|Colney Nature Watch
| A series of articles on the wild life in London Colney
There have been hedgehogs on the planet earth for fifteen million years. In that time, the mammoth and the woolly rhinocerous evolved, to die out at the end of the ice age. Three successive species of sabre toothed tiger evolved - the last to die around the time the first humans arrived in the Americas. And the oldest direct ancestors of humans date back three million years. The earliest hedgehog fossils are similar to today's hedgehogs - which show it is an extremely successful species, or it would have either evolved into something else - or become extinct.
Our British hedgehogs are identical to the ones you see in Europe.
There are slightly different species of hedgehog living in Africa and Asia. Early colonists took hedgehogs to their new countries. The population in New Zealand has thrived and they are now part of the New Zealand fauna, but they could not cope with conditions in Australia and South America - and died out. Introducing wild animals to countries they've never known is foolish, because it is impossible to predict their effect on already established species. Hedgehogs were introduced to several Scottish islands. They out competed local sea birds for their food, and ate their eggs, so regretfully the authorities had to remove the hedgehogs.
Scientists know a lot about the favoured foods of hedgehogs. They examine the stomachs of road accident victims. They found the favoured foods in descending order were beetles, caterpillars, earthworms and wild birds' eggs. They also enjoy fallen fruit and earthworms. And a thing that endears them to gardeners - they eat slugs and snails.
People ask what happens when hedgehogs eat slugs which have eaten slug pellets? The toxic ingredient in slug bait is metaldehyde.
Metaldehyde is mildly toxic to all mammals - including humans. However it is absolutely lethal to slugs and snails. Research by Swiss scientists has shown that after metaldehyde is digested in slugs, it is converted to several chemicals, none of which are poisonous. If a hedgehog eats a slug, which has taken slug bait, there will probably be some undigested bait in its stomach. The Swiss researchers concluded a hedgehog would need to eat five thousand large slugs to ingest a toxic dose.
We all see hedgehog corpses on our roads. However, the commonest cause of hedgehog death occurs during the winter, when they are hibernating. In the autumn, hedgehogs need to build up sufficient body fat to sustain them during their long winter sleep. Hedgehogs which are born in late autumn have no hope of surviving the winter sleep. In southern Europe, it is much warmer, and hedgehogs do not bother to hibernate, particularly as there is food around. Sometimes people find dead hedgehogs in their garden ponds. Hedgehogs are good swimmers, and if they have drowned - it is because they could not find a way to climb from the pond.
You will not get hedgehogs in your garden if it has a wall or an impassible hedge or fence. You can encourage them by leaving out bread soaked in milk, cat or dog food, fruit and nuts. But do not overdo it!
Hedgehogs do best on their natural food. There is an outstanding book on hedgehogs 'The New Hedgehog Book' by Pat Morris. It is extremely readable, full of good drawings and cartoons and is published by Whittet Books. The staff at Borders would be only too pleased to order you a copy.