The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Graeme C Hays - One of the best experts on this subject based on the ideXlab platform.
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flipper beat frequency and amplitude changes in diving green turtles Chelonia mydas
Marine Biology, 2007Co-Authors: Graeme C Hays, Greg J Marshall, Jeff A SeminoffAbstract:Using a turtle-borne camera system, changing flipper beat frequency and amplitude were measured in five diving green turtles (Chelonia mydas Linnaeus 1758) in the Bahia de los Angeles, Mexico (28°58′N, 113°33′W). These observations were made between June and August 2002. Turtles worked hardest (i.e., had the highest flipper beat frequency and amplitude) at the start of descents when positive buoyancy is predicted to oppose their forward motion. During the later part of descents, turtles worked less hard in line with opposing buoyancy forces being reduced. For example, flipper beat frequency declined from about 60–80 beats min−1 at the start of descent to around 25–40 beats min−1 after 30 s of the descent. At the start of ascents the flipper beat frequency was around 30 beats min−1, lower than on descent, and declined as the ascent progressed with often passive gliding for the final few meters to the surface. This pattern of effort during diving appears to apply across a range of marine reptiles, birds and mammals suggesting that graded effort during descent and ascent is an optimum solution to minimising the cost of transport during diving.
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patterns in the emergence of green Chelonia mydas and loggerhead caretta caretta turtle hatchlings from their nests
Marine Biology, 2005Co-Authors: F Glen, Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:The emergence patterns of both green (Chelonia mydas) and loggerhead (Caretta caretta) turtle hatchlings were observed in great detail over three seasons at Alagadi beach, northern Cyprus. In total, 38 green turtle and 50 loggerhead turtle nests were monitored, accounting for the emergence of 2,807 and 2,259 hatchlings, respectively. We quantified these emergences into 397 green turtle and 302 loggerhead turtle emergence groups. Overall, 85.0% of green turtle and 79.5% of loggerhead turtle groups emerged at night; these accounted for 85.5 and 90.8% of hatchlings, respectively. The remaining emergences were dispersed throughout the day for green turtle nests but confined to the morning in loggerhead turtle nests. Hatchling emergence from individual nests occurred over periods of between 1 and 7 nights, with most hatchlings typically emerging on the first night. Group sizes of green turtles emerging during the day were significantly smaller than those emerging at night. Hatchlings of both species that emerged from nests during the day had longer emergence durations than those that emerged from nests at night only.
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multiple paternity assessed using microsatellite markers in green turtles Chelonia mydas linnaeus 1758 of ascension island south atlantic
Journal of Experimental Marine Biology and Ecology, 2003Co-Authors: J S Ireland, Fyten Glen, Patricia L M Lee, Annette C Broderick, Graeme C Hays, Brendan J Godley, David O F SkibinskiAbstract:Paternity was determined for three clutches and up to 20 offspring per clutch in the green turtle (Chelonia mydas) from Ascension Island, South Atlantic, using microsatellite markers. All three clutches were sired by at least two different males. The results were compared with those of previous studies of multiple paternity in turtles. No significant difference among studies was observed in the mean contribution of the males siring the largest proportion of progeny per clutch. The present study also provides evidence for segregation distortion (meiotic drive) in turtles.
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testing the navigational abilities of ocean migrants displacement experiments on green sea turtles Chelonia mydas
Behavioral Ecology and Sociobiology, 2001Co-Authors: Paolo Luschi, Annette C Broderick, Brendan J Godley, Susanne Akesson, F Glen, Floriano Papi, Graeme C HaysAbstract:Like many animals migrating through the oceans, sea turtles face difficult navigational tasks when they have to reach distant, specific sites. The paradigmatic case of Brazilian green turtles (Chelonia mydas), which nest on the tiny Ascension Island in the middle of the Atlantic Ocean, has often been the subject of hypotheses concerning their navigational mechanisms. To investigate their nature, we displaced 18 females from Ascension and tracked them by satellite after release from eight different points in the ocean, 60–450 km away from the island. Four turtles moved to Brazil soon after the release, 4 moved in various directions before heading to Brazil, and 10 reached the island. All the successful trips, bar 1, were winding but ended with a final straight segment of variable length, as if the turtles were searching for a sensory contact with the island which they obtained at various distances. The approach to Ascension mostly occurred from the direction opposite to the trade wind, suggesting a navigational role of wind-borne information originating from the island.
