Mouse Pup Appearance by Age

Descriptions of Developmental Stages: Birth - Day 14

AgeDescription
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

© Jackson Laboratory Mice Pup Appearance by Age