Neonates of altricial species show reduced motor performances with reference to precocial species. Supposedly, their unachieved motor output mirrors the poorly matured underlying structures. Reviewing the developmental timetable of neural, motor and postural structures involved in rats' walking shows that fundamental elements for a basic locomotion are present early after birth, whereas late developing structures are implied in complex behaviours. Whereas rat pups spontaneously show limited motor properties, they can reveal better motor capacities in particular behavioural situations. It is proposed that motor output spontaneously performed by pups does not mirror the actual properties of the motor structures, but results also from a selected behavioural mechanism whose function is to maintain the pups to the nest.
Altricial species, Motor development, Posture, Locomotion, Homing, Rat