scholarly journals Sex Ratio Estimations of Loggerhead Sea Turtle Hatchlings at Kuriat Islands, Tunisia: Can Minor Nesting Sites Contribute to Compensate Globally Female-Biased Sex Ratio?

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Imed Jribi ◽  
Mohamed Nejmeddine Bradai
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Loggerhead Turtle ◽  
Sea Turtle ◽  
Electronic Temperature ◽  
Loggerhead Sea Turtle ◽  
Nesting Site ◽  
Nesting Sites ◽  
Biased Sex Ratio ◽  
A Minor

Hatchling sex ratios in the loggerhead turtleCaretta carettawere estimated by placing electronic temperature recorders in seven nests at Kuriat islands (Tunisia) during the 2013 nesting season. Based on the mean temperatures during the middle third of the incubation period, and on incubation duration, the sex ratio of hatchlings at Kuriat islands was highly male-biased. Presently, the majority of hatchling sex ratio studies are focused on major nesting areas, whereby the sex ratios are universally believed to be heavily female-biased. Here we present findings from a minor nesting site in the Mediterranean, where the hatchling sex ratio was found to be male-biased, suggesting a potential difference between major and minor nesting sites.

Sex Ratio Estimation of the Most Eastern Main Loggerhead Sea Turtle Nesting Site: Anamur Beach, Mersin, Turkey

2012 ◽  
Vol 58 (1) ◽  
pp. 87-100 ◽  
Author(s):  
Aşkin Hasan Uçar ◽  
Yakup Kaska ◽  
Serap Ergene ◽  
Cemil Aymak ◽  
Yasemin Kaçar ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sea Turtle ◽  
Ratio Estimation ◽  
Loggerhead Sea Turtle ◽  
Nesting Site

scholarly journals Effect of sand granulometry on the egg hatchling success of the sea turtle Caretta caretta

2019 ◽  
Vol 14 (1) ◽  
pp. 43-54
Author(s):  
Maria Fernanda Tacchi ◽  
Fernanda Peres Quirino ◽  
Diego Júnior Martins Ferreira ◽  
Lílian Gomes Afonso ◽  
Federico Tognin ◽  
...  
Keyword(s):  
Negative Relationship ◽  
Fine Sand ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Egg Laying ◽  
Northeastern Brazil ◽  
Laying Date ◽  
Loggerhead Sea Turtle ◽  
Nesting Sites ◽  
Potential Alternative

The environmental characteristics of nesting sites of sea turtles may directly interfere with the egg hatchling success. The objective of the present study was to evaluate the factors that affect the success of hatchling in the nests of the loggerhead sea turtle (Caretta caretta). Data from 37 nests of C. caretta from the coast of Mata de São João, Bahia, northeastern Brazil, were obtained from TAMAR, Sauípe station. Samples of sand were collected in each nest to determine the granulometry. A significant negative relationship was found between the stillborn rate and the fine sand ratio (r2 = 0.119; p = 0.036), indicating that a larger fraction of fine sand had a positive effect on nest hatchling success. The egg laying date also had a significant influence on the rate of stillbirths (r2 = 0.163; p = 0.013), with a trend towards a higher stillbirth rate, the later the laying date of the eggs. There is indication that the transfer of eggs to sites with more favorable characteristics may be considered as a potential alternative to increase the hatchling success rate of C. caretta eggs.

scholarly journals Who are the important sea turtle nest predators at Wreck Rock beach?

2017 ◽  
Author(s):  
Juan Lei ◽  
David T Booth
Keyword(s):  
Nest Predation ◽  
Activity Index ◽  
Loggerhead Turtle ◽  
Control Program ◽  
Sea Turtle ◽  
Large Male ◽  
Camera Traps ◽  
Loggerhead Sea Turtle ◽  
Southeast Queensland ◽  
Nesting Aggregation

