Region-specific magnetic fields structure sea turtle populations

AbstractPhilopatry and long distance migrations are common in the animal kingdom, of which sea turtles are flagship examples. Recent studies have suggested sea turtles use the Earth’s magnetic field to navigate across ocean basins to return to their natal area, yet the mechanisms underlying this process remain unknown. If true though, the genetic structure at nesting sites should positively correlate with differences in location-specific magnetic vectors within nesting regions. Here, we confirm this working hypothesis but only in certain regions of the world and for all sea turtle species nesting in those regions. Reversely, where no correlations were found between genetic differentiation and geomagnetic vectors, this was the case for all nesting sea turtle species. Our approach hence reveals parallel but not universal use of geomagnetic cues in sea turtles. We describe magneto-sensing regions as characterized by sharp clines of total and vertical field intensity vectors offering the navigation cues that increase philopatric accuracy and promote genetic structuring among sea turtle populations.

Download Full-text

A Global Assessment of the Potential for Ocean-Driven Transport in Hatchling Sea Turtles

Water ◽

10.3390/w13060757 ◽

2021 ◽

Vol 13 (6) ◽

pp. 757

Author(s):

Morgan J. DuBois ◽

Nathan F. Putman ◽

Susan E. Piacenza

Keyword(s):

Ocean Circulation ◽

Sea Turtles ◽

Circulation Model ◽

Sea Turtle ◽

Physical Factors ◽

Theoretic Approach ◽

Turtle Species ◽

Essential Tool ◽

The World ◽

Nesting Sites

Ocean circulation models are an essential tool for use in estimating the movements of drifting marine species. Across the world, hatchling sea turtle transport to the pelagic ocean is facilitated by the local currents off their natal beaches. It is difficult, if not impossible, to observe this transport reliably for any lengthy period, and, as such, ocean circulation models are an essential tool for studying sea turtles during this vulnerable time. Here, we use the ocean circulation model HYCOM and the particle simulator Ichthyop to model the first month of hatchling transport across all sea turtle species from nesting sites across the world from 25 cohorts of hatchlings at 67 nesting sites. We evaluated transport as a function of spatiotemporal factors that could influence turtle movement, using generalized linear models and the information theoretic approach to model selection. We found that multiple physical factors influence transport across the first month of movement and that annual variability is an important factor in hatchling transport. Our findings suggest that the beaches turtles hatch from and the year in which they hatch may shape their early life and the speed of transport into the relative safety of the open ocean. An increased understanding of the likely survival of a cohort may aid in designating funds and planning conservation strategies for individual beaches to either compensate for or take advantage of the local currents.

Download Full-text

Guide to Nesting Sea Turtles in Florida

EDIS ◽

10.32473/edis-fa235-2021 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

Analisa Duran ◽

Ruth Francis-Floyd ◽

Maia Patterson Mcguire ◽

Iskande Larkin

Keyword(s):

Sea Turtles ◽

Sea Turtle ◽

The State ◽

Critical Habitat ◽

Turtle Species ◽

The World ◽

The Common ◽

Leatherback Sea Turtles

Florida’s coastline provides critical habitat for sea turtle nesting, as it has for millions of years. Throughout the state, three of the seven species of sea turtles in the world have significant nesting populations. Loggerhead, green, and leatherback sea turtles use Florida’s beaches to lay nests each year. This publication provides information on the identification, nesting characteristics, and abundance of each of the common sea turtle species who nest in Florida.

Download Full-text

Physiological determinants of the internesting interval in sea turtles: a novel ‘water-limitation’ hypothesis

Biology Letters ◽

10.1098/rsbl.2019.0248 ◽

2019 ◽

Vol 15 (6) ◽

pp. 20190248 ◽

Cited By ~ 3

Author(s):

Edwin R. Price ◽

Paul R. Sotherland ◽

Bryan P. Wallace ◽

James R. Spotila ◽

Edward M. Dzialowski

Keyword(s):

