0:00:03 > 0:00:05Skilful hunters.
0:00:11 > 0:00:15Violent and terrifying man-eaters.
0:00:15 > 0:00:16Devoted parents.
0:00:20 > 0:00:26'I'm Jonathan Scott and I've been captivated by lions all my life.'
0:00:29 > 0:00:30And for the last 30 years,
0:00:30 > 0:00:34'I've been watching, sketching, photographing and filming'
0:00:34 > 0:00:40one amazing lion pride, by day, and under the cover of darkness.
0:00:43 > 0:00:49And I've seen first-hand what makes lions unique.
0:00:49 > 0:00:54Whilst other big cats live solitary lives, lion's don't.
0:00:54 > 0:00:56They live in large family prides.
0:00:56 > 0:01:00The lion pride is the exception amongst the cat family.
0:01:00 > 0:01:03No other species lives this kind of social existence.
0:01:05 > 0:01:10Now, new research is revealing the reason for the lion's unique lifestyle.
0:01:12 > 0:01:16'Assumptions and misconceptions are being overturned.'
0:01:16 > 0:01:18We want to know, why are lions social?
0:01:18 > 0:01:22I'm going to look again at this unique animal.
0:01:22 > 0:01:26I'm searching for The Truth About Lions.
0:01:53 > 0:01:55I can hardly believe it's almost 40 years ago
0:01:55 > 0:01:58since I arrived in Africa with a degree in Zoology.
0:01:58 > 0:02:03I was passionate about wildlife and, in particular, I was fascinated by big cats.
0:02:03 > 0:02:09I wanted to explore every detail of their lives. I wanted to write about them, photograph them, draw them.
0:02:09 > 0:02:13In fact, I wanted to get right under their skin, to know them as individuals.
0:02:13 > 0:02:15And what better place to do that than right here,
0:02:15 > 0:02:17in the Maasai Mara in Kenya.
0:02:30 > 0:02:34The Maasai Mara is the northern tip of the vast Serengeti
0:02:34 > 0:02:38that stretches for 120 miles to the south, in Tanzania.
0:02:45 > 0:02:50This is classic African savannah, large areas of open grassland,
0:02:50 > 0:02:54scattered trees and small rivers criss-crossing the terrain.
0:03:03 > 0:03:10And running through the whole reserve on its journey to Lake Victoria is the mighty Mara river.
0:03:15 > 0:03:20This place is home to perhaps the most famous lions in the world...
0:03:20 > 0:03:23ROARING
0:03:23 > 0:03:25..The Marsh Pride.
0:03:37 > 0:03:43Together with colleagues from the BBC, I've filmed them extensively for shows such as Big Cat Diary.
0:03:47 > 0:03:50At times, under 24-hour surveillance...
0:03:54 > 0:03:57..revealing their lives in extraordinary detail.
0:04:10 > 0:04:15This particular pride of lions, the Marsh Pride, they're like family to me and I've been recording
0:04:15 > 0:04:20every detail of their life, going back to 1977. This notebook, 1981.
0:04:20 > 0:04:24And that's always been the fascination for me, the detail.
0:04:24 > 0:04:28But what drove lions to form prides in the first place?
0:04:28 > 0:04:32Why are they so different from all of the other cats?
0:04:34 > 0:04:40It's the fundamental question about lions that I'm still unable to answer satisfactorily.
0:04:47 > 0:04:53But over the border in Tanzania's Serengeti National Park is a project which could help me.
0:05:08 > 0:05:14The Serengeti is vast, equivalent in area to the whole of Wales,
0:05:14 > 0:05:16and, like the Mara, it's a stronghold for lions.
0:05:25 > 0:05:28It's home to the Serengeti Lion Project,
0:05:28 > 0:05:32the longest-running lion research project ever.
0:05:34 > 0:05:40This is the reproductive rates. Over 40 years of data, across our study area.
0:05:40 > 0:05:42They're about four or five.
0:05:42 > 0:05:47'It began in 1966 and, since 1978, it's been headed by Craig Packer.
0:05:47 > 0:05:50'the foremost lion scientist in the world.'
0:05:50 > 0:05:56Some places have very low reproduction, others are really high, especially up here.
0:05:56 > 0:05:59'He's been studying these cats for as long as I've been in Africa.
0:05:59 > 0:06:02'yet we've only met once before, 25 years ago.
0:06:06 > 0:06:09'So this meeting is long overdue.'
0:06:09 > 0:06:13My focus has very much been a single pride, the Marsh Pride, which I know
0:06:13 > 0:06:17intimately and I love that sense of knowing the group, but we're talking
0:06:17 > 0:06:2330 lions, maximum. Yes, I see the other lions at times that surround them, but for you, very different.
0:06:23 > 0:06:29Here we're trying to look at a population, so we look at between 13 and 28 prides
0:06:29 > 0:06:35at any one time, so over all the decades here, we've got data now on 5,000 lions.
0:06:35 > 0:06:38- 5,000. - Totally different approach.- Yes.
0:06:38 > 0:06:43The first thing was, we had a long history in the study and so we inherited those records,
0:06:43 > 0:06:48so when I got here we already knew who the grandmothers were of some of the adult females,
0:06:48 > 0:06:52but we didn't know much about paternity until later, when we did DNA fingerprinting.
