Space geckos have been filmed playing on board an unmanned spacecraft during a 30-day orbital experiment.
The thick-toed geckos were wearing coloured collars that allowed scientists to track the behaviour of individuals – but one managed to remove it in the pre-launch period, leaving the collar floating around in the animal holding unit.
"Four of the five geckos participated in play episodes, which were defined as one-time interactions with the collar, as well in a fuller form of play that included approaching the unmoving collar or observing its approach, manipulations with the collar and further tracking the collar," the authors wrote in the Journal of Ethnology.
The geckos were filmed in "complicated play", where they pressed their snout against the collar rim, inserting their head into the collar, holding it to the container floor and tilting their head with the collar on the snout.
Play behaviour in reptiles is rare. Herpetologist Gordon Burghardt, from the University of Tennessee in Knoxville, told New Scientist that this could be due to them having to fend for themselves from birth, with little energy for activities not involved in their survival.
"It's the first demonstration of object play in geckos – something that is rare in any lizard," he told the magazine.
The geckos were launched into space on board the Bion-M1 satellite by the Russian space agency. Their sticky feet means they did not float around the container.
The satellite was launched in 19 April 2013. It was also carrying gerbils, mice, snails and fish and researchers were looking to study the impact of spaceflight on the animals' cerebral arteries, spinal cord, inner ear and genetic processes.