Download or read book Predicting Leatherback Sea Turtles Sex Ratios Using Spatial Interpolation of Nesting Beach Temperatures written by Emily G. Weston and published by . This book was released on 2013 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sex determination in leatherback sea turtles is directed primarily by the temperatures a clutch experiences during the middle third of development. Warmer temperatures tend to produce females while cooler temperatures yield males. Nest temperatures can vary spatially and temporally. During the 2010 and 2011 nesting seasons, this study estimated the hatchling sex ratio of leatherback sea turtles on Sandy Point National Wildlife Refuge (SPNWR), St. Croix, U.S. Virgin Islands. I measured sand temperatures from May - August and across the spatial range of leatherback nesting habitat. I spatially interpolated those temperatures to create maps that predicted temperatures for all nests incubating on SPWNR. Nest temperatures were also directly measured and compared with predicted nest temperatures to validate the prediction model. Sexes of dead-in-nest hatchlings and full term embryos were used to confirm the sex-temperature response. The model showed that microclimatic variation likely impacts the production of both sexes on SPNWR.
Download or read book Sex Ratios of Sea Turtle Hatchlings Direct and Indirect Estimates written by Matthew Howland Godfrey and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: To generate more data on sex ratios of sea turtle hatchlings, I developed a simple method of collecting daily mean sand temperatures on nesting beaches. Sand temperature can be used as an index of sex ratio. I then measured sand temperatures and sampled gonads of hatchlings of two sea turtle species on a nesting beach in Suriname during 1993. From histological analysis of the gonads, combined with information on the relative numbers of turtles nesting during the season, I generated overall estimates of sex ratio for green sea turtles (63.8% female) and for leatherback turtles (69.4% female). Relative numbers of male and female hatchlings varied throughout the season, and this corresponded to changes in sand temperatures and rainfall. From historical rainfall records and from past records of nesting frequency, I estimated overall sex ratios for another 13 seasons. Seasonal sex ratios fluctuated yearly. A revised estimate of the pivotal temperature (that constant incubation temperature which produces equal numbers of each sex) of green turtles in Suriname was 29.4$\sp\circ$C; this was slightly higher than past estimates. The transitional range of temperature (TRT), which is the range of incubation temperatures over which both sexes are produced, spanned several degrees. Metabolic warming was monitored in leatherback nests. It was found that eggs were about 0.8$\sp\circ$C warmer on average than the surrounding sand during the thermosensitive period of sexual differentiation. Because the leatherback has a narrow TRT, the influence of metabolic warming on sex ratio probably is restricted to a narrow range of incubation temperatures. Lastly, a new method of estimating sex ratios was devised, based on the rate of development of eggs and prevailing incubation temperatures. In general, nests with shorter incubation times produce mostly females and nests with longer incubation times produce mostly males. This relationship could be useful for generating predictions of sex ratio from natural nests for which only the incubation duration is known. In addition, by comparing this relationship from laboratory and field studies, it was possible to quantify the time it takes loggerhead hatchlings to dig up from the nest once they have hatched.
Download or read book Biological Ecological and Conservational Implications of Temperature dependent Sex Determination in Sea Turtle Populations written by Jennifer Estes Layton and published by . This book was released on 2011 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aspects of TSD were examined in two different sea turtle populations, representing two sea turtle species. Sex ratio was examined in the juvenile portion of the loggerhead sea turtle population in the southeastern U.S. Blood samples were analyzed in a testosterone radioimmunoassay. The results suggest a significant female-biased sex ratio (2.5F:1.0M). The presence of a female-biased sex ratio has significant implications for the conservation of this population. Another study examined nesting beach temperatures throughout the range of loggerhead nesting in the southeastern U.S. from 2004-2009. Beach temperatures were simultaneously recorded at nest depth on nesting beaches used by this population. The results indicate that temperatures vary significantly between nesting beaches, with potential sex ratios ranging from highly female biased to male biased depending on the beach. The results provide an initial data set for evaluating long-term changes in beach temperatures associated with global climate change. A third study investigated temperature-dependent sex determination in the Hawaiian green turtle. Beach and nest temperatures from 2003-2009 were evaluated. Collectively, the data indicate that temperatures at FFS were low compared to those reported for other sea turtle nesting beaches. Such cool temperatures are not conducive to the production of female-biases which have been reported for other green turtle populations. An experiment was conducted to evaluate the effects of temperatures similar to those from the nesting beach on sex determination in the Hawaiian green. The hatchlings were subsequently reared in captivity and were sexed by laparoscopy prior to their release. The results indicate that the pivotal temperature for the Hawaiian green is not lower than those reported for other green populations. This finding plus the relatively cool temperatures recorded at FFS, indicate the overall hatchling sex ratio of Hawaiian greens is predicted to be unbiased or even male-biased. The purpose of the final chapter was to develop an educational module for high school and college students, which demonstrates how modern molecular genetics can be utilized for conservation of endangered species. This chapter includes implementation of the module into local high schools, UAB CORD Summer Science Institute, and the college curriculum at Dauphin Island Sea Lab.