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metabolic heating and the prediction of sex ratios for green turtles Chelonia mydas
Physiological and Biochemical Zoology, 2001Co-Authors: Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:We compared incubation temperatures in nests (n=32) of the green turtle (Chelonia mydas) on Ascension Island in relation to sand temperatures of control sites at nest depth. Intrabeach thermal variation was low, whereas interbeach thermal variation was high in both control and nest sites. A marked rise in temperature was recorded in nests from 30% to 40% of the way through the incubation period and attributed to metabolic heating. Over the entire incubation period, metabolic heating accounted for a mean rise in temperature of between 0.07 degrees and 2.86 degrees C within nests. During the middle third of incubation, when sex is thought to be determined, this rise in temperature ranged between 0.07 degrees and 2.61 degrees C. Metabolic heating was related to both the number of eggs laid and the total number of hatchlings/embryos produced in a clutch. For 32 clutches in which temperature was recorded, we estimate that metabolic heating accounted for a rise of up to 30% in the proportion of females produced within different clutches. Previous studies have dismissed any effect of metabolic heating on the sex ratio of marine turtle hatchlings. Our results imply that metabolic heating needs to be considered when estimating green turtle hatchling sex ratios.
Brendan J Godley - One of the best experts on this subject based on the ideXlab platform.
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patterns in the emergence of green Chelonia mydas and loggerhead caretta caretta turtle hatchlings from their nests
Marine Biology, 2005Co-Authors: F Glen, Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:The emergence patterns of both green (Chelonia mydas) and loggerhead (Caretta caretta) turtle hatchlings were observed in great detail over three seasons at Alagadi beach, northern Cyprus. In total, 38 green turtle and 50 loggerhead turtle nests were monitored, accounting for the emergence of 2,807 and 2,259 hatchlings, respectively. We quantified these emergences into 397 green turtle and 302 loggerhead turtle emergence groups. Overall, 85.0% of green turtle and 79.5% of loggerhead turtle groups emerged at night; these accounted for 85.5 and 90.8% of hatchlings, respectively. The remaining emergences were dispersed throughout the day for green turtle nests but confined to the morning in loggerhead turtle nests. Hatchling emergence from individual nests occurred over periods of between 1 and 7 nights, with most hatchlings typically emerging on the first night. Group sizes of green turtles emerging during the day were significantly smaller than those emerging at night. Hatchlings of both species that emerged from nests during the day had longer emergence durations than those that emerged from nests at night only.
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multiple paternity assessed using microsatellite markers in green turtles Chelonia mydas linnaeus 1758 of ascension island south atlantic
Journal of Experimental Marine Biology and Ecology, 2003Co-Authors: J S Ireland, Fyten Glen, Patricia L M Lee, Annette C Broderick, Graeme C Hays, Brendan J Godley, David O F SkibinskiAbstract:Paternity was determined for three clutches and up to 20 offspring per clutch in the green turtle (Chelonia mydas) from Ascension Island, South Atlantic, using microsatellite markers. All three clutches were sired by at least two different males. The results were compared with those of previous studies of multiple paternity in turtles. No significant difference among studies was observed in the mean contribution of the males siring the largest proportion of progeny per clutch. The present study also provides evidence for segregation distortion (meiotic drive) in turtles.
