Short-term gain, long-term loss: How a widely-used conservation tool could further threaten sea turtles

Tomillo, Pilar Santidrián; Wallace, Bryan P.; Paladino, Frank V.; Spotila, James R.; Genovart, Meritxell

doi:10.1016/j.biocon.2021.109260

Cited by 15 publications

(17 citation statements)

References 58 publications

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“…Many natural sea turtle populations are female-biased, ranging from ~50−96% female hatchling production (Mrosovsky 1994, Broderick et al 2000. Feminised populations provide an advantage for sea turtles because egg production is increased, allowing faster population growth through greater reproductive capacity (Miller 1997, Santidrián Tomillo et al 2021. However, in time, highly feminised populations are likely to experience a decrease in reproductive output because of a lack of males (Hawkes et al 2009.…”

Section: Moisture Effects On Nest Temperature and Developmentmentioning

confidence: 99%

Effects of moisture during incubation on green sea turtle (Chelonia mydas) development, morphology and performance

Matthews

Gatto

Reina

2021

Endang. Species. Res.

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While the effect of temperature on embryonic development in sea turtles has been well studied over recent years, our understanding of the effect of substrate moisture, another important environmental variable, is limited. High sand moisture decreases nest temperature through evaporative and direct cooling during rainfall, but its direct effect on hatchling development, morphology and performance is unclear. To address this knowledge gap, we incubated 40 green sea turtle Chelonia mydas clutches in a beach hatchery under either high (~8% v/v) or low (~5% v/v) sand moisture concentrations for the duration of embryonic development. In half of the clutches, temperature sensors were deployed to measure any effect of sand moisture on nest temperature. As hatchlings emerged, we measured body size and locomotory performance during the first 24 h, an important period of frenzied activity for sea turtles. We excavated clutches post-emergence to determine hatching success, emergence success and to determine the stage of embryonic death for unsuccessful eggs. High moisture concentrations increased incubation duration, decreased nest temperature and had marginal effects on hatchling morphology, but no effect on hatching success, stage of embryonic death, crawling speed or initial swimming performance. However, after 24 h of swimming, hatchlings from high-moisture clutches produced less mean swim thrust and spent less time powerstroking than hatchlings from low-moisture clutches, suggesting reduced swimming endurance and potentially impacting the ability of hatchlings to successfully disperse. The effect of moisture on nest temperature and hatchling endurance highlights the importance of considering rainfall patterns when predicting future impacts of climate change on sea turtle populations.

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Section: Moisture Effects On Nest Temperature and Developmentmentioning

confidence: 99%

Effects of moisture during incubation on green sea turtle (Chelonia mydas) development, morphology and performance

Matthews

Gatto

Reina

2021

Endang. Species. Res.

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“…Females are produced at warmer incubation temperatures [16], and so there is concern that climate warming might cause the production of highly female-skewed hatchling cohorts, which could ultimately lead to population extinction [6,17]. In addition, lower hatch success at high incubation temperatures threatens population survival [18][19][20]. Currently across species, most sea turtle nesting beaches around the globe produce hatchling sex ratios that are already heavily female-biased [21].…”

Section: Introductionmentioning

confidence: 99%

Can a present-day thermal niche be preserved in a warming climate by a shift in phenology? A case study with sea turtles

Laloë

Hays

2023

R. Soc. open sci.

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How species respond to climate change may impact their extinction probability. Here we link climatology and ecology to tackle a globally important conservation question. For sea turtles, there are concerns that climate warming will cause both the feminization of populations as well as reduced hatchling survival. For 58 nesting sites across the world spanning all seven sea turtle species, we investigated whether warming might be avoided by shifts in nesting phenology to a cooler part of the year. We show that even with the most extreme phenological shift that has been reported to date—an 18-day advance in nesting per °C increase in sea surface temperature (SST)—temperatures will continue to increase at nesting sites with climate warming. We estimate that SST at nesting sites will rise by an average of 0.6°C (standard deviation = 0.9°C, n = 58) when we model a 1.5°C rise in SST combined with a best-case-scenario shift in nesting. Since sea turtles exhibit temperature-dependent sex determination, these temperature rises could lead to increasingly female-biased sex ratios as well as reduced hatchling production at sites across the world. These findings underscore concerns for the long-term survival of this iconic group.

