Mouse Pup Appearance by Age | Laboratory Animal Resource Center (LARC)

Descriptions of Developmental Stages: Birth - Day 14

Age	Description
Day 0	Blood red Possible milk spot
Day 1	Lighter color red Milk spot present
Day 2	Ears appear as nubs Milk spot present
Day 3	Ear flap starting to come away from head (one or both)
Day 4	Ears fully developed, completely off head, some starting to go towards back Increasing skin color
Day 5	Ears are fully back Skin appears much thicker with more color density to skin
Day 6	Milk spot is disappearing or gone Colored fuzz appears behind ears or on neck
Day 7	Colored fuzz starting to cover pup
Day 8	Belly begins to show fur
Day 9	Fur is now thicker Females may show nipples (there are five pairs of mammories)
Day 10	Fur growth is complete Pups are more active
Day 11	Teeth are beginning to erupt Eyes start to open
Day 12	Eyes are open Pups begin to nibble solid food
Day 13	Pups increase solid food intake
Day 14	Pups increase in weight and size, eating more solid food