The "Crew" of "Bion-M", spacecraft consisting of the mice was partially replaced a day before the launch. According information from the source at the Baikonur Cosmodrome, the reason was the death of one mouse.

One group of mice was completely replaced. This was due to the conflict between several males killing a single mouse.

According to the head of the project Yevgeny Ilyin, the mice are aggressive animals, so the death of one of them was not a shock to scientists. Male-mice are often prone to stress and aggression, leading to clashes between them. Therefore, to remove these risks during space-launch preparation, mice were divided into several groups in advance.

Also Ilyin warned that in zero gravity mice can start fighting for food, which will lead to further deaths within the group of "astronauts".

"Inside the machine blows directed flow of air, so the corpse of the animal would not rot, and just mummified instead, although it is possible that other mice can eat the corpse of a fellow," – said the head of the project.

"Bion-M" satellite will be displayed on the Earth's orbit by the launch vehicle "Soyuz-2.1b" April, 19. On the board into space will go 45 mice, 15 geckos, 6-8 Mongolian gerbils, 20 snails, as well as the various colonies of microorganisms, plants and their seeds.

The project will study the reactions of living organisms on the action of microgravity and artificial gravity. Scientists have pointed out that the names of the animals were not assigned. Instead, they were marked with paint or subcutaneous chip implanted.