NEsting by the hawsbill turtle (Eretmochelys imbricata) on Milman Island, Great Barrier Reef, Australia

1995 ◽  
Vol 22 (2) ◽  
pp. 241 ◽  
Author(s):  
KA Loop ◽  
JD Miller ◽  
CJ Limpus
Keyword(s):  
Clutch Size ◽  
Carapace Length ◽  
Average Diameter ◽  
Average Weight ◽  
Nesting Biology ◽  
Eretmochelys Imbricata ◽  
Nest Sites ◽  
Emergence Success ◽  
Incubation Temperatures ◽  
Hawksbill Turtles

Nesting biology of hawksbill sea turtles (Eretmochelys imbricata) is described with morphometric and meristic measurements collected from 365 turtles over 76 nights of beach patrols on Milman I. The nesting season was already in progress when the study began in January and continued after the research team left in March 1991. Average renesting interval was 14.2 days, and the hawksbill turtles laid an average of 2.6 clutches during the study period. Nest sites were located most commonly under trees (67.2%). Average curved carapace length was 81.7 cm, width was 70.6 cm, and weight after laying was 50.3 kg. Mean clutch size was 124 eggs. Eggs had an average diameter of 3.48 cm and an average weight of 25.7 g. Emergence success rate was 79.9% for hawksbill hatchlings, which had an average straight carapace length of 3.96 cm and weight of 13.3 g. Incubation temperatures were monitored and sex ratios determined in four clutches, two in shaded and two in unshaded sand. The sexes of 25 hatchlings from each clutch were identified. Two unshaded clutches produced 92% and 100% female hatchlings while two shaded clutches produced 64% and 44% female hatchlings. Statistical differences were not found between the presented hawksbill turtle curved carapace length, weight after laying and clutch size and those collected elsewhere in Queensland by earlier studies.

The Use of Measured Scutes of Hawksbill Turtles, Eretmochelys-Imbricata, in the Management of the Tortoiseshell (Bekko) Trade

1990 ◽  
Vol 17 (6) ◽  
pp. 633 ◽  
Author(s):  
CJ Limpus ◽  
JD Miller
Keyword(s):  
Carapace Length ◽  
Size Class ◽  
Strong Positive Correlation ◽  
Eretmochelys Imbricata ◽  
Positive Correlation ◽  
Size Class Distribution ◽  
Class Distribution ◽  
Hawksbill Turtles

A strong positive correlation is demonstrated between the size of selected carapacial scutes (costal 1, vertebral 1 and vertebral 5) and the curved carapace length of hawksbill turtles (Eretmochelys imbricata). A count of any one of these distinctive scute types, and the measurement of these scutes, can be used to determine the number and size class distribution of E. imbricata represented in consignments of raw tortoiseshell.

Reproductive patterns of the hawksbill turtle Eretmochelys imbricata in sandy beaches of the Yucatan Peninsula

2007 ◽  
Vol 87 (3) ◽  
pp. 815-824 ◽  
Author(s):  
Roberto Pérez-Castañeda ◽  
Alberto Salum-Fares ◽  
Omar Defeo
Keyword(s):  
Clutch Size ◽  
Yucatan Peninsula ◽  
Sandy Beaches ◽  
Main Peak ◽  
Eretmochelys Imbricata ◽  
Yucatán Peninsula ◽  
Emergence Success ◽  
Important Region ◽  
Long Term Trends ◽  
Nesting Activity

Daily censuses of the hawksbill turtle Eretmochelys imbricata were taken during the nesting seasons 1995–2001 in three sandy beaches of the Yucatan Peninsula, Mexico (Celestun, El Cuyo and Isla Holbox), to evaluate aspects of its reproductive biology. A total of 9059 hawksbill turtle clutches was estimated for the study period. Nesting seasons began in mid-April and ended in early September, peaking in May–June. No significant differences were detected in the mean number of clutches per km among beaches. The largest number of clutches was observed in the supralittoral zone (6341: 70%), followed by the dune (2491: 27.5%) and the intertidal (227: 2.5%) zones. Variation in number of clutches showed a main peak in 1999, decreasing in 2000 and 2001. A significant decrease (3 cm) in body size of nesting females was detected between 1995 and 2001. Mean clutch size was 140 eggs/clutch, and a significant positive relationship between curved carapace length and mean clutch size was found at the three beaches. Incubation period, hatching success and emergence success varied between years (lowest values in 1998) and beaches (highest values at Isla Holbox), with no significant differences between the supralittoral and dune zones. Even though there was no evidence of a decreasing trend in nesting activity for the study period, the decrease in 2000–2001 suggests that additional beach monitoring is necessary to identify long-term trends, and to reduce potential losses of nests by human and natural causes in this globally important region for the hawksbill turtle.

