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0:00:00 > 0:00:05- Rural Wales offers some of the most - spectacular sights in Britain.
0:00:08 > 0:00:12- But the countryside - offers much more than just views.
0:00:12 > 0:00:15- It's home - to some of our best-loved wildlife.
0:00:16 > 0:00:20- But one group of mammals - is living a secret life.
0:00:22 > 0:00:25- By burrowing - in tunnels miles underground...
0:00:26 > 0:00:30- ..the way - these animals live their lives...
0:00:30 > 0:00:35- ..has been a mystery until now.
0:00:35 > 0:00:39- We're going to do something - that's never been done before.
0:00:39 > 0:00:44- By uncovering some of these - burrowers' tunnels and chambers...
0:00:44 > 0:00:48- ..we're going to recreate - an artificial habitat.
0:00:48 > 0:00:51- For the first time ever...
0:00:51 > 0:00:55- ..we'll get an insight - into their secret lives underground.
0:00:55 > 0:01:01- We'll discover what water voles - do every day in their tunnels...
0:01:02 > 0:01:07- ..how rabbits cope with nurturing - dozens of offspring each year...
0:01:07 > 0:01:10- ..and how small badgers - learn to cope...
0:01:11 > 0:01:13- ..with the big world - beyond the sett.
0:01:13 > 0:01:17- Join me, Iolo Williams, - as we venture...
0:01:17 > 0:01:21- ..to the magical, hidden, - subterranean world of the burrowers.
0:01:22 > 0:01:24- Subtitles
0:01:45 > 0:01:49- Midsummer, and our time - with the burrowers is almost over.
0:01:50 > 0:01:54- The warren - is overrun with young rabbits.
0:01:57 > 0:02:02- The water voles are more than ready - for their release into the wild.
0:02:04 > 0:02:09- The badgers are also ready - to face the big, wide world.
0:02:12 > 0:02:15- In line with this experiment...
0:02:15 > 0:02:20- ..we wanted to learn more about the - least familiar burrower of them all.
0:02:20 > 0:02:23- The mole.
0:02:30 > 0:02:35- This is an animal - that rarely surfaces above ground.
0:02:35 > 0:02:38- After long spells of darkness...
0:02:38 > 0:02:41- ..the hidden cameras - captured the mole on film.
0:02:42 > 0:02:44- It was living - in this collection of boxes...
0:02:45 > 0:02:49- ..using some of them to nest - and others to store food...
0:02:49 > 0:02:54- ..moving between the boxes - through inter-connecting tubes.
0:02:54 > 0:02:57- This mole is special - because she was rescued.
0:02:57 > 0:03:03- Moles are regarded as pests for - creating molehills on golf courses.
0:03:03 > 0:03:07- This one was caught - by a professional mole catcher.
0:03:07 > 0:03:10- Normally it would've been killed.
0:03:10 > 0:03:13- This is one of the most - interesting animals in Britain.
0:03:14 > 0:03:18- It spends - most of its life underground.
0:03:19 > 0:03:22- It is the best burrower - out of all the burrowing mammals.
0:03:25 > 0:03:27- They exist - in the safety of the tunnels.
0:03:28 > 0:03:30- Unlike the other burrowers...
0:03:30 > 0:03:34- ..they have a lonely - and self-sufficient existence.
0:03:34 > 0:03:38- In summer, they must find a mate - in order to breed...
0:03:38 > 0:03:40- ..deep underground.
0:03:41 > 0:03:45- The chances of seeing newborn moles - are relatively slim.
0:03:45 > 0:03:49- No-one had ever - filmed baby moles before...
0:03:49 > 0:03:54- ..until the 1970s, - when Peter Stafford's footage...
0:03:54 > 0:03:58- ..won him the Wildlife - Photographer of the Year award.
0:03:59 > 0:04:02- The young burrowers - won't start burrowing...
0:04:02 > 0:04:04- ..until they're two months old.
0:04:05 > 0:04:09- They will learn from - inspecting the mother's tunnels.
0:04:09 > 0:04:12- They compete - with their mother for food...
0:04:12 > 0:04:16- ..which eventually - drives them out of their tunnels.
0:04:16 > 0:04:20- They must establish their own - territories around the mother's.
0:04:20 > 0:04:24- This is when the burrowers - venture above ground...
0:04:24 > 0:04:26- ..before burrowing new tunnels.
0:04:26 > 0:04:30- They sometimes burrow - at the roadside or near buildings.
0:04:30 > 0:04:33- They must then resurface - and try again.
0:04:33 > 0:04:35- Moles are never happy above ground.
0:04:43 > 0:04:46- Owls, like many other animals...
