The female lays up to 100 eggs in late spring and summer. She guards them until they hatch and may stay with the young a while after they hatch. I have seen a mother and many newly hatched mudpuppies in a crushed minnow bucket in a lake in Ottertail County in June. The young are very small and are marked with one yellow dorsolateral stripe down each side of the back. The pattern changes relatively slowly until they look like adults.
Fishermen often catch mudpuppies while they are fishing.
Many believe them to be poisonous and will cut their line before touching them. Food Mudpuppies will eat anything they can catch. Crustaceans, insects, worms, fish, fish eggs, salamanders, and crayfish are all reported foods. Mudpuppies probably do not have keen eyesight and rely heavily upon olfactory cues to find their prey.