Animal Frankensteins David Attenborough's Natural Curiosities


Animal Frankensteins

David Attenborough examines some fascinating creatures. This episode looks at bizarre and sometimes deadly hybrids, like the pizzly bear and killer bee.


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Transcript


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The natural world is full of extraordinary animals

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with amazing life histories.

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Yet certain stories are more intriguing than others.

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The mysteries of a butterfly's life cycle,

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or the strange biology of the emperor penguin.

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Some of these creatures were surrounded by

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fantastic myths and misunderstandings.

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Others have only recently revealed their secrets.

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These are the creatures that stand out from the crowd,

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the curiosities that I find particularly fascinating.

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In this programme, we investigate the stories of two animals

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that owe their existence to human interference.

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Killer bees that were created accidentally

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when a well-meaning breeding experiment went wrong.

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And pizzly bears, the result of polar bears

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and brown bears interbreeding.

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How were these strange animals created,

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and are they unnatural mutants, or valuable new hybrids?

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This is a grizzly bear.

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And that white one there is, of course, a polar bear.

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But in between, there's a different kind of bear.

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It's got the white coat of a polar bear, except that

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around the eyes, it's rather brown, and its front legs are very brown.

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It is, in fact, a hybrid,

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the result of a mating between a polar bear and a grizzly bear,

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and they're sometimes called a pizzly.

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The first-ever pizzly bears were born in a German zoo in 1876,

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after a polar bear and a grizzly - a type of brown bear -

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were housed together.

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Hybrid animals have frequently been born in captivity,

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both intentionally and by accident.

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Tigers and lions produce offspring called ligers,

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and donkeys and zebra, babies known as zonkeys.

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But usually, these hybrid creatures are sterile

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and not well adapted for surviving in the wild.

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Hybrid bears like this were considered to be

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theoretical species, creatures that could never exist in the wild,

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and the pizzlies of the Victorian era were largely forgotten.

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Animals, of course, usually mate with their own kind.

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If different species are to interbreed

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and produce fertile young,

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they have to be extremely closely related.

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Grizzly bears and polar bears are certainly somewhat

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similar in appearance.

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But are they, in fact, closely related?

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In the bear family, the black species came first,

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and then came the brown bear, and finally, the white polar bear.

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This was thought to have happened four to five million years ago,

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but recent fossil evidence suggests that it may have

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happened as recently as only half a million years ago.

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So the polar bear is the relatively recent species of bear,

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one that branched off late in the bear family tree.

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Polar and brown bears are, in evolutionary terms, close cousins.

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They share some characteristics,

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but there are also many physical differences.

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The most obvious is the colour of their fur.

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Colour acts as camouflage, so that's not surprising,

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since they live in very different habitats.

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Grizzly bears have rounded heads and prominent shoulder humps

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that have evolved for digging.

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Polar bears, on the other hand, have more pointed heads,

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but no shoulder humps.

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Their feet are large and flat

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so that they can act as paddles when swimming.

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They also have hairy pads and short claws

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which helps to prevent them slipping on ice.

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The grizzly has more obvious footpads

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and much larger, curved claws.

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We know that polar and grizzly bears can mate successfully

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because they've often done so in captivity.

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But what sort of offspring do they produce?

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For many years, zoos discouraged the breeding of pizzly bears.

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But recently, there was a chance to study them in Germany.

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In 2004, at Osnabruck Zoo, a brown bear called Susi

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and a polar bear called Elvis,

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who had shared an enclosure for 24 years, unexpectedly produced twins.

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The small brown cubs are bigger now and have changed colour.

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The male, named Taps, is brown,

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and the female, Tips, has a lighter coat.

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But otherwise, they have traits inherited from both parents.

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Long necks and visible tails that are more typical of polar bears,

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but also small shoulder humps

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that are reminiscent of those of brown bears.

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Their feet are intermediate in form.

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And their size is between the two -

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smaller than a polar bear, but larger than a brown bear.

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In the wild, of course, it would be rare for the two species to meet,

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for they inhabit very different kinds of country.

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Brown bears are the most widely distributed of all bears.

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They live in North America, in Alaska

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and in Russia and Northern Europe.

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They're omnivores - they'll eat not only flesh,

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but nuts and grass and fruit.

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And the biggest of all live in Alaska.

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They can grow to a length of over three metres and weigh 600 kilos.