0:04:46 > 0:04:49- ..eat food - that is difficult to digest.
0:04:49 > 0:04:51- They swallow food whole.
0:04:51 > 0:04:54- The food - is broken down in the crop...
0:04:54 > 0:04:57- ..and the meat - is separated from the bone.
0:04:57 > 0:05:00- The bones and fur - are compressed into a ball...
0:05:01 > 0:05:03- ..and vomited out of the beak.
0:05:05 > 0:05:08- By collecting - and analysing these balls...
0:05:09 > 0:05:12- ..it's possible to tell - which small mammals...
0:05:12 > 0:05:15- ..inhabit - the same habitat as the owl.
0:05:19 > 0:05:22- I know you've studied - the barn owl, Kelvin...
0:05:22 > 0:05:24- ..and collected their pellets...
0:05:24 > 0:05:27- ..which consist of fur and bones...
0:05:28 > 0:05:30- ..that they've vomited - from the mouth.
0:05:31 > 0:05:32- What information have you gleaned?
0:05:32 > 0:05:34- What information have you gleaned?- - I've two reasons for doing this.
0:05:35 > 0:05:37- It's a great way - of engaging children.
0:05:38 > 0:05:40- By studying what they eat...
0:05:40 > 0:05:43- ..you get a sample - of the territory they inhabit.
0:05:44 > 0:05:47- Some of these - have come from Dinas Dinlle.
0:05:47 > 0:05:51- I know the skull has come from - Dinas Dinlle, at least.
0:05:51 > 0:05:55- But the skull of the water vole - has come from Lleyn.
0:05:55 > 0:05:59- Of all the pellets I've collected, - that's the only one from Lleyn.
0:06:00 > 0:06:03- That goes to show - how rare the water vole has become.
0:06:03 > 0:06:09- We're old enough to remember them - but now they're preyed on by mink.
0:06:09 > 0:06:15- That's not a very big skull because, - quite often, they can be big.
0:06:15 > 0:06:19- They wouldn't eat - the large ones whole, would they?
0:06:19 > 0:06:21- According to our research, yes.
0:06:21 > 0:06:23- They must swallow them whole.
0:06:23 > 0:06:25- They must swallow them whole.- - That's one heck of a mouthful!
0:06:25 > 0:06:29- You also have an example - of the mole's remains.
0:06:31 > 0:06:33- Do you often come across them?
0:06:34 > 0:06:38- No, not very often. It's been - pulverised in the bird's gullet.
0:06:38 > 0:06:41- It swallows the prey whole...
0:06:41 > 0:06:45- ..and then its stomach acid - digests what it can...
0:06:45 > 0:06:48- ..and leaves - the fur and bone for excretion.
0:06:48 > 0:06:51- The mole's skull isn't very strong.
0:06:52 > 0:06:54- What we have here are two chins...
0:06:54 > 0:06:57- ..and are they two hips?
0:06:57 > 0:06:59- No, I'll tell you what they are.
0:07:00 > 0:07:02- I've an example of these here.
0:07:02 > 0:07:06- They're the main bones of the arm - - the humerus.
0:07:07 > 0:07:09- Notice their shape.
0:07:09 > 0:07:12- A human's humerus - looks like a proper bone...
0:07:12 > 0:07:16- ..the kind you'd find - in the mouth of a dog in a cartoon.
0:07:16 > 0:07:20- But this humerus - looks almost like a hip.
0:07:21 > 0:07:24- Because they're so strong, - they use them to burrow.
0:07:24 > 0:07:30- They're very wide, with plenty of - room for the muscles to contract...
0:07:30 > 0:07:33- ..giving them strength and power.
0:07:33 > 0:07:36- I've brought something else along...
0:07:36 > 0:07:40- ..that's been discarded in - an owl pellet - the skull of a mole.
0:07:41 > 0:07:43- As you say, it looks very fragile.
0:07:43 > 0:07:45- It's long and thin.
0:07:45 > 0:07:47- Check out those teeth.
0:07:48 > 0:07:52- They're very sharp. - The only thing it eats are worms.
0:07:52 > 0:07:55- You need teeth like that - to catch them.
0:07:55 > 0:07:59- And to kill them. - Nature has a reason for everything.
0:07:59 > 0:08:03- This is a good way - of mapping an animal like this.
0:08:03 > 0:08:05- There's no need to lay traps.
0:08:06 > 0:08:08- You just have to collect - their remains.
0:08:09 > 0:08:14- You can tell what species they are - - short-tailed voles or bank voles...
0:08:14 > 0:08:16- ..as well as those they aren't.
