Giant Cassowaries are Modern-day Dinosaurs _ Seven Worlds, One Planet _ BBC Earth

In the rainforests of Australia, the giant cassowary is in danger from a feral invader. March 2018, the BBC's Seven Worlds One Planet team arrive in northern Queensland. Their aim? To film one of the world's largest birds, the cassowary. We are in the Daintree rainforest in north Queensland, and it's one of the oldest patches of rainforest in the world. Growing to a height of one and a half metres and equipped with enormous dinosaur-like claws, cassowaries have been described as the planet's most dangerous birds. But these feathered giants are shy and prefer to stay hidden in dense tropical rainforest. There are only around 2,000 left in Australia. To locate them, the team set up a series of camera traps. But instead of cassowaries, they discover another animal that could threaten the future of the entire forest. There's like eight pigs in there. When was that? We put up loads of camera traps around the place, and most of the footage we got back were of feral pigs. Pigs are not meant to be in this rainforest. They were brought to Australia as farm animals by European settlers in the 1700s. They soon escaped, and now there are around 24 million living feral across the continent. This is pig damage. We see it all over the place. They're trying to find some food, but in doing so, they disrupt all the topsoil, so that if it rains heavily, which it does all the time, all the soil washes away, and then the trees can't stand up. So they're basically causing havoc. They also eat all the food and can grow massive, so they can really be a threat to our cassowary, especially the chick. Pigs are omnivores. As well as stripping the forest of the fruit the cassowaries depend on, they can eat their eggs and even their chicks. With such a small population, this new threat could see the cassowary disappear forever from Australia, which would be disastrous for this ancient rainforest. The cassowaries are crucial for the daintree rainforest to survive. They're a keystone species, and this fruit in particular relies on the cassowary to germinate. It goes through cassowary's gut, and once it's done that, it is obviously pruned out, and it is able to grow in its own little pile of cassowary fertiliser. It's estimated that over 100 plant species here depend almost entirely on the cassowary as their method of seed dispersal. They can eat fruits that are, you know, this big. They walk kilometres in a day, so they take them really far away, and they have a really gentle digestive system. So if the cassowaries are at risk, all the other plants and animals that rely on them are also in danger. Invasive species are now the number one threat to Australia's native wildlife. They have already contributed to the extinction of more than 100 indigenous species of flora and fauna. It's hard to predict just how many feral pigs there are in the daintree, but the camera traps suggest their numbers are increasing. At this moment, little is being done to remove or prevent the spread of pigs. So, unless action is taken soon, Australia may lose another of its iconic wildlife species.