Head to head
Cassowary vs Ostrich
The ostrich and the cassowary are the two birds most often named as the most dangerous in the world, both able to kill a person with a kick. They are related, both being ratites, but they live opposite lives in opposite habitats.
| Cassowary | Ostrich | |
|---|---|---|
| Height | Around 1.5 to 1.8 m | Up to 2.8 m; the tallest bird |
| Weight | Up to about 60 kg | Up to about 150 kg; the heaviest bird |
| Habitat | Dense tropical rainforest | Open savanna, grassland, and desert |
| Range | New Guinea and northeast Australia | Africa |
| Social life | Solitary and territorial | Lives in flocks |
| Diet | Mostly fallen rainforest fruit | Plants, seeds, and some invertebrates |
| Toes per foot | Three, with a dagger claw on the inner toe | Two, hoof-like |
| Top speed | Around 50 km/h through forest | Around 70 km/h across open ground |
Cassowary vs Ostrich: common questions
Which is more dangerous, a cassowary or an ostrich?
The cassowary is usually given the title, because of the weapon on its feet. Both birds are big and strong enough to kill a person with a kick, and both mostly just run away, but the cassowary has a straight, sharp claw up to 10 centimetres long on the inner toe of each foot, and it kicks forward and downward, so a strike can cause deep slashing and puncture wounds. An ostrich kick is tremendously powerful and can break bones, but the foot is blunt. In practice, serious attacks by either are rare and almost always involve a cornered bird, a bird defending chicks, or a bird that has been fed by people and lost its fear. Documented human fatalities number only a handful for each species over the past century.
Are cassowaries and ostriches related?
Yes, distantly. Both are ratites, the group of large flightless birds with a flat breastbone that lacks the keel where flight muscles attach. The ratites also include the emu, which is the cassowary's closest relative, the rheas of South America, the kiwi of New Zealand, and the recently extinct moa and elephant birds. For a long time it was assumed the ratites all descended from a single flightless ancestor on the old southern supercontinent, but DNA now suggests flight was lost several times independently within the group, and that the tinamous, which can fly, are nested inside the ratite family tree.
Do both lay the biggest eggs, and who sits on them?
The ostrich lays the largest egg of any living bird, about 15 centimetres long and 1.4 kilograms, though relative to the size of the bird it is actually one of the smallest. A cassowary egg is smaller in absolute terms, around 12 centimetres and 600 grams, and bright green. In both species the male does most or all of the incubation. A male ostrich shares daytime sitting with the dominant female and takes the nights; a male cassowary does the entire 50-day incubation alone, fasting through most of it, and then raises the striped chicks by himself for about nine months.