What is the most common animal in Australia?

Personally, I think it is probably a fish or an insect, but I could not find a source to confirm it. However, I did find the following.

Huge numbers of chickens are raised and killed - 368 million a year are slaughtered in Australia. See:
http://www.animalliberation.org.au/farm.html

The rabbit has damaged the Australian environment and is also a major pest to farmers. Some estimates put the number of rabbits in Australia at over 200 million. Wild rabbits were introduced by Thomas Austin of Barwon Park, Winchelsea in Victoria. In 1859, Austin imported 24 rabbits from England and released them on his property for sport hunting. Today there are over 200 million of them. See:
http://www.ozramp.net.au/~senani/aniausti.htm

Rabbits, 200-300 million before 1995. See:
http://www.animalliberation.org.au/feralint.html

Present distribution of rabbits in Australia. See: https://www.thoughtco.com/feral-rabbits-in-australia-1434350#:~:text=Currently%2C%20the%20rabbit%20inhabits%20around%202.5%20million%20square,is%20arid%20and%20not%20fully%20fit%20for%20agriculture.

According to my search on google.com it is the echidna. An echidna, for those who don't know, is a small egg-laying mammal (monotreme) not unlike a porcupine in appearance.

dragonnet.hkis.edu.hk/hs/science/gallery/Kangaroo%20Island/ki-2.htm no longer exists

Ants are widespread and outnumber sheep and kangaroo.

ento.csiro.au/science/ants/classification.htm no longer exists