Search

We studied the nesting behavior of the pig-nosed turtle, Carettochelys insculpta, in northern Australia. We used remote camera systems and focal observations to test the hypothesis that the nesting behavior in C. insculpta is similar to that of its closest relatives, the softshell turtles (Trionychidae). Carettochelys nested at night, in contrast to diurnal nesting in the majority of softshell turtles. Observations of groups of turtles in the water prior to nesting indicated gregarious or social behavior. On average, gravid turtles emerged around 6 times onto 1-2 beaches spanning 2 nights. Turtles nested at around 2100 ± 3 h, when sand temperatures at nest depth were near their maxima. Minimum air and water temperatures during nesting were 17.5°C and 24.6°C, respectively. Nesting turtles spent an average of 27 min on a beach, similar to softshell turtles but shorter than reported for most other turtle species. Relatively short nesting duration in these species may be caused by the ease in excavating a chamber in sand and the close proximity of nesting areas to water. Overall, the nesting sequence reflected the conservative nesting behavior in turtles, was similar to that of softshells, but differed in subtle ways. Empty nest chambers, commonly referred to in the literature as ''test holes'', were sometimes the result of abandonment resulting from incidental contact between turtles searching for a nest site. [ABSTRACT FROM AUTHOR]

While the effects of climate (long‐term, prevailing weather) on species abundance, range and genetic diversity have been widely studied, short‐term, localized variations in atmospheric conditions (i.e., weather) can also rapidly alter species' geographical ranges and population sizes, but little is known about how they affect genetic diversity. We investigated the relationship between weather and range‐wide genetic diversity in a marsupial, Bettongiagaimardi, using dynamic species distribution models (SDMs). Genetic diversity was lower in parts of the range where the weather‐based SDM predicted high variability in probability of B. gaimardi occurrence during 1950–2009. This is probably an effect of lower population sizes and extinction–recolonization cycles in places with highly variable weather. Spatial variation in genetic diversity was also better predicted by mean probabilities of B. gaimardi occurrence from weather‐ than climate‐based SDMs. Our results illustrate the importance of weather in driving population dynamics and species distributions on decadal timescales and thereby in affecting genetic diversity. Modelling the links between changing weather patterns, species distributions and genetic diversity will allow researchers to better forecast biological impacts of climate change. [ABSTRACT FROM AUTHOR]

Two related aspects of hatchling emergence were studied in a population of pig-nosed turtles (Carettochelys insculpta) in northern Australia. Using emergence phenology data, nest temperatures, historical weather data, and a developmental model, we tested the hypothesis that delayed hatching occurs in C. insculpta, and that such a delay would allow hatchlings to time their emergence to match the onset of the wet season. Carettochelys insculpta hatchlings emerged, on average, 17 days after dates predicted from a developmental model. Combined with observations of hatchlings remaining in eggs until emergence, these results confirmed delayed hatching in nature. This delay was synchronized with initial river rises associated with the onset of wet-season rains, and is consistent with published criteria for embryonic aestivation. On a diel scale, we generated predictions of two potentially competing models of nocturnal emergence in hatchling turtles based on the knowledge that air temperatures decrease with season during the emergence period. A test of these predictions for C. insculpta produced ambiguous results. However, further analysis indicated that C. insculpta, and probably other nocturnally emerging turtle species, respond to a decline in diel temperature rather than to an absolute temperature. The former would ensure nocturnal emergence, while the latter is experienced during the day as well as at night. Nocturnal emergence may be associated with nesting in open microhabitats.Nous avons étudié deux aspects interreliés de l'éclosion chez une population de Tortues palustres (Carettochelys insculpta) du nord de l'Australie. Nous avons utilisé des données sur la phénologie de l'émergence, les températures au nid, les conditions climatiques du passé, ainsi qu'un modèle de développement, pour tester l'hypothèse selon laquelle l'éclosion est tardive chez C. insculpta et qu'un tel retard permet aux petites tortues de synchroniser leur émergence avec le début de la saison humide. Les C. insculpta néonates ont émergé, en moyenne, 17 jours plus tard que prévu par un modèle de développement. Cette émergence tardive, combinée à l'observation de petites tortues restant dans les oeufs jusqu'à l'émergence, confirme l'émergence tardive en nature. Ce retard est synchronisé à la première crue des rivières associée au début de la saison humide et s'accorde avec les critères de la littérature sur l'estivation des embryons. Deux modèles potentiellement opposés ont généré, sur une échelle de 24 h, des prédictions d'une émergence nocturne chez les tortues néonates, tenant compte que les températures saisonnières baissent pendant la période d'émergence. Un test sur ces prédictions a produit des résultats ambigus dans le cas de C. insculpta. Cependant, une analyse subséquente indique que C. insculpta, et probablement aussi d'autres espèces à émergence nocturne, réagit à une chute de température journalière plutôt qu'à une température absolue. La chute journalière de température entraîne une émergence nocturne, alors que la température absolue est subie autant de jour que de nuit. L'émergence nocturne est peut être reliée à la nidification dans des microhabitats ouverts.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]