1
00:00:35,574 --> 00:00:39,362
(BIRDS AND INSECTS CHIRRUP)

2
00:00:42,454 --> 00:00:44,684
(SNAP OF TWIGS)

3
00:00:45,934 --> 00:00:50,564
100 million years ago,
forests like these were just developing.

4
00:00:50,734 --> 00:00:53,202
They were dominated by dinosaurs.

5
00:00:57,134 --> 00:01:03,573
But as the giant reptiles slept,
tiny creatures were stirring.

6
00:01:03,734 --> 00:01:06,168
They were the early mammals.

7
00:01:06,334 --> 00:01:08,165
Despite this humble beginning,

8
00:01:08,334 --> 00:01:12,168
their descendants would
ultimately take over the world.

9
00:01:12,334 --> 00:01:14,848
Yet the rise of this great dynasty

10
00:01:15,014 --> 00:01:17,733
was founded on the most surprising diet.

11
00:01:23,854 --> 00:01:28,644
Creatures very like those first mammals
are still around today -

12
00:01:28,814 --> 00:01:30,805
shrews.

13
00:01:30,974 --> 00:01:35,843
They hunted insects at night
when most of the dinosaurs were sleeping.

14
00:01:40,414 --> 00:01:44,202
As mammals, they could
generate heat in their tiny bodies

15
00:01:44,374 --> 00:01:47,684
so they could stay active in the cold night air.

16
00:01:47,854 --> 00:01:49,970
Doing this burns a lot of food,

17
00:01:50,134 --> 00:01:54,889
so they ate almost continuously,
as shrews still do.

18
00:01:56,894 --> 00:01:59,613
There's never enough food for a shrew,

19
00:01:59,774 --> 00:02:03,847
and rivals fight over hunting rights
with extraordinary ferocity.

20
00:02:04,014 --> 00:02:07,006
(HISSING AND SQUEAKING)

21
00:02:40,414 --> 00:02:44,123
This little insect-eater has now staked his claim

22
00:02:44,294 --> 00:02:47,092
to the food in this part of the woodland.

23
00:02:50,374 --> 00:02:54,686
When he meets a female,
he's almost as aggressive towards her

24
00:02:54,854 --> 00:02:57,322
as he is towards a rival male.

25
00:03:06,334 --> 00:03:10,646
After testing one another's strength,
the female accepts the male

26
00:03:10,814 --> 00:03:13,931
not just as a contestant, but as a mate.

27
00:03:17,974 --> 00:03:21,171
Two weeks later, the young are born.

28
00:03:21,334 --> 00:03:23,928
The mother has nourished them
inside her womb,

29
00:03:24,094 --> 00:03:26,892
so they arrive comparatively well-developed.

30
00:03:30,214 --> 00:03:32,853
Caring for the young is a crucial part

31
00:03:33,014 --> 00:03:37,087
of mammals' ''winning design'',
something few reptiles do.

32
00:03:37,254 --> 00:03:42,772
A mother shrew even quenches her baby's thirst
with her own saliva if necessary.

33
00:03:48,774 --> 00:03:55,612
Most important of all, she provides them
with that uniquely mammalian food, milk.

34
00:03:55,774 --> 00:03:59,892
This milk is so rich
that it takes a mere two weeks

35
00:04:00,054 --> 00:04:02,852
for the young to approach their mother in size.

36
00:04:03,014 --> 00:04:05,448
They are now quite a handful

37
00:04:05,614 --> 00:04:09,607
and need to be weaned from the nipple,
despite their protests.

38
00:04:12,934 --> 00:04:15,164
But the mother doesn't abandon them.

39
00:04:15,334 --> 00:04:18,929
She herself leads them into the world outside.

40
00:04:26,094 --> 00:04:30,804
The young have their own way
of ensuring they don't get lost.

41
00:05:27,494 --> 00:05:31,885
The first mammals lived
alongside the dinosaurs for a long time.

42
00:05:32,054 --> 00:05:34,887
But about 65 million years ago,

43
00:05:35,054 --> 00:05:38,763
when the dinosaurs so suddenly
and dramatically disappeared,

44
00:05:38,934 --> 00:05:42,290
they had their chance
to colonise new environments.

45
00:05:42,454 --> 00:05:47,528
At first they remained very much the same
small, scurrying little creatures.

46
00:05:47,694 --> 00:05:50,731
That, in fact, is a very versatile body pattern,

47
00:05:50,894 --> 00:05:55,092
and one of them, without much change,
took to the water.

