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Arendt MD, Schwenter JA, Owens DW. Climate-mediated population dynamics for the world's most endangered sea turtle species. Sci Rep 2023; 13:14444. [PMID: 37660203 PMCID: PMC10475092 DOI: 10.1038/s41598-023-41647-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 08/29/2023] [Indexed: 09/04/2023] Open
Abstract
Restricted range, and subsequently small population size, render Kemp's ridley sea turtles (Lepidochelys kempii) the most globally endangered sea turtle species. For at least two decades preceding conservation, high egg harvest rates reduced annual cohort recruitment. Despite > 50 years of dedicated conservation, annual nest counts remain well below a landmark 1947 level. Prior studies attribute less robust than anticipated nest count rebound to multiple contemporary concerns; however, analyses herein convey optimistic interpretation. In objective 1, improved analysis of the ratio of hatchlings to nests since 1966 suggested age structure stabilization as a more likely basis for nest count trends after 2005 than density-dependent effects. In objective 2, multiple regression revealed a lagged (≤ 13 years prior) climate influence on nests (adj. r2 = 0.82) and hatchlings per nest (adj. r2 = 0.94) during 2006-2022. In objectives 3 and 4, a simulator modeled population response to changes in a suite of demographic rates including survival. Across 32 models, high survival and dynamic cohort sex ratio, sexual maturity age, and the ratio of clutch frequency to remigration interval best explained nesting trends during 1966-2022. These novel findings provide alternative perspective for evaluating species recovery criteria and in turn refine future nest trend expectations.
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Affiliation(s)
- Michael D Arendt
- South Carolina Department of Natural Resources, Marine Resources Division, 217 Fort Johnson Road, Charleston, SC, 29412, USA.
| | - Jeffrey A Schwenter
- South Carolina Department of Natural Resources, Marine Resources Division, 217 Fort Johnson Road, Charleston, SC, 29412, USA
| | - David W Owens
- College of Charleston, Grice Marine Biology Laboratory (Retired), 205 Fort Johnson Road, Charleston, SC, 29412, USA
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2
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Pereira JA, Martins AS, Seminoff JA, de Azevedo Mazzuco AC. Long-term changes in body size of green turtles nesting on Trindade Island, Brazil: Signs of recovery? MARINE ENVIRONMENTAL RESEARCH 2023; 186:105930. [PMID: 36863078 DOI: 10.1016/j.marenvres.2023.105930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
Trindade Island is an important wildlife refuge in the South Atlantic Ocean and hosts the largest nesting population of green turtles (Chelonia mydas) in Brazil, about which temporal ecological dynamics are still not well understood. The present study examines 23 years of nesting for green turtles at this remote island to evaluate annual mean nesting size (MNS) changes and post-maturity somatic growth rates. Our results show a significant decrease in annual MNS over the study; Whereas MNS during the first three consecutively monitored years (1993-1995) was 115.1 ± 5.4 cm, during the last three years (2014-2016) it was 111.2 ± 6.3 cm. There was no significant change in post-maturity somatic growth rate over the course of the study; the mean annual growth rate was 0.25 ± 0.62 cm/year. These findings suggest an increase in the relative proportion of smaller, presumptive neophyte nesters appearing in Trindade during the study period.
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Affiliation(s)
- Josiele Alves Pereira
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Goiás, Goiânia, GO, Brazil.
| | - Agnaldo Silva Martins
- Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Espírito Santo, Brazil.
| | | | - Ana Carolina de Azevedo Mazzuco
- Grupo de Ecologia Bêntica, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Espírito Santo, Brazil.