Sea Turtles ◽

Sea Turtle ◽

Capacity Limits ◽

Turtle Species ◽

Water Limitation ◽

Physiological Limits ◽

Adult Body Mass ◽

Mixed Support ◽

Egg Albumen ◽

Excretion Rates

The internesting interval separates successive clutches of sea turtle eggs, and its duration varies both among and within species. Here, we review the potential physiological limits to this interval, and develop the hypothesis that desalination capacity limits the internesting interval owing to the requirement for water deposition in eggs. Sea turtles deposit 1–4 kg of water per clutch in egg albumen; for most species, this represents about 2% of adult body mass. We calculate how quickly turtles can recover this water by estimating maximal salt excretion rates, metabolic water production and urinary losses. From this water balance perspective, the ‘water-limitation’ hypothesis is plausible for green turtles but not for leatherbacks. Some plasma biochemistry studies indicate dehydration in sea turtles during the nesting season, although this is not a universal finding and these data have rarely been collected during the internesting interval itself. There is mixed support for a trade-off between clutch size and the length of the interval. We conclude that the ‘water-limitation’ hypothesis is plausible for most sea turtle species, but requires direct experimentation.

Download Full-text

Managing fisheries in a world with more sea turtles

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.0220 ◽

2020 ◽

Vol 287 (1930) ◽

pp. 20200220

Author(s):

Nathan F. Putman ◽

Jesse Hawkins ◽

Benny J. Gallaway

Keyword(s):

Stock Assessment ◽

Sea Turtles ◽

Sea Turtle ◽

Fishing Effort ◽

Eastern United States ◽

Green Turtles ◽

Management Actions ◽

Nesting Sites ◽

Near Shore ◽

Turtle Population

For decades, fisheries have been managed to limit the accidental capture of vulnerable species and many of these populations are now rebounding. While encouraging from a conservation perspective, as populations of protected species increase so will bycatch, triggering management actions that limit fishing. Here, we show that despite extensive regulations to limit sea turtle bycatch in a coastal gillnet fishery on the eastern United States, the catch per trip of Kemp's ridley has increased by more than 300% and green turtles by more than 650% (2001–2016). These bycatch rates closely track regional indices of turtle abundance, which are a function of increased reproductive output at distant nesting sites and the oceanic dispersal of juveniles to near shore habitats. The regulations imposed to help protect turtles have decreased fishing effort and harvest by more than 50%. Given uncertainty in the population status of sea turtles, however, simply removing protections is unwarranted. Stock-assessment models for sea turtles must be developed to determine what level of mortality can be sustained while balancing continued turtle population growth and fishing opportunity. Implementation of management targets should involve federal and state managers partnering with specific fisheries to develop bycatch reduction plans that are proportional to their impact on turtles.

Download Full-text

Incidental capture of sea turtles by industrial bottom trawl fishery in the Tropical South-western Atlantic

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315417000352 ◽

2017 ◽

Vol 98 (6) ◽

pp. 1525-1531 ◽

Cited By ~ 5

Author(s):

Suzana Machado Guimarães ◽

Davi Castro Tavares ◽

Cassiano Monteiro-Neto

Keyword(s):

Sea Turtles ◽

Action Plan ◽

Chelonia Mydas ◽

Sea Turtle ◽

Bottom Trawl ◽

Conservation Strategies ◽

Future Research ◽

Olive Ridley ◽

Western Atlantic ◽

Turtle Species

The five sea turtle species occurring in Brazilian waters are susceptible to threats, including incidental catches by fisheries. Studies on incidental captures in fishing gears are the main focus of several conservation actions due to high sea turtle fishery mortality worldwide. This study provides the first evaluation of incidental sea turtle catches by industrial bottom trawl fisheries operating in Brazilian waters. Four twin-trawler vessels were monitored between July 2010 and December 2011 by captains who voluntarily completed logbooks. Forty-four turtles were captured during the 1996 tows (8313 fishing hours), resulting in a catch of 5.3 ± 0.8 turtles per 1000 h per unit effort. Captured species included the loggerhead turtle (Caretta caretta, 22 individuals), olive ridley turtles (Lepidochelys olivacea, 21 individuals) and one green turtle (Chelonia mydas). Water depth was the only variable that significantly affected sea turtle captures according to Generalized Linear Models. The capture rates reported in this study ranked sixth in relation to other published studies of similar fisheries occurring worldwide. Considering the importance of this region for sea turtles, the increasing evidence of sea turtle mortality and the goals of the National Action Plan for Conservation of Sea Turtles in Brazil, it is essential to identify the main threats towards these animals and propose mitigating solutions to reduce sea turtle mortality induced by fishing activities. This study provides results that may guide future research and goals in meeting sea turtle conservation strategies.