48
00:05:55,254 --> 00:05:59,611
It hunts just as frenetically
as its cousins do on land,

49
00:05:59,774 --> 00:06:03,369
but it has a very different way
of catching insects.

50
00:06:11,574 --> 00:06:16,568
The water shrew's fur is oily
and sheds water with a flick.

51
00:06:21,454 --> 00:06:25,333
Its long whiskers help it
feel for prey underwater.

52
00:06:25,494 --> 00:06:29,373
Its ankles are hairy, so its feet act as paddles.

53
00:06:35,614 --> 00:06:38,572
It shines like silver, glistening from the bubbles

54
00:06:38,734 --> 00:06:43,091
trapped in its fur
as it searches everywhere for prey.

55
00:06:47,854 --> 00:06:51,244
Clinging to the underside
of a root, a dragonfly larva,

56
00:06:51,414 --> 00:06:55,851
but the shrew's whiskers
don't touch it and it's missed.

57
00:07:02,214 --> 00:07:04,887
But not this time!

58
00:07:15,694 --> 00:07:17,685
In Africa's Namib Desert,

59
00:07:17,854 --> 00:07:20,607
another insect-hunter swims after prey,

60
00:07:20,774 --> 00:07:24,084
but without a drop of water in sight.

61
00:07:29,974 --> 00:07:33,967
It's a sand swimmer, a golden mole.

62
00:07:36,214 --> 00:07:40,924
Sand, unlike water, scratches,
and it isn't transparent either,

63
00:07:41,094 --> 00:07:44,006
so the mole's eyes are covered in hairy skin

64
00:07:44,174 --> 00:07:46,449
and its head has become a leathery wedge

65
00:07:46,614 --> 00:07:49,686
with which it forces its way through the sand.

66
00:07:51,814 --> 00:07:55,773
As it digs, the sand collapses behind it

67
00:07:55,934 --> 00:07:58,528
making it impossible for a tunnel to form.

68
00:07:58,694 --> 00:08:03,245
So it doesn't dig through the sand,
it really does swim.

69
00:08:10,774 --> 00:08:13,652
Sound travels well in sand.

70
00:08:13,814 --> 00:08:17,648
Unlike shrews, which are adapted
to hear high-pitch sound,

71
00:08:17,814 --> 00:08:20,282
this mole detects very low ones,

72
00:08:20,454 --> 00:08:23,969
like the faint vibrations
made by foraging termites.

73
00:08:24,134 --> 00:08:26,011
(WHIRRING)

74
00:08:31,014 --> 00:08:34,165
Propelled by its flippers and guided by sound,

75
00:08:34,334 --> 00:08:38,043
the golden mole homes in on its prey.

76
00:09:09,214 --> 00:09:14,607
In North America, another mole
has paws that look like flippers.

77
00:09:18,734 --> 00:09:22,727
These help it to swim under ice
to collect insects,

78
00:09:22,894 --> 00:09:26,091
but this is not their primary purpose.

79
00:09:27,174 --> 00:09:33,044
This creature is a digger, a star-nosed mole.

80
00:09:34,134 --> 00:09:37,888
Its paws are spades for pushing aside soil

81
00:09:38,054 --> 00:09:42,889
while it tries to locate
its prey with its astonishing nose.

82
00:09:45,294 --> 00:09:48,730
This has 22 fleshy arms.

83
00:09:48,894 --> 00:09:51,727
Each is so densely packed with nerve endings

84
00:09:51,894 --> 00:09:57,093
that it could touch a pinhead
with its nose in 600 places at once,

85
00:09:57,254 --> 00:10:00,246
allowing it to locate the tiniest of prey.

86
00:10:02,774 --> 00:10:08,371
Living in soil rather than sand,
this mole can dig proper tunnels.

87
00:10:08,534 --> 00:10:10,764
It constructs a labyrinth of passages

88
00:10:10,934 --> 00:10:15,132
and patrols them to collect
any prey that drops into them.

89
00:10:28,934 --> 00:10:34,088
The star-nose, underground,
is largely beyond the reach of predators.

90
00:10:39,174 --> 00:10:45,409
Other insect-hunters, however, run along
trails above ground, and they are not so lucky.

91
00:10:46,814 --> 00:10:51,934
One of these lives here,
in the scrublands of East Africa.

92
00:10:56,574 --> 00:11:00,886
This tiny pathway through the withered grass

93
00:11:01,054 --> 00:11:06,174
is a sign that the insect-hunting rights
for this part of the world are taken.