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3
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Predicting the distribution of green turtle nesting sites over the Mediterranean with outcoming climate driven changes. J Nat Conserv 2023. [DOI: 10.1016/j.jnc.2022.126320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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4
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Snape RT, Beton D, Davey S, Godley BJ, Haywood J, Omeyer LC, Ozkan M, Broderick AC. Mediterranean green turtle population recovery increasingly depends on Lake Bardawil, Egypt. Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2022.e02336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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5
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Hays GC, Taxonera A, Renom B, Fairweather K, Lopes A, Cozens J, Laloë JO. Changes in mean body size in an expanding population of a threatened species. Proc Biol Sci 2022; 289:20220696. [PMID: 35673864 PMCID: PMC9174726 DOI: 10.1098/rspb.2022.0696] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
With some taxa, a reduction in the mean size of individuals may reflect over-harvesting and/or trophy hunting. However, we show that in sea turtles, a reduction in the mean size of breeding individuals may be part of the good news story of an expanding population. We describe a 70-fold increase in annual nest numbers on the island of Sal (Cape Verde, North Atlantic) between 2008 and 2020 (from 506 to 35 507 nests), making this now one of the largest loggerhead (Caretta caretta) nesting aggregations in the world. We use 20 128 measurements of the size of nesting turtles to show that their mean annual size has decreased by about 2.4 cm, from 83.2 to 80.8 cm. This decrease in the mean size of nesting turtles was not caused by the removal of larger turtles, for example by selective harvesting. Rather we develop a theoretical model to show than this decrease in mean size can be explained by an influx of first-time nesters, combined with a decrease in the size of those first-time nesters over time. A reduction in mean size of nesting turtles has been reported across the Atlantic, Pacific and Indian Oceans, and may be a common feature of population recoveries in sea turtles.
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Affiliation(s)
- Graeme C. Hays
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia
| | | | - Berta Renom
- Project Biodiversity, Santa Maria, Sal, Cape Verde
| | | | - Anice Lopes
- Project Biodiversity, Santa Maria, Sal, Cape Verde
| | | | - Jacques-Olivier Laloë
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia
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6
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Omeyer LCM, Stokes KL, Beton D, Çiçek BA, Davey S, Fuller WJ, Godley BJ, Sherley RB, Snape RTE, Broderick AC. Investigating differences in population recovery rates of two sympatrically nesting sea turtle species. Anim Conserv 2021. [DOI: 10.1111/acv.12689] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- L. C. M. Omeyer
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
| | - K. L. Stokes
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
- Department of Biosciences Swansea University Singleton Park Swansea UK
| | - D. Beton
- Society for the Protection of Turtles Gönyeli North Cyprus
| | - B. A. Çiçek
- Faculty of Arts and Sciences Eastern Mediterranean University Famagusta North Cyprus
| | - S. Davey
- Society for the Protection of Turtles Gönyeli North Cyprus
| | - W. J. Fuller
- Society for the Protection of Turtles Gönyeli North Cyprus
- Faculty of Veterinary Medicine Near East University Nicosia North Cyprus
| | - B. J. Godley
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
| | - R. B. Sherley
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
| | - R. T. E. Snape
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
- Society for the Protection of Turtles Gönyeli North Cyprus
| | - A. C. Broderick
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
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7
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Patrício AR, Hawkes LA, Monsinjon JR, Godley BJ, Fuentes MMPB. Climate change and marine turtles: recent advances and future directions. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01110] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.