Download or read book The Timing of Sexual Differentiation in the Loggerhead Sea Turtle Caretta Caretta and Predicting Sex Ratios in Natural Nests of Loggerhead Sea Turtles Caretta Caretta from Nest Temperatures written by Joseph F. Gouveia and published by . This book was released on 1988 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Implications of Hatchling Sex Ratios and Survival in the Recovery Program for the Endangered Kemp s Ridley Sea Turtle written by Elizabeth Bevan (Biologist) and published by . This book was released on 2013 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Kemp's ridley (Lepidochelys kempii) sea turtle neared extinction during the mid-1980s, but due to intense conservation efforts its population is now gradually recovering. Hatchling sex ratios and natural predation on nests and hatchlings have been monitored at Rancho Nuevo, Mexico to optimize this species' recovery. Sand and nest temperatures were evaluated for the 2009-2012 nesting seasons in the egg corrals and on the nesting beach. Temperatures were cool during the start of the nesting seasons (i.e. below pivotal temperature), and gradually rose and were at or above pivotal temperatures by mid-May. Temperatures remained warm for the remainder of the nesting seasons, except when tropical weather systems impacted the area and lowered incubation temperatures. Thus, a female bias was predicted from 2009 -2012, but some nests early in the nesting season or those subjected to tropical weather systems during the middle third of incubation 2012 nesting seasons in the egg corrals and on the nesting beach. Temperatures were cool during the start of the nesting seasons (i.e. below pivotal temperature), and gradually rose and were at or above pivotal temperatures by mid-May. Temperatures remained warm for the remainder of the nesting seasons, except when tropical weather systems impacted the area and lowered incubation temperatures. Thus, a female bias was predicted from 2009 -2012, but some nests early in the nesting season or those subjected to tropical weather systems during the middle third of incubation were predicted to produce males. The nesting beach was also warm (suggesting a female bias) but it was cooler than the egg corrals. Sex ratios for the egg corrals and nesting beach were recalculated using incubation temperatures that were raised by 1 degree C to hypothetically simulate the effects of increasing global temperatures on hatchling sex ratios. Increases in sand temperatures due to global climate change could result in extreme female biases for the egg corrals and the nesting beach. Subsets of in situ nests from arribadas in 2011 and 2012 were monitored for predation throughout incubation and hatching success was determined following emergence. Predation on in situ nests was low and hatching success relatively high. Additionally, survival of hatchlings during seafinding was evaluated for in situ nests in 2012 and results suggest relatively high survival rates. Evaluation of predation data supports the concept that arribadas may achieve predator satiation, thus enhancing nest and hatchling survival. Leaving arribada nests in situ may be an effective conservation strategy. These sex ratio and predation studies provide data to facilitate an effective transition from the use of egg corrals back to the use of the natural nesting beach as the Kemp's ridley recovers.
