How do mother animals know their own babies?

Mother and Child
Among animals which care for their young it is important for the mother and child to recognise each other, so that they do not lose contact. This can be done through one of the senses, through smell, sound, sight or touch. Among a flock of sheep with new-born lambs every mother recognises her baby by smell, and will
The sea horse has a prehensile tail with which it can hold on to water plants.
ignore other lambs. If a mother has a still-born lamb the shepherd will take another lamb from a mother who has had twins, and place the skin of the dead lamb over it. In most cases the bereaved mother will accept it, although it is really a foster child. This recognition by smell is common among social mammals, such as deer, horses and seals, and can be watched wherever there is a group of such animals with young.
Among birds recognition is more by sound. Each parent bird has her own special 'mother' call which the baby immediately recognises on hatching. Dr Konrad Lorenz, the Austrian naturalist, has made a special study of geese. Just when some goslings were about to hatch he removed the mother goose and sat by the eggs. As the babies hatched he gave the mother call. As a result they followed him everywhere. Unfortunately he was too big for a goose, and they became bewildered when he stood up, but were quite happy to follow him when he crawled about on hands and knees!

Shape, Size and Touch
To some young animals shape and size are important. When a mother bird approaches the nest to feed her young they automatically open their beaks, but she must be the correct size. If too big or too small they ignore her. Some birds swallow food and half digest it in their crops, then cough it up to feed the young. To make the parent open her beak the babies peck at it. But two things are important—the beak must be the
correct shape and colour. The beak of the herring gull is yellow, and has a red spot near the tip of the lower part. This is what the babies peck at— a kind of target. Parents who place food into the mouths of their young are helped by the wide gap and bright colours inside the babies' mouths.
Touch plays a big part in the behaviour of some young mammals, including ourselves. We like to feel something soft and furry, and cannot resist stroking a cat or a rabbit. Young children like to play with cuddly toys, and will cling to mother when frightened. Most mammals are hairy, and hair is one of the first things which a baby touches. Also it feels warm. If a baby monkey is taken from its mother and placed by itself on the ground it will huddle up and show signs of distress. If we pick it up it will cling to our clothing. Place this baby on a model of a mother monkey made of something cold like wire or wood, and again it will seem upset. On the other hand it will cling to a 'mother' made of cloth or wool. Many mammal mothers will pluck hair from their bodies, or gather soft plant material, in order to make a comfortable nest for their newborn family.