An animal’s behaviour encompasses all the things that it does as well as the way that it does them. Behaviour ranges from simple actions, such as eating or keeping clean, to highly elaborate activities, such as hunting in a pack, courting a mate, or building a nest. In some animals, behaviour is almost entirely predictable; in others, it develops with experience, so the more an animal does something, the more skilled it becomes. As with all aspects of animal biology, behaviour is the product of evolution, which means that it gradually changes as time goes by. These changes enable species to react in the most effective way to the opportunities and dangers that they encounter in daily life.
INSTINCT AND LEARNING
ln simple animals, behaviour is “hard wired” — governed by inherited instincts — which means that it consists of fixed sequences of actions prompted by triggers. For example, day-old birds instinctively beg for food when their parents appear at the nest. At this stage, they are usually blind: their behaviour is triggered by noise and movement rather than by the sight of food itself. Instinctive behaviour may seem basic, but it can produce quite remarkable results. The structures that animals build – from nests to dams — are the results of inborn behavioural impulses. When beavers set out to make a dam, they do so without any knowledge of engineering principles.
Yet the structure they make is shaped to withstand water pressure as if it had been scientifically designed. Beavers do not have to think how to build, just as spiders do not need to work out how to weave webs. Even so, the results of instinctive behaviour can change. As animals repeat certain tasks. such as making a nest, their performance often improves. This is particularly important for some animals — such as male weaver birds — which use their nest- building skills to attract a mate. Apart from octopuses and their relatives, most invertebrates have narrow limits when it comes to learning.
For vertebrates, on the other hand, learned behaviour is often extremely important. Frogs and toads quickly learn to avoid animals that taste unpleasant,while mammals acquire a wide range of skills from their parents, including how to hunt. Among primates, individuals very occasionally “invent” new behaviour, which is then copied by their neighbors. This copying process produces culture — patterns of behaviour that are handed on down the generations. Culture is something that humans, as a species, have developed to a unique degree.
For most animals, keeping in touch with their own kind is essential to their survival. Animals communicate with each other for a range of reasons, including finding food, attracting a mate, and bringing up their young.Different methods of communication have their own advantages and drawbacks. Body language — which includes facial expressions and physical displays — works well at close quarters but is ineffective at a distance and in habitats where dense vegetation gets in the way. In such cases, communication by sound is much more practical.
Whales call to each other over immense distances, while some small animals produce remarkably loud sounds for their size. Tree frogs, cicadas, and mole crickets, for example, can often be heard at a distance of over 2 km (1 mile). Each species uses its own distinctive “call sign”, and many behave like ventriloquists, pitching their calls in a way that throws predators off their track. Animals that are capable of producing light also use identifying call signs.These can consist of specific sequences of flashes or — in many deep- sea fish – illuminated body patterns.
But, like body language and sound, this form of communication works only when the signaller is actively signalling. Scent communication is quite different because the signal lingers long after the animal that made it has moved on. Animal scents are specific, allowing animals to lay trails and to advertise their presence to potential mates. Some male insects are able to respond to individual molecules of airborne scent, allowing them to track down females far upwind.
LIVING IN GROUPS
Scme animals spend all their lives alone and never encounter another member of their species. But, for many, getting together is an important part of life. Animal groups vary in size as well as in how long they last : mayflies, for example, form mating swarms that last just a few hours, while migrating birds often assemble for several weeks. Many other animals, including fish an gazing mammals, form groups that are maintained for life. Groups of animals may deem to be easy targets for predators, but the opposite is usually true. Predators find it difficult to single out individuals from a group, so living together gives animals a better chance of survival.
Groups are also more difficult to catch by surprise because there is always more than one animal o alert for signs of danger. In most animal groups the members belong to a single species but do not necessarily share the same partners. However, in the most tight-knit groups, the members are all closely related. Examples of such extended families include wolf packs and kookaburra “clans”, where the young remain with their parents instead of setting up independently. This kind of group living reaches its extreme in social insects, such as termites and ants, which cannot survive alone.
DEFENCE AND ATTACK
Both predatory and prey animals use specialized behaviour to help them survive. For example, while many prey animals simply try to escape, others keep perfectly still, relying on camouflage to protect them. A wide range of species, from moths to lizards, try to make themselves appear dangerous by exaggerating their size or by revealing coloured spots that look like eyes. Sometimes such threats are real: for example, the brilliant colors of poison-arrow frogs indicate that they contain some of the animal kingdom’s most potent poisons.
Predatory animals use one of 2 techniques to catch prey: they either wait for it to come their way or they track it down. “Sit-and-wait” predators are often camouflaged, and some actively entice their victims within range. In angler-fish, for example, the snout has a long. luminous protuberance, called a lure, which the fish dangle appetizingly in front of their mouths: anything swimming close to inspect this lure is snapped up whole. For active hunting, nature puts a premium on speed and keen senses which is why animals such as cheetahs, peregrine falcons, and blue marlins are among the fastest in the world. Some active predators operate in groups. By working together, grey wolves, African Wild dogs, and lions can tackle prey much larger than themselves.
Some kinds of behaviour, including self-defence, can be provoked at any time. Others are cyclical, triggered by cues that keep animals in step with changes around them. One of the most important cycles is the alternation between night and day. Others include the rise and fall of the tide and the annual sequence of changing seasons. Cyclical behaviours are all instinctive. They may be stimulated by external changes, by inbuilt “biological clocks”, or by a combination of the 2.
Birds, for example, often gather to roost late in the day, a form of cyclical behaviour that is triggered by falling light levels as the sun nears the horizon. On a much longer time scale, ground squirrels show an annual cycle in body weight, getting heavier before they enter hibernation. However, ground squirrels maintain their cycle even if kept in conditions of constant temperature and day length, which shows that the rhythm is controlled biologically. Biological clocks often involve hormones, but the way they work is not yet fully understood.