0:00:02 > 0:00:05The natural world is full of extraordinary animals
0:00:05 > 0:00:08with amazing life histories.
0:00:08 > 0:00:11Yet certain stories are more intriguing than others.
0:00:14 > 0:00:17The mysteries of a butterfly's life cycle,
0:00:17 > 0:00:21or the strange biology of the emperor penguin.
0:00:21 > 0:00:24Some of these creatures were surrounded by
0:00:24 > 0:00:27fantastic myths and misunderstandings.
0:00:29 > 0:00:32Others have only recently revealed their secrets.
0:00:34 > 0:00:37These are the creatures that stand out from the crowd,
0:00:37 > 0:00:42the curiosities that I find particularly fascinating.
0:00:53 > 0:00:57In this programme, we investigate the stories of two animals
0:00:57 > 0:00:59that owe their existence to human interference.
0:01:01 > 0:01:03Killer bees that were created accidentally
0:01:03 > 0:01:06when a well-meaning breeding experiment went wrong.
0:01:08 > 0:01:11And pizzly bears, the result of polar bears
0:01:11 > 0:01:14and brown bears interbreeding.
0:01:15 > 0:01:18How were these strange animals created,
0:01:18 > 0:01:23and are they unnatural mutants, or valuable new hybrids?
0:01:25 > 0:01:28This is a grizzly bear.
0:01:28 > 0:01:32And that white one there is, of course, a polar bear.
0:01:32 > 0:01:36But in between, there's a different kind of bear.
0:01:37 > 0:01:41It's got the white coat of a polar bear, except that
0:01:41 > 0:01:48around the eyes, it's rather brown, and its front legs are very brown.
0:01:48 > 0:01:50It is, in fact, a hybrid,
0:01:50 > 0:01:54the result of a mating between a polar bear and a grizzly bear,
0:01:54 > 0:01:57and they're sometimes called a pizzly.
0:01:59 > 0:02:06The first-ever pizzly bears were born in a German zoo in 1876,
0:02:06 > 0:02:09after a polar bear and a grizzly - a type of brown bear -
0:02:09 > 0:02:11were housed together.
0:02:12 > 0:02:16Hybrid animals have frequently been born in captivity,
0:02:16 > 0:02:19both intentionally and by accident.
0:02:19 > 0:02:23Tigers and lions produce offspring called ligers,
0:02:23 > 0:02:27and donkeys and zebra, babies known as zonkeys.
0:02:27 > 0:02:30But usually, these hybrid creatures are sterile
0:02:30 > 0:02:33and not well adapted for surviving in the wild.
0:02:35 > 0:02:37Hybrid bears like this were considered to be
0:02:37 > 0:02:42theoretical species, creatures that could never exist in the wild,
0:02:42 > 0:02:47and the pizzlies of the Victorian era were largely forgotten.
0:02:49 > 0:02:53Animals, of course, usually mate with their own kind.
0:02:54 > 0:02:57If different species are to interbreed
0:02:57 > 0:02:59and produce fertile young,
0:02:59 > 0:03:02they have to be extremely closely related.
0:03:04 > 0:03:07Grizzly bears and polar bears are certainly somewhat
0:03:07 > 0:03:09similar in appearance.
0:03:10 > 0:03:13But are they, in fact, closely related?
0:03:16 > 0:03:20In the bear family, the black species came first,
0:03:20 > 0:03:24and then came the brown bear, and finally, the white polar bear.
0:03:25 > 0:03:29This was thought to have happened four to five million years ago,
0:03:29 > 0:03:32but recent fossil evidence suggests that it may have
0:03:32 > 0:03:35happened as recently as only half a million years ago.
0:03:38 > 0:03:43So the polar bear is the relatively recent species of bear,
0:03:43 > 0:03:46one that branched off late in the bear family tree.
0:03:52 > 0:03:58Polar and brown bears are, in evolutionary terms, close cousins.
0:03:58 > 0:03:59They share some characteristics,
0:03:59 > 0:04:02but there are also many physical differences.
0:04:04 > 0:04:06The most obvious is the colour of their fur.