0:06:52 > 0:06:57We were one of the first animal projects to use the genetic tools
0:06:57 > 0:07:00to understand the kinship within a pride.
0:07:00 > 0:07:04Another thing that I've loved in the Mara is that I've been able to watch lions, leopards, cheetahs
0:07:04 > 0:07:10and I could really, sort of, see how different lions are to those other animals.
0:07:10 > 0:07:13And the key question has always been, I think for you, too,
0:07:13 > 0:07:16is, why are lions social? Can we answer that question now?
0:07:16 > 0:07:21Finally I think we have a good answer on this. It took us a long time. There were different ideas
0:07:21 > 0:07:26that had been floating around. We went through them all, one by one. But each took several years
0:07:26 > 0:07:29to answer, much longer than we thought,
0:07:29 > 0:07:32and it took us 30 years before we felt we'd nailed the answer.
0:07:45 > 0:07:48For over 30 years, Craig and his team of researchers
0:07:48 > 0:07:54have collected vast amounts of data, from 28 study prides,
0:07:54 > 0:08:01testing the many theories that have been proposed to explain the lion's sociality.
0:08:03 > 0:08:08What's the driving force that binds individual lions together in prides?
0:08:09 > 0:08:14A social structure amongst the most complex of any group-living animal.
0:08:18 > 0:08:24There are animals like meerkats and baboons that form troops or packs and they're always together,
0:08:24 > 0:08:28but a lion pride is much more complicated than that.
0:08:28 > 0:08:33The lion pride is more like a human family, where one individual may go off and do something
0:08:33 > 0:08:35on their own for a while, and then they come back.
0:08:35 > 0:08:39And so you begin to realise it's a great intricacy, there's
0:08:39 > 0:08:44a great complexity to this social system, that's far more elaborate than we see in most other animals.
0:08:59 > 0:09:04It's that complexity that's kept me fascinated by the Marsh Pride all these years.
0:09:04 > 0:09:06What I want to do now is take all the information that
0:09:06 > 0:09:12Craig and his team have collected and take another look at my pride. And see how it matches up.
0:09:14 > 0:09:21Ironically, to understand the complexity of a pride, you need to know all its members as individuals.
0:09:23 > 0:09:25Naming them does help.
0:09:25 > 0:09:28But telling lions apart in the field isn't easy.
0:09:30 > 0:09:34Thankfully, in the early 1970's, a method was discovered.
0:09:36 > 0:09:40Every lion, as it turns out, has its own unique pattern of whisker spots,
0:09:40 > 0:09:43which act just like a human fingerprint.
0:09:45 > 0:09:50By recording the behaviour of the named individuals in my pride,
0:09:50 > 0:09:54the reason behind pride living can be revealed and investigated.
0:09:56 > 0:09:59Let's just take a look at what the Marsh Pride are up to right now,
0:09:59 > 0:10:03I'm just going to draw a map here of their territory in the sand.
0:10:03 > 0:10:08It's about 20 miles, that's about 50 square kilometres, so quite big.
0:10:08 > 0:10:11River's over here, the marsh is there
0:10:11 > 0:10:14and right here, we've got two older generation females,
0:10:14 > 0:10:17that's White-Eye, Bibi and four of White-Eye's cubs.
0:10:20 > 0:10:27At 12 years old White-Eye, so called as she is blind in one eye, is the oldest female in the pride.
0:10:27 > 0:10:32I've seen female lions in the Marsh Pride reach 15,
0:10:32 > 0:10:35but despite her age, right now, she's the newest mum.
0:10:40 > 0:10:46Her four young cubs rely on her for everything and will stick with her for at least two years.
0:10:49 > 0:10:51Alongside White-Eye in this part of the territory
0:10:51 > 0:10:56is one of her pride mates, another 12-year-old lioness, called Bibi.
0:10:59 > 0:11:02Over here, towards the west, I've got another older generation female,
0:11:02 > 0:11:06that's Lispy, with nine sub-adults - five males, four females.
0:11:08 > 0:11:14Lispy is Bibi's sister from a litter born in the pride in 1998.
0:11:14 > 0:11:19The sub-adults with her are the sort of teenagers of the pride,
0:11:19 > 0:11:25almost, but not quite, ready to go it alone. They're free to roam throughout the territory,
0:11:25 > 0:11:31They need to, in order to find enough food to satisfy so many hungry mouths.
0:11:32 > 0:11:35And right at the other side of the territory,
0:11:35 > 0:11:38we've got Clawed and Romeo, the big pride males.
0:11:41 > 0:11:45At 12 and ten years old, they're clearly powerful lions.
0:11:49 > 0:11:56Unlike the females, who will live their whole life in the same pride, the adult males have to fend off
0:11:56 > 0:12:02challenges from younger rivals and, on average, their tenure as a pair is rarely longer than two years.
0:12:07 > 0:12:12Clawed and Romeo have now been pride males for over three years.
0:12:16 > 0:12:19They're living on borrowed time.
0:12:23 > 0:12:24And that's not all.
0:12:24 > 0:12:28They're spending much of their time, maybe too much of it,
0:12:28 > 0:12:33with a breakaway trio from the Marsh Pride, that we call The three Graces.
0:12:33 > 0:12:39These females have also had cubs, but are keeping well away from the main pride, for the moment at least.
