[3] It has proven very difficult to confirm the validity of these due to individual variations, age-related variations, the relatively few available specimens (and the bright skin of the head and neck – the basis upon which several subspecies have been described – fades in specimens), and that locals are known to have traded live cassowaries for hundreds, if not thousands of years, some of which are likely to have escaped/been deliberately introduced to regions away from their origin.

[3] Cassowaries are most closely related to the kiwis, both families diverging from a common ancestor approximately 40 million years ago.

[4] The southern cassowary was first described by Carl Linnaeus, in his 18th-century work Systema Naturae, as Struthio casuarius,[5] from a specimen from Seram, in 1758.

When food is scarce, both wild and captive cassowaries have been seen to ingest earth, perhaps seeking supplementary minerals.

[10] Inspection of the faeces reveals that commonly ingested fruits are Davidsonia pruriens, Syzygium divaricatum, and members of the palm (Arecaceae), quandong (Elaeocarpaceae), laurel (Lauraceae), and myrtle (Myrtaceae) families.

[11][10] The southern cassowary is a solitary bird, which pairs only in breeding season, in late winter or spring.

In Australia, 16-year-old Phillip McClean and his brother, age 13, came across a southern cassowary on their property and decided to try and kill it by striking it with clubs.

[16] In a 2017 Australian Birdlife article, Karl Brandt suggested Aboriginal encounters with the southern cassowary may have inspired the myth of the bunyip.

[17] Although subject to ongoing habitat loss (some due to logging), limited range, and overhunting in some areas, the southern cassowary was evaluated as Least concern in 2018 by the International Union for Conservation of Nature (IUCN).

[2] A draft recovery plan to save the species was published by the federal government in June 2023, at which time there were estimated to be around 5,000 individuals in Australia.

A 2021 study had shown that extensive reservation had led to recovery of the species, and legislation had prevented the previously rapid loss of habitat.

[19] The team, led by John Woinarski of Charles Darwin University looked at all species listed as threatened under the act in 2000 and 2022.

[20] Southern cassowaries have been bred in zoos around the world, including White Oak Conservation in Yulee, Florida, United States.