00:03Birds are incredibly successful animals.
00:06They have adapted to suit unique environments on all of Earth's continents.
00:10And one of their most admirable abilities is of course their method of locomotion.
00:15Flight.
00:17Their sleek aerodynamic shape, powerful wings and light body weight
00:22allow them to take off and see the world from a different perspective.
00:26But not all birds can fly.
00:29In fact, the three largest living birds on the planet are terrestrial ground dwellers.
00:36The ostrich, the cassowary and the emu are all flightless birds,
00:41part of a group known as ratites.
00:44While these particular ratites don't have flight on their side,
00:48they certainly have size.
00:50But which of these three flightless birds are the heaviest?
00:53To find out, we're going to have a chat with Sandy
00:56from Lone Pine Koala Sanctuary in Australia.
00:59While the emu and the cassowary are roughly the same height,
01:03the emu is actually a lot lighter in weight
01:06and the cassowary can weigh up to three times heavier than the emu.
01:10But the ostrich is the heaviest flightless bird in the world.
01:14Ah yes, the ostrich, of course.
01:16Just take a look at that strong, muscular build.
01:20Male ostriches have been known to reach weights of up to 250 pounds.
01:25With that much mass, it's easy to see why it might be a little difficult to take off.
01:31But how do these flightless birds defend themselves if they can't just fly away from trouble?
01:35The defence for the emu and the cassowary is to make themselves look way bigger than what they actually are.
01:43And they have two strong, powerful legs which they will charge you with.
01:47But the cassowary has an extra device along with the powerful legs.
01:52They also have a very, very long toenail in the inner side of their foot.
01:57Those defence mechanisms would certainly come in handy during a confrontation with a predator.
02:02But adult cassowaries and emus don't have to defend themselves too often.
02:07Both are native to Australia, where a run-in with a local apex predator such as a saltwater crocodile or
02:12a dingo is possible, but rare.
02:15Ostriches, however, are native to Africa, where there are many more predators to be wary of.
02:25With legs like these and title of heaviest birds in the world, these ratites don't need the ability to fly
02:32to make it big in their natural habitat.
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