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“…Although in most places interventions are not needed, in areas where most egg clutches are already incubated in hatcheries due to a number of threats (e.g., high risk of egg poaching or tidal inundation; Chacón-Chaverri and Eckert 2007;Mutalib and Fadzly 2015), PA-PSR and PET could guide management actions. For example, nest shading and irrigation have been proposed to lower nest temperatures and increase hatching success (Hill et al 2015;Jourdan and Fuentes 2015;Lolavar and Wyneken 2021;Smith et al 2021), but this could also reduce the number of female hatchlings and cause population declines in the long term (Santidrián Tomillo et al 2021). Thus, using PET to reach current PA-PSRs would be a better strategy than using the PT to reach equal sex ratios in hatchlings, where the environmental conditions of nests are already being controlled.…”

Section: Discussionmentioning

confidence: 99%

“…Management strategies, such as nest shading and irrigation, have been proposed to mitigate the impact of high temperatures on eggs and hatchlings and PSRs (Hill et al 2015;Jourdan and Fuentes 2015). However, the need to artificially control PSRs is questionable unless the sex ratio of hatchlings reaches extremely female-biased levels (Patrício et al 2021;Santidrián Tomillo et al 2021). Although very useful concept, the pivotal temperature has sometimes been used to assess the occurrence of feminization (DeGregorio and Williard 2011;Tanabe et al 2020).…”

Section: Introductionmentioning

confidence: 99%

When population-advantageous primary sex ratios are female-biased: changing concepts to facilitate climate change management in sea turtles

Tomillo

2022

Climatic Change

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Sea turtles have temperature-dependent sex determination. Because females are produced at high temperatures, increasing global temperature may lead to population feminization. Primary sex ratios (PSR) of sea turtle hatchlings are naturally female-biased, but this translates into a more balanced operational sex ratio because male turtles reproduce more often than females. As a consequence, a balanced PSR and the temperature that produces it (pivotal temperature) are of limited use to guide climate mitigation management because an equal PSR may be demographically suboptimal. Here, I define population-advantageous primary sex ratios (PA-PSR) as the PSR that will tend to be in equilibrium in a population and that will result in balanced operational sex ratios; I then estimate PA-PSR for different reproductive frequencies (years elapsed between reproductive seasons) of adult female and male turtles. I also define population equilibrium temperature (PET) as the temperature that would result in the equilibrium PSR of hatchlings (i.e., PA-PSR). These concepts may help assess the influence of rising temperatures on populations, as they can better indicate if PSRs depart from those at equilibrium. I compared PA-PSR and beach PSR for two populations of sea turtles for which male and female remigration intervals were known and found that a mild or no feminization over the PA-PSR may be occurring. Because PSR varies inter-annually, and hatchlings coming from beaches of different thermal conditions could recruit to the same population, it is critical to estimate beach PSR at the right temporal and spatial scales. Climate mitigation strategies based on these concepts could provide better management guidance for conservation practitioners. Similar approaches could be considered for other female-biased species with temperature-dependent sex determination.

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Short-term gain, long-term loss: How a widely-used conservation tool could further threaten sea turtles

Cited by 15 publications

References 58 publications

Effects of moisture during incubation on green sea turtle (Chelonia mydas) development, morphology and performance

Effects of moisture during incubation on green sea turtle (Chelonia mydas) development, morphology and performance

Can a present-day thermal niche be preserved in a warming climate by a shift in phenology? A case study with sea turtles

When population-advantageous primary sex ratios are female-biased: changing concepts to facilitate climate change management in sea turtles

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