0:08:16 > 0:08:20- It's interesting when you're - sitting at home at night...
0:08:21 > 0:08:24- ..and it's cold and wet outside - to have a hobby like this.
0:08:25 > 0:08:28- The family might not be so happy - but is passes the time!
0:08:47 > 0:08:51- The young badgers have left the sett - and are inspecting the enclosure.
0:08:52 > 0:08:56- They must learn how to live - above ground as well as underground.
0:08:56 > 0:09:01- So far, they've been fed by those - who are looking after them...
0:09:01 > 0:09:03- ..with all kinds of special foods.
0:09:04 > 0:09:08- But now they have to learn - to fend for themselves...
0:09:09 > 0:09:10- ..by catching worms.
0:09:11 > 0:09:13- Research has been carried out...
0:09:14 > 0:09:16- ..and within a two-hour period...
0:09:16 > 0:09:21- ..a person watched a badger - eat 1,803 worms.
0:09:21 > 0:09:26- A worm weighs around three grams...
0:09:26 > 0:09:30- ..so that's the equivalent - to three kilograms of worms.
0:09:30 > 0:09:32- Worms are vital to their survival.
0:09:33 > 0:09:35- That's a hefty weight...
0:09:35 > 0:09:38- ..when you consider that badgers...
0:09:38 > 0:09:42- ..don't weigh - more than 10kg-11kg themselves.
0:09:42 > 0:09:46- They're eating a third - of their bodyweight in one night.
0:09:47 > 0:09:49- Worms are a vital food source.
0:09:50 > 0:09:54- If it's a dry summer, - badgers find it difficult to forage.
0:09:54 > 0:09:59- They're capable of finding other - foods but worms are their staple.
0:10:01 > 0:10:07- On a wet night, when the worms - surface above ground...
0:10:07 > 0:10:10- ..badgers venture out early evening - to have their fill.
0:10:14 > 0:10:17- Our badgers are obviously capable - of finding food.
0:10:18 > 0:10:20- They sniff out the worms...
0:10:20 > 0:10:23- ..and eat them in the same way - as badgers do in the wild.
0:10:24 > 0:10:28- It's a good sign they'll find their - main food supply once released.
0:10:30 > 0:10:33- But life beyond the sett - is by no means easy.
0:10:39 > 0:10:44- When they return underground, they - bring unwelcome guests with them.
0:10:46 > 0:10:50- One of the disadvantages - of living in an underground sett...
0:10:50 > 0:10:53- ..is that mites co-habit with you.
0:10:54 > 0:10:58- Fleas are - the scourge of animals everywhere.
0:11:01 > 0:11:06- Fleas burrow in the fur - and feed on the poor animal's blood.
0:11:11 > 0:11:16- In spite of all the scratching, - the fleas' legs cling to the fur...
0:11:16 > 0:11:19- ..making it very difficult - to get rid of them.
0:11:24 > 0:11:29- In spite of the fleas, badgers - are incredibly clean animals.
0:11:29 > 0:11:33- Even our orphaned badgers have - learnt to keep their nests clean...
0:11:33 > 0:11:38- ..by dragging the straw outside - for it to dry in the sun and wind.
0:11:45 > 0:11:48- What materials - do they use for their nests?
0:11:48 > 0:11:53- Predominantly straw, but whatever - they can find in their surroundings.
0:11:53 > 0:11:58- Fern, moss and vegetation - that dries quite easily.
0:11:58 > 0:12:02- I've seen them drag their nests - outside for them to dry...
0:12:02 > 0:12:06- ..before dragging them - back in again.
0:12:07 > 0:12:08- Yes, they do that.
0:12:09 > 0:12:12- In warm weather, - they pull out the straw to air it.
0:12:13 > 0:12:17- That must get rid of the fleas and - whatever else is living in it...
0:12:17 > 0:12:20- ..before taking it - back below ground.
0:12:21 > 0:12:24- So it's true - that they're clean creatures?
0:12:24 > 0:12:26- Most definitely.
0:12:33 > 0:12:37- As summer passes, - our experiment comes to an end.
0:12:38 > 0:12:42- But the young burrowers aren't ready - to leave their homes just yet.
0:12:43 > 0:12:47- These final steps towards - independence are the most important.
0:12:51 > 0:12:55- Each of our burrowers has developed - a very different strategy...
0:12:56 > 0:12:58- ..to prepare them - for the big, wide world.
0:12:59 > 0:13:04- The badgers have created - a close-knit social unit...
0:13:04 > 0:13:07- ..which gives the group stability...
0:13:07 > 0:13:12- ..and will be useful - when they come to raise their young.
