As with birds, the new-born mammal may be weak and defenceless or it may quickly get up on its legs and run. The bear cub is naked and blind when it is born and it will remain in the den (the bear's home) for up to three months. The foal of a zebra, however, is on its feet and running with its parents less than one hour after it is born.

The independence of the offspring after birth depends upon how much protection its parents can give it. A herbivore, such as a zebra or a gnu, lives on the open plains. The parents can give very little protection to their offspring. The young animals must move with the herd as it searches for new pastures. Herbivores which make a nest or burrow underground, such as mice, protect their offspring by hiding them. The offspring of these animals are usually naked and blind at birth.

One characteristic which is unique to mammals is that the mother will feed her offspring on milk. Milk is an ideal balanced diet for a young mammal. It is a liquid food so it is easily and quickly digested. It has plenty of fats and sugars for energy, minerals and vitamins for health and proteins for growth. The milk of different species of mammals is not identical as we can see in the table below

You can see that there is a lot of difference between the species. For example a human baby cannot be fed on cow's milk without adding some sugar, and there might be too much protein in cow's milk for a human baby.

Milk is made by the mammary gland or breast of the female. This organ is only found in mammals and this is how this group of animals was given its name.

The mammary gland only produces milk after the mother has given birth to her offspring. The mother will continue to produce milk until the offspring eat solid food. The period when the offspring are drinking milk from the mother is called suckling or nursing. Gradually, as the offspring eat more and more solid food the mother will give them less and less milk. This period, when the mother stops giving milk to her offspring, is called weaning.

The period between birth and weaning is very variable. It depends upon how much the offspring need to grow after their birth and how long they stay with their mother.

In species where the offspring stay for a long time with their mother the offspring will get the opportunity to suckle for a long time. For example, the baby chimpanzee stays with its mother for 5 to 7 years but the offspring of a rat must leave its mother soon after weaning at 3 weeks old.

Gestation and Birth

• Introduction to Animal Reproduction
• Mating on Land
• Reproduction in Birds
• Reproduction in Mammals Homepage
• Different Ways of Growing
• Chapter Summary (useful for revison)
• Questions relating to this chapter
• Top of Page

© Paul Billiet and Shirley Burchill 2008