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- Ghost crab predation of loggerhead turtle eggs across thermal habitatsPublication . Martins, Rita; Marco, Adolfo; Patino-Martinez, Juan; Yeoman, Kate; Vinagre, Catarina; Patrício, Ana RitaThe reproductive success of sea turtles is highly influenced by the environmental and biological conditions of the nesting beach. Maio Island, Cabo Verde, one of the main nesting sites for the Northeast Atlantic loggerhead subpopulation, displays marked heterogeneity of sand coloration, with dark, mixed and light sandy beaches, resulting in different thermal habitats. Considering that sand temperature can influence both sea turtle embryo development and predatory activity by ghost crabs – the main predators of clutches and hatchlings at Cabo Verde – we surveyed loggerhead nesting beaches at Maio Island, with three sand colorations (‘beach type’), to assess: 1) the density and size of ghost crab burrows, as a proxy for ghost crab density and size, and 2) ghost crab predation on 70 loggerhead nests. We further assessed nest site selection, by considering the number of nesting activities and clutches laid across beach type. There were no evident trends in the distributions of ghost crab density and size between years or beach type. We found that ghost crab predation is a major source of mortality in Maio Island, affecting 67.8% (n = 59) of the nests. Ghost crab predation was variable between beaches, but generally, at the warmer dark sand beaches, clutch mortality was mostly caused by ghost crab predation (53.2%, n = 17), while at the mixed sand beaches mortality by predation was low (7.5%, n = 18), compared to mortality due to other causes (49.9%), indicating that other factors can also significantly impact clutch survival. The mixed sand beaches had more nesting activities and higher nest density (2.29/m2; 1.25/m2, respectively), compared to the light sand (0.72/m2; 0.35/m2) and the dark sand beaches (0.73/m2; 0.27/m2), suggesting a possible predation-free nesting preference. Our findings show that some beaches are in need of nest protection, thus we recommend both in situ nest protection and egg translocation to safe hatcheries, depending on the threats identified, to enhance clutch survival at such heterogeneous nesting areas as Maio Island.
- Fine-scale foraging segregation in a green turtle (Chelonia mydas) feeding ground in the Bijagós archipelago, Guinea BissauPublication . Madeira, Fernando Miguel; Rebelo, Rui; Catry, Paulo; Neiva, João Guilherme; Barbosa, Castro; Regalla De Barros, Aissa; Patrício, Ana RitaGreen turtles (Chelonia mydas) are highly dependent on neritic foraging areas throughout much of their life. Still, knowledge of recruitment dynamics, foraging habits, and habitat use in these areas is limited. Here, we evaluated how the distribution and food preferences of green sea turtles from different life stages varied within a foraging aggregation. We focused on two islands in Guinea-Bissau, Unhocomo and Unhocomozinho, using water captures and survey dives to record habitat use and characteristics, and stable isotopes to infer diet. Additionally, we used stable isotopes to infer their diet. Two habitat types were sampled: deeper (2.26 ± 0.4 m) rocky sites fringed by mangrove with macroalgae, and sandy shallows (1.37 ± 0.12 m) surrounded by rocky reefs with macroalgae and seagrass. The two benthic communities were similar isotopically and in terms of species composition, except for the presence or absence of seagrass, which had unique signatures. We captured 89 turtles ranging from 35 cm to 97 cm in curved carapace length (i.e., juvenile to adult stages). Size distribution was habitat-dependent, with most smaller turtles present in sandy shallows and larger turtles favoring slightly deeper rocky sites. Turtle isotopic signatures differed between the habitat of capture, regardless of size, revealing a marked dichotomy in foraging preference. All turtles fed primarily on macroalgae, mostly rhodophytes. However, individuals captured in sandy habitats had evident seagrass skewed isotopic signatures. Larger turtles may be unable to use the more diverse shallower foraging sites due to increased vulnerability to predation. Despite the proximity of the sampled foraging sites (2.7 km apart), the two foraging subgroups seem to maintain consistently different feeding habits. Our study highlights how heterogeneous green turtle foraging habits can be within populations, even at small geographic scales.