0:13:12 > 0:13:16- The rabbits, on the other hand, - are completely different.
0:13:17 > 0:13:19- Their strategy is to breed non-stop.
0:13:20 > 0:13:24- High numbers of rabbits to - replace those killed by predators.
0:13:24 > 0:13:28- The water vole - has a far more orderly strategy.
0:13:34 > 0:13:34- .
0:13:38 > 0:13:38- Subtitles
0:13:38 > 0:13:40- Subtitles- - Subtitles
0:13:58 > 0:14:03- The female water vole - is nurturing her second litter.
0:14:03 > 0:14:08- The mother's milk helps them - gain a gram of weight every day.
0:14:08 > 0:14:11- But there's no sign - of the first litter.
0:14:14 > 0:14:19- The mother has driven them out of - the burrow to live on the riverbank.
0:14:19 > 0:14:22- Three of them - are now fending for themselves.
0:14:23 > 0:14:25- They must be careful.
0:14:25 > 0:14:28- In the wild, a young water vole - is a tasty snack...
0:14:29 > 0:14:31- ..for its arch-rival, the mink.
0:14:35 > 0:14:40- How will they be able to defend - themselves once they're released?
0:14:40 > 0:14:46- Luckily, their father is burrowing - tunnels whilst foraging for food.
0:14:46 > 0:14:49- The young water voles - need a new home.
0:14:49 > 0:14:52- By observing - the actions of their father...
0:14:53 > 0:14:55- ..they learn to do the same.
0:14:56 > 0:15:00- Soon they'll have small shelters - in which to hide when necessary.
0:15:01 > 0:15:05- Thrown out of their home at three - weeks of age might seem cruel...
0:15:05 > 0:15:11- ..but it's essential - to ensure the water voles' survival.
0:15:13 > 0:15:17- Since they're - so ferociously territorial...
0:15:17 > 0:15:21- ..it's remarkable to think - that the female in particular...
0:15:22 > 0:15:27- ..allows her firstborn - to stay relatively close.
0:15:27 > 0:15:31- Once the second litter is born...
0:15:31 > 0:15:34- ..the population - continues to rise...
0:15:35 > 0:15:38- ..so there must be enough room - for them to spread out.
0:15:39 > 0:15:41- The first litter stays close...
0:15:41 > 0:15:45- ..whereas the second litter - is pushed further away...
0:15:46 > 0:15:48- ..from the mother's territory...
0:15:48 > 0:15:51- ..and forced to find new habitats.
0:15:51 > 0:15:56- There might be another female 50 - metres away with the same structure.
0:15:57 > 0:16:03- The young - are pushed further and further away.
0:16:03 > 0:16:06- One of the main - conservational problems...
0:16:06 > 0:16:11- ..is tracking the young that are - consistently pushed further away.
0:16:11 > 0:16:14- That's a difficult strategy...
0:16:14 > 0:16:18- ..because you're - pushing the young further away...
0:16:18 > 0:16:23- ..knowing they are the prey - of buzzards, otters and so on.
0:16:24 > 0:16:28- Yes, - it is a very difficult strategy.
0:16:28 > 0:16:33- But it's important in order - for that strategy to work...
0:16:34 > 0:16:38- ..and for the population - to be self-sufficient.
0:16:38 > 0:16:41- The connection - between the populations is vital.
0:16:42 > 0:16:46- Those ties must be formed - in an ideal habitat...
0:16:46 > 0:16:50- ..where there's enough room - for them to burrow.
0:16:50 > 0:16:53- The males, for example...
0:16:54 > 0:16:58- ..or the young boys, as it were, - that are kicked out...
0:16:58 > 0:17:02- ..must be able to travel - and find other females...
0:17:02 > 0:17:09- ..so that - the genetic diversity is varied.
0:17:09 > 0:17:12- These connections are crucial...
0:17:13 > 0:17:18- ..as are the habitats which - connect these metapopulations...
0:17:19 > 0:17:23- ..over a sprawling landscape.
0:17:23 > 0:17:26- There's - a large population in Wales...
0:17:26 > 0:17:29- ..especially in the upland areas.
0:17:30 > 0:17:33- The habitat is widespread...
0:17:33 > 0:17:36- ..encompassing numerous dykes...
0:17:36 > 0:17:38- ..and pools.
0:17:39 > 0:17:43- Within those small pools - are different populations.
0:17:44 > 0:17:48- It's those important connections - that make the strategy work.
0:18:02 > 0:18:07- Rabbit numbers continue to multiply - in the warren...
0:18:07 > 0:18:10- ..with the dominant female - holding her own.