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testing the navigational abilities of ocean migrants displacement experiments on green sea turtles Chelonia mydas
Behavioral Ecology and Sociobiology, 2001Co-Authors: Paolo Luschi, Annette C Broderick, Brendan J Godley, Susanne Akesson, F Glen, Floriano Papi, Graeme C HaysAbstract:Like many animals migrating through the oceans, sea turtles face difficult navigational tasks when they have to reach distant, specific sites. The paradigmatic case of Brazilian green turtles (Chelonia mydas), which nest on the tiny Ascension Island in the middle of the Atlantic Ocean, has often been the subject of hypotheses concerning their navigational mechanisms. To investigate their nature, we displaced 18 females from Ascension and tracked them by satellite after release from eight different points in the ocean, 60–450 km away from the island. Four turtles moved to Brazil soon after the release, 4 moved in various directions before heading to Brazil, and 10 reached the island. All the successful trips, bar 1, were winding but ended with a final straight segment of variable length, as if the turtles were searching for a sensory contact with the island which they obtained at various distances. The approach to Ascension mostly occurred from the direction opposite to the trade wind, suggesting a navigational role of wind-borne information originating from the island.
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metabolic heating and the prediction of sex ratios for green turtles Chelonia mydas
Physiological and Biochemical Zoology, 2001Co-Authors: Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:We compared incubation temperatures in nests (n=32) of the green turtle (Chelonia mydas) on Ascension Island in relation to sand temperatures of control sites at nest depth. Intrabeach thermal variation was low, whereas interbeach thermal variation was high in both control and nest sites. A marked rise in temperature was recorded in nests from 30% to 40% of the way through the incubation period and attributed to metabolic heating. Over the entire incubation period, metabolic heating accounted for a mean rise in temperature of between 0.07 degrees and 2.86 degrees C within nests. During the middle third of incubation, when sex is thought to be determined, this rise in temperature ranged between 0.07 degrees and 2.61 degrees C. Metabolic heating was related to both the number of eggs laid and the total number of hatchlings/embryos produced in a clutch. For 32 clutches in which temperature was recorded, we estimate that metabolic heating accounted for a rise of up to 30% in the proportion of females produced within different clutches. Previous studies have dismissed any effect of metabolic heating on the sex ratio of marine turtle hatchlings. Our results imply that metabolic heating needs to be considered when estimating green turtle hatchling sex ratios.
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Nesting of green turtles (Chelonia mydas) at Ascension Island, South Atlantic
Biological Conservation, 2001Co-Authors: Brendan J Godley, Annette C Broderick, Graeme C HaysAbstract:Abstract A detailed survey of the nesting by green turtles ( Chelonia mydas ) on Ascension Island (7°57′ S, 14°22′ W) was conducted between 1 December 1998 and 1 October 1999. During this period there was a total estimate of 36,036 marine turtle nesting activities, resulting in the deposition of an estimated 13,881 clutches (95% confidence limits 13,092–14,660). These data suggest that 2–3 times more turtles nested than when previous detailed surveys were undertaken in the 1970′s. The peak of nesting was in March, with 95% of nesting activity being recorded between 4 January and 18 May. Possible reasons for the evolution of the seasonality of nesting are discussed. Individual beaches varied greatly in density of nesting activities (range=534–10,001 activities/km; mean=6204 activities/km), density of nests (range=213–5200 nests/km; mean=2390 nests/km) and the proportion of nesting activities resulting in nests (nesting success; range=0.13–0.52; mean=0.39).
Annette C Broderick - One of the best experts on this subject based on the ideXlab platform.
