Almost all female animals modify their lifestyles or patterns of behaviour prior to giving birth; in those species where pair-bonding persists beyond conception, both partners may be involved. These changes may be subtle and hard to distinguish until the later stages of pregnancy, or may be marked and profound from early on . They could simply involve a change in diet, feeding behaviour, or choice of habitat, or may involve the construction of a nest or the selection of a safe retreat for the female's confinement. Whatever the changes, however, the intention is the same to ensure the health and safety of the mother and to secure the safest surroundings for the birth itself, and sometimes for a considerable period afterward, the mother is almost as vulnerable to attack as the young to which she is giving, or has given, birth.
For the preparation of birth there is a lot of steps that must be done by the animal. Within the mammal group as a whole, each species differs in the same way in which it prepares for birth. For some creatures such as antelopes, birth may simply occur where the female finds herself; with herd animals that are constantly on the move, a precise location for birth is difficult to predict. In some antelope species which have roughly synchronized births, however, migration may occur. The whole herd may move to an area of good grazing in time for the births. This will ensure that the females are in the healthiest state possible and will hopefully provide the youngsters with a good diet once weaning has occurred.
Migration prior to the act of giving birth is found in other animals for different reasons. The humpback whales has been particularly studied and its annual movements are well known. The adults move from their cold water feeding grounds to warmer, but comparatively food-poor tropical waters to give birth. The reason for the journey, which involves thousands of miles of travel each year, is to ensure that the baby whale can spend the first few weeks of life, when the bubbler layer provides inadequate insulation, in optimum water temperatures.
