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Episode 355: Special Announcement with Cassowaries are the Coolest Dads

Looking at the cassowary, the link between prehistoric dinosaurs and birds becomes much clearer. The largest of these ancient looking birds can reach six feet and 160 pounds, and have a serious 4 inch dagger-like claw that looks ready to match up to the velociraptors of Jurassic Park. Their long, powerful legs not only allow them to run up to 30 miles per hour and jump up to 7 feet, but also make them strong swimmers too! 

The magnificent Cassowary (image from Chester Zoo)

There are three currently recognised subspecies: 

  • Casuarius casuarius: The Southern or Double Wattled Cassowary. This subspecies has a blue head, a bright red wattle and glossy black feathers. This is the largest of the three, and is mainly found in lowland rainforests and eucalyptus forests. 
  • Casuarius unappendiculatus: The Northern Cassowary or Single Wattled Cassowary. This species is found through Northern New Guinea, in coastal swamps and lowland rainforests. 
  • Casuarius bennetti: The Dwarf Cassowary. This is much smaller than the other two subspecies, weighing around 50 pounds. This smaller relative prefers higher altitude habitat, like steep mountain terrain. 

Part of the iconic look of the cassowary is their casque, a bony protrusion covered in keratinous skin that grows along with the cassowary. Research suggests that this casque is likely involved in acoustic or visual displays for mating or possibly as a weapon in dominance displays. Some scientists hypothesize that it could also be used in clearing a path through dense vegetation in the undergrowth of their rainforest homes. Given how dense their habitats are, the casque is likely essential in amplifying the low frequency sounds of the cassowary, which are at the lowest limit of human hearing and would be easily drowned out in the thick rainforest vegetation. These sounds have definitely been recorded in the dwarf and southern cassowary species. 

The structure of the cassowary casque (image from Tetrapod Zoology)

Cassowaries are solitary with the exception of the mating season. After mating, the female will lay large green-blue eggs, and unusually, the male will incubate them for 50-52 days, taking home the father of the year award for the animal kingdom. The male will spend his days removing and replacing litter to regulate the temperature of the eggs throughout the day. He is a fierce defender of the nest, chasing away any predators, including any humans unfortunate or stupid enough to stumble over the nest. The female takes absolutely no interest in caring for the eggs, but will instead go on to lay eggs in other males nests. 

Big birds: big risk?

Cassowaries do have quite a dangerous reputation, which is perhaps not surprising given their size, power and that frightening looking dagger like claw. They are naturally very wary of humans, and if they are provoked or stressed, they have the potential to be very dangerous. Their inner second toe, which has that serious claw, is not purely for show; they have been known to attack with it. 

The terrifying claw of the cassowary (image from Live Science)

However, on the whole, attacks are fairly rare. Additionally, a study looking into the incidence and causes of attacks found that 75% of attacks happened when cassowaries were being fed by humans. So if you find yourselves around cassowaries, keep a good distance from them and certainly don’t feed them thinking they are your standard sparrows on the bird feeder!

Cars, collapsing forests and the Cassowary: what threats face these big birds?

Currently, all three subspecies are listed as least concern on the IUCN red list, and their populations are relatively stable. However, this doesn’t mean that they are completely out of the woods. 

One of the biggest threats to cassowaries in Australia is from invasive species, such as wild boar or cats, which can predate on their eggs. Feral pigs will also destroy nests and are serious competition for food as they are super efficient browsers, which is really bad news for cassowaries, especially in bad times. Domesticated dogs can also be a risk to chicks. However in New Guinea, cassowaries there have dealt with invasive species for thousands of years without suffering in the same way Australian populations are; why is this the case? One potential reason is that New Guinea is far more biodiverse than Australia, meaning there are niches for the cassowaries to fit into. In Southern Queensland, the cassowary habitat has shrunk by as much as 75%, leaving less space in the environment for the birds to survive. 

Cassowaries at home in their rainforest habitat (image from Rainforest Rescue)

A cause of mortality study in Australia found that 55% of deaths were caused by car collisions and 18% by dog attacks, with smaller numbers killed by hunting and disease. In Indonesia and Papua New Guinea, hunting is unsustainable and the cassowary is extirpated from some areas. Papua New Guinea also suffers with intense levels of logging of rainforest for palm oil , reducing available habitat for the cassowaries, although lower human populations in these areas do actually help to reduce levels of hunting. 

The loss of cassowaries from their habitat could be potentially devastating for the ecosystem. Across Australia in particular, they are some of the largest seed dispersers, passing the seeds of several hundred rainforest fruit species across areas as large as a kilometer. A study found that germination rates in seeds that have passed through cassowaries can be as much as 92% higher than those not passed through the digestive tract of the birds. The rare rainforest plant Ryparosa is very reliant on the cassowary for its continued survival. 

Cassowaries and Conservation

Although cassowaries face an uncertain future with increasing human development and the presence of invasive species, there is evidence from recent studies that cassowaries are beginning to adapt to urbanization, increasing their consumption of different fruits and food such as scraps from trash cans. Scientists used a telemetry device hidden inside fruit baits that was then ingested and allowed the monitoring of cassowary movement until it was passed. In these more urbanized areas, their activity budgets have changed; they are found to be more active in cities, resting less and moving more than they would in their rainforest habitats. However, they are still dispersing huge amounts of seeds from many species, helping to maintain native plants through fragmented landscapes and gardens. This reaction to increasing human development shows that these birds are pretty flexible creatures, raising hope for their future. Of course it is worth remembering that with increasing time spent in cities, cassowaries are more and more likely to run into humans and their dogs and cars. An important note for anyone living near cassowaries, no hand feeding, as this can lure them into suburban areas, putting them at risk from dog attacks and car collisions, and putting you at risk from a nasty kick from these giant birds! 

Rainforest rescue, a charity aiming to conserve rainforest ecosystems and their species, have set up the Save The Cassowary Project, run by the Cassowary Recovery Team, who aim to implement the recovery plan developed for the species. You can check out their work at Save the Cassowary – Plant a Rainforest – Rainforest Rescue

There are also captive breeding programmes in zoos that, alongside the breeding of insurance populations, also research the movements of captive birds to optimize breeding strategies and understand the habitat requirements of wild birds. 

Awesome Videos!


Borrell, B. (2008) ‘Invasion of the Cassowaries.’ Smithsonian Magazine

Campbell, M.A Lawton, T. Udyawer, V. Bell-Anderson, K.S. and Hamish, A. (2023) ‘The southern cassowary remains an important disperser of native plants in fragmented rainforest landscapes.’ Austral Ecology

Kofron, C.P.(2003) ‘Case histories of attacks by the Southern Cassowary in Queensland.’ Memoirs of the Queensland Museum

Mack, A.L. Jones, J. (2003) ‘Low-frequency vocalisations by cassowaries.’ The Auk

Naish, D. Perron, R. (2016) ‘Structure and function of the cassowary’s casque and its implications for cassowary history, biology and evolution.’ Historical Biology 

Webber, B.L. Woodrow, I.E. (2004) ‘Cassowary frugivory, seed defleshing and fruit fly infestation influence the transition from seed to seedling in the rare Australian rainforest tree, Ryparosa spp.’ Functional Plant Biology 


September 27, 2023
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