Excessive sea turtle nest predation is a problem for conservation management of sea turtle populations. This study assessed the predation of the endangered loggerhead sea turtle (Caretta caretta ) nests at the Wreck Rock beach adjacent to Deepwater National Park in Southeast Queensland, Australia after a control program for feral foxes was instigated. The presence of predators on the nesting dune was evaluated by passive soil plots (2 x 1 m) every 100m along the dune front. There were 21 (2014-2015) and 41 (2015-2016) plots established along the dune and these were monitored for predator tracks daily over three consecutive months in both nesting seasons. Camera traps were also set to record the predator’s activity around selected nests. The tracks of the fox (Vulpes vulpes ) and goanna (lace monitor Varanus varius and/or yellow-spotted goanna V. panoptes; we could not distinguish these two species tracks from each other) were found on sand plots. Goannas were widely distributed along the beach and had an eight times higher Passive Activity Index (PAI) (0.31 in 2014-2015 and 0.16 in 2015-2016) compared to foxes (PAI 0.04 in 2014-2015 and 0.02 in 2015-2016). Camera trap data indicated that the appearance of yellow-spotted goannas at loggerhead turtle nests was more frequent than lace monitors and further that lace monitors only predated these nests after they had been previously opened by yellow-spotted goannas. No foxes were recorded at nests with camera traps. This study suggests that large male yellow-spotted goannas are the major predator of sea turtle nests at the Wreck Rock beach nesting aggregation.

Estimating sex ratios of loggerhead turtles in Brazil from pivotal incubation durations

1997 ◽  
Vol 75 (5) ◽  
pp. 755-770 ◽  
Author(s):  
Maria Ângela Marcovaldi ◽  
Matthew H. Godfrey ◽  
N. Mrosovsky
Keyword(s):  
Sex Ratio ◽  
Sexual Differentiation ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Temperature Dependent ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio ◽  
Nesting Beaches

A method of estimating natural sex ratios of hatchlings of species with temperature-dependent sexual differentiation from data on incubation durations is described. The method was applied to loggerhead turtles (Caretta caretta) nesting in Brazil. Data on incubation durations were collected from 11 nesting beaches monitored for up to six seasons. It was estimated that 82.5% of the loggerhead hatchlings produced were female. The strongly female-biased sex ratio in Brazil is similar to that found previously for loggerheads using beaches in the eastern U.S.A. This suggests that a female-biased hatchling sex ratio may be a feature of loggerhead populations.

Sex ratio estimations of loggerhead sea turtle hatchlings by histological examination and nest temperatures at Fethiye beach, Turkey

2006 ◽  
Vol 93 (7) ◽  
pp. 338-343 ◽  
Author(s):  
Yakup Kaska ◽  
Çetin Ilgaz ◽  
Adem Özdemir ◽  
Eyüp Başkale ◽  
Oğuz Türkozan ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Histological Examination ◽  
Sea Turtle ◽  
Loggerhead Sea Turtle

Male-Biased Sex Ratio in a Cold Nest of a Hawksbill Sea Turtle (Eretmochelys imbricata)

1985 ◽  
Vol 19 (1) ◽  
pp. 158 ◽  
Author(s):  
George H. Dalrymple ◽  
John C. Hampp ◽  
Debra J. Wellins
Keyword(s):  
Sex Ratio ◽  
Sea Turtle ◽  
Eretmochelys Imbricata ◽  
Biased Sex Ratio

scholarly journals Cooperative interactions among females and even more extraordinary sex ratios

2020 ◽  
Author(s):  
Ryosuke Iritani ◽  
Stuart A West ◽  
Jun Abe
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Structured Populations ◽  
Local Mate Competition ◽  
Mate Competition ◽  
Wasp Species ◽  
Cooperative Interactions ◽  
Competition Theory ◽  
Local Mate ◽  
Biased Sex Ratio

AbstractHamilton’s local mate competition theory provided an explanation for extraordinary female biased sex ratios in a range of organisms. When mating takes place locally, in structured populations, a female biased sex ratio is favoured to reduce competition between related males, and to provide more mates for males. However, there are a number of wasp species where the sex ratios appear to more female biased than predicted by Hamilton’s theory. We investigated theoretically the extent to which cooperative interactions between related females can interact with local mate competition to favour even more female biased sex ratios. We found that: (i) cooperative interactions between females can lead to sex ratios that are more female biased than predicted by local competition theory alone; (ii) sex ratios can be more female biased when the cooperative interactions are offspring helping parents before dispersal, rather than cooperation between siblings after dispersal. Our results can be applied to a range of organisms, and provide an explanation for the extreme sex ratio biases that have been observed in Sclerodermus and Melittobia wasps.

scholarly journals Who are the important sea turtle nest predators at Wreck Rock beach?

