3.1 - Generalist and Specialist Species

Learning Objectives

Specialist Species (Niche Specialist)

• Tolerance and needs: They have a really narrow range of ecological tolerance, which means they require very specific habitat and food sources. They’re often described as very picky.

• Adaptability: They’re less adaptable and can’t easily shift to a new resource because their tolerance is so narrow.

• Advantage: In habitats that stay the same, specialists usually come out ahead. They’re built to use one resource very efficiently, and few other species can use that resource, so they face less competition for it. Koalas are a good example: their long gut and gut bacteria let them digest eucalyptus leaves, which are tough and toxic to most other animals.

• Vulnerability: That lack of adaptability puts them at a disadvantage when conditions change. If an environmental disturbance disrupts their specific food source, the habitat becomes less hospitable to them.

• Extinction risk: Specialists are easily disturbed or disrupted. They’re far more likely to be endangered, like the koala and the panda bear, and more likely to go extinct when their ecosystems are threatened or disturbed.

• Examples: The red panda needs massive quantities of bamboo because it doesn’t digest cellulose very well. Other examples include the koala bear and panda bear.

Generalist Species

• Tolerance and needs: They have a very large range of tolerance and a broad niche. They use a variety of resources and have an extremely varied diet.

• Adaptability: They’re very adaptable and can easily switch their diet to a new food source if one becomes less available.

• Advantage: Generalists are advantaged in habitats that are constantly changing, because they can just shift to a new food or habitat resource.

• Extinction risk: They’re less prone to extinction.

• Invasive potential: Their broad range of resource use makes them very competitive, which means they’re very likely to be invasive if introduced to a new ecosystem.

• Examples: Raccoons can eat plants, mushrooms, eggs of birds and reptiles, small insects, and amphibians.

• Changing habitat example: When a forest is cleared for farms and towns, specialists that depend on that forest decline. Giant pandas lost much of their bamboo forest to farming and logging. Generalists such as raccoons and coyotes do well in the same cleared areas, eating crops, garbage, pet food, and small animals near people.

Comparison Summary

Big picture: A specialist species is like a precise tool, such as a surgical scalpel. It performs one task perfectly but is useless if the conditions of the task change. A generalist species is like a Swiss Army Knife. It performs many functions adequately and can adapt easily to whatever simple job is required.