Animal behaviour can be defined as the study of how different species act in their natural environment, in terms of interacting with each other, with individuals of different species and the physical actions they exhibit to survive. The study of animal behaviour is a rather broad topic and includes numerous themes such as migration, population biology, sensory behaviour and behavioural ecology, among others.
Through evolution animals have developed behavioural patterns to allow them the best chance of survival and reproductive success in their environments. As environments change, animal behaviour does too accordingly. For example, migration is a form of animal behaviour and can be due to environmental stressors forcing animals to discover new habitats. However, for different species, migration is an engrained behaviour that follows regular patterns. This is true of migration journeys for birds travelling from their wintering grounds to their breeding grounds. For certain fish, such as salmon, migration from freshwater to seawater follows their life and reproductive cycles.
Furthermore, animal behaviour is also focused on understanding the social behaviour, communication, foraging behaviour and reproductive tactics, of animals. For example, some animals are social creatures which depend on rigid hierarchies in their populations, whereas others are not. For instance, insect colonies are populations which have dominance hierarchies and this influences the reproductive success of individuals. Only a couple insects, or sometimes only one individual, are allowed to reproduce (referred to as queens) and all other individuals compose the worker caste. The worker caste is needed for important activities such as nest maintenance, thermal regulation and foraging.
Evidently, animals behave in a manner which is correlated closely with promoting their growth and survival, as well as success as an entire population. It is through the study of animal behaviour that biologists aim to uncover the diverse tactics which different animals utilize to survive.