Category Zoology

                 Among animals that live in groups, one becomes the clear leader. In chickens, this means that one bird dominates all of the other birds. The next one down in the ‘pecking order’ can dominate all except the leader, and so on, until the bird at the bottom of this process can he bullied by the entire flock. This can also be seen in families with dogs. The dog remains at the bottom of the pecking order, and submits to the human members of the family. Sometimes an aggressive dog tries to raise its status by snarling at a new baby that threatens its position in the family.

                         Cleaners are tiny fish living in coral reefs. They regularly clean parasites from much larger fish. Even large predatory fish queue up to be cleaned of skin parasites. The cleaner fish (or sometimes a shrimp) even swims into the predator’s mouth and gills without being eaten.

                        Birds can do a similar job. A basking crocodile opens its jaws so small birds can pick pieces of food and parasites from between its teeth. Small birds ride on the backs of grazing animals on the African grasslands, picking out skin parasites and feeding on insects as the animal feeds. At the same time the birds act as an early warning system for the host animal, by flying away when danger is near.

                  Predators usually live singly or in small groups, but their prey animals often group together in large numbers.

                  The most important reason for this behaviour is that there is safety in numbers. A predator will often become confused by a large, rapidly shifting group of prey. For example, a tuna will find it very difficult to select one target fish from a closely packed shoal containing several thousand fish. Similarly, a lion will usually not try to catch one of a panicking herd of wildebeest, but will attack  stragglers or injured animals.

                        Sometimes a herd has a defensive function. Adult buffalo and musk ox group together to form a protective circle around their vulnerable youngsters when a predator is near. The predator will not usually attack a fully-grown adult.

                           Scientists used to study just the appearance and structure of animals, but in recent years the study of their behaviour has become just as important.

                           The new science of ethology measures and records animal behaviour. We can now describe behaviour in terms of what the animal actually does, and not as a result of guessing what is going on in an animal’s mind. These studies have shown, for example, that animals such as birds have many inbuilt types of behaviour, which are inherited and not learned from other birds.

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               Parasites are animals that live at the expense of other animals. They rob the host animal of food, and can make it become sick. However, in other forms of relationship different animals can help one another. Some hermit crabs place sea anemones on their shells, hiding under their protective stinging tentacles. At the same time, the sea anemone benefits because it shares the crab’s food. Similarly, a species of shrimp digs a burrow that it shares with the small goby fish. The fish benefits from being able to hide in the burrow, while acting as a lookout to warn the shrimp of approaching predators. This kind of relationship can only be revealed by the careful study of animal behaviour. Most true parasites are very simple animals, because they do not need complicated organs to digest their food. Some parasites are simply a mass of reproductive organs.

                There is evidence from prehistoric cave paintings, and from bones showing signs of cooking or carving, that humans lived alongside some very large extinct animals.

                 Just after the last Ice Age, woolly mammoths, woolly rhinoceroses and giant cave bears lived in Europe. They were hunted by humans and, together with the warming climate; this may have led to their extinction. The giant ox was also prey for hunters. It became extinct in 1627, having survived in the forests of Eastern Europe.

Picture credit: google