Experimental assessment of the effects of moisture on loggerhead sea turtle hatchling sex ratios.
TL;DR: The hypothesis that moisture impacts sex ratios through evaporation and rainfall-based cooling is supported, highlighting the importance of examining other nest environmental factors on sex determination.
About: This article is published in Zoology.The article was published on 2017-08-01. It has received 42 citations till now. The article focuses on the topics: Environmental sex determination & Temperature-dependent sex determination.
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TL;DR: A review of the most recent literature on this topic can be found in this article, highlighting knowledge gains and research gaps since a similar previous review in 2009, and suggesting a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of femalebiased sex ratios and reduced male production, assessment of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds.
Abstract: Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.
54 citations
Cites background from "Experimental assessment of the effe..."
...This is likely due to evaporative cooling (Lolavar & Wyneken 2017, 2020); further studies will allow us to clarify the mechanism behind these observations, as this is a major avenue for future research (Sifuentes-Romero et al. 2018)....
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...Additionally, this threshold seems to depend on the duration over which the eggs are subjected to high temperatures, and it can be modulated by rainfall and nest humidity (Lolavar & Wyneken 2017)....
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...A different study suggested that loggerhead turtles may not be able to track current precipitation conditions (Almpanidou et al. 2018), known to also impact hatching success (Santidrián Tomillo et al. 2015b, Montero et al. 2018a) and primary sex ratio (Lolavar & Wyneken 2017, 2020)....
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TL;DR: Evidence is presented for an additional, novel process that is called isolation by navigation, in which the navigational mechanism used by a long-distance migrant influences population structure independently of isolation by either distance or environment.
37 citations
TL;DR: Results from natural nests and simulations show that the approximation of the thermosensitive period for sex determination to the middle third of incubation duration may create a quasi-systematic bias to lower temperatures when computing the average incubation temperature during this period and thus a male-bias for sex ratio estimate.
36 citations
TL;DR: How moisture may change the incubation conditions inside nests by changing the temperature experienced by eggs, which affects development, growth and sex ratios is shown.
27 citations
Cites background from "Experimental assessment of the effe..."
...This observation and laboratory experiments (Lolavar and Wyneken, 2015; Lolavar and Wyneken, 2017), suggest that moisture influences sex determination and hence sex ratios....
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TL;DR: In this article, the authors address the nest-to-surf data gap for Florida's east coast nesting assemblages of loggerhead sea turtles (Caretta caretta).
Abstract: Sea turtles are vulnerable immediately after emerging from nests and before they reach the surf. Mortality rates during this brief period are largely unknown. Many sea turtle monitoring programs measure hatchling production from nest inventories. These inventories rarely account for post-emergence mortality, leaving an unknown bias in hatchling production estimates. This study addresses the nest-to-surf data gap for Florida’s east coast nesting assemblages of loggerhead sea turtles (Caretta caretta). Five locations were surveyed during the 2016-nesting season. Across all beaches, 7.6% of the observed hatchlings did not survive to reach the water. Mortality sources varied by location. Observed predators include: mammals, birds, and crabs. Hatchling disorientation and misorientation due to photopollution occurred more frequently in urban areas than natural areas. Factors identified as important in hatchling mortality included numbers of hatchlings emerging, nest-to-surf distance, and level of urbanization. The results of this study may help sea turtle nesting managers address nest-to-surf mortality and improve hatchling production estimates.
25 citations
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01 Jan 1984
4,197 citations
"Experimental assessment of the effe..." refers methods in this paper
...Results The overall hatch success of all incubators ([# live hatchlings/# ggs] × 100) was 88.5% (Table 1) and did not differ among incuators (ANOVA F2,45 = 0.90, p > 0.05)....
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...After verifying that the data were normally distributed and ariances were similar, environmental conditions were compared y one-way ANOVA (Zar, 2010)....
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...Incubation durations ranged from 52 to 68 d (Table 1) and difered among incubators (ANOVA F2,45 = 57.61, p 0.001)....
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...Nest box temperatures did not differ among the three incubators (ANOVA F2,45 = 2.42, p > 0.05)....