- Inter-island nesting dynamics and clutch survival of green turtles Chelonia mydas within a marine protected area in the Bijagós Archipelago, West AfricaPublication . Raposo, Cheila; R., Rebelo; Catry, Paulo; Ferreira-Airaud, Betania; Barbosa, Castro; Garcia, Tumbulo Bamba; Regalla De Barros, Aissa; Sá Sampaio, Manuel; Patrício, Ana RitaUnderstanding spatial heterogeneity in reproductive success among at-risk populations facing localised threats is key for conservation. Sea turtle populations often concentrate at one nesting site, diverting conservation efforts from adjacent smaller rookeries. Poilão Island, Bijagós Archipelago, Guinea-Bissau, is a notable rookery for green turtles Chelonia mydas within the João Vieira-Poilão Marine National Park, surrounded by three islands (Cavalos, Meio and João Vieira), with lower nesting activity. Poilão’s nesting suitability may decrease due to turtle population growth and sea level rise, exacerbating already high nest density. As the potential usage of secondary sites may arise, we assessed green turtle clutch survival and related threats in Poilão and its neighbouring islands. High nest density on Poilão leads to high clutch destruction by later turtles, resulting in surplus eggs on the beach surface and consequently low clutch predation (4.0%, n = 69, 2000). Here, the overall mean hatching success estimated was 67.9 ± 36.7% (n = 631, 2015–2022), contrasting with a significantly lower value on Meio in 2019 (11.9 ± 23.6%, n = 21), where clutch predation was high (83.7%, n = 98). Moderate to high clutch predation was also observed on Cavalos (36.0%, n = 64) and João Vieira (76.0%, n = 175). Cavalos and Meio likely face higher clutch flooding compared to Poilão. These findings, alongside observations of turtle exchanges between islands, may suggest a source-sink dynamic, where low reproductive output sink habitats (neighbouring islands) are utilized by migrants from Poilão (source), which currently offers the best conditions for clutch survival.
- track2KBA: An R package for identifying important sites for biodiversity from tracking dataPublication . Beal, Martin; Oppel, Steffen; Handley, Jonathan; Pearmain, Elizabeth J.; Pujol, Virginia Morera; Carneiro, Ana P. B.; Davies, Tammy; Phillips, Richard A.; Taylor, Philip R.; Miller, Mark G. R.; Franco, Aldina; Catry, Inês; Patrício, Ana Rita; Regalla De Barros, Aissa; Staniland, Iain; Boyd, Charlotte; Catry, Paulo; Dias, Maria P.Abstract 1. Identifying important sites for biodiversity is vital for conservation and management. However, there is a lack of accessible, easily applied tools that enable practitioners to delineate important sites for highly mobile species using established criteria. 2. We introduce the R package ‘track2KBA’, a tool to identify important sites at the population level using tracking data from individual animals based on three key steps: (a) identifying individual core areas, (b) assessing population-level representativeness of the sample and (c) quantifying spatial overlap among individuals and scaling up to the population. 3. We describe package functionality and exemplify its application using tracking data from three taxa in contrasting environments: a seal, a marine turtle and a migratory land bird. 4. This tool facilitates the delineation of sites of ecological relevance for diverse taxa and provides output useful for assessing their importance to a population or species, as in the Key Biodiversity Area (KBA) Standard. As such, ‘track2KBA’ can contribute directly to conservation planning at global and regional levels.