Download or read book An Assessment of the Leatherback Turtle Population in the Atlantic Ocean written by and published by . This book was released on 2007 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Modeling of the Effects of Climate Change on Sea Turtle Migration to Nesting Beaches written by Noga Neeman and published by . This book was released on 2014 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this dissertation was to study how sea turtles currently respond to changes in temperature, in order to predict how they may respond to climate change in the future. I looked at two of the most commonly reported responses to changes in temperature: phenology shifts and changes in the duration of remigration intervals. I studied how the timing of leatherback nesting at three nesting beaches responds to temperature changes at both the nesting and the foraging grounds. There was no effect for local temperatures, but there was an overall trend for delayed nesting with increased temperatures at the foraging grounds. Deviations from this trend as well as different trends found in other studies suggest that the phenological response is complex and variable. To look at remigration intervals, I developed a theoretical, physiologically-based model that links temperature to resource availability and its accumulation by sea turtles, remigration intervals, and nesting numbers. The model shows that apparent nesting cohorts are formed not by life history traits but rather by a population-level response to environmental temperatures and that these cohorts are unstable over time. Using the model to explore different temperature history scenarios showed that short pulses of altered temperatures can have a large effect on nesting numbers. Cold pulses tend to synchronize nesting in the following year, owing to decreased remigration intervals, while warm pulses tend to delay nesting in a less synchronized way. Cyclical temperature variation increases remigration intervals in general and leads to a cyclical response in both remigration intervals and nesting numbers, with a lag and amplitude that vary with cycle duration. Adapting this model to specific populations of leatherback turtles reveals that it is able to capture both year-to-year and decade-to-decade trends in remigration intervals for both populations. Due to the difficulties in isolating the effect of strong population trends on nesting numbers and oscillations, it is unable to predict nesting numbers. Future model iterations should include inherent population trends to allow for better comparison and forecasting as well as using the model to help plan conservation efforts and properly interpret changes in nesting numbers.
Download or read book The Leatherback Turtle written by James R. Spotila and published by JHU Press. This book was released on 2015-10-30 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most comprehensive book ever written on leatherback sea turtles. Weighing as much as 2,000 pounds and reaching lengths of over seven feet, leatherback turtles are the world’s largest reptile. These unusual sea turtles have a thick, pliable shell that helps them to withstand great depths—they can swim more than one thousand meters below the surface in search of food. And what food source sustains these goliaths? Their diet consists almost exclusively of jellyfish, a meal they crisscross the oceans to find. Leatherbacks have been declining in recent decades, and some predict they will be gone by the end of this century. Why? Because of two primary factors: human redevelopment of nesting beaches and commercial fishing. There are only twenty-nine index beaches in the world where these turtles nest, and there is immense pressure to develop most of them into homes or resorts. At the same time, longline and gill net fisheries continue to overwhelm waters frequented by leatherbacks. In The Leatherback Turtle, James R. Spotila and Pilar Santidrián Tomillo bring together the world’s leading experts to produce a volume that reveals the biology of the leatherback while putting a spotlight on the conservation problems and solutions related to the species. The book leaves us with options: embark on the conservation strategy laid out within its pages and save one of nature’s most splendid creations, or watch yet another magnificent species disappear.
Download or read book Evaluation of Hatchling Sex Ratios from Natural Nesting Beaches of Hawksbill and Green Sea Turtles with Temperature Dependent Sex Determination written by Jennifer Michelle Estes and published by . This book was released on 2003 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Relating Climate Change to the Nesting Phenology and Nest Environment of Marine Turtles written by Monette Virginia Schwoerer and published by . This book was released on 2013 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ectotherms (including marine turtles) being especially sensitive to climate, are at risk to the accelerated rate of human-driven climate change. This study addresses two concerns associated with marine turtles and climate change--the relationship between the timing of marine turtle nesting and sea surface temperature; and the concern over the feminization of marine turtle populations due to rising sand temperatures. Previous studies of loggerhead sea turtles (Caretta caretta) and green sea turtles (Chelonia mydas) have documented the relationship between sea surface temperatures and nesting phenology. Earlier nesting behaviors in both species have been associated with warmer sea surface temperatures. Also, sex determination for marine turtles is temperature-dependent. Due to current sand temperatures, it is estimated that loggerhead (Caretta caretta) nests along the Atlantic coast of Florida already produce over 89% female hatchlings. Using shade to reduce nest temperature and increase the proportion of male hatchlings is one option for mitigating the impacts of climate change on marine turtle sex ratios. In this study, a 21-year (1988-2008) dataset of hawksbill sea turtle (Eretmochelys imbricata) nesting at Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands was analyzed in a similar manner to previous studies. It was found that warmer sea surface temperatures were associated with longer nesting seasons and later median nesting dates. Additionally, a preliminary sand shading study was conducted in the first field season (2011) with a subsequent loggerhead nest shading study in the following field season (2012). Although hatching success was not significantly impacted, temperatures were significantly reduced in the majority of shaded nests. This practice may not be immediately applicable as a means of managing sex ratios, but it could be used to reverse the temperature effects of nest relocation.
