All animals require food which provides them with energy and raw materials to complete life processes, without which they may die. Because of these, competition for food can be fierce. There are many birds which eat insects in our gardens, and some have evolved to only eat certain types of insect to reduce competition from other species. Others like the blue tit and great tit compete with other members of their own species and as well as others for different insects. Because food is so vital, many animals will fight for it.
Animals within a species also compete for mates. This is essential so they can pass on their genes to their offspring. Animals have evolved to have an innate or natural drive to reproduce, and this competition often results in fights. This is seen each year when animals like red deer group together at the start of the mating season. Large male deer fight with each other by locking antlers and pushing hard, which is called a rut. In deer, and many others species, these fights competing for mates can often result in serious injury or death, but benefits the population as only the strongest pass on their genes to the next generation.
The territories of animals contain all of the resources and conditions they need to survive. These include abiotic factors such as light, temperature and water, and oxygen for aquatic animals. These are also biotic factors such as food and predators. Many animals, including the cats in back gardens, will fight for territory.
An example of intraspecific competition over territory would be between lions on the grass plains of Africa whereas interspecific competition would occur when another predator like leopards lived close to the lions.