94
00:11:06,334 --> 00:11:11,328
To advertise the fact, the owner has left
a little pile of its dung.

95
00:11:11,494 --> 00:11:13,724
But what could have made it?

96
00:11:13,894 --> 00:11:18,285
To find out, I can use
this tiny surveillance camera.

97
00:11:18,454 --> 00:11:21,014
If I put that there...

98
00:11:21,174 --> 00:11:26,806
then in front of it
put some twigs across the path.

99
00:11:27,974 --> 00:11:30,488
The creator of these runways is very fastidious

100
00:11:30,654 --> 00:11:35,170
and, with luck, it will stop
to clear away the twigs

101
00:11:35,334 --> 00:11:38,770
and then give us a chance
to have a good look at it.

102
00:11:40,374 --> 00:11:43,889
This is the picture from the camera I placed

103
00:11:44,054 --> 00:11:48,650
and this is from a camera further up the trail.

104
00:11:48,814 --> 00:11:52,090
Now all I have to do is wait.

105
00:12:03,454 --> 00:12:05,251
It's an elephant shrew.

106
00:12:10,094 --> 00:12:12,813
He's not going to like that!

107
00:12:14,334 --> 00:12:17,610
There you go. He's clearing his trail.

108
00:12:23,174 --> 00:12:25,563
No.

109
00:12:27,934 --> 00:12:31,370
Oh, dear! I'm afraid I've put in too much!

110
00:12:31,534 --> 00:12:37,643
The elephant shrew, or ''sengi'',
keeps its trails immaculate for good reason.

111
00:12:37,814 --> 00:12:41,090
It sprints to evade its enemies.

112
00:12:41,814 --> 00:12:46,092
Even the smallest twig
could cause a disastrous stumble.

113
00:12:57,134 --> 00:13:02,527
The goshawk has such keen eyesight
that spotting a sengi is easy.

114
00:13:05,574 --> 00:13:08,088
Catching one is another matter.

115
00:13:10,654 --> 00:13:13,691
The sengi holds a map of its trails in its mind,

116
00:13:13,854 --> 00:13:17,813
so in emergencies it can cut
corners to dive for cover.

117
00:13:26,214 --> 00:13:30,412
Even a brush with death
doesn't put a sengi off its food.

118
00:13:30,574 --> 00:13:32,644
Like all small insect-hunters,

119
00:13:32,814 --> 00:13:36,966
it needs to constantly fuel its internal fires.

120
00:13:40,534 --> 00:13:44,732
That is especially important
when there are young to feed.

121
00:13:47,294 --> 00:13:50,889
Incredibly, this sengi is only a few hours old.

122
00:13:54,414 --> 00:13:57,884
Few mammals are born
as well-developed as a sengi,

123
00:13:58,054 --> 00:14:00,966
and this gives them a crucial survival edge.

124
00:14:01,134 --> 00:14:04,570
Daytime in the African bush
is no place for the helpless.

125
00:14:04,734 --> 00:14:07,612
Sengis are born to run.

126
00:14:07,774 --> 00:14:10,493
Its appetite for milk is unquenchable,

127
00:14:10,654 --> 00:14:14,408
for growing at this speed
gives it constant hunger.

128
00:14:14,894 --> 00:14:18,284
Its mother has nipples near her shoulders,

129
00:14:18,454 --> 00:14:22,891
which are easier to reach
and presumably help a quick get-away.

130
00:14:29,214 --> 00:14:35,244
The baby will take solid food from its mother
on its very first day, if it gets a chance.

131
00:14:52,414 --> 00:14:54,882
With continued help from its mother,

132
00:14:55,054 --> 00:14:58,364
the youngster will be almost
fully grown within a week

133
00:14:58,534 --> 00:15:02,527
and be able to run as fast as her
along their race tracks.

134
00:15:18,214 --> 00:15:21,365
(BIG BEN CHIMES)

135
00:15:23,654 --> 00:15:28,808
Catching insects one by one
takes a lot of time and energy,

136
00:15:28,974 --> 00:15:31,488
and few creatures that feed that way

137
00:15:31,654 --> 00:15:35,044
can get enough to build and sustain big bodies.

138
00:15:35,214 --> 00:15:39,969
But some insect-eaters,
early in their history, 40 million years ago,

139
00:15:40,134 --> 00:15:43,365
solved that problem by broadening their diet.

140
00:15:43,534 --> 00:15:48,324
And one of their descendants lives
here in my garden in London.