Download or read book The Biology of Sea Turtles Volume II written by Peter L. Lutz and published by CRC Press. This book was released on 2002-12-17 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: The success of the first volume of The Biology of Sea Turtles revealed a need for broad but comprehensive reviews of major recent advances in sea turtle biology. Biology of Sea Turtles, Volume II emphasizes practical aspects of biology that relate to sea turtle management and to changes in marine and coastal ecosystems. These topics i
Download or read book Spatial and Temporal Modeling of Sea Turtle Interactions with the Pelagic Longline Fishery in the Western North Atlantic written by Beth Gardner and published by . This book was released on 2007 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Comparison of Two Techniques Used to Model Sand Temperatures and Sex Ratios at Loggerhead Turtle Caretta Caretta Rookeries in Western Australia written by Lorian Woolgar and published by . This book was released on 2012 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: All marine turtles have temperature-dependent sex determination, and there is wide-spread concern that climate change could increase nest temperatures, leading to pronounced female biases at many of the current rookeries. This study contrasted the outcomes of correlative and mechanistic modelling approaches which predict sand temperatures and subsequent sex ratios of species with temperature-dependent sex determination. Of particular interest were the alignment of results and the ease of use of each modelling approach. Inputs for the models included nest temperature data from three key loggerhead (Caretta caretta) rookeries in Western Australia (WA) and data required to build the model, including; daily air temperatures, monthly sea surface temperatures, high resolution climate data, and information on the physical properties of beach sand. Monthly nest temperatures at each location were reconstructed over a 20 year period (Jan 1990 Mar 2009), and also projected (2030, 2070) under 'conservative' and 'extreme' IPCC climate change emissions scenarios. Subsequent sex ratios were then estimated with reference to the temperature-dependent sex determination (TSD) parameters of C. caretta from WA. The correlative models estimated much warmer sand temperatures at 50 cm nest depth, and a greater feminisation at each rookery under IPCC projections. The mechanistic model required additional levels of complexity with respect to data input, but was capable of producing temporally explicit predictions across the range of nest depths that C. caretta embryos develop. Both models predicted that rookery temperatures were not correlated with latitude, with the coolest rookery at Gnaraloo Bay located at an intermediate latitude between the southernmost rookery on Dirk Hartog Island and a northern rookery in cape range national park.
Download or read book Patterns and Consequences of Individual Variation in the Nest site Preferences of Two Species of Sea Turtle written by Stephanie Jill Kamel and published by . This book was released on 2006 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: Maternal behaviours, such as nest-site choice, can be major determinants of offspring phenotype and fitness. In egg-laying species, incubation environment can influence offspring body size, performance, survival and sex. This thesis focuses on variation among females in maternal nest-site choice and the consequences that this variation can have for offspring survival and performance. I investigated nest-site selection in leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles at three levels: (i) in two species of sea turtle nesting in different environments, (ii) within populations of the same species and (iii) within individual females both within and across nesting seasons. In both species, evidence was found for individual-level nest-site preferences. This was an unexpected result for leatherbacks, as it had long been assumed that females placed their nests randomly due to the unpredictability of their environment. Results were more striking in hawksbills, with individuals exhibiting remarkably high repeatability for nest-site microhabitat characteristics, both within and across nesting seasons. Some females preferred nesting in the forest, some in the forest edge and others still in open areas. With a few exceptions, hatching success and sea-finding ability were similar in all beach microhabitats. This raises the question of what, if not differential offspring survival, is maintaining these preferences. Frequency-dependent selection, wherein females gain a fitness advantage by producing the rare sex, is one possibility. This idea gains some support from the finding that beach temperatures varied dramatically by microhabitat: nests laid in the forest were exposed to male-producing temperatures while those in less vegetated areas were warmer and more female producing. A related aspect of this work has been to consider the conservation implications of nest-site choice. Using seasonal beach temperatures and the distribution of hawksbill nests, I estimated a balanced primary sex ratio, a situation that is likely to change if the current rates of island deforestation in the Caribbean continue. It also appears that Guadeloupe hosts one of the largest hawksbill populations in this region, indicating that data from this nesting beach are critical for developing a more robust demographic picture of Caribbean hawksbills.
