Many animals exhibit parental care behavior, including feeding, grooming, and protecting young offspring. Parental care is universal in mammals and birds, which often have young that are born relatively helpless. Several species of insects and fish, as well as some amphibians, also care for their young.

Birds

Parental care can occur even before hatching in birds, when parents sit on their eggs to incubate them. After hatching, the parents provide food for their offspring, and may continue to brood their young to keep them warm. Both male and female birds provide parental care, depending on the species.

Mammals

In marsupial mammals, such as kangaroos, the embryos are often born at a very early stage and then crawl into their mother’s pouch. Here, the mother nurses and protects her offspring—sometimes for many months—until it can function more independently.

Placental mammals are born more developed than marsupials, but they still require a lot of care. Mammalian parental care is mostly provided by the mother, triggered by the hormones of pregnancy and birth and the necessity of lactation for providing nutrients. Nursing is an essential kind of mammalian parental care since the mother’s milk is the primary source of food for the young. Mammals also often lick their newborns and carry them around—grooming, protecting, and bonding with them.

About 5-10% of mammalian species are routinely cared for by both parents. For example, male monogamous prairie voles provide parental care. Since they only have one mate, they have a greater investment in the care of their offspring than vole species with multiple mates. In non-monogamous vole species, the mother provides the care.

Fish

In aquatic species that reproduce by external fertilization, such as most fish, males play a much greater role in parental care. This is likely because paternity can be more easily determined in these species compared to those that reproduce by internal fertilization. A large number of fish species have exclusively male parental care, with the males protecting the fertilized eggs and young in a nest, or even in their mouths.