The first thing that you can do to help save the Koala is learn about them. Spread the word to others about the need to help save them. Write letters protesting destruction of their habitat. Do not support companies that invade the Koala habitat.
pollution food loss,etc
During the late 1800's, koalas became an export commodity for their fur, mostly for export to the USA. Due to koala numbers dwindling and public outrage, laws were enacted protecting the koala and imports were banned by the USA in the late 1920's. The koala is not extinct, it is not even endangered. They are considered to be "Secure".
kill them...
primarily to prevent extinction
To prevent or reduce the risk of extinction of a specie.
In the late 1800s and early 1900s, koalas were nearly driven to extinction by the demand for their fur. In both the USA and the UK, koala fur was popular for articles of clothing, women's accessories such as purses, and slippers.
When they are endangered put them in a wildlife reservation.
Yes
Using renewable resources, recycling, and reducing pollution are three things that can be done to prevent premature extinction of the worlds existing species from human activities. Enact new laws to prevent species extinction can also help.
Logically, the rare frog should be saved, simply because the koala is not yet officially "endangered". It is therefore not in immediate danger of extinction, unlike the rare frog. There is greater awareness of the threats to the koala, and so the koala will always have an advocate. Far fewer people are aware of the different species of frog, let alone whether it is a rare species or not.
The two devices that assist in the prevention of extinction are: game reserves and lodges (frequently with hunting) and zoos.
Nothing except human intelligence will prevent extinction. We are causing animals to disappear.