Nest temperatures and sex-ratio estimates of loggerhead turtles at Patara beach on the southwestern coast of Turkey

2004 ◽  
Vol 82 (1) ◽  
pp. 94-101 ◽  
Author(s):  
M Öz ◽  
A Erdoğan ◽  
Y Kaska ◽  
S Düşen ◽  
A Aslan ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Incubation Period ◽  
Sea Turtles ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Beach Erosion ◽  
Electronic Temperature ◽  
Sand Temperature ◽  
Loggerhead Turtles ◽  
The Mean

During the nesting period in 2000 and 2001 on Patara beach, total emergence and non-nesting emergence of loggerhead turtles (Caretta caretta), nest distribution, and nest distance from the sea were recorded . The main nesting seasons for sea turtles (family Cheloniidae) were during June and July. Loggerhead turtles comprised the majority of sea turtle emergence records; only two green turtle (Chelonia mydas) emergences were recorded. The small nesting population (52 and 53 nests in 2000 and 2001, respectively) of sea turtles on Patara beach was due to low hatching success resulting from a rise in seawater levels, owing to beach erosion, and the subsequent inundation of most nests. The temperatures of four nests and sand at different distances from the sea were measured with electronic temperature loggers, which recorded mean nest temperatures of 28.8–30.7 °C, with the mean temperature in the middle third of the incubation period from 28.5 to 31.0 °C. The mean temperatures, incubation periods, temperature during the middle third of the incubation period, and percentage of hatchling sexes were evaluated with respect to sand and nest temperatures. The results showed a female-dominated sex ratio, which was probably the result of predation of nests far from the sea and the seawater inundation of nests close to the sea, as the sand temperature was different at sites close and far from the sea.

scholarly journals Sex ratio of the green sea turtle Chelonia mydas (Testudines: Cheloniidae) hatchlings in the Guanahacabibes Peninsula, Cuba

2020 ◽  
Vol 68 (3) ◽  
Author(s):  
Randy Calderón-Peña ◽  
Ryan Betancourt-Avila ◽  
Elizabeth Rodríguez-Fajardo ◽  
Yoel Martínez-González ◽  
Julia Azanza Ricardo
Keyword(s):  
Sex Ratio ◽  
Incubation Period ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Nest Temperature ◽  
Data Loggers ◽  
Incubation Periods ◽  
The Mean ◽  
Study Sites ◽  
Incubation Temperatures

Introduction: Sea turtles have temperature dependent sex determination. The increase in global temperature leads to higher nest temperatures that can cause a prevalence of females, threatening the future of these species. Objective: The present work aims to evaluate the trend of incubation temperatures and the incubation period, as well as to estimate the sex ratio in nests of Chelonia mydas at Antonio and La Barca beaches, Southwestern Cuba, during the seasons from 2012 to 2018. Methods: Temperature data loggers were placed in green turtle nests with a representativeness that varied between the years analyzed. To assess the temporal variation of temperatures and incubation periods, a Kruskal-Wallis test was performed in each case. Sex ratio was estimated from its relation with temperature and incubation duration. Results: At La Barca beach, there was a 1.5 °C increase in the mean nest temperature from 2012 to 2018, although no differences were found in the period from 2015 to 2018. At Antonio beach, there is no trend since no differences were found in the mean nest temperature except for the years 2013 and 2017, which had lower temperatures than the other seasons. In both beaches mean nest temperature exceeded 30 °C in most of the years. As a result, there was a predominance of nests with incubation periods shorter than 55 days. With these values, a female hatchling production over 90 % is expected in both study sites. Conclusions: In correspondence with the registered temperature and incubation period values, most of the years reflect a hatchling production biased towards females in both beaches.

Estimating past and present sex ratios of sea turtles in Suriname

1996 ◽  
Vol 74 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Matthew H. Godfrey ◽  
N. Mrosovsky ◽  
R. Barreto
Keyword(s):  
Sea Turtles ◽  
Sex Ratios ◽  
Negative Relationship ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Dermochelys Coriacea ◽  
Green Turtles ◽  
Sand Temperature ◽  
Turtle Conservation ◽  
Sea Turtle Conservation

