on a single beach. The Caribbean Sea, Gulf of Mexico and Australasia support high nesting diversity, with most regional areas supporting three to five species. Despite large overlap in nesting distributions among species, loggerhead and green turtles have the broadest environmental niches, while Kemp's ridley and flatback turtles have very narrow niches. Main conclusions The terrestrial nesting habitat of sea turtles is characterized by distinct climatic conditions, which are linked to the physical conditions necessary for eggs to hatch successfully and allow hatchlings to disperse from natal areas. Despite broad geographic patterns of overlap and similar embryonic tolerances to temperature and moisture among species, sea turtles partition habitat by nesting in different niche spaces. The tight link between current geographic patterns of nesting and climate, along with the dependence of developing embryos on nest microclimate, imply that regional or global changes in environmental conditions could differentially influence the distribution of sea turtle species under climate change. This could influence the adaptive potential of different populations, and predicting these responses before they occur will be important in mitigating the effects of climate change.

Severe climatic events affect all species, but there is little quantitative knowledge of how sympatric species react to such situations. We compared the reproductive seasonality of sea turtles that nest sympatrically with their vulnerability to tropical cyclones (in this study, "tropical cyclone" refers to tropical storms and hurricanes), which are increasing in severity due to changes in global climate. Storm surges significantly decreased reproductive output by lowering the number of nests that hatched and the number of hatchlings that emerged from nests, but the severity of this effect varied by species. Leatherback turtles (Dermochelys coriacea) began nesting earliest and most offspring hatched before the tropical cyclone season arrived, resulting in little negative effect. Loggerhead turtles (Caretta caretta) nested intermediately, and only nests laid late in the season were inundated with seawater during storm surges. Green turtles (Chelonia mydas) nested last, and their entire nesting season occurred during the tropical cyclone season; this resulted in a majority (79%) of green turtle nests incubating in September, when tropical cyclones are most likely to occur. Since this timing overlaps considerably with the tropical cyclone season, the developing eggs and nests are extremely vulnerable to storm surges. Increases in the severity of tropical cyclones may cause green turtle nesting success to worsen in the future. However, published literature suggests that loggerhead turtles are nesting earlier in the season and shortening their nesting seasons in response to increasing sea surface temperatures caused by global climate change. This may cause loggerhead reproductive success to improve in the future because more nests will hatch before the onset of tropical cyclones. Our data clearly indicate that sympatric species using the same resources are affected differently by tropical cyclones due to slight variations in the seasonal timing of nesting, a key life history process.