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Affiliation(s)
- AR Patrício
- MARE - Marine and Environmental Sciences Centre, ISPA - Instituto Universitário, 1149-041 Lisbon, Portugal
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9FE, UK
| | - LA Hawkes
- Hatherley Laboratories, College of Life and Environmental Sciences, University of Exeter, Streatham Campus, Exeter EX4 4PS, UK
| | - JR Monsinjon
- Department of Zoology and Entomology, Rhodes University, Grahamstown 6139, South Africa
| | - BJ Godley
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9FE, UK
| | - MMPB Fuentes
- Marine Turtle Research, Ecology and Conservation Group, Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
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8
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Exploring connections among the multiple outputs and outcomes emerging from 25 years of sea turtle conservation in Northern Cyprus. J Nat Conserv 2020. [DOI: 10.1016/j.jnc.2020.125816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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9
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Haywood JC, Fuller WJ, Godley BJ, Margaritoulis D, Shutler JD, Snape RTE, Widdicombe S, Zbinden JA, Broderick AC. Spatial ecology of loggerhead turtles: Insights from stable isotope markers and satellite telemetry. DIVERS DISTRIB 2020. [DOI: 10.1111/ddi.13023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Julia C. Haywood
- Marine Turtle Research Group Centre for Ecology and Conservation University of Exeter Cornwall UK
- Plymouth Marine Laboratory Plymouth UK
| | - Wayne J. Fuller
- Faculty of Veterinary Medicine Near East University North Cyprus
| | - Brendan J. Godley
- Marine Turtle Research Group Centre for Ecology and Conservation University of Exeter Cornwall UK
- Environment and Sustainability Institute University of Exeter Cornwall UK
| | | | - Jamie D. Shutler
- Centre for Geography and Environmental Science University of Exeter Cornwall UK
| | - Robin TE. Snape
- Marine Turtle Research Group Centre for Ecology and Conservation University of Exeter Cornwall UK
- Society for the Protection of Turtles North Cyprus
| | | | | | - Annette C. Broderick
- Marine Turtle Research Group Centre for Ecology and Conservation University of Exeter Cornwall UK
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10
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Piacenza SE, Richards PM, Heppell SS. Fathoming sea turtles: monitoring strategy evaluation to improve conservation status assessments. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01942. [PMID: 31267602 PMCID: PMC6851787 DOI: 10.1002/eap.1942] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 04/18/2019] [Accepted: 04/23/2019] [Indexed: 06/09/2023]
Abstract
Population monitoring must be accurate and reliable to correctly classify population status. For sea turtles, nesting beach surveys are often the only population-level surveys that are accessible. However, process and observation errors, compounded by delayed maturity, obscure the relationship between trends on the nesting beach and the population. We present a simulation-based tool, monitoring strategy evaluation (MoSE), to test the relationships between monitoring data and assessment accuracy, using green sea turtles, Chelonia mydas, as a case study. To explore this first application of MoSE, we apply different treatments of population impacts to virtual true populations, and sample the nests or nesters, with observation error, to test if the observation data can be used to diagnose population status accurately. Based on the observed data, we examine population trend and compare it to the known values from the operating model. We ran a series of scenarios including harvest impacts, cyclical breeding probability, and sampling biases, to see how these factors impact accuracy in estimating population trend. We explored the necessary duration of monitoring for accurate trend estimation and the probability of a false trend diagnosis. Our results suggest that disturbance type and severity can have important and persistent effects on the accuracy of population assessments drawn from monitoring nesting beaches. The underlying population phase, age classes disturbed, and impact severity influenced the accuracy of estimating population trend. At least 10 yr of monitoring data is necessary to estimate population trend accurately, and >20 yr if juvenile age classes were disturbed and the population is recovering. In general, there is a greater probability of making a false positive trend diagnosis than a false negative, but this depends on impact type and severity, population phase, and sampling duration. Improving detection rates to 90% does little to lower probability of a false trend diagnosis with shorter monitoring spans. Altogether, monitoring strategies for specific populations may be tailored based on the impact history, population phase, and environmental drivers. The MoSE is an important framework for analysis through simulation that can comprehensively test population assessments for accuracy and inform policy recommendations regarding the best monitoring strategies.
