0:00:04 > 0:00:08There was a time when myths and science were entwined...
0:00:10 > 0:00:15..when mermaids and unicorns could mysteriously appear.
0:00:16 > 0:00:19Nature was weird.
0:00:19 > 0:00:23When science revealed the truth behind these imaginary creatures,
0:00:23 > 0:00:28it found real animals lay behind the legends.
0:00:29 > 0:00:33Today science still makes astonishing discoveries,
0:00:33 > 0:00:36but nature seems just as weird.
0:00:38 > 0:00:42It's just that fact has broken free from fiction.
0:00:55 > 0:00:58Many dances are stylised forms of courtship.
0:00:58 > 0:01:03Scorpions dance for the same seductive reason,
0:01:03 > 0:01:07but a Spanish scorpion must court with care.
0:01:07 > 0:01:12As he takes her by the claws, he fends off her sting with his tail.
0:01:14 > 0:01:18Rejection now would be fatal.
0:01:18 > 0:01:22He keeps up her interest by sweeping her off her feet.
0:01:34 > 0:01:40The dance may last for hours, as he tries to put her into a receptive mood.
0:01:43 > 0:01:49He seals his proposal with a kiss. It stops him becoming a meal.
0:01:49 > 0:01:53Next, he offers a present.
0:01:59 > 0:02:05He leaves a package to fertilise her eggs on the tip of a stalk.
0:02:06 > 0:02:12He guides her to pick up the gift, leaving just the stalk behind.
0:02:15 > 0:02:22This weird journey explores many other strange aspects of nature's ways of breeding.
0:02:32 > 0:02:35In courtship, gifts are always appreciated.
0:02:35 > 0:02:38The satin bowerbird of Australia
0:02:38 > 0:02:40has an eye for the presents his partner adores.
0:02:42 > 0:02:46Her favourite colour is blue.
0:02:50 > 0:02:54This is not his nest, but a bower,
0:02:54 > 0:02:56a place of seduction.
0:02:59 > 0:03:04He must keep up his maintenance to impress any females that call.
0:03:13 > 0:03:17She visits all the bowers in her neighbourhood
0:03:17 > 0:03:21to judge each male on his home decorating skills.
0:03:29 > 0:03:31She's hard to impress.
0:03:31 > 0:03:35An experienced male won't accept rejection lightly.
0:03:35 > 0:03:38He just works harder at winning her over.
0:03:41 > 0:03:44The more blue trinkets he accumulates,
0:03:44 > 0:03:46the more he turns her eye.
0:03:46 > 0:03:50His interest in home decoration is purely biological.
0:03:50 > 0:03:55The harder he works, the more he proves his fitness.
0:04:06 > 0:04:09CAR KEY REMOTE CONTROL BLEEPS
0:04:13 > 0:04:17He has amassed the bowerbird's equivalent of wealth -
0:04:17 > 0:04:21a proof of his genetic worth.
0:04:23 > 0:04:25And this bird has a lot on show.
0:04:27 > 0:04:30STRIDENT SQUAWKING
0:04:30 > 0:04:36On this occasion, a ring seems appropriate and seems to be doing the trick.
0:04:45 > 0:04:48STRIDENT SQUAWKING
0:04:54 > 0:04:57We may see human parallels here,
0:04:57 > 0:05:01but, biologically, OUR behaviour is stranger.
0:05:01 > 0:05:03Where are my keys?
0:05:06 > 0:05:09We are one of the most sexually active of all mammals,
0:05:09 > 0:05:12but we're also one of the least fertile.
0:05:12 > 0:05:16and few animals have such a long courtship or mate throughout the year.
0:05:17 > 0:05:22But by any measure, this marsupial mouse is weird.
0:05:23 > 0:05:28Antechinus squeezes its bouts of passion into a few energetic days.
0:05:31 > 0:05:38In early spring, the male's only goal is to mate with as many partners as possible.
0:05:39 > 0:05:41Each session lasts several hours.
0:05:41 > 0:05:45As soon as it ends, he looks for a new partner.
0:05:48 > 0:05:52He aims to track down every female in the neighbourhood.
0:05:55 > 0:05:58Subtlety is not his forte.
0:06:11 > 0:06:16All this activity leaves him little time to eat, drink or sleep
0:06:16 > 0:06:21and, in time, the stress starts to wear him down.
0:06:22 > 0:06:28Although exhausted, rampant hormones urge him on to yet another encounter.
0:06:35 > 0:06:38But he's feeling the strain.