- Adaptation of sea turtles to climate warming: Will phenological responses be sufficient to counteract changes in reproductive output?Publication . Fuentes, Mariana; Santos, Armando Jose Barsante; Abreu-Grobois, F. Alberto; Briseño‐Dueñas, R.; Al-Khayat, Jassim; Hamza, Shafeeq; Saliba, Sally; Anderson, D.; Rusenko, Kirt; Mitchell, N. J.; Gammon, Malindi Jane; Bentley, Blair P; Beton, Damla; Booth, David; Broderick, Annette; Colman, Liliana; Snape, Robin; Calderon‐Campuzano, M. F.; Cuevas, Eduardo; López-Castro, M. C.; Flores-Aguirre, Cynthia Dinorah; Mendez, Fausto; Segura‐Garcia, Y.; Ruiz‐Garcia, A.; Fossette, Sabrina; Gatto, Christopher; Reina, Richard; Girondot, Marc; Godfrey, M.; Guzman Hernandez, Vicente; Hart, Catherine Edwina; Kaska, Yakup; Lara, P.H.; Marcovaldi, Maria Angela; Leblanc, Nia; Rostal, D.; Liles, Mark; Wyneken, Jeanette; Lolavar, Alexandra; Williamson, Sean; Manoharakrishnan, Muralidharan; Pusapati, Chandana; Chatting, Mark; Mohd Salleh, Sarahaizad; Patrício, Ana Rita; Regalla, A.; Restrepo, J.; Garcia, R.; Tomillo, Pilar Santidrián; Sezgin, Çisem; Shanker, Kartik; Tapilatu, F.; Turkozan, Oguz; Valverde, Clodoaldo; Carroll, Kristina Williams; Yilmaz, Can; Tolen, Nicholas; Tucek, J.; Le Gouvello Du Timat, Diane, Zelica, Marie; Rivas, Marga; Freire, Jordana; Touron, M.; Genet, Q.; Salmon, M.; Araujo, M. R.; Freire, J. B.; Davel Castheloge, Vinicius; Jesus, Paulo Roberto; Júnior, Paulo Dias Ferreira; Paladino, Frank V.; Montero‐Flores, D.; Sözbilen, Doğan; Monsinjon, JonathanSea turtles are vulnerable to climate change since their reproductive output is influenced by incubating temperatures, with warmer temperatures causing lower hatching success and increased feminization of embryos. Their ability to cope with projected increases in ambient temperatures will depend on their capacity to adapt to shifts in climatic regimes. Here, we assessed the extent to which phenological shifts could impacts from increases in ambient temperatures (from 1.5 to 3°C in air temperatures and from 1.4 to 2.3°C in sea surface temperatures by 2100 at our sites) on four species of sea turtles, under a “middle of the road” scenario (SSP2-4.5). Sand temperatures at sea turtle nesting sites are projected to increase from 0.58 to 4.17°C by 2100 and expected shifts in nesting of 26–43 days earlier will not be sufficient to maintain current incubation temperatures at 7 (29%) of our sites, hatching success rates at 10 (42%) of our sites, with current trends in hatchling sex ratio being able to be maintained at half of the sites. We also calculated the phenological shifts that would be required (both backward for an earlier shift in nesting and forward for a later shift) to keep up with present-day incubation temperatures, hatching success rates, and sex ratios. The required shifts backward in nesting for incubation temperatures ranged from −20 to −191 days, whereas the required shifts forward ranged from +54 to +180 days. However, for half of the sites, no matter the shift the median incubation temperature will always be warmer than the 75th percentile of current ranges. Given that phenological shifts will not be able to ameliorate predicted changes in temperature, hatching success and sex ratio at most sites, turtles may need to use other adaptive responses and/or there is the need to enhance sea turtle resilience to climate warming.
- Key issues in assessing threats to sea turtles: Knowledge gaps and future directionsPublication . Fuentes, Mariana M. P. B.; McMichael, Erin; Kot, Connie Y.; Silver-Gorges, Ian; Wallace, Bryan P.; Godley, Brendan; Brooks, Annabelle M. L; Ceriani, Simona A; Cortés-Gómez, Adriana A.; Dawson, Tiffany M.; Dodge, Kara L.; Flint, Mark; Jensen, Michael P; Komoroske, Lisa M.; Kophamel, Sara; Lettrich, Matthew; Long, Christopher A.; Nelms, Sarah E.; Patrício, Ana Rita; Robinson, Nathan J.; Seminoff, Jeffrey; Ware, Matthew; Whitman, Elizabeth R.; Chevallier, Damien; Clyde-Brockway, Chelsea E.; Korgaonkar, Sumedha A.; Mancini, Agnese; Mello-Fonseca, J; Monsinjon, Jonathan; Neves-Ferreira, Isabella; Ortega, Anna A.; Patel, Samir H.; Pfaller, Joseph B.; Ramirez, Matthew D.; Raposo, Cheila; Smith, Caitlin E.; Abreu-Grobois, F. Alberto; Hays, Graeme C.Sea turtles are an iconic group of marine megafauna that have been exposed to multiple anthropogenic threats across their different life stages, especially in the past decades. This has resulted in population declines, and consequently many sea turtle populations are now classified as threatened or endangered globally. Although some populations of sea turtles worldwide are showing early signs of recovery, many still face fundamental threats. This is problematic since sea turtles have important ecological roles. To encourage informed conservation planning and direct future research, we surveyed experts to identify the key contemporary threats (climate change, direct take, fisheries, pollution, disease, predation, and coastal and marine development) faced by sea turtles. Using the survey results and current literature, we also outline knowledge gaps in our understanding of the impact of these threats and how targeted future research, often involving emerging technologies, could close those gaps.
