Background Essay: Animal Babies
Nearly all animals begin their lives as babies. Birds as well as many species of reptiles, amphibians, and fish emerge from eggs. These animals are called hatchlings. Most invertebrates, including insects and mollusks, also emerge from eggs. These creatures are called either larvae or nymphs, depending on the species. Most mammals and some reptiles and fish emerge directly from a parent's body (usually, but not always, the mother's). Animals like these, which are said to be born live, are called newborns.
Regardless of whether one climbs out of an egg or gets pushed through a birth canal, there are dramatic differences in the level of development among hatchlings and newborns of different species.
Some creatures enter the world smaller than adults of their species but otherwise fully formed and able to care for themselves. Most insects and many reptiles, including the mosquito nymphs and hatchling sea turtle pictured in this collection of images, receive absolutely no parental care either before or after hatching. Parents of these animals lay their eggs and leave them to develop on their own. When the young emerge, they know instinctively how to find food and shelter and to otherwise care for themselves.
Most newborns and hatchlings, however, require at least some parental care. Ducklings, for example, need their parents to guide and protect them through their first weeks of life, even though the young birds are able to walk, swim, and feed themselves almost immediately after hatching. Similarly, newborn moose, elephants, and manatees are able to walk or swim within minutes or hours of birth. This allows them to stay with their mothers, who will be their sole source of food and protection for months or even years.
Other newborns and hatchlings, including most mammals and birds, are born or hatch into the world blind, naked, and vulnerable. These animals require intensive parental care and are seldom separated for long from the warmth, food, and protection their parents provide. As the young animals grow and develop, they become less and less dependent upon their parents. However, some animals, especially mammals -- with the extreme case being humans -- take years to gain complete independence from their parents.