Alter incubation temperatures to achieve optimal/desired sex ratio: Sea turtles

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • One study evaluated the effects of altering incubation temperatures to achieve optimal/desired sex ratios on sea turtles. This study was in Canada.



  • Reproductive success (1 study): One replicated study in Canada reported that hatching success of two clutches of artificially incubated green turtle eggs was 8% and 62%.



  • Offspring sex ratio (1 study): One replicated study in Canada found that incubating green turtle eggs at higher temperatures resulted in more females hatchlings.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated study in 1995 in an artificial setting in Toronto, Canada (Godfrey & Mrosovsky 2006) found that more female green turtle Chelonia mydas hatchlings were produced at higher incubation temperatures compared to at lower temperatures. Hatching success for two clutches of eggs was 8% (7 of 90 eggs) and 62% (67 of 108 eggs). Warmer incubation temperatures produced a higher proportion of female hatchings (30.6°C: 100%; 30.0°C: 50%; 29.4°C: 47%; 28.7°C: 36%; 28.4°C: 18%; 28.2°C: 8%; 27.6°C: 0%). The pivotal temperature for determining sex of hatchlings was estimated at 29.4–30°C. In 1995, green turtle eggs were collected from two nests (90 from one nest and 108 from a second) and brought into an artificial setting and placed in an individual container on a sponge with damp vermiculite. Eggs were incubated at one of seven temperatures between 27.6°C to 30.6°C (14–48 eggs/temperature). Hatching success was assessed, and sex of hatchlings was determined by examining the gonads under a microscope.

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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