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Affiliation(s)
- Susan E. Piacenza
- Department of Fisheries and WildlifeOregon State UniversityCorvallisOregon97330USA
- Present address:
Department of BiologyUniversity of West FloridaPensacolaFlorida32514USA
| | - Paul M. Richards
- NOAA NMFS, Southeast Fisheries Science CenterMiamiFlorida33149USA
| | - Selina S. Heppell
- Department of Fisheries and WildlifeOregon State UniversityCorvallisOregon97330USA
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11
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Colman LP, Thomé JCA, Almeida A, Baptistotte C, Barata PCR, Broderick AC, Ribeiro FA, Vila-Verde L, Godley BJ. Thirty years of leatherback turtle Dermochelys coriacea nesting in Espírito Santo, Brazil, 1988-2017: reproductive biology and conservation. ENDANGER SPECIES RES 2019. [DOI: 10.3354/esr00961] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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12
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Varela MR, Patrício AR, Anderson K, Broderick AC, DeBell L, Hawkes LA, Tilley D, Snape RTE, Westoby MJ, Godley BJ. Assessing climate change associated sea-level rise impacts on sea turtle nesting beaches using drones, photogrammetry and a novel GPS system. GLOBAL CHANGE BIOLOGY 2019; 25:753-762. [PMID: 30430701 DOI: 10.1111/gcb.14526] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 10/23/2018] [Indexed: 05/05/2023]
Abstract
Climate change associated sea-level rise (SLR) is expected to have profound impacts on coastal areas, affecting many species, including sea turtles which depend on these habitats for egg incubation. Being able to accurately model beach topography using digital terrain models (DTMs) is therefore crucial to project SLR impacts and develop effective conservation strategies. Traditional survey methods are typically low-cost with low accuracy or high-cost with high accuracy. We present a novel combination of drone-based photogrammetry and a low-cost and portable real-time kinematic (RTK) GPS to create DTMs which are highly accurate (<10 cm error) and visually realistic. This methodology is ideal for surveying coastal sites, can be broadly applied to other species and habitats, and is a relevant tool in supporting the development of Specially Protected Areas. Here, we applied this method as a case-study to project three SLR scenarios (0.48, 0.63 and 1.20 m) and assess the future vulnerability and viability of a key nesting habitat for sympatric loggerhead (Caretta caretta) and green turtle (Chelonia mydas) at a key rookery in the Mediterranean. We combined the DTM with 5 years of nest survey data describing location and clutch depth, to identify (a) regions with highest nest densities, (b) nest elevation by species and beach, and (c) estimated proportion of nests inundated under each SLR scenario. On average, green turtles nested at higher elevations than loggerheads (1.8 m vs. 1.32 m, respectively). However, because green turtles dig deeper nests than loggerheads (0.76 m vs. 0.50 m, respectively), these were at similar risk of inundation. For a SLR of 1.2 m, we estimated a loss of 67.3% for loggerhead turtle nests and 59.1% for green turtle nests. Existing natural and artificial barriers may affect the ability of these nesting habitats to remain suitable for nesting through beach migration.
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Affiliation(s)
- Miguel R Varela
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
| | - Ana R Patrício
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
- MARE - Marine and Environmental Sciences Centre, ISPA- Instituto Universitário, Lisboa, Portugal
| | - Karen Anderson
- Environment and Sustainability Institute, University of Exeter, Exeter, UK
| | | | - Leon DeBell
- Environment and Sustainability Institute, University of Exeter, Exeter, UK
| | - Lucy A Hawkes
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
| | - Dominic Tilley
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
| | - Robin T E Snape
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
- Society for Protection of Turtles, Girne, Turkey
| | - Matthew J Westoby
- Department of Geography and Environmental Sciences, Northumbria University, Newcastle, UK
| | - Brendan J Godley
- Centre for Ecology and Conservation, University of Exeter, Exeter, UK
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13
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Omeyer LCM, Fuller WJ, Godley BJ, Snape RTE, Broderick AC. The effect of biologging systems on reproduction, growth and survival of adult sea turtles. MOVEMENT ECOLOGY 2019; 7:2. [PMID: 30723544 PMCID: PMC6350314 DOI: 10.1186/s40462-018-0145-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/10/2018] [Indexed: 06/09/2023]
