Freedom to publish everything on the web has shown the narrow perspective, not to say ignorance, of people writing about Cassowaries.
There are three species of Cassowaries: Casuarius casuarius, Casuarius unappendiculatus and Casuarius bennetti. A sub-species of Casuarius bennetti has been suggested as being a full species Casuarius papuanus, but research by me and others has not yet been conclusive.
The Cassowary can be naturally found on New Guinea, some of the nearby larger islands and in Queensland, Australia. All three species are endemic to the island of New Guinea and one species, Casuarius casuarius, is also endemic to northern Australia. By far the greater number of Cassowaries found in captivity in zoos throughout the world are Casuarius casuarius, often called Double-wattled Cassowary or Southern Cassowary.
My research suggests that the genus Casuarius originated in Australia and was able to migrate northwards to New Guinea and probably the Aru Islands, when land bridges existed during the ice ages which happened after New Guinea became an island about one million years ago. Essentially the birds which migrated northwards were those we know today as the Double-wattled Cassowary.
Due to the continuing northward movement of the Australian plate and its impact on the Pacific plate, the area of New Guinea was squeezed and a chain of higher land, eventually becoming mountains, was created laterally East to West. Over time, the vegetation and altitude changed and some Cassowaries became isolated from the main genetic source and adapted to the changing environment. Exactly when and in which order is not yet established, but probably the Single-wattled or Northern Cassowary, Casuarius unappendiculatus, was the first to become separated, adapting to higher elevations and changed biotope, on the northern side of the mountains, from Casuarius casuarius, followed by the Dwarf or Bennett’s Cassowary, Casuarius bennetti, which can survive at more than three thousand metres and has a reduced size compared to the other species to make the altitudinal and feeding adjustments.
The fourth projected species, Casuarius (bennetti) papuanus, the Bird’s Head or Papuan Cassowary has its range in the mountains of the Bird’s Head peninsular.
This speciation must have taken many thousands of years to get to the current biological differences. The great diversity of specimens seen in Casuarius unappendiculatus and Casuarius bennetti may be an indication of continuing genetic evolution.
Although the Australian population is classified taxonomically as Casuarius casuarius johnsonii, on the basis of geographical situation, it is genetically probably only about six or seven thousand years away from the mainland New Guinea and Aru Island birds because of the recent closing of the land bridges and it is not possible morphologically to separate them from other Casuarius casuarius populations with any certainty.
Although we have a rough idea of the Queensland population due to local research, 1,500 to 2,500 birds, we can only guess about the size of the other ones. Simply extrapolating habitable area would suggest a Casuarius casuarius population outside of Australia to be in excess of 50,000, but these figures cannot be treated as being in any way accurate.
The population sizes of the other two species are even more uncertain and no-one has any reliable data. The only indication we may have about all three species is circumstantial and not directly quantifiable. From sighting reports over the last twenty years, Queensland is a special case partly because extensive forest damage due to storms has brought more Cassowaries out in search of food, there would seem to be fewer birds about. Cassowaries are still hunted for food in New Guinea and chicks are reared in villages prior to being eaten or traded, but more research is needed before drawing any conclusions.
Our knowledge about Cassowaries is mainly based on Casuarius casuarius and over 600 are in captivity wordwide. Relatively, we know little about Casuarius unappendiculatus and Casuarius bennetti, together perhaps less than 50 in captivity, and badly need more information about their distribution and habitat. Photographs of birds in captivity and in the wild, especially with places of origin, would help enormously with taxonomy and establishing any population decline. I would love to hear from anyone about their experiences and see their photos.
One last point, all Cassowaries can be very aggressive and direct contact should be avoided. Do not, under any circumstances, approach even a tiny chick in the wild (father is not far away). However, if you ever meet one, do not run away from it. Stand still or move very slowly to any nearby solid protection, like a tree – or get into water (they can swim, but won’t attack you in 1metre of water). The only confirmed recorded time anyone has been killed by a Cassowary was when two boys ran away on meeting a bird and it chased them, killing one by slashing open an artery. Normally Cassowaries are very shy, humans have been their enemy for about 60,000 years, but any close contact carries the risk of injury – I have a few scars from handling them and many zoo personnel have been seriously injured.
They are magnificent birds, ones we need to understand to protect them properly.