0:04:08 > 0:04:11Colour acts as camouflage, so that's not surprising,
0:04:11 > 0:04:14since they live in very different habitats.
0:04:16 > 0:04:20Grizzly bears have rounded heads and prominent shoulder humps
0:04:20 > 0:04:22that have evolved for digging.
0:04:24 > 0:04:28Polar bears, on the other hand, have more pointed heads,
0:04:28 > 0:04:31but no shoulder humps.
0:04:31 > 0:04:33Their feet are large and flat
0:04:33 > 0:04:36so that they can act as paddles when swimming.
0:04:36 > 0:04:38They also have hairy pads and short claws
0:04:38 > 0:04:41which helps to prevent them slipping on ice.
0:04:42 > 0:04:45The grizzly has more obvious footpads
0:04:45 > 0:04:47and much larger, curved claws.
0:04:51 > 0:04:55We know that polar and grizzly bears can mate successfully
0:04:55 > 0:04:57because they've often done so in captivity.
0:04:59 > 0:05:02But what sort of offspring do they produce?
0:05:07 > 0:05:12For many years, zoos discouraged the breeding of pizzly bears.
0:05:13 > 0:05:16But recently, there was a chance to study them in Germany.
0:05:21 > 0:05:27In 2004, at Osnabruck Zoo, a brown bear called Susi
0:05:27 > 0:05:29and a polar bear called Elvis,
0:05:29 > 0:05:34who had shared an enclosure for 24 years, unexpectedly produced twins.
0:05:35 > 0:05:40The small brown cubs are bigger now and have changed colour.
0:05:40 > 0:05:43The male, named Taps, is brown,
0:05:43 > 0:05:48and the female, Tips, has a lighter coat.
0:05:48 > 0:05:52But otherwise, they have traits inherited from both parents.
0:05:52 > 0:05:57Long necks and visible tails that are more typical of polar bears,
0:05:57 > 0:06:00but also small shoulder humps
0:06:00 > 0:06:02that are reminiscent of those of brown bears.
0:06:05 > 0:06:08Their feet are intermediate in form.
0:06:12 > 0:06:15And their size is between the two -
0:06:15 > 0:06:19smaller than a polar bear, but larger than a brown bear.
0:06:21 > 0:06:25In the wild, of course, it would be rare for the two species to meet,
0:06:25 > 0:06:28for they inhabit very different kinds of country.
0:06:31 > 0:06:35Brown bears are the most widely distributed of all bears.
0:06:35 > 0:06:38They live in North America, in Alaska
0:06:38 > 0:06:41and in Russia and Northern Europe.
0:06:41 > 0:06:44They're omnivores - they'll eat not only flesh,
0:06:44 > 0:06:49but nuts and grass and fruit.
0:06:49 > 0:06:52And the biggest of all live in Alaska.
0:06:52 > 0:06:58They can grow to a length of over three metres and weigh 600 kilos.
0:06:58 > 0:07:00Together with polar bears,
0:07:00 > 0:07:04they are the biggest carnivores on this planet.
0:07:07 > 0:07:13The other parent of the pizzly, the polar bear, lives high in the Arctic
0:07:13 > 0:07:17and is slightly bigger than the brown bear in both size and weight.
0:07:20 > 0:07:23It lives on snow and ice and hunts seals.
0:07:28 > 0:07:33We know from Osnabruck Zoo that when polar bears and grizzlies mate,
0:07:33 > 0:07:36they can produce pizzly cubs.
0:07:38 > 0:07:41But what are the chances of these very different bears
0:07:41 > 0:07:42meeting in the wild?
0:07:46 > 0:07:51This is the grizzly bear's home range in North America.
0:07:51 > 0:07:54Polar bears live higher up in the Arctic.
0:07:54 > 0:07:58So the two species are neighbours, but ones with very different
0:07:58 > 0:08:02lifestyles and feeding habits that restrict their ranges.
0:08:05 > 0:08:09But their habitats are changing as the climate is warming.
0:08:13 > 0:08:17Ice is melting and more land is being exposed.
0:08:22 > 0:08:25And that is beginning to have an effect on the behaviour
0:08:25 > 0:08:27of the two species in the wild.