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Diet-related selectivity of macroplastic ingestion in green turtles (Chelonia mydas) in the eastern Mediterranean
Scientific Reports, 2019Co-Authors: Emily M. Duncan, Jessica A. Arrowsmith, Charlotte E. Bain, Hannah Bowdery, Tierney Chalmers, Wayne J. Fuller, Jonathon H. Lee, Annette C Broderick, Tamara S. Galloway, Penelope K. LindequeAbstract:Understanding the drivers of key interactions between marine vertebrates and plastic pollution is now considered a research priority. Sea turtles are primarily visual predators, with the ability to discriminate according to colour and shape; therefore these factors play a role in feeding choices. Classification methodologies of ingested plastic currently do not record these variables, however here, refined protocols allow us to test the hypothesis that plastic is selectively ingested when it resembles the food items of green turtles ( Chelonia mydas ). Turtles in the eastern Mediterranean displayed strong diet-related selectivity towards certain types (sheet and threadlike), colours (black, clear and green) and shapes (linear items strongly preferred) of plastic when compared to the environmental baseline of plastic beach debris. There was a significant negative relationship between size of turtle (curved carapace length) and number/mass of plastic pieces ingested, which may be explained through naivety and/or ontogenetic shifts in diet. Further investigation in other species and sites are needed to more fully ascertain the role of selectivity in plastic ingestion in this marine vertebrate group.
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patterns in the emergence of green Chelonia mydas and loggerhead caretta caretta turtle hatchlings from their nests
Marine Biology, 2005Co-Authors: F Glen, Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:The emergence patterns of both green (Chelonia mydas) and loggerhead (Caretta caretta) turtle hatchlings were observed in great detail over three seasons at Alagadi beach, northern Cyprus. In total, 38 green turtle and 50 loggerhead turtle nests were monitored, accounting for the emergence of 2,807 and 2,259 hatchlings, respectively. We quantified these emergences into 397 green turtle and 302 loggerhead turtle emergence groups. Overall, 85.0% of green turtle and 79.5% of loggerhead turtle groups emerged at night; these accounted for 85.5 and 90.8% of hatchlings, respectively. The remaining emergences were dispersed throughout the day for green turtle nests but confined to the morning in loggerhead turtle nests. Hatchling emergence from individual nests occurred over periods of between 1 and 7 nights, with most hatchlings typically emerging on the first night. Group sizes of green turtles emerging during the day were significantly smaller than those emerging at night. Hatchlings of both species that emerged from nests during the day had longer emergence durations than those that emerged from nests at night only.
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multiple paternity assessed using microsatellite markers in green turtles Chelonia mydas linnaeus 1758 of ascension island south atlantic
Journal of Experimental Marine Biology and Ecology, 2003Co-Authors: J S Ireland, Fyten Glen, Patricia L M Lee, Annette C Broderick, Graeme C Hays, Brendan J Godley, David O F SkibinskiAbstract:Paternity was determined for three clutches and up to 20 offspring per clutch in the green turtle (Chelonia mydas) from Ascension Island, South Atlantic, using microsatellite markers. All three clutches were sired by at least two different males. The results were compared with those of previous studies of multiple paternity in turtles. No significant difference among studies was observed in the mean contribution of the males siring the largest proportion of progeny per clutch. The present study also provides evidence for segregation distortion (meiotic drive) in turtles.
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testing the navigational abilities of ocean migrants displacement experiments on green sea turtles Chelonia mydas
Behavioral Ecology and Sociobiology, 2001Co-Authors: Paolo Luschi, Annette C Broderick, Brendan J Godley, Susanne Akesson, F Glen, Floriano Papi, Graeme C HaysAbstract:Like many animals migrating through the oceans, sea turtles face difficult navigational tasks when they have to reach distant, specific sites. The paradigmatic case of Brazilian green turtles (Chelonia mydas), which nest on the tiny Ascension Island in the middle of the Atlantic Ocean, has often been the subject of hypotheses concerning their navigational mechanisms. To investigate their nature, we displaced 18 females from Ascension and tracked them by satellite after release from eight different points in the ocean, 60–450 km away from the island. Four turtles moved to Brazil soon after the release, 4 moved in various directions before heading to Brazil, and 10 reached the island. All the successful trips, bar 1, were winding but ended with a final straight segment of variable length, as if the turtles were searching for a sensory contact with the island which they obtained at various distances. The approach to Ascension mostly occurred from the direction opposite to the trade wind, suggesting a navigational role of wind-borne information originating from the island.