Download Full-text

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.

Download Full-text

Variation in Species Composition, Size and Fitness of Two Multi-Species Sea Turtle Assemblages Using Different Neritic Habitats

Frontiers in Marine Science ◽

10.3389/fmars.2020.608740 ◽

2021 ◽

Vol 7 ◽

Author(s):

Margaret M. Lamont ◽

Darren Johnson

Keyword(s):

Gulf Of Mexico ◽

Species Composition ◽

Body Condition ◽

Sea Turtles ◽

Condition Index ◽

Sea Turtle ◽

Body Condition Index ◽

Turtle Species ◽

Green Turtles ◽

Sand Bottom

The neritic environment is rich in resources and as such plays a crucial role as foraging habitat for multi-species marine assemblages, including sea turtles. However, this habitat also experiences a wide array of anthropogenic threats. To prioritize conservation funds, targeting areas that support multi-species assemblages is ideal. This is particularly important in the Gulf of Mexico where restoration actions are currently ongoing following the Deepwater Horizon oil spill. To better understand these areas in the Gulf of Mexico, we characterized two multi-species aggregations of sea turtles captured in different neritic habitats. We described species composition and size classes of turtles, and calculated body condition index for 642 individuals of three species captured from 2011 to 2019: 13.6% loggerheads (Caretta caretta), 44.9% Kemp’s ridleys (Lepidochelys kempii) and 41.4% green turtles (Chelonia mydas). Species composition differed between the two sites with more loggerheads captured in seagrass and a greater proportion of green turtles captured in sand bottom. Turtles in sand bottom were smaller and weighed less than those captured in seagrass. Although small and large turtles were captured at both sites, the proportions differed between sites. Body condition index of green turtles was lower in sand habitat than seagrass habitat; there was no difference for Kemp’s ridleys or loggerheads. In general, smaller green turtles had a higher body condition index than larger green turtles. We have identified another habitat type used by juvenile sea turtle species in the northern Gulf of Mexico. In addition, we highlight the importance of habitat selection by immature turtles recruiting from the oceanic to the neritic environment, particularly for green turtles.

Download Full-text

West Florida Shelf pipeline serves as sea turtle benthic habitat based on in situ towed camera observations

Aquatic Biology ◽

10.3354/ab00722 ◽

2019 ◽

Vol 29 ◽

pp. 17-31 ◽

Cited By ~ 1

Author(s):

HA Broadbent ◽

SE Grasty ◽

RF Hardy ◽

MM Lamont ◽

KM Hart ◽

...

Keyword(s):

Habitat Use ◽

Sea Turtles ◽

Sea Turtle ◽

Environmental Data ◽

Benthic Habitat ◽

West Florida Shelf ◽

Benthic Habitats ◽

Florida Shelf ◽

Turtle Species

The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the difficulty of obtaining in situ data. Understanding benthic habitat use that is important to the species’ reproduction, foraging, and migrations is critical for guiding management decisions. A towed camera-based assessment survey system (C-BASS) equipped with environmental sensors was used to characterize and assess benthic habitats on the West Florida Shelf (WFS) from 2014 to 2018. During these cruises, sea turtles were opportunistically observed during the surveys, and critical in situ data such as spatiotemporal information, species identification, habitat use, behavior, and environmental data were collected and evaluated. In total, 79 sea turtles were observed during 97 transects of approximately 2700 km of seafloor, which was recorded on 380 h of video. Several sea turtle species were spotted within the WFS, including loggerhead Caretta caretta, Kemp’s ridley Lepidochelys kempii, and green turtles Chelonia mydas. These opportunistic sightings revealed an area of high use on the WFS, an anthropogenic structure known as the Gulfstream natural gas pipeline (GSPL). C-BASS survey results suggest that 2 sea turtle species (C. caretta and L. kempii) utilize this artificial structure primarily as a resting area. We emphasize the importance of combining habitat mapping techniques (towed underwater video and multibeam bathymetry/backscatter) with tracking technology to better understand the fine-scale habitat use of sea turtles.

Download Full-text

Quantifying Illegal Extraction of Sea Turtles in Costa Rica

Frontiers in Conservation Science ◽

10.3389/fcosc.2021.705556 ◽

2021 ◽

Vol 2 ◽

Author(s):

Helen Pheasey ◽

George Glen ◽

Nicole L. Allison ◽

Luis G. Fonseca ◽

Didiher Chacón ◽

...