0:08:33 > 0:08:39In 2003, a researcher working on a remote island between Churchill
0:08:39 > 0:08:44and the North Pole discovered strange bear footprints in the snow
0:08:44 > 0:08:45together with brown hairs.
0:08:47 > 0:08:51The hair came from a grizzly. This was extraordinary.
0:08:51 > 0:08:54The grizzly must have strayed hundreds of miles from its home
0:08:54 > 0:08:58and travelled deep into polar bear territory.
0:08:58 > 0:09:01So it was clear that the chances of these cousins meeting
0:09:01 > 0:09:05and mating in the wild was becoming a real possibility.
0:09:06 > 0:09:09But would their offspring survive?
0:09:09 > 0:09:14Research on captive pizzly bears suggested that they could.
0:09:16 > 0:09:18The hair of brown bear, polar bear
0:09:18 > 0:09:20and pizzly bear are quite different -
0:09:20 > 0:09:23not only in colour, but in structure.
0:09:23 > 0:09:27Here are cross-sections of a hair from each of them.
0:09:27 > 0:09:29The brown bear has a central canal
0:09:29 > 0:09:32which is filled with a honeycomb structure.
0:09:32 > 0:09:36The polar bear, that central canal is almost empty, making that hair
0:09:36 > 0:09:41good for insulation - just what you need in a cold climate.
0:09:41 > 0:09:45And the pizzly bear is a sort of compromise between the two.
0:09:45 > 0:09:48The central canal has just a little infilling, so you might
0:09:48 > 0:09:53say that it is not bad for cold temperatures and not bad for warm.
0:09:56 > 0:09:59Possessing a mix of characteristics of both parent bears
0:09:59 > 0:10:04could actually help these hybrids to survive in a rapidly changing world.
0:10:06 > 0:10:10Their hunting skills have also become more variable.
0:10:10 > 0:10:13Not only that, so has their hunting behaviour.
0:10:14 > 0:10:17Tips and Taps sometimes fish like brown bears,
0:10:17 > 0:10:20but at other times behave like polar bears.
0:10:22 > 0:10:24Stomping, for instance.
0:10:24 > 0:10:27Polar bears push down on ice to break it
0:10:27 > 0:10:29during their search for seals.
0:10:29 > 0:10:32The Osnabruck pizzlies perform a similar action.
0:10:34 > 0:10:38Hurling is also one of their favourite pastimes.
0:10:40 > 0:10:43Polar bears fling their prey about in order to kill it.
0:10:47 > 0:10:51This mixture of physical and behavioural characteristics
0:10:51 > 0:10:54suggest that pizzlies may be well-equipped to
0:10:54 > 0:10:58survive in the wild if conditions in the Arctic continue to change.
0:11:05 > 0:11:09And, in 2006, this notion became reality.
0:11:10 > 0:11:13An odd-looking bear was shot during a polar bear hunt
0:11:13 > 0:11:15in northern Canada.
0:11:15 > 0:11:20It was small, hunched and had dark smudges around its eyes and muzzle.
0:11:21 > 0:11:25DNA testing showed that its mother was a polar bear
0:11:25 > 0:11:28and its father, a grizzly, that had travelled further north
0:11:28 > 0:11:32and was hundreds of miles beyond its normal range.
0:11:32 > 0:11:36This was the first proof of a hybrid pizzly bear in the wild.
0:11:38 > 0:11:42So pizzly bears aren't just the result of captive breeding.
0:11:42 > 0:11:46Several have been reliably identified in the wild,
0:11:46 > 0:11:49though none has yet been caught alive.
0:11:49 > 0:11:53But as the climate warms, so brown bears are moving north
0:11:53 > 0:11:56and polar bears coming south,
0:11:56 > 0:11:59and their close genetic relationship means that not only can
0:11:59 > 0:12:05they interbreed, but the offspring are likely to be fertile.
0:12:09 > 0:12:12So, what will happen in the future?
0:12:12 > 0:12:16Will this mixing of bear DNA increase?
0:12:17 > 0:12:20Will pizzly bears become so common
0:12:20 > 0:12:23that they might seriously dilute the polar bear species?
