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Tuesday, 3 February 2009

Death of the Dodo

In 1662 some survivors of the shipwrecked Arnhem were exploring the coast of Mauritius. They waded over at low tide to an islet (probable Isle d’Ambre off the north-west cost), where they found doddaersan “larger than geese but not able to fly, instead of wings they had small flaps, but they could run very fast”. Starving, they killed them all. These may have been among the last of their kind – a few probably survived in remote areas for a decade or two more, but most later accounts probably refer to another flightless bird, a large kind of rail, itself now extinct.

The conventional story of the Dodo’s demise is that, living on an island without predators, it took to nesting on the ground and lost the power of flight, and was as a result helpless against people killing it for food. Despite the story above, this, like most conventional stories, is not the whole truth. For one thing, except when desperate people avoided eating Dodos, as they apparently did not taste good, much preferring to eat the tortoises which abounded on the island. In addition, the Dodo had by all accounts a nasty bite.

Nor were the islands devoid of predators. There were owls, a harrier (similar to the Marsh harrier that breeds in the UK), three species of snake, at least one of which was over 1.5 m long, and several large skinks, one over 60cm long. In addition, the forest floor swarmed with land crabs, as numerous as those that can be found on Christmas Island today. None of these were large enough to tackle an adult Dodo, with the possible exception of the harrier, but any could have taken eggs or young. In fact, it is a bit unclear why the Dodo took to ground nesting at all.

The true cause of the extinction of the Dodo probably lies in the usual suspects – introduced species and habitat destruction. The reason Mauritius was colonised was because it made a convenient way station to the East Indies (now Indonesia). It was also discovered that the lowland forests were rich in ebony trees, a highly prized commodity. The deforestation that resulted probably destroyed both the Dodo’s habitat and its food source, which was probably the fruits of forest trees and terrestrial invertebrates. The arrival of black rats – which arrived from shipwrecks even before the islands were permanently settled, would have added competition for food, but the Dodo would have been used to defending its nest against crabs and other predators, and would have been able to drive off raids on its eggs.

The main cause of the Dodo’s demise however, was probably the introduction of the pig. It was common for sailors to leave livestock behind to breed on islands they discovered, with the aim of having food when they next passed that way, and they would certainly have devoured any eggs they came across.

The Dodo died out so early that many naturalists did not even believe that it ever existed., but was only a travellers tale. Only in the 19th century was the Dodo “rediscovered”, and the phrase “As dead as the Dodo” entered the language.
There was a good deal of debate about what a Dodo actually was, but it is now known to have been a kind of fruit pigeon, whose nearest relatives are to be found in south east Asia.Here at Bristol we are fortunate to have two of the Dodo’s closest living relatives. Probably the closest of all is the Nicobar Pigeon Caloenas nicobarica, now found only in Indonesia. However, it migrates between islands even today and although it nests in trees it spends all its time feeding on the ground. Also mainly a ground feeder is the Victoria Crowned Pigeon (Goura victoriae), which is the largest living pigeon, and comes from New Guinea. Both of these species have been bred here at Bristol and are well represented in collections worldwide.

I will be following this post with a series on the natutral history of Mauritius and its related islands. To see what is happening there today, and what is being done about it, have a look at the Mauritius Wildlife Foundation website on the links section

Alan

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