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Together with polar bears,

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they are the biggest carnivores on this planet.

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The other parent of the pizzly, the polar bear, lives high in the Arctic

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and is slightly bigger than the brown bear in both size and weight.

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It lives on snow and ice and hunts seals.

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We know from Osnabruck Zoo that when polar bears and grizzlies mate,

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they can produce pizzly cubs.

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But what are the chances of these very different bears

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meeting in the wild?

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This is the grizzly bear's home range in North America.

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Polar bears live higher up in the Arctic.

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So the two species are neighbours, but ones with very different

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lifestyles and feeding habits that restrict their ranges.

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But their habitats are changing as the climate is warming.

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Ice is melting and more land is being exposed.

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And that is beginning to have an effect on the behaviour

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of the two species in the wild.

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In 2003, a researcher working on a remote island between Churchill

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and the North Pole discovered strange bear footprints in the snow

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together with brown hairs.

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The hair came from a grizzly. This was extraordinary.

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The grizzly must have strayed hundreds of miles from its home

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and travelled deep into polar bear territory.

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So it was clear that the chances of these cousins meeting

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and mating in the wild was becoming a real possibility.

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But would their offspring survive?

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Research on captive pizzly bears suggested that they could.

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The hair of brown bear, polar bear

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and pizzly bear are quite different -

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not only in colour, but in structure.

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Here are cross-sections of a hair from each of them.

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The brown bear has a central canal

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which is filled with a honeycomb structure.

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The polar bear, that central canal is almost empty, making that hair

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good for insulation - just what you need in a cold climate.

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And the pizzly bear is a sort of compromise between the two.

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The central canal has just a little infilling, so you might

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say that it is not bad for cold temperatures and not bad for warm.

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Possessing a mix of characteristics of both parent bears

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could actually help these hybrids to survive in a rapidly changing world.

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Their hunting skills have also become more variable.

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Not only that, so has their hunting behaviour.

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Tips and Taps sometimes fish like brown bears,

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but at other times behave like polar bears.

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Stomping, for instance.

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Polar bears push down on ice to break it

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during their search for seals.

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The Osnabruck pizzlies perform a similar action.

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Hurling is also one of their favourite pastimes.

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Polar bears fling their prey about in order to kill it.

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This mixture of physical and behavioural characteristics

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suggest that pizzlies may be well-equipped to

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survive in the wild if conditions in the Arctic continue to change.

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And, in 2006, this notion became reality.

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An odd-looking bear was shot during a polar bear hunt

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in northern Canada.

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It was small, hunched and had dark smudges around its eyes and muzzle.

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DNA testing showed that its mother was a polar bear

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and its father, a grizzly, that had travelled further north

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and was hundreds of miles beyond its normal range.

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This was the first proof of a hybrid pizzly bear in the wild.

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So pizzly bears aren't just the result of captive breeding.

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Several have been reliably identified in the wild,

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though none has yet been caught alive.

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But as the climate warms, so brown bears are moving north

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and polar bears coming south,

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and their close genetic relationship means that not only can

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they interbreed, but the offspring are likely to be fertile.

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So, what will happen in the future?

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Will this mixing of bear DNA increase?

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Will pizzly bears become so common

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that they might seriously dilute the polar bear species?

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The ranges of these bears are now increasingly overlapping

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and they're roaming deeper into each other's former ranges.

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It's now not uncommon to see polar and grizzly bears feasting together

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when there's plenty of meat around, as there is after a whale hunt.

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So are we seeing a new development

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in the evolutionary history of bears?

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Hybridised brown and polar bears may not be such a new phenomenon.

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DNA analysis of both bears indicates that they have previously mixed

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their genes thousands of years ago, but now we're witnessing it again.

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In April 2010, biologists in the Northwest Territories

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of Canada shot a dangerous polar bear.

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It was strange in appearance,

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and DNA analysis showed something very significant -

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this was a second-generation pizzly bear,

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the result of a female pizzly mating with a polar bear.

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This proves that these hybrids are not sterile

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and could potentially form wild populations.

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As global warming continues to diminish the Arctic sea ice habitat,

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climate scientists believe that the polar bear will struggle

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to survive as a species.

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But at least some of the polar bear traits will be

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preserved in these strange-looking hybrids.

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So, pizzly bears are not bizarre, Frankenstein-like creatures.