Running against time: conservation of the remaining hawksbill turtle (Eretmochelys imbricata) nesting population in the Dominican Republic

2012 ◽  
Vol 93 (4) ◽  
pp. 1133-1140 ◽  
Author(s):  
Ohiana Revuelta ◽  
Yolanda M. León ◽  
Francisco J. Aznar ◽  
Juan A. Raga ◽  
Jesús Tomás
Keyword(s):  
Sex Ratio ◽  
Dominican Republic ◽  
Preliminary Survey ◽  
Eretmochelys Imbricata ◽  
Emergence Success ◽  
Human Predation ◽  
Incubation Temperatures ◽  
Artificial Incubation

Saona Island hosts the last hawksbill turtle (Eretmochelys imbricata) nesting population in the Dominican Republic, which has experienced a severe decline in the last decades, mostly due to illegal egg take. Here we present the results of an artificial incubation programme started in 2007 to protect the clutches from human predation. A preliminary survey in 2006 showed that about 60% of clutches laid were taken by humans. Over the study period (2007–2010) we recorded 400 clutches, of which 38.2% were predated by humans, 40.7% were artificially incubated and 21% were incubated in situ. Overall, the artificial incubation programme allowed the release of 12,340 hatchlings. No differences were found in hatching and emergence success between clutches incubated in situ and clutches artificially incubated. However, incubation temperatures and incubation durations recorded suggest a male-biased hatchling sex-ratio in artificially incubated clutches. Although artificial incubation may mitigate the effect of egg take, our results indicate that other measures, such as clutch relocation to protected sections of the beach should be taken. Beach patrolling and education are currently implemented so that artificial incubation will be eventually phased out in favour of in situ incubation.

The hawksbill turtle, Eretmochelys imbricata, in Queensland: population structure within a southern Great Barrier Reef feeding ground.

1992 ◽  
Vol 19 (4) ◽  
pp. 489 ◽  
Author(s):  
CJ Limpus
Keyword(s):  
Great Barrier Reef ◽  
Carapace Length ◽  
Regression Equations ◽  
Barrier Reef ◽  
Growth Data ◽  
Eretmochelys Imbricata ◽  
Nesting Beaches ◽  
Hawksbill Turtles ◽  
Feeding Grounds

Hawksbill turtles, Eretmochelys imbricata, live at low density on coral reefs in the southern Great Barrier Reef. The biomass of the species on Heron Reef was estimated at 0.82 kg ha-1. This is equivalent to 3.34 turtles km-1. The nesting beaches used by these E. imbricata are unknown. However, within the Great Barrier Reef and Coral Sea region, no regular nesting by the species occurs within 1200 km of these reefal feeding grounds. E. imbricata take up long-term residence in these feeding grounds at a minimum curved carapace length of 35.0cm. The E. imbricata feeding over these reefs ranged in size from these small immatures up to adults with curved carapace length of 87.5cm, but the maturity ratio was very strongly biased toward immatures (maturity ratio=0.01 adults). The sex ratio of all size classes was significantly skewed in favour of females (2.57 : 1 females : male overall) while 2% of the turtles were identified as intersex. Growth data from these turtles indicate that they will be decades old at first breeding. A key for sexing and assessing reproductive maturity of E. imbricata is provided. Regression equations for converting between curved carapace length and other standard measures including straight carapace measures, weight, head length and width and plastron length are described.

scholarly journals Nesting Biology of Lesser Canada Geese, Branta canadensis parvipes, along the Tanana River, Alaska

2008 ◽  
Vol 122 (1) ◽  
pp. 29
Author(s):  
Craig R. Ely ◽  
John M. Pearce ◽  
Roger W. Ruess
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Branta Canadensis ◽  
Haliaeetus Leucocephalus ◽  
Canada Geese ◽  
Red Foxes ◽  
Nesting Biology ◽  
Bald Eagles ◽  
Nest Sites ◽  
Nest Initiation

