What Is a Cassowary? It May be the Most Dangerous Bird in the World

Jet black, hair-like feathers. Vivid blue heads adorned with a spongy crest. Most strikingly, a pair of leathery looking feet, armed with a 12 centimeter talon.

This is the cassowary, one of the largest and also most dangerous birds in the world. Though it looks like it walked right out of prehistory, it roams the land Down Under. It’s got a killer reputation – quite literally, as cassowaries are among the few bird species that boasts human fatalities on their rosters.

But how dangerous is the cassowary, really? Here’s what to know about these birds.

There are three species of cassowaries: the Southern Cassowary, Dwarf Cassowary, and Northern Cassowary. Of the three species in the Casuariidae family, the southern cassowary is the largest and most well-known. The title of "the most dangerous bird in the world" is often given to the Southern Cassowary, known for its potentially aggressive behavior.

Cassowaries live in varying regions of New Guinea and Australia, as well as surrounding islands. 

These birds can weigh up to 160 pounds and reach heights of six feet. The casques, or crests, atop their heads are made of the same substance forming human nails and hair, and some scientists suspect it helps as a thermal window.

While cassowaries cannot fly, their powerful legs allow them to jump up to seven feet in the air, as well as dash through their dense rainforest habitats at over 30 miles per hour – faster than Usain Bolt.

Within rainforests, cassowaries mainly eat fallen fruit, scraping them off the earth with their sharp claws. They’re feathered farmers of sorts, consuming these fruits and dispersing their seeds throughout the ecosystem. In fact, certain species of plant seeds won’t flower without having passed through a cassowary’s digestive tract first.

Though they mainly live off of fruits, they can additionally snack on insects, snails, and even other dead animals.

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Cassowaries exhibit a range of interesting behaviors that reflect their adaptation to the dense rainforest habitats they live in. Understanding their behavior provides insights into how these elusive birds interact with their environment and other species, including humans.

Cassowaries communicate through various sounds, from hissing to whistling to grunting to even booming.

Their signature calls are so low that they border the limits of human hearing, powerful enough that wildlife specialists have reported feeling their deep rumbles in their bones.

Additionally, as their rainforest homes make it difficult to spot these generally shy birds in the wild, the Australian Museum states that you’d likely hear a cassowary before seeing one.

Cassowary eggs are green because of biliverdin, a pigment often found in bird eggs. Since cassowaries nest on the ground, the green eggs blend in with the plants in the tropical forest, helping to hide them from predators. Female cassowaries lay a clutch of about 3-5 eggs at once, each of which can weigh about the same as 10 chicken eggs. With their sheer size and bright green shells, cassowary eggs look straight out of myths.

In the cassowary’s world, males are tasked with child-rearing responsibilities. They sit on and incubate eggs for about two months. Once chicks hatch, brown and fuzzy, cassowary fathers care for them for about a year, showing them around their territories and where to seek important resources like food and water.

This goes on until the youngsters grow independent enough to strike out on their own or are eventually chased out.

Especially during this breeding season, which stretches from June to October, cassowaries can get aggressive and territorial. While they use their claws to scrape fruit off the forest floor, they might brandish the dagger-like claw adorning their innermost toe against threats and opponents as well. This spiky talon makes for a formidable weapon when paired with a cassowary’s powerful kicks.

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As Henry Gee once questioned in Nature, “Are the streets of Australian cities patrolled by marauding gangs of these peculiar animals, intent on giving the residents a good kicking?”

Not really.

While cassowaries are one of the only birds (among ostriches and chickens) known to have killed humans before, attacks resulting in human fatalities are rare.

In fact, there are only two recorded, confirmed instances of a lethal cassowary attack – one taking place in 1926, when a cassowary killed a teenage Australian boy after he’d attempted hunting one, and another in 2019, when a cassowary owner in Florida was mortally injured after falling between his cassowaries’ pens.

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In 1999, Christopher Kofron, of the Queensland Parks and Wildlife Service, analyzed 221 cassowary attacks for the Journal of Zoology. Of the 150 that were on humans (with other opponents including dogs, horses, and even windows or doors), he found that cassowaries primarily attacked humans over food.

 Feeding cassowaries can lead them to associate humans with food, even relying on them as resources. If cassowaries approach a person who can’t satisfy their peckish demands, they might become aggressive.

A few other reasons for cassowary attacks, according to Kofron, included defense of food or youngsters, though a majority of human attacks were related to procuring food.

“Cassowaries may be big, but their attitude to life is disarmingly straightforward,” wrote Gee. “Once they get the idea that human beings offer food, they assume that we are all walking meal tickets.”

That’s not to say cassowaries don’t pose threats to humans at all. Though they’re generally shy when unprovoked, they do become aggressive if agitated. Their kicks and claws are also no joke, able to slice open perceived threats or even break bones and rupture organs.

In the event that you do encounter a cassowary, Kofron’s advice is to remain standing and try to leave the area without turning your back. On top of that, avoid feeding them. As is the rule with most wildlife, if you leave it alone, you’re more likely to come out unscathed.

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According to emu researcher Julia Ryeland, if a cassowary and an emu were to fight, the cassowary would most likely win. Here are the reasons behind her prediction:

Cassowaries are equipped with sharp, dagger-like claws, with the innermost claw being a spike-like dagger measuring up to 12 centimeters. These claws, combined with their powerful legs, allow cassowaries to deliver potent and potentially lethal kicks, which could overwhelm an emu in a fight.

In a hypothetical scenario where an emu invades a cassowary's territory, the emu is more likely to retreat at the first sign of danger, especially when protecting its chicks. This instinct to flee rather than fight could lead to a quick surrender if faced with the aggressive and powerful cassowary.

Despite their potential for aggression, the cassowary is more often shy and elusive, living quietly in their rainforest homes. Understanding and respecting their space is key to coexisting with these magnificent birds, ensuring both their safety and ours.

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