Download or read book Reproductive Endocrinology of Nesting Leatherback Sea Turtles in St Croix U S Virgin Islands written by Jeanne Garner and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The global population of leatherback sea turtles is decreasing worldwide, with extinction predicted for some populations within 15 years. The population of leatherbacks nesting at Sandy Point National Wildlife Refuge (SPNWR), St. Croix, USVI, displayed a significant population increase from 1982 2001 but has experienced a slowed recovery since then. To better understand the causes of this decline, a historical database of SPNWR nesting female data was utilized to investigate trends in reproductive indices. Since 2001, average remigration interval (RI) has increased significantly, while average number of clutches laid, hatch success, hatchling production, and the percentage of neophytes recruited annually have decreased. Annual remigrant numbers have been stable to increasing, suggesting that adult survivorship remains high. To assess whether maternally derived factors may be influencing clutch production and low hatch success, blood samples were collected by saturation sampling during nesting. Circulating estradiol, testosterone, and progesterone were evaluated in conjunction with reproductive data. All hormones were highest at deposition of the first clutch and declined progressively with each consecutive clutch, as previously observed in other sea turtle species. Increased clutch production in remigrants was associated with higher estradiol levels compared to neophytes, presumably due to ovarian size and maturity. Contrary to observations in Pacific leatherbacks, progesterone decreased significantly with successive nests and total levels of estrogen were significantly lower, suggesting Atlantic leatherbacks may undergo a longer migration or spend more time in the feeding grounds prior to migrating. Linear Mixed Effect (LME) modeling was employed to determine whether hormone levels at nesting might serve as indicators of reproductive variables. Because models for all hormones were individual specific, a population model could not be developed that effectively utilized hormone levels at nesting to predict clutch size, hatch success, age or RI. However, number of clutches laid may potentially be predicted based on individually tailored estrogen models. Decreased recruitment (due to increased mortality of early life stages, altered sex ratios, or delayed age to sexual maturity), decreased productivity, and increased RI (possibly due to diminished foraging ground productivity) appear primarily responsible for current population trends which threaten the population's future.
Download or read book Sex Ratios of Juvenile Green Turtles Chelonia Mydas in Three Developmental Habitats Along the East Coast of Florida written by Cheryl Lynn Sanchez and published by . This book was released on 2013 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: The concept of temperature dependent sex determination (TSD) has been somewhat of an evolutionary enigma for many decades and has had increased attention with the growing predictions of a changing climate, particularly in species that are already threatened or endangered. TSD taxa of concern include marine turtles, which go through various life stages covering a range of regions. This, in turn, creates difficulties in addressing basic demographic questions. Secondary sex ratios (from life stages post-hatchling) were investigated by capturing juvenile green turtles (Chelonia mydas), 22.6-60.9 cm in straight carapace length (SCL), from three developmental areas along the east coast of Florida (a region known to have important juvenile aggregations) by analyzing circulating testosterone levels. All three aggregations exhibited significant female biases with an overall ratio of 3.2:1 (female: male). The probability of a turtle being female increased as the size of the individual decreased. Ratios obtained in this study were slightly less female-biased, but not significantly different, than those observed in the late 1990s. However, they were significantly more biased than those found in a late 1980s pilot study. The shift to significantly female-biased ratios may be beneficial to a recovering population, an evolutionary adaptation, and is common among juvenile aggregations. A more skewed female bias in smaller size classes may be indicative of recent, warmer periods during incubation on the nesting beaches. This female bias could become more exaggerated if temperatures meet future climate warming predictions.
Download or read book Field Pivotal Temperature and Hatchling Sex Ratios of Olive Ridley Sea Turtles Lepidochelys Olivacea at Ostional Beach Costa Rica written by Florence Wen and published by . This book was released on 2018 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