0:06:38 > 0:06:41Over the two-week breeding season,
0:06:41 > 0:06:44he ages a lifetime.
0:06:44 > 0:06:49Rundown and tired, he is literally on his last legs.
0:06:53 > 0:06:56All the males are soon gone, leaving the females
0:06:56 > 0:06:58to bring up the babies.
0:06:58 > 0:07:01His sacrifice makes genetic sense.
0:07:01 > 0:07:07More offspring will survive if he isn't there to compete for food.
0:07:08 > 0:07:11BIRDSONG
0:07:12 > 0:07:18Male mice may cause their own demise, but in the meadows of Southern France,
0:07:18 > 0:07:23it's the female that's the deadlier of the species.
0:07:26 > 0:07:31The femme fatale in question is the European preying mantis.
0:07:32 > 0:07:36The smaller male courts his partner carefully.
0:07:36 > 0:07:41She can literally make a meal of any male.
0:07:42 > 0:07:47But he has to mate to pass on his genes.
0:07:53 > 0:07:59In this gruesome embrace, her love bite is the last thing he knows.
0:08:04 > 0:08:08But even this trauma doesn't seem to unnerve him.
0:08:08 > 0:08:13He continues to mate as though nothing has happened.
0:08:16 > 0:08:21Losing his head over a female helps nourish his future offspring.
0:08:24 > 0:08:29Astonishingly, decapitation improves his performance.
0:08:29 > 0:08:33A tiny brain in his rear keeps him active.
0:08:42 > 0:08:46This macabre coupling can last a day.
0:08:50 > 0:08:55Even then, the discarded carcass doesn't give up readily.
0:09:00 > 0:09:04In the oceans, courtship is even more complicated.
0:09:05 > 0:09:09It's a world of sexual confusion and gender-bending.
0:09:12 > 0:09:16One of the commonest reef fish are anthias.
0:09:19 > 0:09:22They gather in shoals many-hundreds strong.
0:09:29 > 0:09:32Oddly, most of them are female.
0:09:34 > 0:09:40They can be identified by their violet eyebrow line and orange colour.
0:09:40 > 0:09:45The few males are purple with a plume-like fin on their back.
0:09:55 > 0:09:59Should the male be removed, something strange happens.
0:10:01 > 0:10:06The leading lady takes over his role - literally!
0:10:09 > 0:10:12Her sexuality is flexible.
0:10:12 > 0:10:16She can perform a quick sex change to take his place.
0:10:18 > 0:10:25Not only does her colour and appearance change, she becomes he by developing male sex organs.
0:10:30 > 0:10:36It takes less than a week for this lady to become a fully-functioning gent.
0:10:43 > 0:10:48Gender-bending is also a speciality of sea hares.
0:10:49 > 0:10:53Like other sea slugs, sea hares are bisexual.
0:10:53 > 0:10:59Their hindquarters are female and their head ends are male.
0:11:00 > 0:11:04Sexual orientation depends on which ends meet first.
0:11:04 > 0:11:08When several sea hares get together,
0:11:08 > 0:11:11they often form a mating chain.
0:11:11 > 0:11:14The front slug has to be female.
0:11:14 > 0:11:19Those in the middle mate both ways and the last slug is always male.
0:11:19 > 0:11:25If the leader joins the end of the chain, a bisexual reel forms.
0:11:29 > 0:11:32Birth inevitably follows mating.
0:11:32 > 0:11:36For some, bubbles hold the secret of childcare.
0:11:38 > 0:11:40These Thai men
0:11:40 > 0:11:44are experts on breeding Siamese fighting fish.
0:11:48 > 0:11:53Traditionally, bets are placed on contests between prize specimens.
0:11:53 > 0:11:57Such fights occur naturally in nearby lakes and rivers.
0:11:57 > 0:11:59In either place,
0:11:59 > 0:12:07the winner gains the female and a chance to show a more tender side to his nature.
0:12:08 > 0:12:13An egg-like marking on her belly shows she's ready to breed -
0:12:13 > 0:12:18a come-on for the male to start courtship.
0:12:19 > 0:12:24He does something reminiscent of a child's game.
0:12:25 > 0:12:27He blows bubbles.
0:12:32 > 0:12:37He stops his bubbles popping by coating them with saliva.
0:12:50 > 0:12:54Soon a cluster of glistening baubles starts to accumulate.
0:12:54 > 0:12:59These will form a bubble nest for the care of his young.
0:13:10 > 0:13:12Then his aggression returns.
0:13:16 > 0:13:21But only to put her in the mood to accept his embrace.
