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

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

Canadian Journal of Zoology ◽

10.1139/z92-080 ◽

1992 ◽

Vol 70 (3) ◽

pp. 530-538 ◽

Cited By ~ 71

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.

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

Canadian Journal of Zoology ◽

10.1139/z97-097 ◽

1997 ◽

Vol 75 (5) ◽

pp. 755-770 ◽

Cited By ~ 79

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.

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Pivotal temperature for loggerhead turtles (Caretta caretta) from Kyparissia Bay, Greece

Canadian Journal of Zoology ◽

10.1139/z02-204 ◽

2002 ◽

Vol 80 (12) ◽

pp. 2118-2124 ◽

Cited By ~ 40

Author(s):

N Mrosovsky ◽

Stephanie Kamel ◽

Alan F Rees ◽

D Margaritoulis

Keyword(s):

United States ◽

Sex Ratio ◽

Constant Temperature ◽

Sea Turtles ◽

Caretta Caretta ◽

The United States ◽

Loggerhead Sea Turtles ◽

Incubation Duration ◽

Different Populations ◽

Pivotal Temperature

Pivotal temperature (the constant temperature giving 50% of each sex) for two clutches of loggerhead sea turtles (Caretta caretta) from Kyparissia Bay, Greece, was 29.3°C. Pivotal incubation duration (the time from laying to hatching giving 50% of each sex) was 52.6 days. These values are close to those obtained for this species in Brazil and the United States, providing further evidence that these characteristics are relatively conservative in different populations. Methodological differences between different experiments and limitations on accuracy of equipment make the detection of small differences problematic. Comparison of incubation durations in the field with the pivotal durations obtained here suggest that hatchling sex ratio on some Mediterranean beaches is female biased but probably varies considerably within this region.

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Sex ratio of loggerhead sea turtles hatching on a Florida beach

Canadian Journal of Zoology ◽

10.1139/z89-358 ◽

1989 ◽

Vol 67 (10) ◽

pp. 2533-2539 ◽

Cited By ~ 40

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.

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Reconstructed paternal genotypes reveal variable rates of multiple paternity at three rookeries of loggerhead sea turtles (Caretta caretta) in Western Australia

Australian Journal of Zoology ◽

10.1071/zo14076 ◽

2014 ◽

Vol 62 (6) ◽

pp. 454 ◽

Cited By ~ 16

Author(s):

J. N. Tedeschi ◽

N. J. Mitchell ◽

O. Berry ◽

S. Whiting ◽

M. Meekan ◽

...

Keyword(s):

Population Size ◽

Western Australia ◽

Sea Turtles ◽

Sex Ratios ◽

Multiple Paternity ◽

Caretta Caretta ◽

Loggerhead Sea Turtles ◽

Female Population ◽

Species Specific ◽

Operational Sex Ratios

Female sea turtles are promiscuous, with clutches of eggs often sired by multiple males and rates of multiple paternity varying greatly within and across species. We investigated levels of multiple paternity in loggerhead sea turtles (Caretta caretta) from three rookeries in Western Australia by analysing polymorphic species-specific genetic markers. We predicted that the level of multiple paternity would be related to female population size and hence the large rookery at Dirk Hartog Island would have higher rates of multiple paternity than two smaller mainland rookeries at Gnaraloo Bay and Bungelup Beach. Contrary to our prediction, we found highly variable rates of multiple paternity among the rookeries that we sampled, which was unrelated to female population size (25% at Bungelup Beach, 86% at Gnaraloo Bay, and 36% at Dirk Hartog Island). Approximately 45 different males sired 25 clutches and the average number of sires per clutch ranged from 1.2 to 2.1, depending on the rookery sampled. The variance in rates of multiple paternity among rookeries suggests that operational sex ratios are variable in Western Australia. Periodic monitoring would show whether the observed patterns of multiple paternity for these three rookeries are stable over time, and our data provide a baseline for detecting shifts in operational sex ratios.

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Increase of sea turtles stranding records in Rhodes Island (eastern Mediterranean Sea): update of a long-term survey

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315413000556 ◽

2013 ◽

Vol 93 (7) ◽

pp. 1991-2002 ◽

Cited By ~ 3

Author(s):

Maria Corsini-Foka ◽

Gerasimos Kondylatos ◽

Elias Santorinios

Keyword(s):

Eastern Mediterranean ◽

Sea Turtles ◽

Loggerhead Turtle ◽

Aegean Sea ◽

Chelonia Mydas ◽

Caretta Caretta ◽

Fishing Ground ◽

Green Turtles ◽

Loggerhead Turtles

A total of 209 strandings of sea turtles (152 loggerhead turtles Caretta caretta, 42 green turtles Chelonia mydas, 15 unidentified) were recorded during the period 1984–2011 along the coasts of Rhodes (Aegean Sea, Greece). The proportion of dead to live individuals was different in the two species. Stranded Caretta caretta were larger than Chelonia mydas. The size range of stranded green turtles, usually juveniles, appeared to increase since 2000, including the largest specimens ever observed in Greek waters. For both species, a tendency to strand more frequently on the west coast of the island, along fishing ground areas, was noted. The higher incidence of loggerhead turtle strandings was observed in summer, while more green turtle strandings were documented in winter. Factors involved in the increased trend of stranding records of both species, along with the acceleration of this phenomenon in the last decade, are discussed. Data from Rhodes provide evidence that human activities detrimentally affect mainly larger-sized loggerhead turtles living in shallow waters.