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They're valuable new hybrids that may become increasingly common

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as the Arctic landscape changes.

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INSECTS BUZZ

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Our next story concerns a more sinister hybrid,

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the killer bee,

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that was created when a well-meaning experiment to breed

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a superior honeybee went disastrously wrong.

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In the 1960s and '70s,

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bees hit the headlines.

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Huge swarms were attacking people

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and livestock for no apparent reason.

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The bees launching these attacks were, in fact, honeybees -

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the sort from which we've been collecting honey for centuries.

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In the Western world, monks traditionally kept bees

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for honey and for the wax that they used to make candles.

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Bee colonies were originally kept in closed wicker skeps

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and later, in more accessible hives

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that allowed keepers to tend the bees

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and get the honey without harming the nest.

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For centuries, bees have had an association with human beings

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and passive, easy-to-handle bees have been selectively bred,

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so the European honeybee became a tolerant, well-tempered bee.

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So, why would a species of bee that has lived amiably alongside

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people for so long suddenly change its nature?

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The temperament of a bee colony is determined

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by that of the queen bee -

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the one seen here marked with a blue spot.

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She lays all the eggs in the hive

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so her genes are passed on to

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all the female workers and the male drones.

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An aggressive queen will produce very ferocious workers,

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while a passive queen produces calmer ones.

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European honeybees are generally very passive.

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African bees, however, are very different.

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They are extremely aggressive.

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Historically, they were seldom kept domestically because they were

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so common that it was easier to collect honey from the wild.

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But doing that inevitably disturbs the bees,

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and as a result,

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the wild species is now inclined to be very aggressive.

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When other creatures, including human beings,

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get too close to their colonies,

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the bees are likely to attack...

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..and in large numbers.

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Nonetheless, they're very hard-working

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and manage to produce substantial quantities of honey in dry

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habitats where good quality flowers are often hard to find.

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In the 1950s, honey production in Brazil was failing

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and it was thought that African bees might be able to help.

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European bees had previously been introduced to Brazil,

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but they didn't succeed in making much honey in their new environment.

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So a Brazilian scientist, Dr Warwick Kerr,

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who was a specialist in bee genetics, was consulted.

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The Brazilian Ministry of Agriculture asked Kerr

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if he could obtain some

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African queens to experiment with

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in order to breed a bee that

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combined the passive nature of the European bee with the higher

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productivity of the African bee.

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The bees there had originated from stock imported to

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North America by British colonists.

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Although these bees were productive in the North, the more tropical

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climates of Central and South America didn't suit them so well.

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Here, they were not so productive.

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To make just one drop of honey,

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a bee has to visit up to 1,500 flowers.

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It's made from liquid nectar that the worker bees collect using

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a long proboscis.

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European honeybees normally live in temperate climates where

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an abundance of flowering plants provide a lot of nectar.

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So they're able to produce honey quite easily.

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But conditions were not like that in Brazil, and the imported

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European bees struggled to make honey in any quantity.

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The habits of the African bee

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seemed more suited to the South American climate.

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They thrive in hot, dry conditions and make plenty of honey.

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But they have to work very hard to do so,

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starting their day several hours earlier

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than their European cousins...

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..and foraging for longer.

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Honeybees are very choosy feeders.

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They will carefully select those flowers that have the strongest

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nectar, the sweetest nectar,

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and I can demonstrate that by this.

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Here is a little bee

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in a bee holder.

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Let me first try her

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with a dilute solution of sugar.

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No reaction.

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Now let me try her

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with a stronger solution,

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a sweeter solution.

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And out comes her proboscis.

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You won't let go!

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Western European bees can afford to be choosy because there's flowers

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with rich nectar available

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for such a long period of time.

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African bees have no such luxury.

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They have to feed at times when there are very few flowers

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open anyway and those that are, are not very rich in nectar.

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So they are much more industrious.

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Now, let's release you,

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so you can go back

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and collect some more nectar.

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Gone.

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Kerr planned to take the industrious,

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less fussy African bee and combine it with the passive European bee

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to produce one that would work hard, but not be aggressive.

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He persuaded particularly successful African beekeepers from Tanzania

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and South Africa to let him have some of their most gentle

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and passive queens - 133 in all.

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Unfortunately, on his journey back to Brazil,

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a customs agent sprayed his bees

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with insecticide and they all died.

