The resources animals need to survive — food, water and space — are limited in the Earth’s ecosystems. As a result, organisms compete for these vitals. Competition is the struggle or fight that living things do to get the most out of these resources and is also what creates such amazing diversity in nature, from a robin holding a worm in its beak to two bucks fighting during the rut for the right to mate.

Most animal competition occurs within a single species. Known as intraspecific competition, it is usually due to a lack of food resources and limits a species’ population numbers. This type of competition often results in survival of the fittest, as the most well-adapted animals succeed and the less adapted die out.

Some animals rely on the old adage that “desperate times call for desperate measures” and resort to cannibalism when food is scarce. While sharks are probably the best example of this, many other animals such as rodents and their mothers also exhibit cannibalism to provide food for their young in times of scarcity.

Another type of animal competition is between different species, called interspecific competition. This is most noticeable in habitats where animals are both preyed on and predators. For instance, the various species of Anole lizards (Anolis) of tropical rainforests compete for the same insects that are found on the forest floor, resulting in specializations like the ability to climb. Other predators, such as hawks and owls of the German Falconiformes and Strigiformes groups, are all competing for the same prey species, such as the vole Microtus arvalis.