Patterns of parental care and their evolution in tetrapods

Parental care is generally very developed in terrestrial vertebrates. The great enhancement of parental investment of both parents led to greater survival probabilities of offspring, and their number of eggs produced each time was consequently reduced. This is clearly evedent in endotherm classes, which show the tendency to shift from a reproductive strategy following the _r_ selection, typical of amphibians and reptiles, to one following the _K_ selection. The strong development of social behaviour among birds and mammals assumes great importance in these classes, leading to another transformation of the concept of parental care. In fact, now there is no longer a simple mechanism to ensure offspring survival but a medium for the social transmission of information. The impact of adults is merely indirect in less specialized forms, as in imprinting, but we can have cases where the adult voluntarily teaches the young certain behaviour patterns. Parental care then becomes a way to modify or to develop some aspects of the behaviour repertoire which, otherwise, would not be performed at all or, at least, only imperfectly.