Leatherback (Dermochelys coriacea) and green (Chelonia mydas) sea turtles in Suriname lay eggs over several months of the year. During this nesting season, changes in rainfall produce changes in sand temperature, which in turn influence the sexual differentiation of incubating sea turtle embryos. The overall sex ratio of leatherback and green sea turtle hatchlings produced at Matapica beach in Suriname was investigated. Estimates of the sex ratios of these turtles in 1993 (green turtles 63.8% female, leatherbacks 69.4% female) were roughly 10% more female-biased than those from an earlier study in 1982. For both species, a significant negative relationship was found between monthly rainfall and monthly sex ratios. Using this relationship and data on rainfall in the past, it was possible to estimate overall sex ratios for an additional 12 years. These estimates varied considerably among different years, ranging from 20 to 90% female in the case of green turtles. Nevertheless, males tended to be produced primarily in April and May, while some females were produced in all months. Such seasonal patterns of production of turtles of different sexes have implications for sea turtle conservation programs that involve manipulating or harvesting eggs.

scholarly journals Climate change and green sea turtle sex ratio – Preventing possible extinction

2020 ◽  
Author(s):  
Jana Blechschmidt ◽  
Meike J. Wittmann ◽  
Chantal Blüml
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Nest Site ◽  
Sea Turtles ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Change Scenario ◽  
Green Sea Turtles ◽  
The Face ◽  
Nest Depth

AbstractClimate change poses a threat to species with temperature-dependent sex determination. A recent study on green sea turtles (Chelonia mydas) at the northern Great Barrier Reef (GBR) showed a highly female-skewed sex ratio with almost all juvenile turtles being female. This shortage of males might eventually cause population extinction, unless rapid evolutionary rescue, migration or conservation efforts ensure a sufficient number of males. We built a stochastic individual-based model inspired by C. mydas, but potentially transferrable to other species with TSD. Nest depth, level of shade, and pivotal temperature were evolvable traits. Additionally, we considered the effect of crossbreeding between the northern and southern GBR, nest-site philopatry, and conservation efforts. Among the evolvable traits, nest depth was the most likely to rescue the population in the face of climate change, but even here the more extreme climate-change scenario led to extinction. Surprisingly, nest-site philopatry elevated extinction rates. Conservation efforts to artificially increase nest depth promoted population survival and did not preclude trait evolution. Although extra information is needed to make reliable predictions for the fate of green sea turtles, our results illustrate how evolution can shape the fate of long lived, vulnerable species in the face of climate change.Graphical Abstract

Natural temperature regimes for loggerhead and green turtle nests in the eastern Mediterranean

1998 ◽  
Vol 76 (4) ◽  
pp. 723-729 ◽  
Author(s):  
Y Kaska ◽  
R Downie ◽  
R Tippett ◽  
R W Furness
Keyword(s):  
Sex Ratio ◽  
Incubation Period ◽  
Green Turtle ◽  
Eastern Mediterranean ◽  
Loggerhead Turtle ◽  
Chelonia Mydas ◽  
Maximum Temperature ◽  
Diel Cycles ◽  
Mean Temperature ◽  
The Mean

Temperatures of green turtle (Chelonia mydas) and loggerhead turtle (Caretta caretta) nests on the beaches of northern Cyprus and Turkey were examined. Electronic continuous-temperature recorders programmed by computer were placed at the top, middle, and bottom of the nests. The sex of 3-7 hatchlings from each level was determined from gonadal histology. The maximum temperature increase during the incubation period was 9.6oC for both species. The mean temperature during the middle third of the incubation period is a good indicator of the sex ratio of the clutch. The percentage of female embryos increased with temperature, 50% being female at 29°C. The mean temperature over the entire incubation period is not a good indicator of sex ratio but can be used to predict the duration of incubation period. The temperature differences within the clutch were larger in loggerhead than in green turtle nests. Eggs at the top of the nest experienced generally warmer (up to 1.4°C) conditions than eggs at the bottom of the same nest, and this caused variation in sex ratio within nests. Over all nests, the sex ratio (percent female) of hatchlings was 91% at the top, 83% at the middle, and 69% at the bottom. There was considerable interbeach thermal variation. Marked diel cycles of up to 1.5°C were detected in loggerhead turtle nests but not in the deeper nests of green turtles.

