News: How the emu got grounded

Given he couldn't fly, Tyrone thought he'd canoe across the ocean to Africa to visit the relatives.   Illustrated by Mike McRae

Old man emu isn’t well known for his swimming ability, nor is his cassowary cousin. The flightless African rhea can’t operate small aircraft, ostriches aren’t very good at teleportation and as large as the extinct New Zealand moa was, it’s unlikely it got there by jumping across the Tasman.

They are all related as a group of birds called ‘ratites’. Biologists from the Australian National University wondered just how it was that these birds managed to spread to different parts of the globe if they couldn’t fly. Yet the DNA of the moa revealed an interesting secret – its closest ancestor is a small South American bird called a ‘tinamous’.

Biologists had assumed that ratites all shared a common ancestor around 80 million years ago that looked somewhat like them – tall with a long neck, long legs and tiny wings. The only problem with this picture was that the continents spread apart long before then. How, then, did this ratite grandmother manage to spread her children so far and wide?

It now seems that the scientist’s previous estimates were a little off, breaking away from a common ancestor only 65 million years ago. New evidence suggests that the birds lost their ability to fly with the extinction of the dinosaurs. Although it could simply be a coincidence, it’s possible the disappearance of the big meat-eaters made it safer for the small, ground-feeding ancestor of the emu and ostrich to let their bellies grow.

On islands that lack predators, it’s not uncommon to see birds with wings or flight muscles too puny for lift-off. The plump dodo on the island of Mauritius is a perfect example, as is New Zealand’s kiwi.

While flight is useful for many things, such as avoiding being eaten or migrating long distances to new feeding grounds, it’s also a rather demanding exercise. Not only does the animal need to grow big wings, they need well developed chest muscles and light bones as well. If it’s not necessary, birds can devote their food and energy to making more babies instead of wasting it on flapping around.

More information

• Dino departure fattened emu
• ANU Research School of Biology
• CSIRO link: Birds of the Australian National Wildlife Collection

Quiz Questions

1. What is the Pacific Ring of Fire?
2. Are the tears caused by cutting onions different from sadness tears?
3. What primary sense does the common barn owl (Tyto alba) use to hunt?
4. In 1851, the Foucault pendulum demonstrated what? (a) The Earth revolves around the Sun (b) The first perpetual motion machine (c) That grandfather clocks were still in fashion (d) The earth rotates on its own axis
5. What is the difference between rogue waves and tsunamis?

Quiz Answers

1. It is a 40 000km wide horseshoe-shaped area where over 75 per cent of the world’s volcanoes exist and about 90 per cent of the world’s earthquakes occur.
2. Emotional tears contain more protein-based hormones (including natural painkillers) that the body produces when under stress.
3. Don’t let those big eyes fool you! The answer is hearing.
4. d
5. Tsunamis generally only become a danger in shallow water close to the shorelines, and are not a danger to ships or platforms far out at sea. Rogue waves, however, are. These are generally found far out at sea, and can measure up to 30 meters high! CSIRO has recently begun modelling these waves, using fluid-flow mathematics and computer modelling. By smashing these virtual waves into oil and gas platforms, the CSIRO hopes to improve the design of structures used in the deep ocean.