141
00:15:48,494 --> 00:15:51,770
I can tempt it out
with a wide variety of food,

142
00:15:51,934 --> 00:15:54,892
including, for example, minced meat.

143
00:16:11,694 --> 00:16:15,164
The hedgehog is still very much
a creature of the night,

144
00:16:15,334 --> 00:16:18,485
but it's too big to hide in the leaf-litter,

145
00:16:18,654 --> 00:16:22,408
making it vulnerable to attack
from animals like foxes.

146
00:16:22,574 --> 00:16:26,567
To make up for this,
its hairs have become a cloak of prickles.

147
00:16:29,334 --> 00:16:35,523
If it thinks it's in real danger,
it's got a special trick.

148
00:16:41,494 --> 00:16:45,089
It will stay an impregnable spiny ball like this

149
00:16:45,254 --> 00:16:48,451
until it decides that danger has passed.

150
00:16:59,414 --> 00:17:04,568
One thing is guaranteed to make
a male hedgehog drop his guard -

151
00:17:04,734 --> 00:17:08,204
the promise of an amorous liaison.

152
00:17:09,654 --> 00:17:12,043
If you're outside on a spring evening,

153
00:17:12,214 --> 00:17:16,969
you may be lucky enough
to witness an extraordinary sight.

154
00:17:32,894 --> 00:17:36,045
You might think having
a coat of spines on your back

155
00:17:36,214 --> 00:17:41,447
would be a handicap
for the intimacies of courtship.

156
00:17:42,294 --> 00:17:47,209
Classical naturalists thought
hedgehogs actually mated

157
00:17:47,374 --> 00:17:50,172
belly to belly!

158
00:17:50,334 --> 00:17:54,532
The male noses the female's spines,
which seems to excite her.

159
00:17:56,654 --> 00:18:01,967
As far as he's concerned,
it does look rather painful.

160
00:18:07,974 --> 00:18:13,173
Whether the female flattens
her prickles to help is unclear,

161
00:18:13,334 --> 00:18:15,848
but it seems the old joke that asks

162
00:18:16,014 --> 00:18:19,051
''How do hedgehogs mate?''
was right all along.

163
00:18:19,214 --> 00:18:22,524
The answer is, of course, with great care.

164
00:18:39,374 --> 00:18:44,289
The early American insect-eaters
also had to protect themselves.

165
00:18:44,454 --> 00:18:48,129
They did so not with spines
but with armour plating.

166
00:18:50,654 --> 00:18:55,933
Armadillos, like hedgehogs,
grew large by broadening their diet.

167
00:18:56,094 --> 00:18:59,086
Their tastes change with the seasons.

168
00:19:01,574 --> 00:19:03,929
Fruit is easy to collect,

169
00:19:04,094 --> 00:19:07,211
but the nine-banded armadillo is not fastidious

170
00:19:07,374 --> 00:19:10,013
and picks anything that looks edible.

171
00:19:10,894 --> 00:19:13,852
(FRANTIC CHIRPING)

172
00:19:25,854 --> 00:19:30,769
It still eats insects,
but ants present it with a problem.

173
00:19:30,934 --> 00:19:34,165
Its armour may protect it from large predators,

174
00:19:34,334 --> 00:19:38,532
but it isn't a particularly good defence
against small prey.

175
00:19:45,934 --> 00:19:51,770
One extraordinary African
insect-hunter has no such trouble.

176
00:19:51,934 --> 00:19:54,494
It's a pangolin.

177
00:19:54,654 --> 00:19:57,851
Those horny scales, like the hedgehog's prickles,

178
00:19:58,014 --> 00:20:00,687
are made from modified hair.

179
00:20:05,494 --> 00:20:09,328
It's front claws are so big,
they're useless for walking.

180
00:20:09,494 --> 00:20:12,054
It trundles along on its hind legs,

181
00:20:12,214 --> 00:20:15,411
balancing its torso with its tail.

182
00:20:19,494 --> 00:20:23,328
Its front claws are reserved
for digging up ants.

183
00:20:23,494 --> 00:20:26,292
As it does so, it swallows stones.

184
00:20:26,454 --> 00:20:31,892
They accumulate in its muscular
stomach and grind up the ants.

185
00:20:48,254 --> 00:20:54,363
But these small underground ant colonies
are mere snacks to a pangolin.

186
00:20:58,454 --> 00:21:03,244
This is a real meal, a full-sized ants' nest.

187
00:21:03,414 --> 00:21:06,531
There are a million or so of them here.