Abstract
BACKGROUND Telemetry and biologging systems, 'tracking' hereafter, have been instrumental in meeting the challenges associated with studying the ecology and behaviour of cryptic, wide-ranging marine mega-vertebrates. Over recent decades, globally, sea turtle tracking has increased exponentially, across species and life-stages, despite a paucity of studies investigating the effects of such devices on study animals. Indeed, such studies are key to informing whether data collected are unbiased and, whether derived estimates can be considered typical of the population at large. METHODS Here, using a 26-year individual-based monitoring dataset on sympatric green (Chelonia mydas) and loggerhead (Caretta caretta) turtles, we provide the first analysis of the effects of device attachment on reproduction, growth and survival of nesting females. RESULTS We found no significant difference in growth and reproductive correlates between tracked and non-tracked females in the years following device attachment. Similarly, when comparing pre- and post-tracking data, we found no significant difference in the reproductive correlates of tracked females for either species or significant carry-over effects of device attachment on reproductive correlates in green turtles. The latter was not investigated for loggerhead turtles due to small sample size. Finally, we found no significant effects of device attachment on return rates or survival of tracked females for either species. CONCLUSION While there were no significant detrimental effects of device attachment on adult sea turtles in this region, our study highlights the need for other similar studies elsewhere and the value of long-term individual-based monitoring.
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Affiliation(s)
- Lucy C. M. Omeyer
- Marine Turtle Research Group, Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9FE United Kingdom
| | - Wayne J. Fuller
- Faculty of Veterinary Medicine, Near East University, Nicosia, Mersin 10, North Cyprus Turkey
- Society for the Protection of Turtles, PK.65 Kyrenia, Mersin 10, North Cyprus Turkey
| | - Brendan J. Godley
- Marine Turtle Research Group, Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9FE United Kingdom
| | - Robin T. E. Snape
- Marine Turtle Research Group, Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9FE United Kingdom
- Society for the Protection of Turtles, PK.65 Kyrenia, Mersin 10, North Cyprus Turkey
| | - Annette C. Broderick
- Marine Turtle Research Group, Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9FE United Kingdom
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Casale P, Broderick AC, Camiñas JA, Cardona L, Carreras C, Demetropoulos A, Fuller WJ, Godley BJ, Hochscheid S, Kaska Y, Lazar B, Margaritoulis D, Panagopoulou A, Rees AF, Tomás J, Türkozan O. Mediterranean sea turtles: current knowledge and priorities for conservation and research. ENDANGER SPECIES RES 2018. [DOI: 10.3354/esr00901] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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15
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Esteban N, Mortimer JA, Hays GC. How numbers of nesting sea turtles can be overestimated by nearly a factor of two. Proc Biol Sci 2018; 284:rspb.2016.2581. [PMID: 28202810 DOI: 10.1098/rspb.2016.2581] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 01/23/2017] [Indexed: 11/12/2022] Open
Abstract
Estimating the absolute number of individuals in populations and their fecundity is central to understanding the ecosystem role of species and their population dynamics as well as allowing informed conservation management for endangered species. Estimates of abundance and fecundity are often difficult to obtain for rare or cryptic species. Yet, in addition, here we show for a charismatic group, sea turtles, that are neither cryptic nor rare and whose nesting is easy to observe, that the traditional approach of direct observations of nesting has likely led to a gross overestimation of the number of individuals in populations and underestimation of their fecundity. We use high-resolution GPS satellite tags to track female green turtles throughout their nesting season in the Chagos Archipelago (Indian Ocean) and assess when and where they nested. For individual turtles, nest locations were often spread over several tens of kilometres of coastline. Assessed by satellite observations, a mean of 6.0 clutches (range 2-9, s.d. = 2.2) was laid by individuals, about twice as many as previously assumed, a finding also reported in other species and ocean basins. Taken together, these findings suggest that the actual number of nesting turtles may be almost 50% less than previously assumed.
