Altricial - Basis

Basis

Different animals employ different precocial and altricial strategies; there is no clear distinction between the two states, and a wide range of intermediate states. The ability of the parents to obtain nutrition and contribute to the pre-natal and post-natal development of their young appears to be associated.

Precocial birds are able to provide protein-rich eggs and thus their young hatch in the fledgling stage – able to protect themselves from predators (ducks or turkeys) and the females have less involvement post-natal. Altricial birds are less able to contribute nutrients in the pre-natal stage; their eggs are smaller and their young still in need of much attention and protection from predators. This may be related to r/K selection; however, this association fails with a number of cases.

In the case of mammals it has been suggested that large adult body sizes favor production of large, precocious young, which develop with a long gestation period. Large young may be associated with long lifespan, extended reproductive period, and reduced litter size. It has been suggested that altricial strategies in mammals may be favoured if there is a selective advantage to mothers that are capable of resorbing embryos in early stages of development.