188
00:21:06,694 --> 00:21:11,609
The pangolin smashes through
the nest wall with formidable power.

189
00:21:11,774 --> 00:21:15,005
Only an adult has the strength to do this,

190
00:21:15,174 --> 00:21:18,052
so the young stay with their mother,

191
00:21:18,214 --> 00:21:22,969
feeding in her wake until they're big enough
to dig for themselves.

192
00:21:34,494 --> 00:21:38,248
The angry ants swarm all over their attacker,

193
00:21:38,414 --> 00:21:41,406
but the pangolin's armour
is a very effective defence.

194
00:21:41,574 --> 00:21:44,611
Its eyes are protected by thick lids

195
00:21:44,774 --> 00:21:50,406
and its nostrils and ears have special valves
to keep the biting insects out.

196
00:21:54,694 --> 00:21:59,893
For its size, the pangolin
has the longest tongue of any mammal,

197
00:22:00,054 --> 00:22:02,329
and the stickiest saliva.

198
00:22:13,774 --> 00:22:17,050
Mammals didn't always
have ant colonies to feed on.

199
00:22:17,214 --> 00:22:19,284
The rise of social insects,

200
00:22:19,454 --> 00:22:22,605
60 million years after the first mammals,

201
00:22:22,774 --> 00:22:25,288
was a landmark in evolution.

202
00:22:25,774 --> 00:22:30,689
It was then termites and ants
began to build huge nests,

203
00:22:30,854 --> 00:22:33,812
each containing millions of individuals.

204
00:22:33,974 --> 00:22:38,445
Here was so much food
that insect-eaters could grow big.

205
00:22:44,574 --> 00:22:49,329
There are termites in the Americas
just as there are in Africa,

206
00:22:49,494 --> 00:22:52,611
so there are termite-eaters too.

207
00:22:52,774 --> 00:22:56,403
Here in Brazil is the biggest of them all,

208
00:22:56,574 --> 00:22:59,247
the giant anteater.

209
00:23:10,694 --> 00:23:13,083
(WHISPERING) Its eyesight is very poor

210
00:23:13,254 --> 00:23:19,363
and it relies mostly on its sense
of smell, which is very acute.

211
00:23:19,534 --> 00:23:24,528
If I keep downwind of it,
I may not disturb it too much.

212
00:23:26,734 --> 00:23:31,649
The truth is, ants and termites
aren't very nutritious,

213
00:23:31,814 --> 00:23:36,285
so the giant anteater
has to try and conserve energy,

214
00:23:36,454 --> 00:23:41,448
and one way is to sleep
for 15 out of 24 hours.

215
00:23:42,814 --> 00:23:46,693
It covers itself too with that big bushy tail

216
00:23:46,854 --> 00:23:50,244
to reduce heat loss to a minimum.

217
00:23:51,734 --> 00:23:56,888
It keeps its body temperature
as low as any mammal, 32 degrees.

218
00:23:58,054 --> 00:24:01,842
That means its brain doesn't work very fast.

219
00:24:02,014 --> 00:24:05,086
It's not an animal with lightning reactions

220
00:24:05,254 --> 00:24:07,688
or dazzling intelligence,

221
00:24:07,854 --> 00:24:11,130
but you don't really need that
if you're an anteater.

222
00:24:11,294 --> 00:24:13,933
I think I'll get out of its way.

223
00:24:21,014 --> 00:24:24,484
Termite mounds are more
numerous here than anywhere,

224
00:24:24,654 --> 00:24:29,170
but the challenges facing
a termite-eater are considerable.

225
00:24:31,974 --> 00:24:35,444
Anteaters and pangolins
have different ancestors,

226
00:24:35,614 --> 00:24:40,324
but the demands of their diet
have shaped them in similar ways.

227
00:24:40,494 --> 00:24:42,803
Both have big claws.

228
00:24:42,974 --> 00:24:46,046
The giant's are the largest of any mammal.

229
00:24:46,214 --> 00:24:48,967
Both have an immensely long tongue

230
00:24:49,134 --> 00:24:53,207
that slips through the tube
formed by the toothless jaws,

231
00:24:53,374 --> 00:24:57,049
so that both can virtually drink termites.

232
00:25:28,854 --> 00:25:32,642
He may lack teeth,
but I'm going to treat him with caution

233
00:25:32,814 --> 00:25:38,411
because those huge claws
and powerful front legs

234
00:25:38,574 --> 00:25:40,849
can be very dangerous.