0:12:40 > 0:12:44Now you might think it's unusual to have members of the same pride
0:12:44 > 0:12:46scattered all over the territory like this,
0:12:46 > 0:12:49but I've seen it many times before.
0:12:57 > 0:13:02The fact that the individuals of the Marsh Pride aren't all together right now is brilliant timing.
0:13:07 > 0:13:14Watching how the three distinct factions operate and seeing when and why they come back together
0:13:14 > 0:13:19as a whole pride will help me make sense of Craig and his team's huge amount of work
0:13:19 > 0:13:24and unravel the fundamental reason behind pride living.
0:13:24 > 0:13:31Along the way, discovering a wealth of surprises about these magnificent creatures.
0:13:42 > 0:13:45March is normally dry in the Maasai Mara,
0:13:45 > 0:13:48a traditionally lean time for my lions.
0:13:50 > 0:13:56The famous wildebeest migration is 120 miles south in Tanzania and my lions are hungry.
0:14:04 > 0:14:09The need for food unites all three factions of the Marsh Pride.
0:14:20 > 0:14:24But the starkest difference between the pride factions at the moment
0:14:24 > 0:14:27is between those with young cubs and those without.
0:14:32 > 0:14:35White-Eye has four young cubs to feed.
0:14:35 > 0:14:37And they're thin.
0:14:42 > 0:14:48With such a sparsity of prey at this time of year, White-Eye and her only adult lioness companion, Bibi,
0:14:48 > 0:14:51are forced to hunt even during the heat of the day.
0:14:54 > 0:14:58And they must travel large distances away from the cubs, leaving them vulnerable.
0:15:12 > 0:15:19But the nine young lions in Lispy's gang are far more self-reliant and can hunt as a team.
0:15:20 > 0:15:25This is the group that is perhaps most like many people's idea of a lion pride.
0:15:29 > 0:15:33Does their strength in numbers mean they'll fair better than White-Eye and Bibi?
0:15:38 > 0:15:42Could co-operative hunting - lions helping each other to gain a meal -
0:15:42 > 0:15:45be the reason why they became social in the first place?
0:15:45 > 0:15:47Is that why they form prides?
0:15:51 > 0:15:58Co-operative hunting has long been considered by many as THE reason why lions live in prides.
0:16:00 > 0:16:04But how does it stack up, when looked at closely?
0:16:05 > 0:16:08The gang spot an opportunity too good to miss,
0:16:08 > 0:16:12a pair of mating warthogs, whose attention lies elsewhere.
0:16:28 > 0:16:31Older, more experienced, Lispy leads the front -
0:16:31 > 0:16:35the perfect ambush predator.
0:16:41 > 0:16:45But the sub-adults do appear to be co-operating and working with her.
0:16:50 > 0:16:53Eyes are locked on the target, as they fan out...
0:16:55 > 0:16:57..closing the net on their prey.
0:17:02 > 0:17:06Surely with this many lions, the warthogs don't stand a chance?
0:17:29 > 0:17:32In fact, the warthogs give them the slip.
0:17:32 > 0:17:36It seems here, at least, that hunting as a group didn't help,
0:17:36 > 0:17:39so just how strong is the evidence?
0:17:40 > 0:17:45This was Craig and the project's first line of investigation.
0:17:45 > 0:17:53If co-operation was a strong advantage from hunting, we would think of two possible ways
0:17:53 > 0:17:59that it helps. First is, it means the group will be more successful than a solitary,
0:17:59 > 0:18:03so they might succeed 40-50% of the time, instead of 10% of the time.
0:18:03 > 0:18:09And in fact, that's not seen, there's not a huge improvement in group performance
0:18:09 > 0:18:11by having more animals hunting together.
0:18:13 > 0:18:20And the second way that co-operation can be important is that a larger group can pull down a prey item
0:18:20 > 0:18:26that a solitary cannot possibly capture on her own and that we do see.
0:18:31 > 0:18:36So, group hunting is needed, in order to take large prey.
0:18:40 > 0:18:45And it is usually seen as the main advantage lion prides have over solitary cats.
0:18:53 > 0:18:56The buffalo is the lion's most formidable opponent.
0:18:57 > 0:19:00Over half a tonne of solid muscle.
0:19:05 > 0:19:09Where a single lion would struggle, together there is strength in numbers.
0:19:15 > 0:19:19Lions do co-operate when they're trying to catch buffalo and in
0:19:19 > 0:19:23reports of lions catching hippo, those have to be done by a group.
0:19:26 > 0:19:32But those are not essential in terms of keeping the pride well nourished through a year.
0:19:35 > 0:19:42Co-operative hunting, it turns out, is essential to take down large prey but the advantage it brings to lions
0:19:42 > 0:19:50isn't enough to drive the evolution of pride life alone. And it could be looked at as a disadvantage,
0:19:50 > 0:19:54forcing lions to work together to bring down large animals, like buffalo.
0:19:56 > 0:19:57If you are in a group,
0:19:57 > 0:20:02you have the problem of dividing the prey into ever smaller shares,
0:20:02 > 0:20:06but you can overcome that cost by actually going for the larger prey.
0:20:06 > 0:20:12So we could almost look at a preference for larger prey, as a way of compensation
0:20:12 > 0:20:18against the cost of having to share out one meal amongst many mouths.
0:20:23 > 0:20:30When, as I've seen, individual lions catch smaller prey, they can keep all the food for themselves.