2017 ◽  
Author(s):  
Juan Lei ◽  
David T Booth
Keyword(s):  
Nest Predation ◽  
Activity Index ◽  
Loggerhead Turtle ◽  
Control Program ◽  
Sea Turtle ◽  
Large Male ◽  
Camera Traps ◽  
Loggerhead Sea Turtle ◽  
Southeast Queensland ◽  
Nesting Aggregation

Excessive sea turtle nest predation is a problem for conservation management of sea turtle populations. This study assessed the predation of the endangered loggerhead sea turtle (Caretta caretta ) nests at the Wreck Rock beach adjacent to Deepwater National Park in Southeast Queensland, Australia after a control program for feral foxes was instigated. The presence of predators on the nesting dune was evaluated by passive soil plots (2 x 1 m) every 100m along the dune front. There were 21 (2014-2015) and 41 (2015-2016) plots established along the dune and these were monitored for predator tracks daily over three consecutive months in both nesting seasons. Camera traps were also set to record the predator’s activity around selected nests. The tracks of the fox (Vulpes vulpes ) and goanna (lace monitor Varanus varius and/or yellow-spotted goanna V. panoptes; we could not distinguish these two species tracks from each other) were found on sand plots. Goannas were widely distributed along the beach and had an eight times higher Passive Activity Index (PAI) (0.31 in 2014-2015 and 0.16 in 2015-2016) compared to foxes (PAI 0.04 in 2014-2015 and 0.02 in 2015-2016). Camera trap data indicated that the appearance of yellow-spotted goannas at loggerhead turtle nests was more frequent than lace monitors and further that lace monitors only predated these nests after they had been previously opened by yellow-spotted goannas. No foxes were recorded at nests with camera traps. This study suggests that large male yellow-spotted goannas are the major predator of sea turtle nests at the Wreck Rock beach nesting aggregation.

scholarly journals Nesting activity of the Loggerhead sea turtle, Caretta caretta, in Calabria: 2016-2020 reproductive seasons

2021 ◽  
Author(s):  
MARIA DENARO ◽  
TERESA MALITO ◽  
CARMELA MANCUSO ◽  
GIOVANNI PARISE ◽  
SALVATORE URSO
Keyword(s):  
New Technologies ◽  
Survey Methods ◽  
Loggerhead Turtle ◽  
Sea Turtle ◽  
Success Rates ◽  
Monitoring Method ◽  
Loggerhead Sea Turtle ◽  
Emergence Success ◽  
The Mean ◽  
Nesting Activity

The nesting activity of the loggerhead turtle along the coast of Calabria during five reproductive seasons (2016-2020) is presented. From May to August, survey methods were conducted using traditional observations on foot and utilizing additional innovative technologies, including electric fat bikes and drones. Monitoring was intensively focused on a key nesting area of approximately 40 km located on the southernmost Ionian coast of Reggio Calabria, and, for only the 2020 season, the area was extended an additional 40 km northeast. In the five nesting seasons, 419 female emergences were recorded, 192 of which were classified as nests. Overall, 65.1% (n = 125) of nests were found along the area regularly monitored in all nesting seasons. The maximum nesting activity was observed during July, and the mean nesting success was 45.8%. The average number of eggs for all seasons was 92.2 (n = 163; S.D.: ± 21.1; range: 39-160). The mean hatching and emergence success rates were 70.8% and 62.5%, respectively. The mean incubation period was 49 days (n = 122; S.D.: ± 5.4; range: 42-82). Considering previous data from the same area, our study shows an actual increase in nesting activity, probably due to the implementation of an effective monitoring method that includes the use of new technologies, which made it possible to expand the regularly monitored area, and a greater awareness campaign in recent years. Regarding the reproductive parameters, our data is similar to that reported for other Mediterranean nesting grounds.

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