- Satellite tracking and field assessment highlight major foraging site for green turtles in the Banc d'Arguin, MauritaniaPublication . Catry, Paulo; Senhoury, Cheibani; Sidina, Ebaye; El Bar, Nahi; Samba Bilal, Abdellahi; Ventura, Francesco; Godley, Brendan; Pires, António A.; Regalla, Aissa; Patrício, Ana RitaThere is a remarkable paucity of estimates of the numeric importance of sea turtles at foraging grounds. The Banc d'Arguin (BA) is a vast shallow marine area off the coast of Mauritania, known as a site of world importance for coastal migratory birds and other biodiversity, including extensive seagrass beds. We sampled foraging green turtles on the BA, and extensively tracked adult female green turtles from the Bijagós archipelago, the only significant nesting aggregation within 3000 km of the BA, to estimate the abundance of this foraging aggregation. Additionally, we used a demographic simulation to support our findings. Based on satellite tracking of adult females (n = 46), we estimate that 50 % of the nesting population from the Bijagós migrate to the BA post-nesting. We combine data on numbers nesting in the Bijagós with information on proportion migrating to the BA in the same years to conservatively estimate that 8285 adult female green turtles forage at this site. We also estimate that adult females represent only 5.6 % of the green turtles in the BA, implying that the number of turtles there is of the order of 150,000 individuals. Most of the BA enjoys effective protection as part of the Parc National du Banc d'Arguin where significant fisheries regulations are well enforced by a marine surveillance program. We show that the BA is one of the major foraging sites for green turtles nesting in the Bijagós and a site of critical importance for immature and adult green turtles in a global context.
- Movement patterns of green turtles at a key foraging site: the Banc d’Arguin, MauritaniaPublication . Mestre, Julie; Patrício, Ana Rita; Sidina, Ebaye; Senhoury, Cheibani; El’bar, Nahi; Beal, Martin; Regalla De Barros, Aissa; Catry, PauloABSTRACT: Interactions with fisheries is a major threat to sea turtles. However, space-use at foraging locations remains overlooked in many populations, preventing effective protection. We assess the space-use of 14 juvenile and 24 adult green turtles (Chelonia mydas) satellite-tracked in 2018–2022 within a foraging site of global importance for this species, the Banc d’Arguin in Mauritania, West Africa. Turtles exhibited a patchy distribution and used overlapping habitats irrespective of sexes and life stages. Mean individual home range was larger (151.5 ± 160.5 km²) than values reported in most green turtle populations. Individuals concentrated in two main areas used year-round. Inshore/offshore movements seem to occur within the central part of the Banc d’Arguin, with turtles moving to deeper areas during colder months. More than half of the turtles performed within-season range shifts and switched between up to four distinct areas, with some individuals returning to previously visited sites. Turtles mostly exploited shallow areas (4.30 ± 3.42 m) and seemed to use disproportionally more of the areas inside the Parc National du Banc d’Arguin, than areas of similar bathymetry outside this marine protected area. This suggests that foraging green turtles have been benefiting from the management of the Park since it was established in 1976. However, turtles’ home range overlapped greatly with artisanal fisheries, which operate in the central shallow waters of the Park. The present study provides valuable ecological information that can be used to inform the planning of fisheries management zones, aiming to reduce the interactions between turtles and artisanal fisheries. © The Author(s) 2024.
