The Cassowary Is the World's Most Dangerous Bird

By: Wendy Bowman  | 
The Southern Cassowary (Casuarius casuarius) is endangered in Australia, the only place it exists on Earth, with land clearing, car strikes, pigs and dogs the main threats to their survival. Henry Cook/Getty Images

This massive, flightless emu-like creature has been called "the most dangerous bird in the world." The reason is that this exotic bird can seriously injure or kill a human or dog in an instant with its deadly claws. In fact, cassowaries are listed as Class II animals (along with alligators and wild cats) in Florida due to the risk they pose, which means anyone who wishes to own one must pass numerous tests and get a special permit from local authorities. And even then, tragedies still can occur, as happened to the 75-year-old Florida man a cassowary killed. He was attacked by at least one of the birds he rears on his properties and later succumbed to his injuries in the hospital. They're quick too, cassowaries have adapted those powerful legs to run fast at about 31 miles per hour through dense forest underbrush.

So, what exactly is a cassowary? Like their cousins the emu, they are ratites, or birds that have flat breastbones and are unable to fly, native to tropical forests of Australia and Southeast Asia. As far as this striking bird's appearance, it boasts bristly feathers, a vivid blue face, two red wattles hanging from its neck and a prominent helmet (or casque) atop its head. Although size varies across the three different species of cassowaries — the Southern, Northern and Dwarf — they can stand up to 6 feet, 6 inches (2 meters) tall and weigh as much as 132 pounds (60 kilograms). For a comparison, you can think of one as being the equivalent of six swans.


Close-up of southern cassowary claw.
The claw on the inner toe is particularly frightening, reaching lengths of 5 in!
Marianne Purdie / Getty Images

The portion of their body that makes them so dangerous? Muscular legs with three claw-tipped toes that can pack a pretty powerful punch, including lethal wounds to internal organs and severe bleeding. "The claw on the inner toe of each foot is what is so impressive," says Rick Schwartz, a global ambassador for California's San Diego Zoo, which currently houses several Southern cassowaries in its Safari Park, in an email interview. "Between the three species, that claw is very sharp, and can range from 3 to 5 inches (7 to 12 centimeters) long. The cassowary will use these sharp claws and their powerful kick to defend themselves. It is often stated that they can eviscerate a human in a single kick, though there is no record of this happening."

The good news, according to Guinness World Records, is that you're far more likely to suffer a snake bite or even an infection transmitted by a dog than you are injury by one of these birds. In fact, the most dangerous animal of all is no bigger than a thumb nail. By transmitting disease-causing pathogens, mosquitoes are estimated to be responsible for between 725,000 and 1 million human deaths per year, making them far and away the most lethal animal on Earth.

Now that you know you probably shouldn't provoke a cassowary — or a mosquito, for that matter — here are 10 other interesting facts about this unusual bird.


1. They Are Not Emus

While a cassowary is not an emu, both emus and cassowaries can be considered related in taxonomy (the science of classification of living and extinct species), according to Schwartz. "They share the same scientific order [Casuariiformes]," he explains. "But, within that order, they are in different scientific families."


2. They Are Quite Hefty

"Cassowaries are the heaviest bird in Australia, and the Southern cassowary is the second-heaviest in the world (the world's heaviest bird is the ostrich)," says Schwartz. "With that in mind, they also have very small wings. When stretched out, their wings extend less than a foot (0.3 meters) from their body." According to Schwartz, female Southern cassowary's can weigh up to 170 pounds (79 kilograms) and males up to 125 pounds (56 kilograms); Northern females can weigh up to 128 pounds (58 kilograms) and males up to 80 pounds (36 kilograms); and Dwarf females can weigh up to 55 pounds (24 kilograms) and males up to 40 pounds (18 kilograms). Making them some of the largest flightless bird species in the world.


3. Their Feathers Are Not Suitable for Flight

A cassowary has dense, black feathers that are long and thin compared with the wide and shapely feathers of a flighted bird, according to Schwartz. "From a distance, some people even say the feathers of the cassowary look more like hair," he adds. "The cassowary's feathers are not suitable for flight, but they work very well for a ground-dwelling bird living in a forest ecosystem. The longer, thinner feathers help direct water away from the body, and also protect the bird's body from low branches, sharp twigs and thorns."