0:12:25 > 0:12:29The ranges of these bears are now increasingly overlapping
0:12:29 > 0:12:33and they're roaming deeper into each other's former ranges.
0:12:33 > 0:12:37It's now not uncommon to see polar and grizzly bears feasting together
0:12:37 > 0:12:42when there's plenty of meat around, as there is after a whale hunt.
0:12:42 > 0:12:45So are we seeing a new development
0:12:45 > 0:12:47in the evolutionary history of bears?
0:12:49 > 0:12:54Hybridised brown and polar bears may not be such a new phenomenon.
0:12:54 > 0:12:58DNA analysis of both bears indicates that they have previously mixed
0:12:58 > 0:13:04their genes thousands of years ago, but now we're witnessing it again.
0:13:04 > 0:13:08In April 2010, biologists in the Northwest Territories
0:13:08 > 0:13:11of Canada shot a dangerous polar bear.
0:13:11 > 0:13:13It was strange in appearance,
0:13:13 > 0:13:17and DNA analysis showed something very significant -
0:13:17 > 0:13:21this was a second-generation pizzly bear,
0:13:21 > 0:13:26the result of a female pizzly mating with a polar bear.
0:13:26 > 0:13:29This proves that these hybrids are not sterile
0:13:29 > 0:13:33and could potentially form wild populations.
0:13:33 > 0:13:37As global warming continues to diminish the Arctic sea ice habitat,
0:13:37 > 0:13:40climate scientists believe that the polar bear will struggle
0:13:40 > 0:13:43to survive as a species.
0:13:43 > 0:13:46But at least some of the polar bear traits will be
0:13:46 > 0:13:49preserved in these strange-looking hybrids.
0:13:50 > 0:13:56So, pizzly bears are not bizarre, Frankenstein-like creatures.
0:13:56 > 0:14:00They're valuable new hybrids that may become increasingly common
0:14:00 > 0:14:03as the Arctic landscape changes.
0:14:04 > 0:14:06INSECTS BUZZ
0:14:06 > 0:14:10Our next story concerns a more sinister hybrid,
0:14:10 > 0:14:11the killer bee,
0:14:11 > 0:14:15that was created when a well-meaning experiment to breed
0:14:15 > 0:14:19a superior honeybee went disastrously wrong.
0:14:21 > 0:14:23In the 1960s and '70s,
0:14:23 > 0:14:26bees hit the headlines.
0:14:28 > 0:14:30Huge swarms were attacking people
0:14:30 > 0:14:33and livestock for no apparent reason.
0:14:37 > 0:14:41The bees launching these attacks were, in fact, honeybees -
0:14:41 > 0:14:44the sort from which we've been collecting honey for centuries.
0:14:48 > 0:14:51In the Western world, monks traditionally kept bees
0:14:51 > 0:14:56for honey and for the wax that they used to make candles.
0:14:56 > 0:15:00Bee colonies were originally kept in closed wicker skeps
0:15:00 > 0:15:03and later, in more accessible hives
0:15:03 > 0:15:06that allowed keepers to tend the bees
0:15:06 > 0:15:08and get the honey without harming the nest.
0:15:09 > 0:15:13For centuries, bees have had an association with human beings
0:15:13 > 0:15:17and passive, easy-to-handle bees have been selectively bred,
0:15:17 > 0:15:22so the European honeybee became a tolerant, well-tempered bee.
0:15:26 > 0:15:31So, why would a species of bee that has lived amiably alongside
0:15:31 > 0:15:34people for so long suddenly change its nature?
0:15:36 > 0:15:38The temperament of a bee colony is determined
0:15:38 > 0:15:40by that of the queen bee -
0:15:40 > 0:15:43the one seen here marked with a blue spot.
0:15:43 > 0:15:46She lays all the eggs in the hive
0:15:46 > 0:15:48so her genes are passed on to
0:15:48 > 0:15:51all the female workers and the male drones.
0:15:53 > 0:15:56An aggressive queen will produce very ferocious workers,
0:15:56 > 0:15:59while a passive queen produces calmer ones.