Lesser Canada Geese (Branta canadensis parvipes) are widespread throughout interior regions of Alaska and Canada, yet there have been no published studies documenting basic aspects of their nesting biology. We conducted a study to determine reproductive parameters of Lesser Canada Geese nesting along the Tanana River near the city of Fairbanks, in interior Alaska. Fieldwork was conducted in May of 2003, and consisted of locating nests along the riparian corridor between Fairbanks and Northpole, Alaska. Nests were found on gravel islands and shore habitats along the Tanana River, and were most commonly observed among driftwood logs associated with patches of alder (Alnus spp.) and willow (Salix spp.). Peak of nest initiation was 3-8 May, with a range from 27 April to 20 May; renesting was likely. Clutches ranged in size from 2 to 7 eggs and averaged 4.6 eggs. There was a negative correlation between clutch size and date of nest initiation. Egg size (mean mass = 128 g) was similar to other medium-sized Canada Geese. A positive correlation between egg size and clutch size was likely related to female age. Nineteen of 28 nests (68%) were active when visited; nests located on islands with nesting Mew Gulls (Larus canus) were more likely to be active than nests located elsewhere. Evidence at nest sites implicated Bald Eagles (Haliaeetus leucocephalus) and Red Foxes (Vulpes vulpes) as nest predators.

Pivotal temperature and predicted sex ratios for hatchling hawksbill turtles from Brazil

1999 ◽  
Vol 77 (9) ◽  
pp. 1465-1473 ◽  
Author(s):  
Matthew H Godfrey ◽  
Adriana F D'Amato ◽  
Maria  Marcovaldi ◽  
N Mrosovsky
Keyword(s):  
Low Temperatures ◽  
Sex Ratios ◽  
Sea Turtle ◽  
Temperature Dependent ◽  
Eretmochelys Imbricata ◽  
Conservation Implications ◽  
Incubation Duration ◽  
Incubation Temperatures ◽  
Hawksbill Turtles ◽  
Pivotal Temperature

Like all other species of sea turtle, the hawksbill turtle (Eretmochelys imbricata) exhibits temperature-dependent sexual differentiation, with high incubation temperatures producing females and low temperatures producing males. Relatively little is known about the sex ratios of hatchlings produced by nesting populations of hawksbill turtles. Here we estimate the overall seasonal sex ratios of hatchling hawksbill turtles produced in Bahia, Brazil, during 6 nesting seasons, based on incubation durations, pivotal temperature, and pivotal incubation duration. The overall sex ratio of hatchlings produced in Bahia from 1991-1992 through 1996-1997 was estimated to be >90% female, which is more female-biased than estimated sex ratios of hatchling loggerhead turtles from Bahia and Florida, U.S.A. The biological and conservation implications of skewed sex ratios are discussed.

Nesting ecology and reproductive biology of the hawksbill turtle, Eretmochelys imbricata, at Kish Island, Persian Gulf

2015 ◽  
Vol 96 (7) ◽  
pp. 1373-1378 ◽  
Author(s):  
M. Askari Hesni ◽  
M. Tabib ◽  
A. Hadi Ramaki
Keyword(s):  
Incubation Period ◽  
Reproductive Biology ◽  
Persian Gulf ◽  
Regression Models ◽  
Carapace Length ◽  
Carapace Width ◽  
Nesting Ecology ◽  
Eretmochelys Imbricata ◽  
Exponential Regression ◽  
Nest Sites

The ecology and reproductive biology of the hawksbill turtle, Eretmochelys imbricata were studied in Kish Island, Persian Gulf. The studied parameters include: environmental factors such as air temperature and humidity, soil types in different habitats during the breeding season; parameters related to the females' body and hatchlings biometrics i.e. weight, curved carapace length (CCL), straight carapace length (SCL), curved carapace width (CCW) and straight carapace width (SCW); and parameters related to reproductive biology, i.e. breeding time during diurnal, total eggs laid, the numbers of normal and abnormal eggs, weight and diameter of the eggs, incubation period and hatching success (HS). The temperature, humidity and soil size in different nest sites were 18.5–31°C, 70 to 88% and 0.063 to 4 mm, respectively. Means of weight, CCL, SCL, CCW and SCW of the females were 39.8 kg, 71.6, 65.1, 65.2 and 51.8 cm, respectively. The average of total egg numbers, normal and abnormal eggs by each individual female were 92.9, 75.2 and 17.7 respectively. Diameter and weight of every egg measured 38.4 mm and 33.6 g. Average of incubation period and HS were 60.9 days and 75.8%. According to the positive and significant correlation between CCL and CCW with weight took exponential regression models.

