The Southern Cassowary (Casuarius casuarius) is the truly the iconic animal of Australia’s tropical rainforests.
It features on countless posters, and the name has been applied to geographic areas (the Cassowary Coast), and the common names (plum, satin ash, pine) and scientific names (the genus Casuarina) of several plants. It also features on 2 commemorative Australian coins and is used to celebrate outstanding community contributions to Wet Tropics World Heritage Area management through the WTMA annual Cassowary awards.
The vivid red and blue facial skin, and the pendulous wattles of mature Cassowaries, probably serve to signal sexual readiness and warn off competitors during the breeding season, and may also serve to deter predators. The uniquely large head casque is a prominent feature of fully adult birds and is now thought to play a role as a heat exchanger to regulate body temperature. The Southern Cassowary is the second biggest bird, by weight, in the world, exceeded only by the Ostrich.
Cassowaries are primarily frugivorous. In Australia, they are recorded to eat the fruit of at least 75 plant species. They can travel into nearby habitats such as eucalyptus woodlands, beaches and mangroves in search of fruiting trees. Like most non-carivourous birds, Cassowaries will supplement their diet with invertbrated and small vertebrates including nestlings of several birds, frogs, fish and snails.
Cassowaries play a critical role in the ecology of our rainforests. In particular their penchant for freshly fallen fruit results in them serving as a primary agent of seed dispersal for many rainforest trees. One rare, near-threatened species of tree in the Daintree has been shown to be virtually incapable of germination without first passing through the gut of a Cassowary. It is aptly referred to as the “rainforest gardener” by many naturalists.
Cassowaries are often referred to as ratites, which also includes Ostriches, Emus, Rheas and Kiwis. These large flightless birds lack a keel on their breastbone, which forms the anchor point for flight muscles. Since this condition is now known to have evolved more than once, the term is no longer used by taxonomists.
Cassowaries are most closely related to Emus, both of which belong to the family Casuariidae. There are three species of Cassowary. Only the Southern Cassowary occurs in Australia, as well as the southern lowlands of New Guinea. The other two are restricted to PNA and some offshore islands.
Cassowary Breeding follows the seasonal pattern of fruiting. In Australia, breeding extends from June to October. Very low-frequency calls are common at this time. Like most ratites, male Cassowaries are responsible for incubation of eggs and care of the young up to 12 months after hatching. Males can be aggressively protective of their young. During the first year, the pale brown striped young gradually turn darker and lose their stripes. Full adult plumage and a fully developed casque can take up to 4-5 years.
Apart from their size and impressive colouration, part of the allure of Cassowaries is that they are never very abundant, even in their prime habitat. Catching a glimpse or an extended view of an individual or family group is a special occasion even for long-term residents of Paluma.
Paluma is near the southern limit of the Cassowary’s range and the density of birds here is significantly lower than in areas further north. Even at peak densities, Cassowaries are not very abundant (less than 2 adults per km2). Our best current estimates of abundance are based on a study that examined DNA of droppings (a shitty job if ever there was one!)
Peak density estimates were found for Tully and Russel River. (~1.8 and 1.5 adult birds per km2). No dung was found around Paluma during the study, but an extrapolated density of 0.02/km2 or about 15 individuals was predicted for the region.
This very low estimate, and the general lack of data on densities around Paluma, prompted the recent work by Wren Mclean to carry out a more comprehensive survey that used counts of scat (and other signs) as well as camera traps to derive an updated population size for the Paluma region.
Last month, Paluma hosted a presentation from Wren and others to report on the results of this project.
During the weekend survey on Oct 31 -Nov 1, teams covered 53km of ground and detected 4 cassowary scats [2 fresh and 2 mature] on Jourama and Dolerite Falls tracks to the north and north east of Paluma dam. These observations and other signs, contributed to a new encounter rate of Cassowary signs for the overall project to one sign per/14.5km.
While further analysis will be needed to turn these results into a reliable new estimate of Cassowary densities around Paluma, the data do suggest that Cassowaries are certainly still present in the Paluma Range and, interestingly, that they move between the upland rainforests and lower altitudes at different times of the year, presumably in pursuit of fruiting trees.
While the project is wrapping up, if you see any Cassowaries, or signs of their presence, feel free to contact me, or use the QR Code on the Rotunda sign at the village green to lodge a report.
PS – If you are lucky enough to encounter a group of cassowaries in the forest, the popular literature says they can be referred to as a “dash of Cassowaries”. Google searches and careful consultation with ChatGPT suggest that this is a recent appellation and it might not take hold, if only because it would be so rare to see one!
Text by Jamie Oliver; photos as indicated
Key references:
- Wikipedia articles on ratites, Southern Cassowary
- Cornell Lab -Birds of the World
- Westcott et al 2014, Estimation of the population size
and distribution of the southern cassowary, Casuarius casuarius, in the Wet Tropics Region of Australia - Webber and Woodrow 2005, Genetic diversity and plant propagation in the rare rainforest tree, Ryparosa kurrangii