- Genetic characterization of green turtles (Chelonia mydas) from São Tomé and Príncipe: Insights on species recruitment and dispersal in the Gulf of GuineaPublication . Hancock, Joana M.; Vieira, Sara; Taraveira, Lúcio; Santos, Aladino; Schmitt, Vanessa; Semedo, Alcides; Patrício, Ana Rita; Ferrand, Nuno; Gonçalves, Helena; Sequeira, FernandoGenetic studies on green sea turtles (Chelonia mydas) in the Eastern Atlantic have mostly focused on reproductive females, with limited information available regarding juveniles and foraging grounds. Improved understanding of genetic diversity and patterns of connectivity between nesting and foraging grounds is critical to identify management units and delineate suitable conservation strategies. Here we analyzed data from 11 microsatellite markers and sequences of the mitochondrial control region from both juveniles and females sampled in foraging and nesting aggregations around São Tomé and Príncipe islands, in the Gulf of Guinea, West Africa. Both nuclear and mtDNA data were congruent in showing that São Tomé and Príncipe's green turtles population exhibit high levels of genetic diversity, which are similar to those reported for other foraging aggregates in the Atlantic. Although signs of population substructure among foraging and nesting grounds of São Tomé and Príncipe islands were not apparent, our analysis based on mtDNA marker showed that both juvenile and adult turtles were genetically differentiated from other foraging and nesting Atlantic populations. The similar levels of genetic diversity found in both juveniles and females are consistent with the results from mixed stock analyses, which suggested that São Tomé and Príncipe's rookery is the primary source of juveniles to the local foraging aggregation. Taken these aspects in consideration, we argue that São Tomé and Príncipe green turtles show limited dispersal and should be considered an important management unit, and conservation actions in this archipelago must be implemented not only at the level of the rookery but should also include the foraging aggregations.
- Atlantic connectivity of a major green sea turtle Chelonia mydas foraging aggregation at the Banc d’Arguin, MauritaniaPublication . Patrício, Ana Rita; Coveney, Sophia A.; Barbanti, Anna; Barbosa, Castro; Broderick, Annette; El’Bar, Nahi; Godley, Brendan; Hancock, Joana M.; Regalla De Barros, Aissa; Senhoury, Cheibani; Sidina, Ebaye; de Thoisy, Benoît de; Tilley, Dominic; Weber, Sam; Catry, PauloABSTRACT: Understanding population connectivity is paramount for effective conservation. While genetic tools have elucidated sea turtle migration patterns, notable data gaps limit our understanding of ocean-wide connectivity, especially regarding east Atlantic green turtles. We characterized the genetic composition of a globally important green turtle foraging aggregation at the Banc d’Arguin, Mauritania, incorporating data from 323 individuals captured between 2018 and 2021. Using extended mitochondrial DNA D-loop (738 base pairs [bp]) and mitochondrial short tandem repeat (mtSTR; ~200 bp) markers, we assessed the genetic structure of Atlantic green turtle foraging aggregations and estimated the most likely origin of immature green turtles from the Banc d’Arguin using mixed stock analyses (MSAs). We identified 6 D-loop haplotypes, with a clear dominance of CM-A8.1 (91.8%) followed by CM-A5.1 (6.3%) and 4 rare haplotypes: CM-A1.4, CMA6.1, CM24.1 and CM36.1. We found 13 mtSTR haplotypes, with ‘7-12-4-4’ being dominant (89.0%). The genetic composition at the Banc d’Arguin differed significantly from the only foraging aggregation studied in West Africa to date — in the archipelago of Cabo Verde (located ca. 750 km from the Banc d’Arguin) — dominated by haplotype CM-A5. The MSA combining both genetic markers indicated that 87.6% of immature green turtles at the Banc d’Arguin originate from the major East Atlantic rookery at Poilão (Guinea-Bissau), but 11.6% come from more distant rookeries in South America (8.1%) and potentially Ascension Island (3.4%). We suggest that green turtle transatlantic movements may be more common than previously thought and highlight the importance of the Banc d’Arguin as a regional foraging hub for this species.