scholarly journals Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation

2021 ◽  
Vol 44 ◽  
pp. 149-158
Author(s):  
M Chatting ◽  
S Hamza ◽  
J Al-Khayat ◽  
D Smyth ◽  
S Husrevoglu ◽  
...  
Keyword(s):  
Climate Change ◽  
Sex Ratios ◽  
First Century ◽  
Climate Data ◽  
Temperature Dependent ◽  
Eretmochelys Imbricata ◽  
Climate Forecasts ◽  
The Face ◽  
Incubation Temperatures ◽  
Hawksbill Turtles

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtle Eretmochelys imbricata hatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21st century. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.

Spatiotemporal preferences in nesting of the hawksbill turtle (Eretmochelys imbricata) in Melaka, Malaysia

2017 ◽  
Vol 98 (8) ◽  
pp. 2145-2152 ◽  
Author(s):  
Sarahaizad Mohd Salleh ◽  
Hideaki Nishizawa ◽  
Shahrul Anuar Mohd Sah ◽  
Mohd Fardianshah Safri
Keyword(s):  
Monsoon Season ◽  
Peninsular Malaysia ◽  
Vegetation Zone ◽  
Eretmochelys Imbricata ◽  
Nest Sites ◽  
South West Monsoon ◽  
Nesting Preferences ◽  
Nesting Beaches ◽  
Hawksbill Turtles ◽  
West Monsoon

Nesting of hawksbill turtles (Eretmochelys imbricata) was monitored in 2013 and 2014 at 20 nesting beaches along the shores of Melaka, Peninsular Malaysia. Total nest numbers found were 481 and 463 in 2013 and 2014, respectively. The mean clutch size in 2013 of 123.5 ± 32.3 (SD) was similar to that in 2014 (118.5 ± 39.7). The distributions of nests were not uniform among the 20 beaches, and a large number of nests were found in Padang Kemunting, Kem Terendak, and Pulau Upeh, where the beaches were not always long. The nest sites indicated that the hawksbill turtle preferred to build its nest within the woody vegetation zone. The preferred vegetation species was Scaevola taccada. The temporal nesting pattern was year-round in both years, but the peak nesting season was between May and August, in the south-west monsoon season, possibly due to the gentle winds during this period. The turtles tended to nest between 22:01 and 24:00 h. This study provides basic information about hawksbill turtle nesting and insights into their spatial and temporal nesting preferences, which will contribute towards the conservation of this endangered species.

scholarly journals Natal foraging philopatry in eastern Pacific hawksbill turtles

2017 ◽  
Vol 4 (8) ◽  
pp. 170153 ◽  
Author(s):  
Alexander R. Gaos ◽  
Rebecca L. Lewison ◽  
Michael P. Jensen ◽  
Michael J. Liles ◽  
Ana Henriquez ◽  
...  
Keyword(s):  
Genetic Research ◽  
Eastern Pacific ◽  
Marine Turtle ◽  
Natal Philopatry ◽  
Eretmochelys Imbricata ◽  
Turtle Species ◽  
Marine Turtles ◽  
Complex Processes ◽  
Natal Homing ◽  
Hawksbill Turtles

The complex processes involved with animal migration have long been a subject of biological interest, and broad-scale movement patterns of many marine turtle populations still remain unresolved. While it is widely accepted that once marine turtles reach sexual maturity they home to natal areas for nesting or reproduction, the role of philopatry to natal areas during other life stages has received less scrutiny, despite widespread evidence across the taxa. Here we report on genetic research that indicates that juvenile hawksbill turtles ( Eretmochelys imbricata ) in the eastern Pacific Ocean use foraging grounds in the region of their natal beaches, a pattern we term natal foraging philopatry. Our findings confirm that traditional views of natal homing solely for reproduction are incomplete and that many marine turtle species exhibit philopatry to natal areas to forage. Our results have important implications for life-history research and conservation of marine turtles and may extend to other wide-ranging marine vertebrates that demonstrate natal philopatry.

Sign in / Sign up

Export Citation Format

Share Document