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TL;DR: A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5 and the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade.
Abstract: We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade.
2,989 citations
TL;DR: The years 1995 to 2000 experienced the highest level of North Atlantic hurricane activity in the reliable record, and the present high level of hurricane activity is likely to persist for an additional ∼10 to 40 years.
Abstract: The years 1995 to 2000 experienced the highest level of North Atlantic hurricane activity in the reliable record. Compared with the generally low activity of the previous 24 years (1971 to 1994), the past 6 years have seen a doubling of overall activity for the whole basin, a 2.5-fold increase in major hurricanes (>/=50 meters per second), and a fivefold increase in hurricanes affecting the Caribbean. The greater activity results from simultaneous increases in North Atlantic sea-surface temperatures and decreases in vertical wind shear. Because these changes exhibit a multidecadal time scale, the present high level of hurricane activity is likely to persist for an additional approximately 10 to 40 years. The shift in climate calls for a reevaluation of preparedness and mitigation strategies.
1,601 citations
TL;DR: Temperature-dependent sex determination (TSD) is common in turtles and has been reported in two lizards and alligators; however, data on TSD are available for few non-turtle species and an attempt is made to deduce their ancestries.
Abstract: Two factors in reptile sex determination have been studied: (1) the presence or absence of heteromorphic sex chromosomes, and (2) the influence of temperature. Recognizable sex chromosomes are common in snakes and lizards, but are apparently rare in turtles and absent in crocodilians and the tuatara. Temperature-dependent sex determination (TSD) is common in turtles and has been reported in two lizards and alligators; however, data on TSD are available for few non-turtle species. Present findings on TSD suggest that (1) temperature actually determines sex rather than simply causing differential mortality, and (2) temperature controls sex determination in nature as well as in the laboratory. Only one study, however, has convincingly demonstrated the latter. Sex determination by nest temperature is proposed to interfere with the evolution of sex chromosomes and live-bearing (ovoviviparity); a negative correlation should thus be observed between TSD and sex chromosomes/live-bearing. Present evidence is consi...
728 citations
"Experimental assessment of the effe..." refers background in this paper
...Temperature-dependent sex determination (TSD), a form of ESD, is found among many turtle species, crocodilians, some lizard species, and tuataras (Bull, 1980; Valenzuela, 2004)....
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...All sea turtle species have a cooler male/warmer female TSD system (Bull, 1980; Miller and Limpus, 1981; Standora and Spotila, 1985; Pieau et al., 1995)....
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TL;DR: This article reviewed the data from peer-reviewed publications to assess the likely impacts of climate change on marine turtles and highlight the types of data that would be most useful for an accurate assessment of future effects.
Abstract: Marine turtles occupy a wide range of terrestrial and marine habitats, and many aspects of their life history have been demonstrated to be closely tied to climatic variables such as ambient temperature and storminess. As a group, therefore, marine turtles may be good indicators of climate change effects on coastal and marine habitats. Despite the small number of species in the taxon and a growing body of research in the field, the evidence base to predict resultant impacts of climate change remains relatively poor. We review the data from peer-reviewed publications to assess the likely impacts of climate change on marine turtles and highlight the types of data that would be most useful for an accurate assessment of future effects. The cumulative indications from these previous studies indicate that future research should focus on: (1) climate change effects on key habitats upon which turtles depend; (2) factors that influence nest site selection; (3) the consequences of skewed primary sex ratios; and (4) the effect of climate change on turtles at sea, for example range shifts and dietary breadth. Although it is too early to give detailed management recommendations, careful protection of coastlines along which turtles nest should be considered, as should the protection of beaches that produce male hatchlings, which may be of increased importance in the future. More active management approaches, for example translocation of eggs to suitable yet vacant nesting beaches, may be necessary to consider under worst-case scenarios.
377 citations
"Experimental assessment of the effe..." refers background in this paper
...Global climate change is onsidered a threat to sea turtle sex ratios (Hawkes et al., 2009; ulin et al., 2009; Poloczanska et al., 2009; Jourdan and Fuentes, 015)....
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