Early ontogeny of locomotor behaviour: a comparison between altricial and precocial animals.

The focus of this review is to examine the physiological and behavioural differences between the early ontogeny of locomotion in precocial and altricial species. Both groups of animals are capable of performing alternating stepping movements upon birth or hatching, indicating that the basic elements underlying locomotor synergy are present prior to expression of mature overground gait. Nevertheless, the notable difference between precocial and altricial animals is the ability of the former to walk and run soon after birth or hatching. The weight of experimental evidence suggests that postural constraints play an important role in preventing early expression of locomotor behaviour in altricial species. Even some precocial animals, however, need time to develop sufficient stability and balance to walk as an adult. Therefore, components of locomotor behaviour involving the maintenance of equilibrium need a period of maturation in both precocial and altricial species, possibly requiring locomotor experience to become fully mature.