The first detailed behavioural analysis of mice flown in the NASA Rodent Habitat on the International Space Station (ISS) is reported in a study in Scientific Reports. This animal study could help us to understand more about how exposure to a weightless space environment for extended durations might affect humans.

April Ronca and colleagues recorded videos of 20 female mice (16 and 32 weeks old) flown on the ISS, and matched ground controls, during a long-duration mission (17-33 days) relative to the rodent lifespan. The authors aimed to gain greater insight into how animals adapt to the space environment. These findings may impact the interpretation ofresults of animal studies that are needed to better understand human responses to long-duration space flight.

The authors found that flight mice engaged in a full range of species-typical behaviors, including feeding, self-grooming, huddling and social interactions. At the end of the study, all flight mice were in good health and their body weights were similar to those of ground controls. Flight mice remained active and mobile throughout the experiment; they explored their environment and occupied all areas of the habitat.

Within seven to ten days after launch, the younger flight mice started showing a distinctive circling or ‘race-tracking’ behaviour around the habitat walls, which quickly evolved into a coordinated group activity. Explanations for this behaviour may include exercise acting as a rewarding activity, a stress response or stimulation of the balance system of the ear, parts of which otherwise receive no outside impulse in microgravity. However, the authors conclude that additional studies are needed to understand the reasons for this behaviour.