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Affiliation(s)
- Nicole Esteban
- Department of Biosciences, Swansea University, Swansea SA2 8PP, Wales, UK
| | - Jeanne A Mortimer
- Turtle Action Group of Seychelles, PO Box 1443, Victoria, Mahé, Seychelles.,Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Graeme C Hays
- Deakin University, Geelong, Australia, School of Life and Environmental Sciences, Centre for Integrative Ecology, Warrnambool, VIC 3280, Australia
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16
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Omeyer LCM, Godley BJ, Broderick AC. Growth rates of adult sea turtles. ENDANGER SPECIES RES 2017. [DOI: 10.3354/esr00862] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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17
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Lee PLM, Schofield G, Haughey RI, Mazaris AD, Hays GC. A Review of Patterns of Multiple Paternity Across Sea Turtle Rookeries. ADVANCES IN MARINE BIOLOGY 2017; 79:1-31. [PMID: 30012274 DOI: 10.1016/bs.amb.2017.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Why females would mate with multiple partners and have multiple fathers for clutches or litters is a long-standing enigma. There is a broad dichotomy in hypotheses ranging from polyandry having benefits to simply being an unavoidable consequence of a high incidence of male-female encounters. If females simply give in to mating when it is too costly to avoid being harassed by males (convenience polyandry), then there should be a higher rate of mating as density increases. However, if females actively seek males because they benefit from multiple mating, then mating frequency, and consequently the incidence of multiple paternity of clutches, should be high throughout. To explore these competing explanations, here we review the incidence of multiple paternity for sea turtles nesting around the World. Across 30 rookeries, including all 7 species of sea turtle, the incidence of multiple paternity was only weakly linked to rookery size (r2=0.14). However, using high resolution at-sea GPS tracking we show that the specifics of movement patterns play a key role in driving packing density and hence the likely rate of male-female encounters. When individuals use the same focal areas, packing density could be 100× greater than when assuming individuals move independently. Once the extent of adult movements in the breeding season was considered so that movements and abundance could be combined to produce a measure of density, then across rookeries we found a very tight relationship (r2=0.96) between packing density and the incidence of multiple paternity. These findings suggest that multiple paternity in sea turtles may have no benefit, but is simply a consequence of the incidence of male-female encounters.
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Affiliation(s)
- Patricia L M Lee
- Centre for Integrative Ecology, Deakin University, Geelong, VIC, Australia
| | - Gail Schofield
- Centre for Integrative Ecology, Deakin University, Geelong, VIC, Australia
| | - Rebecca I Haughey
- Centre for Integrative Ecology, Deakin University, Geelong, VIC, Australia
| | - Antonios D Mazaris
- School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Graeme C Hays
- Centre for Integrative Ecology, Deakin University, Geelong, VIC, Australia.
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Piacenza SE, Richards PM, Heppell SS. An agent-based model to evaluate recovery times and monitoring strategies to increase accuracy of sea turtle population assessments. Ecol Modell 2017. [DOI: 10.1016/j.ecolmodel.2017.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Groom RA, Griffiths AD, Chaloupka M. Estimating long-term trends in abundance and survival for nesting flatback turtles in Kakadu National Park, Australia. ENDANGER SPECIES RES 2017. [DOI: 10.3354/esr00795] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Rees AF, Alfaro-Shigueto J, Barata PCR, Bjorndal KA, Bolten AB, Bourjea J, Broderick AC, Campbell LM, Cardona L, Carreras C, Casale P, Ceriani SA, Dutton PH, Eguchi T, Formia A, Fuentes MMPB, Fuller WJ, Girondot M, Godfrey MH, Hamann M, Hart KM, Hays GC, Hochscheid S, Kaska Y, Jensen MP, Mangel JC, Mortimer JA, Naro-Maciel E, Ng CKY, Nichols WJ, Phillott AD, Reina RD, Revuelta O, Schofield G, Seminoff JA, Shanker K, Tomás J, van de Merwe JP, Van Houtan