0:20:38 > 0:20:43So why are Lispy and the gang hunting small warthog as a group?
0:20:51 > 0:20:54This, it turns out, is an illusion.
0:20:54 > 0:20:58Small prey predominates in the territory right now.
0:21:00 > 0:21:05Only one lion actually takes down the warthog, yet it appears as if
0:21:05 > 0:21:11they're co-operating, as the rest of the group have to be close to stand a chance of getting any food.
0:21:14 > 0:21:19Scrapping over the spoils is normal in lion prides and those closest
0:21:19 > 0:21:23to the action get significantly more food than the others.
0:21:24 > 0:21:31Once the prey is down, any pretence of co-operation is gone.
0:21:31 > 0:21:36They're so incredibly selfish and aggressive to each other.
0:21:36 > 0:21:40They're snarling at each other, they're pulling food out of each other's mouth.
0:21:40 > 0:21:45How could you really imagine that this animal's so nobly co-operative, given the incredibly
0:21:45 > 0:21:49grabby table manners they have, once they've actually got dinner in front of them?
0:21:49 > 0:21:56It's like they're eating together, despite the fact that it's such an annoying thing to do.
0:21:56 > 0:21:58They're together for some other reason.
0:22:08 > 0:22:13So, co-operative hunting alone can't explain why lions form groups.
0:22:16 > 0:22:20Co-operative hunting is something that lions can do because they live in groups,
0:22:20 > 0:22:25but it isn't the reason why they evolved this social way of life in the first place.
0:22:42 > 0:22:45Craig and his team needed to keep looking for answers.
0:22:49 > 0:22:50So what about the cubs?
0:22:55 > 0:23:02After all, the success of any lion pride is judged by the numbers of cubs it can raise over time.
0:23:10 > 0:23:15Watching how the cubs in my pride are nurtured and protected is revealing.
0:23:20 > 0:23:25They grow fast and begin eating meat at just six to eight weeks old.
0:23:28 > 0:23:33The young cubs feeding on a fresh kill belong to the three Graces' faction of the pride.
0:23:39 > 0:23:45In these lean times, cubs would normally have to scrap at the dinner table with the adults,
0:23:45 > 0:23:47fighting their corner for food.
0:23:49 > 0:23:50But not here.
0:23:54 > 0:23:58The mothers are being kept from the kill by adult pride male, Romeo.
0:24:04 > 0:24:08Himself, also showing surprising restraint.
0:24:12 > 0:24:17This is behaviour I've witnessed before and is a graphic illustration of how vital cubs are,
0:24:17 > 0:24:22not only to their mothers, but also to their fathers, the pride males.
0:24:25 > 0:24:29As the likely father to these cubs, Romeo's behaviour actively ensures
0:24:29 > 0:24:35his offspring, the future of his genes, gets the best start in life.
0:24:39 > 0:24:44Males of all other cat species play no role in the raising of their cubs
0:24:44 > 0:24:47but here, once again, lions are different.
0:24:51 > 0:24:54If cubs growing up in a pride had better nutrition
0:24:54 > 0:25:01and, as a result, better survival prospects, then this advantage could be the explanation for pride living.
0:25:02 > 0:25:06It's been one of the most strongly favoured theories over the years.
0:25:06 > 0:25:08Until now.
0:25:08 > 0:25:11When I first started studying lions, people used to think of
0:25:11 > 0:25:14mother lionesses as suckling their cubs communally,
0:25:14 > 0:25:18as nurturing them as a group. Could that be the reason why lions became social in the first place?
0:25:41 > 0:25:45For the first three months of life, White-Eye's four young cubs are dependent on milk.
0:25:50 > 0:25:55As her companion Bibi isn't lactating, the cubs are entirely dependent on their mum.
0:25:57 > 0:26:00There are no other females in this section of the territory.
0:26:06 > 0:26:10The more usual situation in a pride, is one of multiple mothers
0:26:10 > 0:26:13and multiple litters of cubs, forming a creche.
0:26:17 > 0:26:18It's a situation I've seen
0:26:18 > 0:26:20many times in the Marsh Pride.
0:26:23 > 0:26:28When White-Eye herself was a cub, she was nurtured in a creche with multiple mothers.
0:26:29 > 0:26:34And it does appear that cubs are being suckled by all the mothers indiscriminately.
0:26:36 > 0:26:40But does communal suckling give cubs in a creche an advantage over those
0:26:40 > 0:26:44raised by single mothers, like White-Eye?
0:26:44 > 0:26:47It's really fascinating that lions are one of the few species
0:26:47 > 0:26:50where cubs may nurse from more than one female.
0:26:55 > 0:26:57But when we looked at it in much more detail,
0:26:57 > 0:27:00we found there's a lot of conflict of interest going on.
0:27:00 > 0:27:04In fact, each mother would prefer to nurse only her own cubs.
0:27:07 > 0:27:08The problem for the mothers is,
0:27:08 > 0:27:11they've been out all night, looking for food.
0:27:11 > 0:27:16They've come back and they've got to sleep and so they've got to
0:27:16 > 0:27:21divide their time between allowing their cubs to catch up with them and then also to get a good nap.
0:27:21 > 0:27:25So it turns out the cubs are very crafty and they'd wait till the mothers were asleep
0:27:25 > 0:27:28and then they'd go sneaking in to another female that wasn't their own.
