A mouse spent two weeks in space, then returned to Earth and produced more pups than the average lab mouse on the ground. That's one reason researchers are interested in how the experiment informs future space biology studies. According to a report, ‘China's "space mouse" Births Third Healthy Litter,’ published by the Chinese Academy of Sciences in 2026, four mice were launched aboard the Shenzhou-21 spacecraft on October 31, 2025, as part of China's first experiment with small mammals in space. The animals lived in a specially adapted habitat for two weeks in zero gravity before returning to Earth on November 14. The experiment drew widespread attention.
Back on Earth, the female mouse became pregnant within weeks.
Shortly after returning, one of the female mice became pregnant and gave birth to her first litter of nine pups on December 10, according to China Media Group and the Chinese Academy of Sciences' Institute of Zoology. She also had two more litters of ten and nine pups, the same sources reported. According to the Chinese Academy of Sciences, each litter was larger than the five-to-seven-pup average commonly cited for laboratory mice, though litter sizes in outbred strains can range more broadly. Researchers at the Institute of Zoology, Chinese Academy of Sciences, noted the result as part of the mission's findings.
Three litters, three distinct personalities
The first litter of pups, born soon after the mother returned from the mission, was less adventurous and stayed close to the walls of its enclosure. The second generation had more exploratory personalities. The third litter, however, was described by the scientists as the most confident and well-adjusted. Researchers will now observe how the animals develop and whether they can produce healthy offspring of their own. Because all three litters were conceived and born on Earth after the mother's return, the personality differences likely reflect environmental and birth-order factors rather than an inherited effect of spaceflight.
