Behaviour that aids the development of offspring. Rudimentary forms of parental behaviour may involve simply placing the eggs in a sheltered or secure location, and leaving them to develop unaided. This is common among insects and some amphibians and fishes. Some, such as the digger wasp (Bembex rostrata), not only place the eggs in a sheltered spot (a burrow in the ground), but also provide food for the emergent larvae. The female digger wasp provisions her nest with the carcass of a paralysed insect.
Among fishes and amphibians there is a spectrum of parental behaviour, from external fertilization and virtual abandonment of the eggs, through various types of egg-guarding, to true viviparity. This occurs in sharks (Selachii) and a number of species of bony fishes (Teleostei). In the toad Nectophrynoides spp., the young develop completely within the reproductive tract of the female, the tadpoles gaining their nutrients through the blood vessels of the tail, which co-circulate with those of the oviduct. This arrangement is the equivalent of the mammalian placenta.
Amongst reptiles, internal fertilization is almost universal, and various forms of viviparity have evolved. Parental behaviour is highly developed in crocodiles. Elaborate nests may be built and the nest is usually guarded. The female of the Nile crocodile (Crocodilus niloticus) transports the young in her mouth to the edge of the water as soon as they are hatched. She stays in the vicinity of her young for many weeks during their early development.
Viviparity has not evolved in birds, but care of the young is often complex, and may last until the young reach maturity. It may involve nest-building, incubation, nest guarding, and feeding the young, often by both parents. The degree of parental investment is considerable, and consequently pair bonds are strong and monogamy common.
Among mammals, the picture is completely different, because the females are specially equipped (with mammary glands) to feed the young. Pair bonds tend to be temporary, and monogamy uncommon, although it does occur in some primates. The maternal behaviour that is characteristic of mammals, often involves imprinting by the young, and teaching of the young. The role played by males is often minimal.
Subjects: Zoology and Animal Sciences.