Keyword(s):

Costa Rica ◽

Sea Turtles ◽

Chelonia Mydas ◽

Sea Turtle ◽

Wildlife Trade ◽

Caribbean Coast ◽

Turtle Species ◽

Illegal Wildlife Trade ◽

The Caribbean ◽

The Impact

Estimates of illegal wildlife trade vary significantly and are often based on incomplete datasets, inferences from CITES permits or customs seizures. As a result, annual global estimates of illegal wildlife trade can vary by several billions of US dollars. Translating these figures into species extraction rates is equally challenging, and estimating illegal take accurately is not achievable for many species. Due to their nesting strategies that allow for census data collection, sea turtles offer an exception. On the Caribbean coast of Costa Rica, three sea turtle species (leatherback, Dermochelys coriacea; green, Chelonia mydas; and hawksbill, Eretmochelys imbricata) are exploited by poachers. Despite the consumption of turtle eggs and meat being illegal, they are consumed as a cultural food source and seasonal treat. Conservation programmes monitor nesting beaches, collect abundance data and record poaching events. Despite the availability of robust long-term datasets, quantifying the rate of poaching has yet to be undertaken. Using data from the globally important nesting beach, Tortuguero, as well as beaches Playa Norte and Pacuare on the Caribbean coast of Costa Rica, we modelled the spatial and temporal distribution of poaching of the three sea turtle species. Here, we present data from 2006 to 2019 on a stretch of coastline covering c.37 km. We identified poaching hotspots that correlated with populated areas. While the poaching hotspots persisted over time, we found poaching is declining at each of our sites. However, we urge caution when interpreting this result as the impact of poaching varies between species. Given their low abundance on these beaches, the poaching pressure on leatherback and hawksbill turtles is far greater than the impact on the abundant green turtles. We attribute the decline in poaching to supply-side conservation interventions in place at these beaches. Finally, we highlight the value of data sharing and collaborations between conservation NGOs.

Download Full-text

Comparative Cytogenetics of Four Sea Turtle Species (Cheloniidae): G-Banding Pattern and in situ Localization of Repetitive DNA Units

Cytogenetic and Genome Research ◽

10.1159/000511118 ◽

2020 ◽

Vol 160 (9) ◽

pp. 531-538

Author(s):

Caroline R.D. Machado ◽

Larissa Glugoski ◽

Camila Domit ◽

Marcela B. Pucci ◽

Daphne W. Goldberg ◽

...

Keyword(s):

Ribosomal Dna ◽

Sea Turtles ◽

Chelonia Mydas ◽

Sea Turtle ◽

Marine Biodiversity ◽

Comparative Cytogenetics ◽

Turtle Species ◽

Lepidochelys Olivacea ◽

Karyotypic Formula

Sea turtles are considered flagship species for marine biodiversity conservation and are considered to be at varying risk of extinction globally. Cases of hybridism have been reported in sea turtles, but chromosomal analyses are limited to classical karyotype descriptions and a few molecular cytogenetic studies. In order to compare karyotypes and understand evolutive mechanisms related to chromosome differentiation in this group, Chelonia mydas, Caretta caretta, Eretmochelys imbricata, and Lepidochelys olivacea were cytogenetically characterized in the present study. When the obtained cytogenetic data were compared with the putative ancestral Cryptodira karyotype, the studied species showed the same diploid number (2n) of 56 chromosomes, with some variations in chromosomal morphology (karyotypic formula) and minor changes in longitudinal band locations. In situ localization using a 18S ribosomal DNA probe indicated a homeologous microchromosome pair bearing a 45S ribosomal DNA locus and size heteromorphism in all 4 species. Interstitial telomeric sites were identified in a microchromosome pair in C. mydas and C. caretta. The data showed that interspecific variations occurred in chromosomal sets among the Cheloniidae species, in addition to other Cryptodira karyotypes. These variations generated lineage-specific karyotypic diversification in sea turtles, which will have considerable implications for hybrid recognition and for the study, the biology, ecology, and evolutionary history of regional and global populations. Furthermore, we demonstrated that some chromosome rearrangements occurred in sea turtle species, which is in conflict with the hypothesis of conserved karyotypes in this group.

Download Full-text