A generalist species is one that can live in a wide variety of habitats and have a varied diet, while specialist species are adapted to a particular environment or a specific diet. Koalas and tiger salamanders are examples of specialist species, while raccoons and mice are generalist species.
Koalas are considered specialists because they can only live under very specific conditions. For instance, their diet consists solely of eucalyptus leaves, and they also require a warm climate and trees for shelter. Similarly, tiger salamanders are specialists because they can only live in wetlands that stay moist throughout the year. They also require areas with large insect and worm populations, as this constitutes the whole of their diet. Raccoons and mice are both generalist species because they can live in a huge range of different environments and can adapt their diet to whatever food is available.
Some species of animals are only partial specialists, such as the North American pygmy rabbit. This rabbit eats a varied diet in the summer but switches to a specialized diet of sagebrush during the winter. Specialist species are so specially adapted that they can only thrive under perfect conditions, which means that these species are quite susceptible to extinction under changing environmental conditions.