0:27:30 > 0:27:33So there wasn't that much real co-operation going on,
0:27:33 > 0:27:38but that the cubs are more like parasites, taking advantage of the inattentiveness of the mothers.
0:27:41 > 0:27:45And crucially, watching White-Eye's four cubs here
0:27:45 > 0:27:49shows that they are getting enough milk just from their own mother.
0:28:01 > 0:28:05Boisterous enough now to get on Bibi's nerves.
0:28:09 > 0:28:15Closer investigation by Craig and his team showed that whilst cubs in a creche can suckle
0:28:15 > 0:28:20from multiple mothers, they don't get any nutritional advantage.
0:28:24 > 0:28:29And the data clearly shows their survival chances are not increased.
0:28:33 > 0:28:37If communal suckling doesn't help us to answer why lions are the only
0:28:37 > 0:28:43living social cat, what else is there that could have driven lions to form prides?
0:28:50 > 0:28:52Perhaps the answer is defence.
0:28:56 > 0:29:00THUNDER
0:29:00 > 0:29:05They may be near the top of the food chain, but lions of the Marsh Pride
0:29:05 > 0:29:09still live in danger, from predators close to home.
0:29:15 > 0:29:20Two young, strong male outsiders are sniffing around the edge of the Marsh Pride,
0:29:20 > 0:29:24in search of territory and females with whom they can breed.
0:29:24 > 0:29:28Males, who given the chance will try to oust the current
0:29:28 > 0:29:31aging pride males, Clawed and Romeo.
0:29:45 > 0:29:48They spot Lispy and the eight young lions.
0:29:53 > 0:29:59It may be two against nine, but Lispy and the gang recognise the threat posed by them.
0:30:13 > 0:30:16The pair target their attack on the young males in the group,
0:30:16 > 0:30:20as chasing them off could give them access to the females.
0:30:37 > 0:30:42This bold incursion into Marsh Pride territory is perhaps
0:30:42 > 0:30:45their first show of serious intent - and more may follow.
0:30:48 > 0:30:53To win the Marsh Pride territory, the outsiders will ultimately
0:30:53 > 0:30:56need to displace the current pride males, Romeo and Clawed,
0:30:56 > 0:31:00an encounter which could happen at any moment.
0:31:05 > 0:31:09But Romeo and Clawed may be spending too much time with the three Graces,
0:31:09 > 0:31:13leaving the rest of the pride vulnerable.
0:31:13 > 0:31:16And for vulnerable, read, "cubs".
0:31:19 > 0:31:24If we think of cub rearing, it's not just a matter of delivering food to their young.
0:31:24 > 0:31:29Mothers also have to protect their young against various different enemies.
0:31:29 > 0:31:34We often think of an enemy of a lion as maybe being a leopard that might eat the cubs,
0:31:34 > 0:31:39but, in fact there's a much more common and more pervasive enemy - and that's their own species,
0:31:39 > 0:31:43And it's the male, the male that's not the father of the cubs.
0:31:48 > 0:31:55New males from outside the pride encountering young lions like White-Eye's cubs will kill them.
0:31:56 > 0:32:00Violent behaviour, known as infanticide.
0:32:02 > 0:32:09Infanticide is very common in nature and it's really widespread in the cats.
0:32:09 > 0:32:13If the fathers happen to be out patrolling the edge of the territory and a guy sneaks in,
0:32:13 > 0:32:18then the females may encounter a nomadic male, who will quickly try to eliminate the cubs.
0:32:24 > 0:32:28I've seen the impact of infanticide affect the Marsh Pride.
0:32:28 > 0:32:33Most dramatically, for a lone mother, known as Tamu, and her four young cubs,
0:32:33 > 0:32:37spotted by a nomadic male.
0:32:49 > 0:32:52To the male lion, the mother is a resource.
0:32:54 > 0:33:01He wants to be able to have her rear his offspring. He doesn't want to be a stepfather.
0:33:02 > 0:33:06So when he first encounters a new pride, he'll quickly
0:33:06 > 0:33:11try to eliminate those cubs that prevent the mothers from mating again for a year and a half.
0:33:13 > 0:33:19For as long as Tamu had dependent cubs, at least 18 months, she would not be ready to mate.
0:33:21 > 0:33:24Killing her offspring would bring her into season again
0:33:24 > 0:33:28and give this male a chance to father his own cubs with her.
0:33:30 > 0:33:34But lone females fight hard to protect their cubs.
0:33:46 > 0:33:51Tamu fought off the nomadic male, but there was a heavy price to pay.
0:34:00 > 0:34:03One cub was badly injured and later died.
0:34:08 > 0:34:11This mother's struggle to chase away the incoming male
0:34:11 > 0:34:14simply wasn't enough to protect all her cubs...
0:34:18 > 0:34:22..which may be why most prides contain multiple mothers,
0:34:22 > 0:34:25who, with their cubs, stick close together, forming a creche.
0:34:31 > 0:34:36If Tamu and her cubs had been part of a creche, perhaps things would have been different.
0:34:42 > 0:34:46A lone female has almost no chance to protect her cubs against a male.
0:34:46 > 0:34:50The male's much bigger, but sisterhood is powerful.
0:35:04 > 0:35:09Groups of females, working together, can stand up against the males,
0:35:09 > 0:35:12chase them away and effectively protect their cubs.