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Upset and frustrated, Kerr then chose a second batch,

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but this time he didn't screen out the most aggressive bees.

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47 of these queens survived, but they were far too fierce to

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give to the local Brazilian beekeepers, so Kerr decided

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to breed them with some gentler drones to reduce their ferocity.

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Dr Kerr set up 35 colonies

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in an isolated area of eucalyptus forest

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near Sao Paulo.

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And to prevent the queens from escaping,

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he used a device called a queen excluder.

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It fits on top of the brood box, here.

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The bars are sufficiently wide apart

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to allow worker bees to pass through,

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but not so wide that the queen can.

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And Dr Kerr fitted, to be absolutely sure, two of them to each hive.

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AND employed a caretaker to watch over them

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AND built a wall around the entire group of colonies.

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But you can't cater for human error.

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And in his absence, a local beekeeper came

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and noticed that the worker bees as they passed through here

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were losing some of the pollen that they had collected,

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so he removed the queen excluders

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and by the time Dr Kerr came back...

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..26 of the queens had escaped into the wild

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and were already swarming.

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Swarming is the way bees naturally increase their population,

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by dividing the colony.

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A hive usually has a single queen.

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If she is old or the hive becomes crowded,

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she starts to lay eggs that hatch into new daughter queens.

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If a queen leaves the nest, many workers will follow her.

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They gather around her in a swarm

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and eventually fly off together to found a new colony.

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This is exactly what Kerr's queen bees did as soon as they escaped.

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African bees swarm more frequently than their European cousins

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and divide to form multiple colonies.

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Kerr's escaped queens and the Africanised worker bees inherited

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this tendency to swarm and they spread quickly across South America.

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It was assumed that the abundant native European bees would

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weaken the escaped African bees' more aggressive nature,

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but this didn't happen.

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The African genes were strong and their behaviour dominated.

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By 1965, most Brazilian hives had been devastated

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and the aggressive Africanised bees swept their way through

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South America and headed up into North America.

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They started to attack people with little provocation

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and with sometimes fatal results.

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Africanised bees became sensationalised

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and the story of the "killer bee" was born.

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Horror movies pictured them as crazed killers with lethal stings.

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But this was far from the truth.

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In any case, it wasn't the African bees' sting that was fatal...

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..it was their behaviour.

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European bees send out just a few defenders to sting an enemy.

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African bees however, react differently.

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Up to 90% of a colony will launch an attack.

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Their venom is not actually more potent than that of European bees,

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but they sting in such number -

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sometimes in thousands - that they can kill an enemy.

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Kerr's hybrid bees were fearless and had inherited this attack behaviour.

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African bees will chase African elephants

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and sting the soft tissue around their ears and faces.

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They will particularly target baby elephants that are smaller

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and softer skinned.

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Not surprisingly, elephants have developed a strong

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dislike of bees and make a great effort to avoid them.

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They recognise the sound of angry bees

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and have a specific call to warn each other if one is attacked.

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They even warn distant members of the herd by sending out

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low-frequency rumbles.

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The escape of such aggressive bees into the wild was

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devastating for Kerr's career.

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Africanised bees spread as far as the lower parts of North America,

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but here, their takeover halted.

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The more temperate climate didn't suit them.

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Kerr's intentions had been good,

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and he later dedicated his research to try to correct the problem.

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Eventually, Kerr did help to create a productive,

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more passive bee, as had originally been his plan.

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And South America is now one of the world's largest exporters of honey.

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The creation of a so-called killer bee by Dr Kerr's experiments

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was indeed a grave mistake.

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But in recent years, a more gentle form of African bee has been bred.

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And it's also possible that the ferocity of the African bee

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has now been turned to our advantage.

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Elephants are said to be terrified of bees and in recent years,

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farmers in Africa have started playing the sounds of swarming bees

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over their fields and the elephants have kept away.

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So as well as pollinating plants, bees can actually protect them.

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So both the Africanised honeybee

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and the pizzly bear are here to stay,

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but these unusual hybrids owe their success in one way or another

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to humans.

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Hybrids can be bizarre and they can be deadly. We look at two hybrid animals that owe their existence to human interference - the pizzly bear (a cross between a polar bear and grizzly), which has come into being because of global warming, and the killer bee, brought into existence because of the transfer of African bees to South America.


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