Loggerhead sea turtle hatchling sex ratio differences between two nesting beaches in Turkey

2015 ◽  
Vol 61 (3-4) ◽  
pp. 115-129 ◽  
Author(s):  
Fikret Sarı ◽  
Yakup Kaska
Keyword(s):  
Sex Ratio ◽  
Incubation Period ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Nest Temperature ◽  
Loggerhead Sea Turtles ◽  
Electronic Temperature ◽  
Gonad Histology ◽  
Incubation Periods ◽  
Nesting Beaches

Hatchling sex ratios of loggerhead sea turtles (Caretta caretta) were estimated on two main nesting beaches (Dalyan Beach and Göksu Delta) in Turkey using three methods: nest temperature, incubation period and gonad histology. The electronic temperature recorders were placed in 35 selected nests. The mean nest temperature in the middle third of the incubation period was calculated as 29.5 °C on Dalyan Beach and as 31 °C on Göksu Delta. Incubation periods on Dalyan Beach and Göksu Delta were found as 52.9 days and 50.4 days, respectively. Gonad histology method was used only on Dalyan Beach and it was determined that 235 (55.6%) hatchlings were female out of 423 histologically examined hatchlings. Using nest temperatures and incubation periods, sex ratios on Dalyan Beach were estimated as 61% and 69.3%, and on Göksu Delta as 81% and 73.1%, respectively. In light of our sex ratio results, Dalyan Beach has a relatively high proportion of male hatchlings possibly due to its relatively western location. Our findings indicate that Dalyan Beach is an important nesting beach for loggerhead sea turtles in the eastern Mediterranean not only in terms of nest numbers and hatching success but also for its high proportion of male hatchlings. As for the methods used in this study, for further studies, we can suggest that nest temperature method provides the most accurate sex ratio result compared with incubation period and gonad histology methods, if temperature-recorded nests are selected in a manner of representing temporal distribution of the total nests on study beach.

scholarly journals Climate Change and Green Sea Turtle Sex Ratio—Preventing Possible Extinction

Genes ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 588 ◽  
Author(s):  
Jana Blechschmidt ◽  
Meike J. Wittmann ◽  
Chantal Blüml
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Nest Site ◽  
Sea Turtles ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Climate Change Scenarios ◽  
Population Extinction ◽  
Green Sea Turtles ◽  
Nest Depth

Climate change poses a threat to species with temperature-dependent sex determination (TSD). A recent study on green sea turtles (Chelonia mydas) at the northern Great Barrier Reef (GBR) showed a highly female-skewed sex ratio with almost all juvenile turtles being female. This shortage of males might eventually cause population extinction, unless rapid evolutionary rescue, migration, range shifts, or conservation efforts ensure a sufficient number of males. We built a stochastic individual-based model inspired by C. mydas but potentially transferrable to other species with TSD. Pivotal temperature, nest depth, and shading were evolvable traits. Additionally, we considered the effect of crossbreeding between northern and southern GBR, nest site philopatry, and conservation efforts. Among the evolvable traits, nest depth was the most likely to rescue the population, but even here the warmer climate change scenarios led to extinction. We expected turtles to choose colder beaches under rising temperatures, but surprisingly, nest site philopatry did not improve persistence. Conservation efforts promoted population survival and did not preclude trait evolution. Although extra information is needed to make reliable predictions for the fate of green sea turtles, our results illustrate how evolution can shape the fate of long lived, vulnerable species in the face of climate change.

scholarly journals Red blood cell osmotic fragility in healthy loggerhead and green sea turtles

2020 ◽  
Vol 32 (6) ◽  
pp. 908-911
Author(s):  
Rebecca Radisic ◽  
Sean D. Owens ◽  
Charles A. Manire ◽  
Nicole Montgomery ◽  
Doug Mader ◽  
...  
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Sea Turtles ◽  
Osmotic Fragility ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Green Sea Turtles ◽  
Nacl Concentration ◽  
Life Threatening ◽  
Rehabilitation Facilities

Loggerhead ( Caretta caretta; Cc) and green sea ( Chelonia mydas; Cm) turtles admitted to rehabilitation facilities may require blood transfusions for supportive treatment of disorders resulting in life-threatening anemia, but, considering the unique erythrocyte chemistry of sea turtles, standardized donor red blood cell (RBC) storage protocols have not been established. Prolonged cold storage and the effects of various anticoagulant-preservative solutions have been associated with increased RBC osmotic fragility across a broad range of species. Increased RBC fragility in stored RBC products has been associated with acute transfusion reactions. The osmotic fragility test is used to measure erythrocyte resistance to hemolysis while being exposed to a series of dilutions of a saline solution. We obtained baseline measurements for osmotic fragility in healthy Cc and Cm. Osmotic fragility testing was performed on samples from 10 Cc to 10 Cm. Fifty percent (50%) RBC hemolysis was identified at a mean NaCl concentration of 0.38% in both species. Results of our study will help guide future studies evaluating optimal storage solutions for sea turtle blood products.