0:35:16 > 0:35:20So what you see with a creche, with a communal litter, is a defensive formation of females
0:35:20 > 0:35:24always ready to defend their cubs against invading males.
0:35:31 > 0:35:36At last, a reason for lionesses to group together - to protect their offspring.
0:35:36 > 0:35:41Who could argue with that? But there is a niggle with this theory.
0:35:44 > 0:35:50Lion's are not the only species with murderous stepfathers. You have other species that
0:35:50 > 0:35:56are infanticidal, like leopards, tigers, house cats, but all those species are solitary.
0:35:56 > 0:35:59So there's nothing unique about lions and facing that threat
0:35:59 > 0:36:02of having males that might come in and kill the cubs.
0:36:03 > 0:36:08The lions are already in a social formation, but then in this special
0:36:08 > 0:36:11case where they have the young, they draw together even tighter,
0:36:11 > 0:36:14so they're already living in a group, for some other reason.
0:36:14 > 0:36:18Infanticide is not the root cause of their sociality.
0:36:28 > 0:36:30So, on detailed investigation,
0:36:30 > 0:36:35it turns out that many of the obvious theories citing co-operative hunting...
0:36:36 > 0:36:38..communal suckling...
0:36:40 > 0:36:42..or protection from infanticide
0:36:42 > 0:36:45as the cause of lion prides don't provide the answer.
0:36:51 > 0:36:56'And remember these are theories I've held myself for many years.'
0:37:13 > 0:37:18With the main behavioural theories discounted, Craig and his team turned their attention
0:37:18 > 0:37:21to the places where lion prides lived.
0:37:24 > 0:37:28For my pride, the Marsh Pride, the extent of their territory
0:37:28 > 0:37:32has remained constant over all my years of watching them.
0:37:36 > 0:37:41Looking at how they use, defend and roam within their territory
0:37:41 > 0:37:44could hold the secret to understanding pride living.
0:37:53 > 0:37:58After their encounter with the nomadic males, Lispy and the gang
0:37:58 > 0:38:01have scattered and relocated to the opposite side of the territory.
0:38:03 > 0:38:07Away from the intruders, but into the area that the splinter group,
0:38:07 > 0:38:10known as the three Graces consider theirs.
0:38:22 > 0:38:26The three Graces, although once part of the main pride,
0:38:26 > 0:38:30do not tolerate other lions in what they consider as their territory...
0:38:31 > 0:38:34..even if they are part of the same extended family.
0:38:50 > 0:38:54The three Graces give short shrift to two of the young lions
0:38:54 > 0:38:58from Lispy's gang, who have become separated from the main group.
0:39:51 > 0:39:54This is the real relationship between neighbouring prides.
0:39:54 > 0:40:02Constant readiness to do battle, held in check by the threat of mutually-assured destruction.
0:40:05 > 0:40:10Having shown who's boss, the three Graces move off.
0:40:20 > 0:40:25The most violent encounters amongst lion prides are always over territory.
0:40:32 > 0:40:37The space in which lions live is so important that they literally shout about it.
0:40:37 > 0:40:42ROARING
0:41:04 > 0:41:09The lion's roar is amazingly primal, a terrifying sound.
0:41:09 > 0:41:14It's the declaration of territory ownership - "This is my place."
0:41:17 > 0:41:20But what can it tell us about the evolution of prides?
0:41:22 > 0:41:28To understand the roar in more detail, Craig and his team needed to start talking to the lions directly.
0:41:31 > 0:41:35We were able to record roars and then broadcast them back to the lions.
0:41:37 > 0:41:41And much to our surprise, they responded as if there was
0:41:41 > 0:41:43a real invader, right there in their bedroom.
0:41:50 > 0:41:55And the fact that lions often roar as a group gave the team a bit of a headache.
0:41:55 > 0:41:59To investigate, they had to play back different numbers of lions
0:41:59 > 0:42:03roaring to different numbered groups of real lions,
0:42:03 > 0:42:10but it produced perhaps the most surprising results of all of Craig's research.
0:42:10 > 0:42:15When we played back the roars, if we did one against one, there was no response,
0:42:15 > 0:42:18but three against one, they would always respond.
0:42:20 > 0:42:23And then we played the roars of three back to a group
0:42:23 > 0:42:26and three against three was the same as one against one
0:42:26 > 0:42:29and five against three was exactly the same as three against one.
0:42:31 > 0:42:36So with three invaders, five real lions would always go forward. That meant they could count.
0:42:36 > 0:42:40They could count how many invaders there were and how many they had in their own group,
0:42:40 > 0:42:43to be able to fight against the strangers. They could calculate the odds.
0:42:47 > 0:42:50As long as they outnumbered their opponents by two,
0:42:50 > 0:42:55lions would move towards rivals that appeared to be in their territory.
0:42:55 > 0:42:59That was the first experiment to show any animal, besides humans, could count
0:42:59 > 0:43:04and so we were really astonished. We thought these dumb blondes were not up to this kind of thing,
0:43:04 > 0:43:09but when it came to the fights against their neighbours, this was where they really were co-operative.
0:43:09 > 0:43:14The most co-operative we've ever seen the lions is when it's life or death, it's us against them.
0:43:16 > 0:43:22It's over territory that lions are the most co-operative, working together to declare
0:43:22 > 0:43:26ownership and even willing to risk their lives in its defence.
