Escalating habitat warming in Amazonian rivers shifting turtle hatchlings sex-ratios towards feminization

Abstract Amazonia is experiencing more frequent and severe weather extremes. Freshwater species, like the endangered Giant Amazonian turtles, Podocnemis expansa , are key for assessing how climate change influences Amazonian rivers and biodiversity. Extreme habitat temperatures can increase turtle embryo mortality; however, other non-lethal effects are expected due to their temperature-dependent sex determination, which can eventually drive populations to become predominantly female-biased. Using in-situ and satellite-based data from 1998 to 2024, we show escalating warming trends, up to + 0.3ºC a year, in the water and sandbanks of three major Amazon Basin rivers (Purus, Trombetas, and Tapajós) used by turtles for nesting. We then estimated the sex-ratio of all hatchlings bourn at these sandbanks monitored by local communities. We observed that, as warming intensifies, cohorts unlikely reach balanced sex-ratios, with the magnitude of the bias progressively shifting towards more females, while males comprise less than 15% of offspring. Our results emphasize the need for long-term nest-temperature observations and monitoring as a critical conservation effort to access ongoing population changes under future warming scenarios.

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Publication Details

Journal
Research Square
Published
2026-11-06
DOI
https://doi.org/10.21203/rs.3.rs-11460215/v1
Primary Topic
Turtle Biology and Conservation
Type
preprint

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preprint

Escalating habitat warming in Amazonian rivers shifting turtle hatchlings sex-ratios towards feminization

Fernanda P. Werneck, Rodolfo Nóbrega, Diogo de Lima Franco, Shirley Famelli et al.
1 links
Research Square
Turtle Biology and Conservation
preprint

Escalating habitat warming in Amazonian rivers shifting turtle hatchlings sex-ratios towards feminization

Fernanda P. Werneck, Rodolfo Nóbrega, Diogo de Lima Franco, Shirley Famelli, Gustavo Willy Nagel, Raphael Alves Fonseca, Paulo César Machado Andrade, Priscila Saikoski Miorando, Ayan Santos Fleischmann, Palmira Francisca Gonçalves Ferreira, Camila Rudge Ferrara, Roberto Lacava, Filipe Machado França, Evlyn Márcia Leão de Moraes Novo
preprint en

Abstract

Abstract Amazonia is experiencing more frequent and severe weather extremes. Freshwater species, like the endangered Giant Amazonian turtles, Podocnemis expansa , are key for assessing how climate change influences Amazonian rivers and biodiversity. Extreme habitat temperatures can increase turtle embryo mortality; however, other non-lethal effects are expected due to their temperature-dependent sex determination, which can eventually drive populations to become predominantly female-biased. Using in-situ and satellite-based data from 1998 to 2024, we show escalating warming trends, up to + 0.3ºC a year, in the water and sandbanks of three major Amazon Basin rivers (Purus, Trombetas, and Tapajós) used by turtles for nesting. We then estimated the sex-ratio of all hatchlings bourn at these sandbanks monitored by local communities. We observed that, as warming intensifies, cohorts unlikely reach balanced sex-ratios, with the magnitude of the bias progressively shifting towards more females, while males comprise less than 15% of offspring. Our results emphasize the need for long-term nest-temperature observations and monitoring as a critical conservation effort to access ongoing population changes under future warming scenarios.

Research Square
Brazilian Institute of Environment and Renewable Natural Resources (BR), Universidade Federal do Oeste do Pará (BR), Wildlife Conservation Society (US), Instituto Nacional de Pesquisas da Amazônia (BR), University of Bristol (GB), Instituto de Desenvolvimento Sustentável Mamirauá (BR), University of Southampton (GB), Universidade Federal do Amazonas (BR), Instituto Nacional de Pesquisas Espaciais (BR)
University of Bristol, Universidade Federal da Paraíba, Natural Environment Research Council, Instituto Chico Mendes de Conservação da Biodiversidade
Life on land
Turtle Biology and Conservation
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