In rare cases, a set of two narwhal teeth erupt as tusks.

Milk teeth erupt around the same time, and the feet begin to darken.

Open contacts can exist naturally, such as when teeth erupt into a nonideal occlusion or when they shift as a result of tooth loss.

Their eyes open at four to five weeks and their milk teeth erupt about the same time.

The milk teeth erupt at 2 to 3 weeks of age, at which point the young start to eat solid food, though lactation can last 12 weeks.