Right Bias in Tortoise Righting

If one were to overturn a tortoise, would it be more likely to right itself (i.e. get back on its feet) to the right or to the left?

To find out, a joint research team from the Comparative Psychology Research Group, University of Padova, Italy and the B.R.A.I.N. Centre for Neuroscience, University of Trieste, Italy, performed a unique set of experiments with 34 overturned tortoises.

“Each trial consisted of overturning a tortoise (about its sagittal axis) and gently placing it on the above described apparatus. [The test apparatus consisted of a plastic arena 38.5 cm × 29cm × 15 cm high filled with sand up to 2 cm from the top.] Before of each single test the layer was levelled evenly. The righting response was video-recorded and the direction of righting was scored. After completing each response the tortoise was free to rest and walk around for some minutes before being administered a next righting trial.”

The experiments revealed a distinct bias in the tortoises’ righting behaviour – for reasons which are, as yet, poorly understood.

“A bias at the individual as well as at the population level was found for preferentially turning on the right side.”

‘Lateralized righting behavior in the tortoise (Testudo hermanni)’ is published in Behavioural Brain Research, 173: pp. 315-319.

Notes:
• All tortoises successfully completed the righting procedure within 2 minutes.

• No invasive procedures were used. Tortoises’ experimental and housing conditions were in accordance with the Italian and European Community laws on protected wild species (Art. 8/bis 150/92 all. A Reg.(CE) 338/97).

Queries:

•  Would the results have been different if the tortoises had been overturned about another axis  – e.g. the coronal axis or transverse axis?

 






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