: 31 Big yawn from this big Goanna (varanus). Around 30 species of goanna are known, 25 of which are found in Australia. Being predatory lizards, goannas are often quite large, or at least bulky, with sharp teeth and claws they can grow over 2.5 m length. Combining predatory and scavenging behaviours. A goanna will prey on any animal it can catch and is small enough to eat whole.A recent study suggests goannas are venomous and have oral toxin-producing glands.