0:13:31 > 0:13:35His quickly siphons up the fertilised eggs.
0:13:39 > 0:13:43Then spits them into the bubbles.
0:13:46 > 0:13:51This bubble-wrapping protects them from predators or infection.
0:13:56 > 0:14:02Two days later, the fry hatch and start to feed from their egg sacks.
0:14:09 > 0:14:12The fighting fish keeps up his vigil.
0:14:12 > 0:14:18Stray fry are caught and returned to the care of the bubble nest.
0:14:19 > 0:14:25Caring for young by bubble-wrapping them is popular in nature.
0:14:26 > 0:14:32The preying mantis lathers up a foam of microscopic bubbles to cocoon HER offspring.
0:14:36 > 0:14:41The foam hardens into a protective case that cossets her young.
0:14:48 > 0:14:51CHILDREN SHOUT
0:14:54 > 0:14:59Foam-nesting frogs also get into a lather tending their young.
0:14:59 > 0:15:05The mother secretes a fluid that the pair whip up into a foam similar to egg white.
0:15:05 > 0:15:09She lays her fertilised eggs inside.
0:15:09 > 0:15:12The outer wall of bubbles hardens like meringue
0:15:12 > 0:15:15and protects the eggs from predators, bacteria and the weather.
0:15:15 > 0:15:18Three days later,
0:15:18 > 0:15:22the first of several hundred tadpoles emerge.
0:15:22 > 0:15:27While some bubble-wrap their young, others literally splash out
0:15:27 > 0:15:30on childcare.
0:15:31 > 0:15:36In the Amazon, splash tetras stage a leaping contest.
0:15:46 > 0:15:51These strange fish out of water lay their eggs on leaves.
0:15:51 > 0:15:56The males leap to inspect suitable sites.
0:15:56 > 0:16:02They prefer protected leaves with a surface that's easy to stick to.
0:16:03 > 0:16:06The leap requires perfect posture.
0:16:08 > 0:16:11The fish must align itself
0:16:11 > 0:16:15so it grips the leaf by surface tension as it lands.
0:16:23 > 0:16:28The male guards his chosen leaf until a female arrives.
0:16:30 > 0:16:36They line up under the leaf and perform the ultimate act of synchronised swimming.
0:16:48 > 0:16:52As a cue, the female nudges the male with her head,
0:16:52 > 0:16:57then a flick of their tails propels them in perfect unison.
0:17:04 > 0:17:07They are so synchronised,
0:17:07 > 0:17:10to the human eye they appear as one.
0:17:24 > 0:17:31The eggs are laid. The male's work has just begun - he must keep them wet until they hatch.
0:17:35 > 0:17:42The splash tetra must have the most labour-intensive childcare of any fish.
0:17:45 > 0:17:50But his eggs are safer from predators on leaves, rather than in the river.
0:17:50 > 0:17:55After two days of hard splashing, the fry emerge.
0:18:06 > 0:18:12The Surinam toad's version of parenting is even more eccentric.
0:18:12 > 0:18:15Her young literally get under her skin.
0:18:21 > 0:18:26They develop from eggs to tadpoles in a wad of skin on her back
0:18:26 > 0:18:29and emerge as fully-formed toadlets.
0:18:42 > 0:18:46Most toads lay hundreds of eggs and only a few survive.
0:18:46 > 0:18:52Using skincare ensures that all the Surinam's offspring become baby toads.
0:19:00 > 0:19:03Once free, they fend for themselves.
0:19:04 > 0:19:08For some, parental care is the father's responsibility.
0:19:08 > 0:19:12The African bullfrog is one such doting parent.
0:19:14 > 0:19:20Tadpoles develop in shallow pools where he acts as their lifeguard.
0:19:20 > 0:19:24But water is siphoned up by many thirsty creatures.
0:19:36 > 0:19:41Faced with towering competition, the bullfrog retreats,
0:19:41 > 0:19:45but as the water levels drop, he still remembers his offspring.
0:19:47 > 0:19:52The sun also causes the precious water to vanish.
0:19:59 > 0:20:02Soon the mud will be concrete-hard.
0:20:11 > 0:20:15His poor tadpoles are left high and dry.
0:20:17 > 0:20:21They call to their father for help.
0:20:21 > 0:20:25He reacts by digging an escape route.
0:20:36 > 0:20:38It's a race against time.
0:20:46 > 0:20:51He paddles away to soften the rock-hard earth as he digs a canal.
0:21:00 > 0:21:03Their pleas for help urge him on.
0:21:14 > 0:21:18Breakthrough happens in the nick of time.