0:43:29 > 0:43:33ROAR AND COUNTER ROAR
0:43:36 > 0:43:41Territory clearly held the key to understanding why lions evolved their unique way of life.
0:44:21 > 0:44:24'The Marsh pride are a boundary pride.'
0:44:25 > 0:44:29Whilst much of their territory is within the protection of the Mara reserve,
0:44:29 > 0:44:35the absence of fences marking the boundary means part of their territory lies outside it.
0:44:50 > 0:44:55It brings them into close contact with the local Maasai.
0:45:34 > 0:45:39Lions have lived alongside pastoralists for hundreds, if not thousands, of years.
0:45:43 > 0:45:48Tompoi and his family have grazed cattle here for as long as I can remember.
0:45:52 > 0:45:54I first met him 30 years ago.
0:45:56 > 0:46:00THEY CONVERSE IN MAASAI
0:46:02 > 0:46:06Each day, he brings his cattle down to the edge of the reserve,
0:46:06 > 0:46:11to the spring that feeds the marsh, for water, a route he's taken for many years.
0:46:11 > 0:46:14And he regularly sees my lions in the area.
0:46:21 > 0:46:24- You see the lions, the Marsh lions, every day?- Every day.
0:46:28 > 0:46:32The marsh is a key part of my lions' territory.
0:46:32 > 0:46:35After all, that's why we call them the Marsh Pride.
0:46:36 > 0:46:38Why is it so important?
0:46:38 > 0:46:43Because this area provides shelter and ambush sites for them.
0:46:45 > 0:46:49And, crucially, attracts the lions' prey, looking for water and grazing.
0:46:58 > 0:47:02It's just as important an area for Tompoi,
0:47:02 > 0:47:05giving his cattle year-round access to water.
0:47:10 > 0:47:14- All of those cows are yours? - Yeah.- 200?- Yeah.- Whoa.
0:47:21 > 0:47:24'In many ways, the lion pride has similarities to human societies.'
0:47:26 > 0:47:30A pride territory is like the ancestral family estate.
0:47:35 > 0:47:42'In the same way that generation after generation of Tompoi's family have grown up and grazed cattle
0:47:42 > 0:47:45in this area, generations of the Marsh Pride, too,
0:47:45 > 0:47:49have been raised in this territory and continue to be so.
0:47:56 > 0:47:59With so little prey in the area at this time of year,
0:47:59 > 0:48:03the pride have been operating as three distinct factions.
0:48:05 > 0:48:07But things are about to change.
0:48:11 > 0:48:18Lispy approaches her two pride mates White-Eye and Bibi and is warmly greeted.
0:48:29 > 0:48:33Lispy's approach is followed by the young lions of the group.
0:48:35 > 0:48:42Whilst the mother's reaction to their daughters is warm, their sons receive a less welcoming reception.
0:48:51 > 0:48:56The young males will be driven out of this territory, but females stay,
0:48:56 > 0:49:01ultimately replacing their mothers, when they die, as the core of the pride.
0:49:09 > 0:49:14Pride's are, at their heart, a matriarchal society.
0:49:17 > 0:49:22The fact that I knew this generation's grandmothers and great-grandmothers as individuals
0:49:22 > 0:49:26is proof how successful this pride has been in this territory.
0:49:37 > 0:49:41But whilst I've studied the success of just this pride of lions,
0:49:41 > 0:49:44the Serengeti Lion Project has been busy recording
0:49:44 > 0:49:48the breeding success of a grand total of 28 study prides.
0:49:51 > 0:49:57And only by doing that, have they been able to collect enough data to discover the critical role
0:49:57 > 0:50:01territories played in shaping lion societies.
0:50:03 > 0:50:07Plotting the long-term success of their study prides
0:50:07 > 0:50:11on a map of the Serengeti revealed striking differences.
0:50:13 > 0:50:18Some prides had vastly greater breeding success than others.
0:50:18 > 0:50:21Shown here on a map as the deepest colour.
0:50:33 > 0:50:40'And, most tellingly, those prides with the greatest success shared something in common.'
0:50:45 > 0:50:50Craig, you've spent years examining the reasons as to why lions might be social.
0:50:50 > 0:50:54You've ticked off the reasons that don't seem to fit the picture, so what is it?
0:50:54 > 0:50:59Well, I wanted to bring you up here because I think the best way
0:50:59 > 0:51:02to think about lion sociality is to look at the landscape.
0:51:02 > 0:51:07If you look out across the plains, we see a river running through it
0:51:07 > 0:51:13and along the river there are certain spots that tributaries run together. They're confluences.
0:51:15 > 0:51:18Where you get water that persists well into the dry season,
0:51:18 > 0:51:23moisture that attracts the prey, so that the lions can feed
0:51:23 > 0:51:26throughout all of the year and shelter for the cubs.
0:51:28 > 0:51:31These are the places that have the highest real estate value.
0:51:31 > 0:51:34These are the places that a very successful female,
0:51:34 > 0:51:38if she were a solitary, would not be able to hold onto by herself.
0:51:38 > 0:51:41She would need to have her daughter stay with her.
0:51:41 > 0:51:45Her daughter who would then work with her mum, as a unit,
0:51:45 > 0:51:49to keep the strangers away and all the family jewels would be safe.
0:51:49 > 0:51:53The lion pride is a joint defence system against invaders
0:51:53 > 0:51:56who want to take away that high-valuable real estate.