0:16:00 > 0:16:04European honeybees are generally very passive.
0:16:09 > 0:16:12African bees, however, are very different.
0:16:14 > 0:16:16They are extremely aggressive.
0:16:17 > 0:16:21Historically, they were seldom kept domestically because they were
0:16:21 > 0:16:24so common that it was easier to collect honey from the wild.
0:16:25 > 0:16:29But doing that inevitably disturbs the bees,
0:16:29 > 0:16:31and as a result,
0:16:31 > 0:16:35the wild species is now inclined to be very aggressive.
0:16:40 > 0:16:43When other creatures, including human beings,
0:16:43 > 0:16:45get too close to their colonies,
0:16:45 > 0:16:47the bees are likely to attack...
0:16:48 > 0:16:50..and in large numbers.
0:16:54 > 0:16:56Nonetheless, they're very hard-working
0:16:56 > 0:17:00and manage to produce substantial quantities of honey in dry
0:17:00 > 0:17:04habitats where good quality flowers are often hard to find.
0:17:05 > 0:17:10In the 1950s, honey production in Brazil was failing
0:17:10 > 0:17:13and it was thought that African bees might be able to help.
0:17:14 > 0:17:18European bees had previously been introduced to Brazil,
0:17:18 > 0:17:22but they didn't succeed in making much honey in their new environment.
0:17:23 > 0:17:27So a Brazilian scientist, Dr Warwick Kerr,
0:17:27 > 0:17:30who was a specialist in bee genetics, was consulted.
0:17:32 > 0:17:35The Brazilian Ministry of Agriculture asked Kerr
0:17:35 > 0:17:36if he could obtain some
0:17:36 > 0:17:39African queens to experiment with
0:17:39 > 0:17:41in order to breed a bee that
0:17:41 > 0:17:45combined the passive nature of the European bee with the higher
0:17:45 > 0:17:48productivity of the African bee.
0:17:48 > 0:17:51The bees there had originated from stock imported to
0:17:51 > 0:17:55North America by British colonists.
0:17:55 > 0:17:58Although these bees were productive in the North, the more tropical
0:17:58 > 0:18:03climates of Central and South America didn't suit them so well.
0:18:03 > 0:18:05Here, they were not so productive.
0:18:09 > 0:18:11To make just one drop of honey,
0:18:11 > 0:18:14a bee has to visit up to 1,500 flowers.
0:18:15 > 0:18:19It's made from liquid nectar that the worker bees collect using
0:18:19 > 0:18:21a long proboscis.
0:18:24 > 0:18:28European honeybees normally live in temperate climates where
0:18:28 > 0:18:31an abundance of flowering plants provide a lot of nectar.
0:18:33 > 0:18:36So they're able to produce honey quite easily.
0:18:39 > 0:18:43But conditions were not like that in Brazil, and the imported
0:18:43 > 0:18:46European bees struggled to make honey in any quantity.
0:18:48 > 0:18:50The habits of the African bee
0:18:50 > 0:18:52seemed more suited to the South American climate.
0:18:54 > 0:18:59They thrive in hot, dry conditions and make plenty of honey.
0:18:59 > 0:19:01But they have to work very hard to do so,
0:19:01 > 0:19:04starting their day several hours earlier
0:19:04 > 0:19:05than their European cousins...
0:19:07 > 0:19:08..and foraging for longer.
0:19:14 > 0:19:18Honeybees are very choosy feeders.
0:19:18 > 0:19:22They will carefully select those flowers that have the strongest
0:19:22 > 0:19:24nectar, the sweetest nectar,
0:19:24 > 0:19:26and I can demonstrate that by this.
0:19:26 > 0:19:29Here is a little bee
0:19:29 > 0:19:31in a bee holder.
0:19:31 > 0:19:33Let me first try her
0:19:33 > 0:19:35with a dilute solution of sugar.
0:19:39 > 0:19:41No reaction.
0:19:43 > 0:19:44Now let me try her
0:19:44 > 0:19:46with a stronger solution,
0:19:46 > 0:19:48a sweeter solution.
0:19:52 > 0:19:53And out comes her proboscis.
