Male-Biased Sex Ratio of Adult-Sized Loggerhead Turtles (Caretta caretta) Migrating to High-Latitude Summer-Restricted Foraging Grounds in the Northwest Pacific1

2020 ◽  
Vol 74 (2) ◽  
Author(s):  
Shohei Kobayashi ◽  
Takuya Fukuoka ◽  
Chihiro Kinoshita ◽  
Katsufumi Sato ◽  
Katsuhiko Arai ◽  
...  
Keyword(s):  
Sex Ratio ◽  
High Latitude ◽  
Caretta Caretta ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio

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 of hatchling loggerhead sea turtles: data and estimates from a 5-year study

1992 ◽  
Vol 70 (3) ◽  
pp. 530-538 ◽  
Author(s):  
N. Mrosovsky ◽  
Jane Provancha
Keyword(s):  
Global Warming ◽  
Sex Ratio ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio ◽  
Nesting Season

Hatchling loggerhead sea turtles (Caretta caretta) were collected over three nesting seasons from a rookery at Cape Canaveral, Florida. From data on the distribution of nests over the season, we estimated that 92.6–96.7, 94.7–99.9, and 87.0–89.0% of the hatchlings produced on this beach in 1986, 1987, and 1988, respectively, were females. These skewed sex ratios were consistent with the fact that for most of the season, sand temperatures were above the pivotal level for loggerhead turtles. The present results show that the female-biased sex ratio reported previously by these authors for the 1986 nesting season at this site was not an isolated, atypical event. In addition to a total of 3 years of sampling for sex ratio, measurements of beach temperatures at the depth of turtle nests were extended to cover 5 years. These temperatures were commonly above the pivotal level. The strongly female-biased hatchling sex ratio found in this population of loggerhead turtles poses theoretical challenges. It may also complicate conservation efforts, since global warming might be expected to skew the sex ratio still further toward females.

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.

Sex ratio of loggerhead sea turtles hatching on a Florida beach

1989 ◽  
Vol 67 (10) ◽  
pp. 2533-2539 ◽  
Author(s):  
N. Mrosovsky ◽  
Jane Provancha
Keyword(s):  
Global Warming ◽  
Sex Ratio ◽  
Sea Turtles ◽  
Caretta Caretta ◽  
Loggerhead Sea Turtles ◽  
Histological Criteria ◽  
The Future ◽  
Loggerhead Turtles ◽  
Nesting Season

Hatchling loggerhead sea turtles (Caretta caretta) were collected over the summer nesting season from a major rookery at Cape Canaveral, Florida, in 1986. Sex was assessed using histological criteria. From data on the distribution of nests over the season, we estimated that in 1986, > 93% of the hatchlings produced on this beach were females. This huge bias toward females is consistent with sand temperatures at the depth of turtle nests; for most of the season these temperatures were above the pivotal level for loggerhead turtles. The results suggest that in the future, turtles in this area will encounter difficulty in overcoming the feminizing effect of global warming and that biologists should pay more attention to the beaches at the northern end of the loggerhead's nesting range.

No room for males in caves: Female‐biased sex ratio in subterranean amphipods of the genus Niphargus

2021 ◽  
Author(s):  
Ester Premate ◽  
Špela Borko ◽  
Simona Kralj‐Fišer ◽  
Michael Jennions ◽  
Žiga Fišer ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Biased Sex Ratio

Male-biased sex ratio in Argulus canadensis Wilson, 1916 (Crustacea: Branchiura) ectoparasitic on sticklebacks

1989 ◽  
Vol 67 (8) ◽  
pp. 2078-2080 ◽  
Author(s):  
Robert Poulin ◽  
Gerard J. FitzGerald
Keyword(s):  
Salt Marsh ◽  
Sex Ratio ◽  
Laboratory Experiments ◽  
Fish Predation ◽  
Reproductive Behaviour ◽  
Egg Deposition ◽  
Alternative Hypotheses ◽  
Biased Sex Ratio ◽  
The Difference ◽  
Fish Hosts

Females of the ectoparasitic crustacean Argulus canadensis must leave their fish hosts at least temporarily to deposit their eggs on the substrate. To test the hypothesis that this difference in reproductive behaviour between the two sexes could result in male-biased sex ratios on their stickleback hosts, we sampled sticklebacks in tide pools of a Quebec salt marsh from early July to early September 1986. During this period, fish harboured significantly more male than female A. canadensis. Laboratory experiments were done to test two alternative hypotheses offered to explain this biased sex ratio. The first hypothesis was that male A. canadensis were more successful than females in attacking their stickleback hosts; however, we found no differences in attack success on their hosts between the two parasite sexes. The second hypothesis was that sticklebacks ate more female than male A. canadensis. Although males were less vulnerable to fish predation than females, the difference was not significant. We conclude that sexual differences in reproductive behaviour, i.e., egg deposition behaviour of females, can account for the male-biased sex ratio of A. canadensis on sticklebacks.

Female-Biased Sex Ratio at Hatching in the Green Woodhoopoe

The Auk ◽  
1990 ◽  
Vol 107 (4) ◽  
pp. 765-771 ◽  
Author(s):  
J. David Ligon ◽  
Sandra H. Ligon
Keyword(s):  
Sex Ratio ◽  
Biased Sex Ratio
Sign in / Sign up

Export Citation Format

Share Document