0:52:02 > 0:52:09The map revealed the common feature for all the enduringly successful prides.
0:52:09 > 0:52:14Their territories were all centred around river confluences...
0:52:17 > 0:52:19..areas Craig has dubbed "lion hot-spots".
0:52:25 > 0:52:33There was a huge evolutionary advantage for lions to gang up, form prides, to hold and protect
0:52:33 > 0:52:36those areas which offered the best long-term success.
0:52:42 > 0:52:47Survival of the fittest - and the fittest here were those in prides.
0:52:49 > 0:52:53The Project finally had their answer.
0:53:01 > 0:53:07Pride life is a direct result of the landscape and the habitat in which lions evolved.
0:53:13 > 0:53:18For over 30 years, I've thought that the reason for lions' social living
0:53:18 > 0:53:20was somehow rooted in their behaviour.
0:53:22 > 0:53:26But Craig and his team's work has elegantly shown that, in fact,
0:53:26 > 0:53:30the root cause is not how, but where, they live.
0:53:32 > 0:53:36The reason I've been able to watch so many generations
0:53:36 > 0:53:39of the Marsh Pride is that their territory is a lion hot-spot.
0:53:50 > 0:53:54This is what I came to Africa to see and I've been fortunate
0:53:54 > 0:53:59to document the last 30 years of this amazing lion pride.
0:54:02 > 0:54:05Whilst watching my lions has helped me make sense
0:54:05 > 0:54:12of Craig and his team's work, their success and TV popularity masks a rather uncomfortable truth.
0:54:18 > 0:54:24Something Craig brought home to me graphically, projecting 35,000-year-old cave paintings
0:54:24 > 0:54:27from Europe onto a rock face in the Serengeti.
0:54:31 > 0:54:34These are pictures from France.
0:54:34 > 0:54:37This is amongst the oldest art in the world.
0:54:37 > 0:54:43They were discovered about 15 years ago and it has more pictures of lions than almost any other species.
0:54:43 > 0:54:46I mean, it's mind-boggling.
0:54:46 > 0:54:5235,000 years ago, to capture the sense of the lion.
0:54:52 > 0:54:56I mean, the quality of the observation is remarkable.
0:55:01 > 0:55:06This shows something that you and I have been talking about already - the way you identify the lions.
0:55:06 > 0:55:09- The whisker spots. - They've drawn the whisker spots
0:55:09 > 0:55:12and they didn't have Land Rovers, they didn't have binoculars.
0:55:12 > 0:55:15So unless we had The Flintstones, I mean, this is all being done
0:55:15 > 0:55:20without any assistance, from a safe distance presumably,
0:55:20 > 0:55:24because look, the lions are relaxed and the artist was able to get all these details.
0:55:24 > 0:55:27They were not scared of the lions while they were drawing.
0:55:27 > 0:55:30And the next slide, we can see the way they're...
0:55:30 > 0:55:35'Here were paintings from Southern France of lion prides in action, in staggering detail,
0:55:35 > 0:55:39'much as I would draw them today, even down to the whisker spots.'
0:55:48 > 0:55:51The Chauvet Cave, where the paintings are found,
0:55:51 > 0:55:55is in the limestone cliffs that have been carved out by the Ardeche River.
0:55:59 > 0:56:05And along with other paintings and artefacts, found as far apart as Alaska and Asia,
0:56:05 > 0:56:09they reveal, graphically, how lions were once a truly global species.
0:56:17 > 0:56:24In fact, after humans, the lion was once the most widespread land mammal on earth.
0:56:32 > 0:56:39Today, the lion is restricted solely to Africa and a tiny population of perhaps just 350 lions in India.
0:56:40 > 0:56:43And most of these populations are under threat.
0:56:45 > 0:56:48There's real cause for concern.
0:56:50 > 0:56:57The latest studies in the Mara show a decline of 30% in the lion population during the last 20 years.
0:56:57 > 0:57:03And in Africa, as a whole, the population has dropped to perhaps just 25,000 lions.
0:57:03 > 0:57:06Everywhere, virtually, the trend is downwards.
0:57:07 > 0:57:13Understanding the way in which the habitat has shaped lion societies and how change to it can affect
0:57:13 > 0:57:19these complex and fascinating creatures, is essential to helping to ensure their future success,
0:57:19 > 0:57:23a future which right now is anything but certain.
0:57:26 > 0:57:29Next time on The Truth About Lions....
0:57:30 > 0:57:34The world of the Marsh Pride changes dramatically with the arrival
0:57:34 > 0:57:36of the annual wildebeest migration.
0:57:36 > 0:57:39There are some new cubs,
0:57:39 > 0:57:42but the old guard are beginning to show their age.
0:57:45 > 0:57:51And I discover how the lion's unique social nature could be part of the reason for their worrying decline.
0:57:51 > 0:57:54If we look at all the remaining lion populations,
0:57:54 > 0:57:57there's a number of tiny populations scattered around Africa,
0:57:57 > 0:58:03but they need to be big enough, in order to be viable for the next century or the next millennium.
0:58:03 > 0:58:06And we believe there's only six of those left in Africa.
0:58:27 > 0:58:30Subtitles by Red Bee Media Ltd
0:58:30 > 0:58:33E-mail subtitling@bbc.co.uk