Close-up of a Southern Cassowary in Daintree, North Queensland, Australia.
Artie Photography (Artie Ng)/Getty Images


4. That Thing Atop Their Head Is Called a Casque

It's made of keratin, the same protein that the bird's feathers, nails and beak are made of, according to Schwartz. "The outer covering is thick and hard, but the inside is very porous. The purpose of the casque is not completely understood, but several theories exist — including that it can help amplify vocalizations, serve as head protection as the bird pushes headfirst through the dense forest, or it may be another way for the birds to display age and vitality."


5. Their Wattles Serve a Purpose

"Of the three species of cassowaries, only the Northern and Southern cassowaries have wattles," says Schwartz. As with the casque, there are a few theories on the purpose of the brightly colored wattles, he adds. Among them: "It is thought that they can help communicate the bird's current demeanor; indicate an individual bird's vitality to other cassowaries; or give other cues and communications only known by cassowaries at this time," says Schwartz.


6. They Are Frugivores

That means they feed on fruits, which makes them very important to their surrounding ecosystem, according to Schwartz. "As they eat fruit, they walk around and pass the seeds through their digestive tract," he explains. "Thus, their droppings deposit seeds that are surrounded in natural fertilizer, helping to spread the diversity of plants in their region." They are considered a key-stone species as they play an important role in spreading fruit seeds far and wide. Due to their large size they are able to spread larger seeds than most birds like those of the rare Australian rainforest tree Ryparosa. Those claws help them dig deep in the leaf litter for fallen fruit other species might miss.


7. You'll Probably Never Encounter One in the Wild

Searching the dense rainforest you will likely not hear them as their bird calls are right at the edge of human hearing. "With their excellent hearing, they will hear you coming long before you even know they are there, and they will most likely disappear into the forest to avoid you," says Schwartz. "However, should you ever come across one in the wild, it is best to give them plenty of room and not approach them or try to feed them."

Cassowary Adult with Cassowary Chick
Cassowary Adult with Cassowary Chick
Martin Harvey / Getty Images
Bright Green Cassowary Egg in Nesting Material
Female Lays Bright Green Cassowary Egg in Nesting Material
PansLaos / Getty Images


8. The Males Care for the Young

In several species of animals, the male participates in incubation and care for the young cassowary chicks after the eggs are laid. So the female cassowaries only lay eggs but do not take part in the upbringing, according to Schwartz. "The female returns to her solitary life, and does not participate in incubating the eggs or caring for the young," he says. "This may be a way to allow her to have several clutches of eggs in one breeding season with different males, thus diversifying her genetics into the next generation."


9. Cassowaries Make a Variety of Sounds

The most impressive, according to Schwartz? "A deep, low-frequency booming sound," he says. "It's the lowest known call of any bird, and it's so low that it borders on being inaudible to the human ear. If you are nearby when it does this call, you can feel the vibrations in your chest."


10. Their Population Is Dwindling

Per the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (the world's most comprehensive inventory of the global conservation status of plant and animal species), all three species are listed as either Vulnerable or Near Threatened. "Like many species, their biggest challenges are the loss of habitat due human population growth; roads being built (causing car strikes); and human-introduced species of animals raiding nests," says Schwartz. "The good news is that the governments of the countries cassowaries call home are stepping up their conservation efforts." Man's best friend the dog is a big threat to young cassowaries. Young birds were also captured and sold for meat and their stunning feathers which many are working to eradicate today.

There are less than 1,000 cassowaries left in the wild, according to Rainforest Rescue. With the Northern cassowary, also known as the dwarf cassowary or Bennett's cassowary, in New Guinea being the most threatened. Toward that end, the Australian-based group works to protect and restore the cassowary's habitat, as well as to create safe passage for these and other rainforest creatures via strategic buy-back of rainforest properties and regenerating damaged rainforest.