Highly feminised sex ratio estimations for the world’s third largest nesting aggregation of loggerhead sea turtles

Claire Tanner, Adolfo Marco, Samir Martins, Elena Abella Perez, Lucy Hawkes

Research output: Contribution to journalArticlepeer-review

33 Citations (SciVal)


Despite being a fundamental life-history character, there is a paucity of populationwide, data-driven studies of primary sex ratios for any marine turtle species. The Republic of Cape Verde hosts the third-largest nesting population of loggerhead turtles Caretta caretta in the world (hosting up to 15% of global nesting by the species). Weighting for the spatial distribution of nests, we estimate that 84% of female hatchlings are currently likely produced across the population, with 85% of nests laid on Boa Vista, where incubation temperatures are coolest. In future climate change scenarios (by 2100), irrespective of beach, island or sand colour, sex ratios reach over 99% female, and 3 islands (Fogo, Sao Nicolau, Santiago) would cease to produce males, with >90% of nests incubating at lethally high temperatures. Given that most of the population cannot move to nest on cooler islands, we highlight that temporal refugia are amongst the primary means available to this population to adapt. Under a low-emissions scenario, without phenological adaptation, there would only be an estimated 0.14% males produced across the whole population, while under mid- and high-emissions scenarios, male production may cease on most islands.

Original languageEnglish
Article number621
Pages (from-to)209-219
Number of pages11
JournalMarine Ecology Progress Series (MPES)
Publication statusPublished - 4 Jul 2019


  • Sex Ratio
  • Climate change
  • Caretta caretta
  • Loggerhead turtle
  • Marine turtle
  • Cape Verde

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology
  • Global and Planetary Change
  • Ecology


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