Study

A comparison of maternal and temperature effects on sex, size, and growth of hatchlings of the Magdalena river turtle (Podocnemis lewyana) incubated under field and controlled laboratory conditions

  • Published source details Paez V.P., Correa J.C., Cano A.M. & Bock B.C. (2009) A comparison of maternal and temperature effects on sex, size, and growth of hatchlings of the Magdalena river turtle (Podocnemis lewyana) incubated under field and controlled laboratory conditions. Copeia, 2009, 698-704.

Actions

This study is summarised as evidence for the following.

Action Category

Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation
  1. Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles

    A study in 2005–2007 in laboratory conditions in Colombia (Paez et al. 2009) found that higher incubation temperatures increased Magdalena river turtle Podocnemis lewyana hatching success, and that females were only produced above a temperature threshold. In the first year, eggs incubated at 33.0°C had a higher hatching success rate (28 of 29, 97% eggs hatched) than eggs incubated at 28.0°C (14 of 38, 37% eggs hatched) and all hatchlings at both temperatures were male. In the second year, five of 10 eggs (50%) incubated at 33.4°C and seven of seven eggs (100%) incubated at 34.7°C produced female hatchlings. The authors reported that nests monitored in the field showed a similar pattern, with the coldest nests having lower hatching rates (see original paper for details). In 2006, river turtle eggs were obtained from 28 nests and incubated in a laboratory at: 28.0°C (38 eggs), 29.5°C (43 eggs), 32.0°C (39 eggs) and 33.0°C (29 eggs). In 2007, river turtle eggs were obtained by inducing four female river turtles using an injection of oxytocin and incubated at: 33.4°C (14 eggs) and 34.7°C (13 eggs). Eggs were monitored through to hatching. Only hatching success data from 2006 laboratory eggs are included as the authors reported that the use of oxytocin to obtain eggs in 2007 may have affected hatching rates. Natural nests were monitored in the field in 2005 (8 nests) and 2006 (11 nests) for incubation temperature and hatching success.

    (Summarised by: Katie Sainsbury)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 19

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust