Fauna of Australia species are nocturnal and many arboreal. Two of the five living species of monotreme occur in Australia: the platypus and the short-beaked echidna. The monotremes differ from other mammals in their methods of reproduction; in particular, they lay eggs instead of giving birth to live young. The platypus—a venomous, egg-laying, duck-billed amphibious mammal—is considered to be one of the strangest creatures in the animal kingdom. When it was first presented by Joseph Banks to English naturalists it was thought to be so strange that it was a cleverly created hoax. The short-beaked echidna is similarly strange, covered in hairy spikes
Mammal buffalo]] is most threatened with extinction by genetic pollution from the [[Water buffalo|domestic water buffalo]]. Such extinctions are not always apparent from a [[morphology (biology)|morphological]] standpoint. Some degree of [[gene flow]] is a normal evolutionary process, nevertheless, hybridization threatens the existence of rare species. [[File:Extinctions Africa Austrailia NAmerica Madagascar.gif|thumb|upright=1.4|Biodiversity of large mammal species per continent before and after humans arrived there]] The loss of species from ecological communities, [[defaunation]], is primarily driven by human activity. This has resulted in [[empty forest]]s, ecological communities depleted of large vertebrates. In the [[Quaternary extinction event]], the mass die-off of [[megafauna]]l variety coincided with