Nest-site selection and nest size influence the incubation temperature of Morelet's crocodiles

López-Luna, Marco A.; González-Soberano, Jesús; González-Jaurégui, Mauricio; Escobedo-Galván, Armando H.; Suárez-Domínguez, Emilio Alfonso; Rangel-Mendoza, Judith A.; Morales‐Mávil, Jorge É.

doi:10.1016/j.jtherbio.2020.102624

Cited by 7 publications

(7 citation statements)

References 52 publications

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“…Prior to selection of an optimal nesting site nesting females evaluate a variety of parameters such as substrate texture, shadowing, accessibility, distance to water, slope etc. (López‐Luna et al., 2020; Platt et al., 2008; Somaweera & Shine, 2013; Somaweera et al., 2011; Villamarín et al., 2011). Ninety‐five per cent of total nests under SA in 2020 were laid at the two managed sites N4 and N6 compared to only 31% of the total nests laid at N4 in 2019 under VR.…”

Section: Discussionmentioning

confidence: 99%

“…Shaded, vegetated areas had lower soil temperatures compared to open unvegetated sites such as N1 and N4 (Figure 6). This was possibly an outcome of reduced solar irradiation (Charruau, 2012; López‐Luna et al., 2020). However, it must be noted that we recorded substrate temperature at a fixed depth of 60 cm to analyze effects of VR on substrate soil temperature.…”

Section: Discussionmentioning

confidence: 99%

“…Most crocodilians including gharial have incubation temperature‐determined sex determination (TSD; Andrews & Whitaker, 2004; Lang & Andrews, 1994). Nest sites influence the substrate temperatures of crocodilian nests (Bock et al., 2020; Charruau, 2012; López‐Luna et al., 2020). Substrate temperatures in turn determine embryonic development as well as hatchling phenotypes including sex.…”

Section: Discussionmentioning

confidence: 99%

“…Phragmites is an invasive species which has a high tolerance for adverse habitat conditions and is known to invade and dominate freshwater ecosystems worldwide (Eller et al, 2017 6). This was possibly an outcome of reduced solar irradiation (Charruau, 2012;López-Luna et al, 2020). However, it must be noted that we recorded substrate temperature at a fixed depth of 60 cm to analyze effects of VR on substrate soil temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Taken together, the four sites where sand was added totalled less area (5%) in comparison with the area cleared of vegetation, yet these SA sites had approximately six times higher number of nests (nest n = 34) than sites in VR (n = 6). Other operational features comparing SA versus VR are detailed in Table3.F I G U R E 4Note: Unhatched eggs = damaged eggs+ infertile eggs+ embryonic deaths.Abbreviations: SA, sand addition; VR, vegetation removal.Nest-site selection has a critical role in crocodile nesting success.Prior to selection of an optimal nesting site nesting females evaluate a variety of parameters such as substrate texture, shadowing, accessibility, distance to water, slope etc (López-Luna et al, 2020;Platt et al, 2008;Somaweera & Shine, 2013;Somaweera et al, 2011;Villamarín. …”

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confidence: 99%

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Sand addition promotes gharial nesting in a regulated river‐reservoir habitat

Vashistha

Lang

Dhakate

et al. 2021

Ecol Sol and Evidence

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1. The gharial (Gavialis gangeticus) is a critically endangered, long-snouted crocodilian, endemic to the Indian sub-continent. Today, the species' distribution and numbers have reduced by more than 95% in all the large rivers where it was formerly abundant. Living upstream in a reservoir dammed in 1976, the Katerniaghat gharial population has continued to nest along the Girwa River, subject to seasonal flooding in recent decades. In 2010, a natural flood upstream in Nepal resulted in a permanent reduction in the mainstream river flow. As a consequence of reduced flow, the formerly open sand banks and mid-river islands have converted gradually to riverbanks with woody vegetation. Coincident with the increased vegetation growth, gharial nesting sites and nest numbers declined by more than 40% by 2018.2. In an attempt to reverse the observed decline in nesting, we intervened with vegetation removal (VR) in 2019 and sand addition (SA) in 2020, to augment available nesting opportunities at previous and potential nesting locations.3. The number of nests increased with SA (n = 36 in 2020) but decreased with VR (n = 19 in 2019), relative to the prior year without intervention (n = 25 in 2018). Furthermore, hatching success increased significantly to 93% with SA, compared to 63% in VR. Creating an artificial sand bank required approximately one-third work hours and cost much less than removing vegetation. Substrate temperatures in and around nests approximated the viable incubation range (29-33.5 • C) when vegetation is absent, but were lower in sites covered with woody vegetation and/or dense, high grass.4. Our study indicates that gharial will respond favourably to newly created sand banks that provide open, sandy riverside nesting areas, in contrast to cut-over sites with dense vegetation removed.5. Finally, we note that this strategy of augmenting nesting sites is only an interim attempt to solve the 'nesting site' dilemma for the river-adapted gharial. Landscapelevel solutions related to resumption of seasonal flooding, and particularly naturalThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Sand addition promotes gharial nesting in a regulated river‐reservoir habitat

Vashistha

Lang

Dhakate

et al. 2021

Ecol Sol and Evidence

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Geographic Distribution, Habitat, Reproduction, and Conservation Status of Crocodilians in the Americas

Villamarı́n

Escobedo‐Galván

Siroski

et al. 2020

Conservation Genetics of New World Crocodilians

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Nest-site selection influences offspring sex ratio in green turtles, a species with temperature-dependent sex determination

Saura

Jáñez-Escalada

Cordero³

et al. 2022

Climatic Change

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Climate change threatens species with temperature-dependent sex determination as further warming could result in extremely biased sex ratios or offspring of only one sex. Among the possible adaptations of sea turtles to climate change, are behavioral responses toward nesting in cooler areas. We analyzed nesting patterns of East Pacific green turtles (Chelonia mydas) in Costa Rica to determine the occurrence of nest-site selection and how this could influence primary sex ratios (PSR). Green turtles exhibited nest-site repeatability. Nests placed by the same individual were generally closer (mean distance: 237.4 m) than other nests on the beach (mean distance: 411.0 m) and this repeatability was maintained in different nesting seasons. Additionally, turtles tended to place late nests closer to each other than their early nests, suggesting an adjusting nesting behavior throughout the nesting season. A great majority of nests were placed in the vegetation (80.9%) and within this zone, turtles preferred nesting under trees (78%) than in grass areas (28%), where temperatures were cooler and PSR were less female biased. Mean nest temperature (°C) during the thermosensitive period and mean PSR were 30.7 ± 1.2 °C and 79 ± 4%, respectively. Most years were female-biased or extremely female-biased but there was approximately one male-biased year in the decade. Although many nests produced 100% females, some male hatchlings were produced every year, even during the extreme 2015–2016 El Niño event. The preference of green turtles for nesting in shaded areas could help to mitigate the negative impacts of climate change unless temperatures in shaded areas rose above the male producing temperatures.

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Nest-site selection and nest size influence the incubation temperature of Morelet's crocodiles

Cited by 7 publications

References 52 publications

Sand addition promotes gharial nesting in a regulated river‐reservoir habitat

Sand addition promotes gharial nesting in a regulated river‐reservoir habitat

Geographic Distribution, Habitat, Reproduction, and Conservation Status of Crocodilians in the Americas

Nest-site selection influences offspring sex ratio in green turtles, a species with temperature-dependent sex determination

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