0:21:27 > 0:21:31He leads his offspring to safety.
0:21:39 > 0:21:43The bullfrog is one of the world's most devoted fathers,
0:21:43 > 0:21:45but he has competition.
0:21:47 > 0:21:50The Siberian dwarf hamster
0:21:50 > 0:21:55must win the prize for being nature's new man.
0:21:55 > 0:21:59The male acts as midwife during his partner's labour.
0:22:10 > 0:22:16Male midwifery is unique among mammals and - even in humans - it's a recent development.
0:22:20 > 0:22:24Biologically, human birthing behaviour is strange.
0:22:24 > 0:22:31Only humans have such painful extended labour. Few animals have such helpless young.
0:22:31 > 0:22:35Human males traditionally stay away at the birth.
0:22:35 > 0:22:41However, the hamster's mate is her constant birth companion.
0:22:42 > 0:22:47Russian hospitals follow tradition, excluding fathers from the birth.
0:22:47 > 0:22:52But the hamster's partner shows a feminine care and concern.
0:22:52 > 0:22:55He cleans each newborn baby in turn.
0:22:55 > 0:22:59His human counterpart can only wait in the sidelines.
0:23:07 > 0:23:13At birth, the hamster even cuts the umbilical cord with his teeth.
0:23:13 > 0:23:15BABY CRIES
0:23:23 > 0:23:28Traditionally, women continue to help once the birth is over.
0:23:31 > 0:23:35Again, the male hamster takes on this caring role.
0:23:35 > 0:23:40He retrieves any youngsters that wriggle from the nest.
0:23:49 > 0:23:55In many countries, human fathers are now encouraged to attend the birth,
0:23:55 > 0:23:59but in Russia, old traditions die hard.
0:24:01 > 0:24:05The hamster may be the only mammal that naturally acts like a new man.
0:24:05 > 0:24:11But there's a catch - he soon reveals a less sensitive side.
0:24:11 > 0:24:15His partner can only mate over the next three hours.
0:24:15 > 0:24:20Helping at the birth stops him missing the moment.
0:24:28 > 0:24:33But the dwarf hamster has a rival for his new-age credentials.
0:24:42 > 0:24:46Sea horses are the only animals in which the male
0:24:46 > 0:24:49actually becomes pregnant.
0:24:50 > 0:24:55He carries his partner's eggs in a brood pouch on his stomach.
0:24:55 > 0:24:58The pouch lining acts like a placenta
0:24:58 > 0:25:02and nourishes the developing young.
0:25:02 > 0:25:08When the times comes to give birth, he even suffers contractions.
0:25:14 > 0:25:18They become more violent as the birth approaches.
0:25:31 > 0:25:34He gives birth to around 100 young.
0:25:38 > 0:25:41Each is a miniature replica of their father.
0:25:52 > 0:25:55Sea horses are the only animals
0:25:55 > 0:25:59whose males experience the birth process.
0:25:59 > 0:26:05His young grip the nearest thing they can find - even each other.
0:26:13 > 0:26:19He may be the spitting image of his father, but from now on, he's on his own.
0:26:19 > 0:26:21For sea horses,
0:26:21 > 0:26:25parental care stops at birth.
0:26:26 > 0:26:29Extended childcare is most common in mammals.
0:26:29 > 0:26:35The Asian musk shrew has perhaps the oddest way of keeping her young in line.
0:26:38 > 0:26:43Moving a large family between nests is a big responsibility.
0:26:47 > 0:26:53To avoid getting lost, each youngster bites the fur by its neighbour's tail and hangs on.
0:26:57 > 0:27:01To the young, it's a game of follow-my-leader.
0:27:01 > 0:27:05Wherever their mother goes, they keep in step.
0:27:13 > 0:27:17But if the mother becomes separated from her brood,
0:27:17 > 0:27:21the youngster grab any moving thing that passes.
0:27:30 > 0:27:34Their persistence and strength of grasp is phenomenal.
0:27:37 > 0:27:39As long as the train keeps moving,
0:27:39 > 0:27:42they'll hold on tight...
0:27:46 > 0:27:49..even in the air.
0:28:01 > 0:28:04Stop the train and they let go.
0:28:04 > 0:28:09When the mother returns, order is restored to her chaotic brood.
0:28:13 > 0:28:17She guides her daisy chain to safety.
0:28:17 > 0:28:21Such care may seem odd, but in a world
0:28:21 > 0:28:24of bizarre breeding, we are stranger.
0:28:24 > 0:28:28No other animal tends its young for as long as us.