0:19:57 > 0:19:58You won't let go!
0:20:02 > 0:20:07Western European bees can afford to be choosy because there's flowers
0:20:07 > 0:20:09with rich nectar available
0:20:09 > 0:20:11for such a long period of time.
0:20:11 > 0:20:14African bees have no such luxury.
0:20:14 > 0:20:18They have to feed at times when there are very few flowers
0:20:18 > 0:20:22open anyway and those that are, are not very rich in nectar.
0:20:22 > 0:20:26So they are much more industrious.
0:20:26 > 0:20:29Now, let's release you,
0:20:29 > 0:20:31so you can go back
0:20:31 > 0:20:34and collect some more nectar.
0:20:40 > 0:20:41Gone.
0:20:44 > 0:20:46Kerr planned to take the industrious,
0:20:46 > 0:20:51less fussy African bee and combine it with the passive European bee
0:20:51 > 0:20:56to produce one that would work hard, but not be aggressive.
0:20:56 > 0:21:00He persuaded particularly successful African beekeepers from Tanzania
0:21:00 > 0:21:03and South Africa to let him have some of their most gentle
0:21:03 > 0:21:07and passive queens - 133 in all.
0:21:07 > 0:21:10Unfortunately, on his journey back to Brazil,
0:21:10 > 0:21:13a customs agent sprayed his bees
0:21:13 > 0:21:16with insecticide and they all died.
0:21:17 > 0:21:22Upset and frustrated, Kerr then chose a second batch,
0:21:22 > 0:21:26but this time he didn't screen out the most aggressive bees.
0:21:26 > 0:21:3047 of these queens survived, but they were far too fierce to
0:21:30 > 0:21:34give to the local Brazilian beekeepers, so Kerr decided
0:21:34 > 0:21:38to breed them with some gentler drones to reduce their ferocity.
0:21:40 > 0:21:43Dr Kerr set up 35 colonies
0:21:43 > 0:21:46in an isolated area of eucalyptus forest
0:21:46 > 0:21:49near Sao Paulo.
0:21:49 > 0:21:52And to prevent the queens from escaping,
0:21:52 > 0:21:55he used a device called a queen excluder.
0:21:57 > 0:22:00It fits on top of the brood box, here.
0:22:00 > 0:22:03The bars are sufficiently wide apart
0:22:03 > 0:22:06to allow worker bees to pass through,
0:22:06 > 0:22:10but not so wide that the queen can.
0:22:10 > 0:22:16And Dr Kerr fitted, to be absolutely sure, two of them to each hive.
0:22:16 > 0:22:19AND employed a caretaker to watch over them
0:22:19 > 0:22:24AND built a wall around the entire group of colonies.
0:22:24 > 0:22:26But you can't cater for human error.
0:22:27 > 0:22:30And in his absence, a local beekeeper came
0:22:30 > 0:22:34and noticed that the worker bees as they passed through here
0:22:34 > 0:22:37were losing some of the pollen that they had collected,
0:22:37 > 0:22:40so he removed the queen excluders
0:22:40 > 0:22:43and by the time Dr Kerr came back...
0:22:44 > 0:22:47..26 of the queens had escaped into the wild
0:22:47 > 0:22:49and were already swarming.
0:23:00 > 0:23:04Swarming is the way bees naturally increase their population,
0:23:04 > 0:23:07by dividing the colony.
0:23:07 > 0:23:10A hive usually has a single queen.
0:23:10 > 0:23:12If she is old or the hive becomes crowded,
0:23:12 > 0:23:17she starts to lay eggs that hatch into new daughter queens.
0:23:18 > 0:23:22If a queen leaves the nest, many workers will follow her.
0:23:25 > 0:23:27They gather around her in a swarm
0:23:27 > 0:23:31and eventually fly off together to found a new colony.
0:23:33 > 0:23:39This is exactly what Kerr's queen bees did as soon as they escaped.
0:23:43 > 0:23:48African bees swarm more frequently than their European cousins
0:23:48 > 0:23:51and divide to form multiple colonies.
0:23:51 > 0:23:55Kerr's escaped queens and the Africanised worker bees inherited
0:23:55 > 0:24:00this tendency to swarm and they spread quickly across South America.
