The average muskrat span of life is 2 to 4 years only in the wild. But on the other hand if a muskrat is living in captivity, they can live up to 9 years! The tadpole of a muskrat (baby) is brown with tan tails. That means they are Lampreys. Lampreys are a group of ancient fish species that appeared 360 million years ago! That was before the dinosaurs were roaming the earth!