Don't worry, it's not cannibalism. When some of babies die, which sometimes happens unfortunately, females starts to eat it. When people find this dead baby, it's often almost eaten and sometimes maybe we don't know there were more babies, if it's eaten completely. It's because the smell of blood or dead baby could bring enemies to degus' home in nature.

Some other rodents like hamster sometimes kill their babies and eat it when they are worried or when they don't have enough protein. That's why so many people are worried of this cannibalism, but I doesn't happen with degus.