Very few of the animals in Australia are poisonous, especially if they're prepared and cooked correctly. If you meant venomous, however, that's another question entirely...
it isn't poisonous
Because Australia was separated from the rest of the world so all of the flora and fauna in Australia continued to grow only in Australia.
Animals can use colours in many different ways : Some use colour as a warning against other animals , indicating that they are poisonous/venomous so that they don't get attacked. Some animals can even mimic the colours of other animals that are poisonous to avoid being preyed upon. Some use it as a means of camouflage so that they go undetected by predators.
The "bleeding heart" flower is a poisonous flower so not many to not at all animals can eat it.
Australia is such a beautiful country because of its oceans and its animals and its culture. There are so many things amazing about Australia. Australia is beautiful no matter what. And I am surprised that noone answered this until I did.
Some frogs are poisonus. If animals eat them they will die.
The animals that show off there color are poisonous or are trying to look poisonous so it will not get eaten
It is used so that no outside bugs / diseases / animals are introduced to Australia.
There are over 5000 species of ladybugs, many of which are poisonous. Note that this is mainly in the "poisonous to eat" sense, not the "venomous" sense like, say, rattlesnakes. A few species are capable of spraying a toxin that affects mammals.
I know they are safe for zoo animals so I don't know why not for cows.
They do to advertise their toxicity. Poisonous animals are almost always brightly colored so that predators know and stay away.
some animals that live in the river are: -black swan -herring -flat head and many other aquatic and land animals. good luck finding some others because i am struggling!