0:24:06 > 0:24:10It was assumed that the abundant native European bees would
0:24:10 > 0:24:15weaken the escaped African bees' more aggressive nature,
0:24:15 > 0:24:17but this didn't happen.
0:24:17 > 0:24:21The African genes were strong and their behaviour dominated.
0:24:21 > 0:24:27By 1965, most Brazilian hives had been devastated
0:24:27 > 0:24:30and the aggressive Africanised bees swept their way through
0:24:30 > 0:24:34South America and headed up into North America.
0:24:43 > 0:24:46They started to attack people with little provocation
0:24:46 > 0:24:48and with sometimes fatal results.
0:24:51 > 0:24:54Africanised bees became sensationalised
0:24:54 > 0:24:57and the story of the "killer bee" was born.
0:24:58 > 0:25:03Horror movies pictured them as crazed killers with lethal stings.
0:25:05 > 0:25:07But this was far from the truth.
0:25:08 > 0:25:12In any case, it wasn't the African bees' sting that was fatal...
0:25:13 > 0:25:15..it was their behaviour.
0:25:17 > 0:25:21European bees send out just a few defenders to sting an enemy.
0:25:21 > 0:25:25African bees however, react differently.
0:25:25 > 0:25:28Up to 90% of a colony will launch an attack.
0:25:28 > 0:25:32Their venom is not actually more potent than that of European bees,
0:25:32 > 0:25:34but they sting in such number -
0:25:34 > 0:25:38sometimes in thousands - that they can kill an enemy.
0:25:42 > 0:25:47Kerr's hybrid bees were fearless and had inherited this attack behaviour.
0:25:50 > 0:25:52African bees will chase African elephants
0:25:52 > 0:25:56and sting the soft tissue around their ears and faces.
0:25:57 > 0:26:01They will particularly target baby elephants that are smaller
0:26:01 > 0:26:02and softer skinned.
0:26:07 > 0:26:10Not surprisingly, elephants have developed a strong
0:26:10 > 0:26:13dislike of bees and make a great effort to avoid them.
0:26:16 > 0:26:19They recognise the sound of angry bees
0:26:19 > 0:26:23and have a specific call to warn each other if one is attacked.
0:26:26 > 0:26:29They even warn distant members of the herd by sending out
0:26:29 > 0:26:32low-frequency rumbles.
0:26:36 > 0:26:39The escape of such aggressive bees into the wild was
0:26:39 > 0:26:41devastating for Kerr's career.
0:26:43 > 0:26:46Africanised bees spread as far as the lower parts of North America,
0:26:46 > 0:26:49but here, their takeover halted.
0:26:51 > 0:26:53The more temperate climate didn't suit them.
0:26:57 > 0:26:59Kerr's intentions had been good,
0:26:59 > 0:27:03and he later dedicated his research to try to correct the problem.
0:27:06 > 0:27:09Eventually, Kerr did help to create a productive,
0:27:09 > 0:27:13more passive bee, as had originally been his plan.
0:27:14 > 0:27:19And South America is now one of the world's largest exporters of honey.
0:27:23 > 0:27:28The creation of a so-called killer bee by Dr Kerr's experiments
0:27:28 > 0:27:31was indeed a grave mistake.
0:27:31 > 0:27:37But in recent years, a more gentle form of African bee has been bred.
0:27:37 > 0:27:43And it's also possible that the ferocity of the African bee
0:27:43 > 0:27:46has now been turned to our advantage.
0:27:46 > 0:27:52Elephants are said to be terrified of bees and in recent years,
0:27:52 > 0:27:55farmers in Africa have started playing the sounds of swarming bees
0:27:55 > 0:27:59over their fields and the elephants have kept away.
0:28:00 > 0:28:05So as well as pollinating plants, bees can actually protect them.
0:28:07 > 0:28:10So both the Africanised honeybee
0:28:10 > 0:28:13and the pizzly bear are here to stay,
0:28:13 > 0:28:18but these unusual hybrids owe their success in one way or another
0:28:18 > 0:28:20to humans.