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Satellite tracking of rehabilitated sea turtles suggests a high rate of short-term survival following release

PLoS ONE ◽

10.1371/journal.pone.0246241 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0246241

Author(s):

David P. Robinson ◽

Kevin Hyland ◽

Gerhard Beukes ◽

Abdulkareem Vettan ◽

Aneeshkumar Mabadikate ◽

...

Keyword(s):

Sea Turtles ◽

Sea Turtle ◽

Satellite Tracking ◽

Anthropogenic Factors ◽

Gulf Region ◽

Term Survival ◽

Turtle Species ◽

Movement Characteristics ◽

Loggerhead Turtles ◽

Hawksbill Turtles

The rehabilitation of wildlife can contribute directly to the conservation of threatened species by helping to maintain wild populations. This study focused on determining the post-rehabilitation survival and spatial ecology of sea turtles and on comparing the movements of individuals with flipper amputations (amputees) to non-amputee animals. Our aims were to assess whether rehabilitated sea turtles survive after release, to compare and contrast the movement characteristics of the different species of sea turtles we tracked, and to examine whether amputees and non-amputees within species behaved similarly post-release. Twenty-six rehabilitated sea turtles from four species, including hawksbill Eretmochelys imbricata (n = 12), loggerhead Caretta caretta (n = 11), green Chelonia mydas (n = 2), and olive ridley Lepidochelys olivacea (n = 1) sea turtles from the United Arab Emirates were fitted with satellite tags before release. Rehabilitation times ranged from 89 to 817 days (mean 353 ± 237 days). Post-release movements and survival were monitored for 8 to 387 days (mean 155 ± 95 days) through satellite tracking. Tag data suggested that three tracked sea turtles died within four days of release, one after 27 days, and one after 192 days from what are thought to be anthropogenic factors unrelated to their pre-rehabilitation ailments. We then compared habitat use and movement characteristics among the different sea turtle species. Although half of all turtles crossed one or more international boundaries, dispersal varied among species. Loggerhead turtles had a high dispersal, with 80% crossing an international boundary, while hawksbill turtles displayed higher post-release residency, with 66% remaining within UAE territorial waters. Amputee turtles moved similarly to non-amputee animals of the same species. Loggerhead turtles travelled faster (mean ± sd = 15.3 ± 8 km/day) than hawksbill turtles (9 ± 7 km/day). Both amputee and non-amputee sea turtles within a species moved similarly. Our tracking results highlight that rehabilitated sea turtles, including amputees, can successfully survive in the wild following release for up to our ~one-year monitoring time therefore supporting the suitability for release of sea turtles that have recovered from major injuries such as amputations. However, more broadly, the high mortality from anthropogenic factors in the Arabian Gulf region is clearly a serious issue and conservation challenge.

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Sex ratios of juvenile loggerhead sea turtles Caretta caretta in the Mediterranean Sea

Marine Ecology Progress Series ◽

10.3354/meps324281 ◽

2006 ◽

Vol 324 ◽

pp. 281-285 ◽

Cited By ~ 21

Author(s):

P Casale ◽

B Lazar ◽

S Pont ◽

J Tomás ◽

N Zizzo ◽

...

Keyword(s):

Mediterranean Sea ◽

Sea Turtles ◽

Sex Ratios ◽

Caretta Caretta ◽

Loggerhead Sea Turtles ◽

The Mediterranean

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Podoceru Chelonophilus (Amphipoda: Podoceridae) Associated with Epidermal Lesions of the Loggerhead Turtle, Caretta Caretta (Chelonia)

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400015344 ◽

1995 ◽

Vol 75 (1) ◽

pp. 253-255 ◽

Cited By ~ 4

Author(s):

P.G. Moore

Keyword(s):

Fibrous Material ◽

Sea Turtles ◽

Loggerhead Turtle ◽

Caretta Caretta ◽

Small Sample ◽

Gut Contents ◽

Loggerhead Turtles ◽

Marine Vertebrates

Examination of a small sample of Podocerus chelonophilus found clustered around mucus-exuding epidermal lesions of juvenile loggerhead turtles (Caretta caretta) collected off Madeira revealed the presence of fibrous material in the gut contents. The absence of planktonic remains suggested that these amphipods had been exploiting turtle material directly.With the exception of the Cyamidae (whale lice), rather few amphipod taxa consistently live in association with marine vertebrates. Sea turtles, however, have been recorded carrying gammaridean and caprellidean epibionts by Caine (1986), who reported eight gammaridean species (including two domicolous fouling species) from nesting loggerhead turtles in Florida.

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