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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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00:23:33,680 --> 00:23:39,280
This is exactly what Kerr's queen bees did as soon as they escaped.
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00:23:43,560 --> 00:23:48,160
African bees swarm more frequently than their European cousins
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00:23:48,285 --> 00:23:51,360
and divide to form multiple colonies.
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00:23:51,485 --> 00:23:55,600
Kerr's escaped queens and the Africanised worker bees inherited
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00:23:55,725 --> 00:24:00,560
this tendency to swarm and they spread quickly across South America.
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00:24:06,800 --> 00:24:10,920
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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00:24:15,125 --> 00:24:17,040
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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00:25:22,085 --> 00:25:25,120
African bees however, react differently.
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00:25:25,245 --> 00:25:28,680
Up to 90% of a colony will launch an attack.
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00:25:28,805 --> 00:25:32,480
Their venom is not actually more potent than that of European bees,
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00:25:32,605 --> 00:25:34,400
but they sting in such number -
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00:25:34,525 --> 00:25:38,000
sometimes in thousands - that they can kill an enemy.
364
00:25:42,000 --> 00:25:47,320
Kerr's hybrid bees were fearless and had inherited this attack behaviour.
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00:25:50,160 --> 00:25:52,680
African bees will chase African elephants
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00:25:52,805 --> 00:25:56,480
and sting the soft tissue around their ears and faces.
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00:25:57,920 --> 00:26:01,840
They will particularly target baby elephants that are smaller
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00:26:01,965 --> 00:26:02,920
and softer skinned.
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00:26:07,760 --> 00:26:10,520
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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00:26:19,525 --> 00:26:23,280
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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00:26:36,440 --> 00:26:39,920
The escape of such aggressive bees into the wild was
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devastating for Kerr's career.
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00:26:43,000 --> 00:26:46,760
Africanised bees spread as far as the lower parts of North America,
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00:26:46,885 --> 00:26:49,640
but here, their takeover halted.
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00:26:51,160 --> 00:26:53,640
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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00:27:09,845 --> 00:27:13,280
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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00:27:23,560 --> 00:27:28,280
The creation of a so-called killer bee by Dr Kerr's experiments
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00:27:28,405 --> 00:27:31,200
was indeed a grave mistake.
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00:27:31,325 --> 00:27:37,920
But in recent years, a more gentle form of African bee has been bred.
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00:27:38,045 --> 00:27:43,000
And it's also possible that the ferocity of the African bee
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00:27:43,125 --> 00:27:46,320
has now been turned to our advantage.
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00:27:46,445 --> 00:27:52,000
Elephants are said to be terrified of bees and in recent years,
391
00:27:52,125 --> 00:27:55,960
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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00:28:00,880 --> 00:28:05,240
So as well as pollinating plants, bees can actually protect them.
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00:28:07,760 --> 00:28:10,520
So both the Africanised honeybee
395
00:28:10,645 --> 00:28:13,840
and the pizzly bear are here to stay,
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00:28:13,965 --> 00:28:18,440
but these unusual hybrids owe their success in one way or another
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to humans.
34114
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