You will hear a lecturer giving a talk about the dodo bird and the reasons for its extinction.
First, you have some time to look at questions 31 to 40.
Now listen carefully and answer questions 31 to 40.
Today I'm going to examine one of the best-known examples of extinction, the dodo.
The English expression, as dead as the dodo, is still used for something that has completely disappeared.
Yet the bird lived successfully for a very long time on Mauritius, an island in the Indian Ocean.
It stood roughly a metre high and, although it could no longer fly, it survived among the trees that covered the island.
Europeans first recorded the island in 1507, when Portuguese ships stopped there on their return journey to Europe.
They were transporting spices and used Mauritius as a place to obtain fresh food and water.
But they did not remain there.
Permanent occupation began in 1638, when the Dutch established a settlement.
The newcomers hunted dodos for meat, even though some sailors said the flavour was unpleasant.
The last known bird was killed in 1681.
Reconstructing the dodo's appearance is difficult.
Sailors left written accounts and artists produced several pictures, but neither source is necessarily accurate.
In the most familiar Dutch painting, the bird looks extremely fat.
By contrast, an Indian artist working at about the same time showed a much slimmer animal, so the Dutch image may be misleading.
People did try to preserve specimens, but no complete body remains.
At the beginning of the 17th century, four dried pieces were recorded.
Three were subsequently lost, leaving a head as the only surviving example of the bird's soft tissue.
Various bones have been recovered too, although just one complete skeleton is known.
That skeleton has recently been analysed, and the findings challenge several traditional ideas.
Old descriptions called the dodo slow and awkward, whereas its powerful knee joints suggest it was capable of rapid movement.
One early sailor even complained that the birds were difficult to catch.
Its small wings could not lift it into the air, but probably helped it maintain balance on uneven ground.
Examination of the skull also showed that its brain was average in size, rather than unusually small.
Relative to the body, it resembled the brain of a pigeon, a bird recognised for its intelligence.
Finally, the skull indicates a particularly developed sense of smell, which would have helped the dodo locate ripe fruit and other food in dense vegetation.
These findings imply that the dodo was more capable of protecting itself than earlier accounts suggested.
Nevertheless, it vanished less than two centuries after Europeans arrived.
Hunting was once regarded as the explanation, but researchers now think several factors were involved.
Sailors deliberately brought dogs, which could attack the birds, and monkeys, which competed for the fruit they ate.
Ships also carried rats accidentally.
They spread rapidly across the island and consumed dodo eggs.
Because a female laid only one egg at a time, this would have caused serious damage to the population.
Even so, the strongest explanation now concerns agriculture rather than hunting or introduced animals.
The forest that once covered Mauritius provided the dodo's habitat.
Settlers cut it down to create farmland and grow crops such as sugar.
So the bird lost the environment on which it depended.
After surviving for thousands of years, the dodo disappeared within a remarkably short period.
That is the end of part four.
You now have one minute to check your answers to part four.