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metabolic heating and the prediction of sex ratios for green turtles Chelonia mydas
Physiological and Biochemical Zoology, 2001Co-Authors: Annette C Broderick, Brendan J Godley, Graeme C HaysAbstract:We compared incubation temperatures in nests (n=32) of the green turtle (Chelonia mydas) on Ascension Island in relation to sand temperatures of control sites at nest depth. Intrabeach thermal variation was low, whereas interbeach thermal variation was high in both control and nest sites. A marked rise in temperature was recorded in nests from 30% to 40% of the way through the incubation period and attributed to metabolic heating. Over the entire incubation period, metabolic heating accounted for a mean rise in temperature of between 0.07 degrees and 2.86 degrees C within nests. During the middle third of incubation, when sex is thought to be determined, this rise in temperature ranged between 0.07 degrees and 2.61 degrees C. Metabolic heating was related to both the number of eggs laid and the total number of hatchlings/embryos produced in a clutch. For 32 clutches in which temperature was recorded, we estimate that metabolic heating accounted for a rise of up to 30% in the proportion of females produced within different clutches. Previous studies have dismissed any effect of metabolic heating on the sex ratio of marine turtle hatchlings. Our results imply that metabolic heating needs to be considered when estimating green turtle hatchling sex ratios.
Camille Albouy - One of the best experts on this subject based on the ideXlab platform.
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From the cradle to the grave: Green turtle hatchlings (Chelonia mydas) preyed upon by two-spots red snappers (Lutjanus bohar)
Food Webs, 2019Co-Authors: Jean-baptiste Juhel, Eva Maire, Elliott Sucre, Marie-charlotte Cheutin, Virginie Marquès, Cassandra Benkwitt, Rachel Gunn, Eilísh Richards, Camille AlbouyAbstract:The observation of trophic interactions such as predation provide valuable information to model food webs and better understand ecosystem functioning. Such information is crucial for rare and endangered species in order to adapt management measures and ensure their conservation. However, trophic interactions are rarely observed in the marine realm, even for well-known or widespread species. During a scientific cruise in the Scattered Islands (Southwestern Indian Ocean), we observed endangered green turtle hatchlings (Chelonia mydas) in the gut content of two subadults two-spots red snappers (Lutjanus bohar). This trophic link involving emblematic species has not been previously described. The two-spots red snapper is a widespread coral reef fish in the tropical Indo-Pacific. Although it is unclear how fish predation affects marine turtle population dynamics, the occurrence of hatchlings in all the snapper samples suggests that fish could be significant sources of predation. Yet this predation pressure remains to be further studied and quantified to be considered in marine turtle population monitoring.
Jean-baptiste Juhel - One of the best experts on this subject based on the ideXlab platform.
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From the cradle to the grave: Green turtle hatchlings (Chelonia mydas) preyed upon by two-spots red snappers (Lutjanus bohar)
Food Webs, 2019Co-Authors: Jean-baptiste Juhel, Eva Maire, Elliott Sucre, Marie-charlotte Cheutin, Virginie Marquès, Cassandra Benkwitt, Rachel Gunn, Eilísh Richards, Camille AlbouyAbstract:The observation of trophic interactions such as predation provide valuable information to model food webs and better understand ecosystem functioning. Such information is crucial for rare and endangered species in order to adapt management measures and ensure their conservation. However, trophic interactions are rarely observed in the marine realm, even for well-known or widespread species. During a scientific cruise in the Scattered Islands (Southwestern Indian Ocean), we observed endangered green turtle hatchlings (Chelonia mydas) in the gut content of two subadults two-spots red snappers (Lutjanus bohar). This trophic link involving emblematic species has not been previously described. The two-spots red snapper is a widespread coral reef fish in the tropical Indo-Pacific. Although it is unclear how fish predation affects marine turtle population dynamics, the occurrence of hatchlings in all the snapper samples suggests that fish could be significant sources of predation. Yet this predation pressure remains to be further studied and quantified to be considered in marine turtle population monitoring.