KS, Vander Zanden HB, Wallace BP, Wedemeyer-Strombel KR, Work TM, Godley BJ. Are we working towards global research priorities for management and conservation of sea turtles? ENDANGER SPECIES RES 2016. [DOI: 10.3354/esr00801] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Placing Madagascar's marine turtle populations in a regional context using community-based monitoring. ORYX 2016. [DOI: 10.1017/s0030605315001398] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AbstractMadagascar is an important foraging ground for marine turtles in the Western Indian Ocean, yet the status of the country's nesting aggregations remains poorly documented. We assess the current status and trend in nesting throughout Madagascar, including data recorded by a community-based monitoring project in the Barren Isles (western Madagascar). We contextualize the findings in comparison with data from Madagascar's closest neighbouring states. Reports indicate that nesting levels have declined at many coastal sites, with no known recordings since 2000 at > 40 nesting sites. We estimate there are a minimum of 1,200 nests per year in Madagascar, with the largest recorded nesting aggregation (< 1,000 nests per year) found on islands off the west and northern coasts. The majority of nesting aggregations, including those recorded by the community-based monitoring project in the Barren Isles, are relatively small, in the order of < 50 nests per year, yet they are potentially important sources of regional genetic diversity. Nesting on many of the islands (e.g. Tromelin, Europa) around Madagascar has increased over the last 20 years, despite the fact that thousands of turtles probably originating from these sites are taken by fishers in the waters of Madagascar annually. We discuss the importance of protecting small nesting populations, and how community-based monitoring could be an important tool for conserving remote and vulnerable populations and building capacity for natural resource management.
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Casale P, Heppell SS. How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean. ENDANGER SPECIES RES 2016. [DOI: 10.3354/esr00714] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Stokes KL, Broderick AC, Canbolat AF, Candan O, Fuller WJ, Glen F, Levy Y, Rees AF, Rilov G, Snape RT, Stott I, Tchernov D, Godley BJ. Migratory corridors and foraging hotspots: critical habitats identified for Mediterranean green turtles. DIVERS DISTRIB 2015. [DOI: 10.1111/ddi.12317] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- K. L. Stokes
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
| | - A. C. Broderick
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
| | - A. F. Canbolat
- Department of Biology; Faculty of Science; Hacettepe University; 06532 Beytepe Ankara Turkey
| | - O. Candan
- Department of Biology; Faculty of Sciences and Arts; Ordu University; Cumhuriyet Campus 52200 Ordu Turkey
| | - W. J. Fuller
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
- Faculty of Veterinary Medicine; Near East University; Nicosia North Cyprus Mersin 10 Turkey
- Society for Protection of Turtles; PK65 Kyrenia North Cyprus Mersin 10 Turkey
| | - F. Glen
- 16 Eshton Terrace; Clitheroe Lancashire BB7 1BQ UK
| | - Y. Levy
- Marine Biology Department; Leon H. Charney School of Marine Sciences; University of Haifa; Haifa 31905 Israel
- Israel's Sea Turtle Rescue Centre; Nature & Parks Authority; Mevoot Yam Michmoret 40297 Israel
| | - A. F. Rees
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
- ARCHELON; The Sea Turtle Protection Society of Greece; Solomon S7 GR 104 32 Athens Greece
| | - G. Rilov
- Marine Biology Department; Leon H. Charney School of Marine Sciences; University of Haifa; Haifa 31905 Israel
- National Institute of Oceanography; Israel Oceanographic and Limnological Research; PO Box 8030 Haifa 31080 Israel
| | - R. T. Snape
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
- Society for Protection of Turtles; PK65 Kyrenia North Cyprus Mersin 10 Turkey
| | - I. Stott
- Environmental & Sustainability Institute; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
| | - D. Tchernov
- Marine Biology Department; Leon H. Charney School of Marine Sciences; University of Haifa; Haifa 31905 Israel
| | - B. J. Godley
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus Cornwall TR10 9FE UK
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