Predation on green sea turtle, Chelonia mydas, hatchlings by invasive rats

2019 ◽  
Vol 25 (4) ◽  
pp. 423 ◽  
Author(s):  
Markus Gronwald ◽  
Quentin Genet ◽  
Margaux Touron
Keyword(s):  
Food Source ◽  
Sea Turtles ◽  
Rattus Rattus ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
French Polynesia ◽  
Camera Traps ◽  
Green Sea Turtle ◽  
Green Sea Turtles ◽  
Invasive Rats

We used camera traps to identify invasive Rattus rattus as predators at a green sea turtle, Chelonia mydas, nest in French Polynesia. The footage shows that the hatchlings are a familiar food source for rats and that the control of invasive rats has to be considered for the protection of endangered green sea turtles.

scholarly journals Incidental capture of sea turtles by industrial bottom trawl fishery in the Tropical South-western Atlantic

2017 ◽  
Vol 98 (6) ◽  
pp. 1525-1531 ◽  
Author(s):  
Suzana Machado Guimarães ◽  
Davi Castro Tavares ◽  
Cassiano Monteiro-Neto
Keyword(s):  
Sea Turtles ◽  
Action Plan ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Bottom Trawl ◽  
Conservation Strategies ◽  
Future Research ◽  
Olive Ridley ◽  
Western Atlantic ◽  
Turtle Species

The five sea turtle species occurring in Brazilian waters are susceptible to threats, including incidental catches by fisheries. Studies on incidental captures in fishing gears are the main focus of several conservation actions due to high sea turtle fishery mortality worldwide. This study provides the first evaluation of incidental sea turtle catches by industrial bottom trawl fisheries operating in Brazilian waters. Four twin-trawler vessels were monitored between July 2010 and December 2011 by captains who voluntarily completed logbooks. Forty-four turtles were captured during the 1996 tows (8313 fishing hours), resulting in a catch of 5.3 ± 0.8 turtles per 1000 h per unit effort. Captured species included the loggerhead turtle (Caretta caretta, 22 individuals), olive ridley turtles (Lepidochelys olivacea, 21 individuals) and one green turtle (Chelonia mydas). Water depth was the only variable that significantly affected sea turtle captures according to Generalized Linear Models. The capture rates reported in this study ranked sixth in relation to other published studies of similar fisheries occurring worldwide. Considering the importance of this region for sea turtles, the increasing evidence of sea turtle mortality and the goals of the National Action Plan for Conservation of Sea Turtles in Brazil, it is essential to identify the main threats towards these animals and propose mitigating solutions to reduce sea turtle mortality induced by fishing activities. This study provides results that may guide future research and goals in meeting sea turtle conservation strategies.

Validation of incubation duration as an index of the sex ratio of hatchling sea turtles

1999 ◽  
Vol 77 (5) ◽  
pp. 831-835 ◽  
Author(s):  
N Mrosovsky ◽  
Cecília Baptistotte ◽  
Matthew H Godfrey
Keyword(s):  
Sex Ratio ◽  
High Temperatures ◽  
Low Temperatures ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Turtle Species ◽  
Loggerhead Turtles ◽  
Incubation Duration

One method of estimating the sex ratio of hatchling sea turtles is to use the incubation duration. Long and short durations imply low and high temperatures, respectively. In turtle species whose sex is determined by temperature, males are produced at low temperatures and females at high temperatures. This study assesses the validity of using incubation duration to estimate the sex ratio. Samples of hatchling loggerhead turtles (Caretta caretta) were collected from nests with known incubation durations, and sex was ascertained by means of histology. The sex ratio of groups of nests determined by histology was compared with that predicted from previous relationships between incubation duration and sex ratio. For conditions causing relatively long or relatively short incubation durations, the sex ratio could be predicted with considerable accuracy. For conditions causing durations nearer to the pivotal duration (that which gives 50% of each sex), predictions could be off by 10%, depending on the distribution of incubation durations, but it was still possible to determine whether ratios were highly skewed or approximately balanced. Estimating sex ratios of hatchling sea turtles from incubation durations is simple, cheap, and can be used retrospectively.

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