0:18:10 > 0:18:13- She keeps other rabbits at bay.
0:18:13 > 0:18:15- She and the dominant male...
0:18:15 > 0:18:17- ..rule the roost.
0:18:17 > 0:18:21- There are now 40 kits - in the rabbit warren.
0:18:22 > 0:18:26- But as numbers increase, - one pair of subservient rabbits...
0:18:26 > 0:18:30- ..must live in the chambers - at the bottom of the warren.
0:18:30 > 0:18:33- Though the doe - has recently given birth...
0:18:33 > 0:18:36- ..the dominant male - prepares to mate with her.
0:18:36 > 0:18:41- But the subservient male challenges - him and it leads to a fight...
0:18:42 > 0:18:44- ..in and out of the tunnels.
0:18:45 > 0:18:48- This behaviour - endangers the newborns.
0:18:48 > 0:18:52- When the mother returns to the nest, - she finds blood.
0:18:52 > 0:18:56- It appears - that most of the kits are alive...
0:18:57 > 0:19:01- ..but the fight between the two - bucks has left at least one dead.
0:19:04 > 0:19:09- This is one of the females that's - been thrown out of the warren.
0:19:10 > 0:19:14- She has started burrowing a new - tunnel as a nest for her offspring.
0:19:14 > 0:19:17- This is how a new warren begins.
0:19:26 > 0:19:29- In the winter - we studied an empty warren.
0:19:30 > 0:19:34- In a unique experiment, - we filled the warren with concrete.
0:19:34 > 0:19:37- Once it had set, - we dug up the earth...
0:19:37 > 0:19:39- ..to uncover an elaborate warren.
0:19:40 > 0:19:43- This is the first time - such a task has been undertaken.
0:19:44 > 0:19:49- The warren we built has shown us - many new and exciting things.
0:19:50 > 0:19:53- But there's one thing - it cannot show us.
0:19:57 > 0:20:01- For the first time, we're about to - find out how a wild warren grows...
0:20:01 > 0:20:04- ..to accommodate - a rising number of rabbits.
0:20:05 > 0:20:08- Experts in mapping technology - collate data...
0:20:08 > 0:20:12- ..that will enable us - to create a 3D scan of the warren.
0:20:13 > 0:20:17- The warren - has developed in three stages...
0:20:17 > 0:20:22- ..with each part corresponding - to a new generation of rabbits.
0:20:25 > 0:20:29- This is the first part, with - short tunnels, large chambers...
0:20:29 > 0:20:31- ..and numerous entrances.
0:20:31 > 0:20:35- The second part - seems larger than the first...
0:20:35 > 0:20:40- ..with fewer slants and - more tunnels between every chamber.
0:20:43 > 0:20:47- The third part, the most recent, - looks longer than the other two.
0:20:49 > 0:20:52- But looking - at the design mathematically...
0:20:53 > 0:20:57- ..the tunnels are almost - the same size and length...
0:20:57 > 0:21:00- ..even in the most recent section...
0:21:01 > 0:21:04- ..where the chambers - look further apart.
0:21:04 > 0:21:08- It's interesting to think animals - adhere to mathematical rules.
0:21:09 > 0:21:12- They can't afford - to do things in a haphazard way.
0:21:15 > 0:21:19- There's a chance for - the subservient rabbits to escape...
0:21:19 > 0:21:24- ..and create a new warren - that would thrive in the future.
0:21:40 > 0:21:45- The badgers have shown they are - capable of surviving in the wild.
0:21:48 > 0:21:50- But one test remains.
0:21:50 > 0:21:53- They must prove - they can build their own sett.
0:21:53 > 0:21:59- The young badgers know instinctively - what to do. It's inherent in them.
0:22:01 > 0:22:06- They have already - been burrowing their own sett.
0:22:20 > 0:22:23- These animals - have given us an insight...
0:22:23 > 0:22:26- ..into - their secret lives underground.
0:22:26 > 0:22:28- We've learnt so many new things.
0:22:31 > 0:22:35- We now know the shape and form - of a rabbit warren in the wild...
0:22:38 > 0:22:43- ..and the individual role the - water vole plays in its survival.
0:22:46 > 0:22:51- We know that moles can exist - underground in total darkness...
0:22:55 > 0:22:58- ..and how a group - of orphaned badgers...
0:22:59 > 0:23:02- ..can form a lifelong relationship.
0:23:02 > 0:23:04- Our journey underground...
0:23:04 > 0:23:07- ..has been an incredible adventure.
0:23:37 > 0:23:39- S4C Subtitles by Adnod Cyf.
0:23:39 > 0:23:39- .