Koalas are most definitely specialist species. They're a marsupial that is able to eat eucalyptus leaves, which most animals find toxic. Thanks to their unique genetics, koalas can produce an enzyme that breaks down the toxins in the leaves. And although there are about 600 different types of eucalyptus, koalas focus on about 120 of these types of trees. Koalas have many other unique characteristics, such as very limited genetic diversity. To learn more about koalas and their evolution, check out this Washington Post article about koalas by Joel Achenbach.
Specialist species are often at greater risk of extinction, simply because they can't easily adjust to environmental changes. So what's being done to protect koalas? Check out this video and visit the Australian Koala Foundation website where you can learn about koala protection and help out by donating, planting a tree, or adopting a koala.