235
00:25:41,414 --> 00:25:45,009
He can rip apart this termite hill,

236
00:25:45,174 --> 00:25:48,166
and if he wants to defend himself,

237
00:25:48,334 --> 00:25:53,124
he will use those big,
bowed legs and claws and grip you.

238
00:25:53,294 --> 00:25:56,969
It has been said that a carcass of a jaguar

239
00:25:57,134 --> 00:26:01,252
was found in the embrace of one of these.

240
00:26:05,454 --> 00:26:09,845
It only collected a few hundred
termites on that brief visit.

241
00:26:10,014 --> 00:26:12,130
As soon as it breaks into a mound,

242
00:26:12,294 --> 00:26:16,287
the inhabitants attack it
so ferociously they drive it away.

243
00:26:16,454 --> 00:26:19,651
Quick sampling like this
does have an advantage.

244
00:26:19,814 --> 00:26:23,250
The termites will soon replace
the ones they've lost,

245
00:26:23,414 --> 00:26:28,613
so in effect, it's harvesting
the termite hills in its territory

246
00:26:28,774 --> 00:26:31,686
in a way that ensures a continuous supply.

247
00:26:33,534 --> 00:26:36,207
It may not have a dazzling intelligence,

248
00:26:36,374 --> 00:26:42,643
but nothing exploits termites more effectively
than the giant anteater.

249
00:26:56,534 --> 00:27:00,925
To explore the origins
of this extraordinary animal,

250
00:27:01,094 --> 00:27:04,404
you have to go to a very surprising place.

251
00:27:09,974 --> 00:27:13,933
I'm near Messel, in Germany.
Behind me is a quarry

252
00:27:14,094 --> 00:27:19,043
rich in the fossilised remains
of animals that died 50 million years ago,

253
00:27:19,214 --> 00:27:23,287
and that was a pivotal time
in the history of the mammals.

254
00:27:29,694 --> 00:27:32,686
Even though these animals
lived a very long time ago,

255
00:27:32,854 --> 00:27:35,448
some look remarkably familiar.

256
00:27:35,614 --> 00:27:38,890
This is a tree anteater,

257
00:27:39,054 --> 00:27:43,366
very like the tamandua anteater
in South America today.

258
00:27:43,534 --> 00:27:46,810
All the insect collecting equipment is there -

259
00:27:46,974 --> 00:27:49,613
huge claws on the front legs,

260
00:27:49,774 --> 00:27:53,653
no teeth, and jaws fused into a tube

261
00:27:53,814 --> 00:27:56,408
through which a long tongue would have flicked.

262
00:27:56,574 --> 00:28:01,648
Alongside the anteater, the pangolin.

263
00:28:01,814 --> 00:28:06,649
Once more, it has huge claws and no teeth.

264
00:28:06,814 --> 00:28:10,773
Again, it looks identical to its living equivalent,

265
00:28:10,934 --> 00:28:14,085
the African pangolin of today.

266
00:28:20,054 --> 00:28:25,208
Why should these animals remain
unchanged for 50 million years?

267
00:28:25,374 --> 00:28:28,923
The rocks of Messel
provide an answer to that too.

268
00:28:29,094 --> 00:28:31,767
From them have come a termite -

269
00:28:31,934 --> 00:28:35,131
more importantly,
the queen of a termite colony -

270
00:28:35,294 --> 00:28:38,206
and it's the same in every important respect

271
00:28:38,374 --> 00:28:40,205
as its living relatives...

272
00:28:40,374 --> 00:28:42,649
and this is the key.

273
00:28:42,814 --> 00:28:46,284
If termites haven't changed for 50 million years,

274
00:28:46,454 --> 00:28:50,208
why change the design
of the perfect termite-eater?

275
00:28:52,254 --> 00:28:55,929
Even back then, the majority
of insects were airborne

276
00:28:56,094 --> 00:28:58,847
and out of reach
of ground-dwelling mammals.

277
00:28:59,014 --> 00:29:02,529
One mammal followed the insects into the air,

278
00:29:02,694 --> 00:29:07,006
and fossils of it have been
found in the Messel deposits.

279
00:29:10,374 --> 00:29:12,285
It's a bat.

280
00:29:12,454 --> 00:29:15,287
Flight and the ability
to catch insects on the wing

281
00:29:15,454 --> 00:29:19,811
is an extraordinary achievement.
How do bats do it?

282
00:29:23,694 --> 00:29:29,087
This is a great place for bats,
lots of insects flying around.

283
00:29:29,254 --> 00:29:34,408
Birds are feeding on them
as the bats sleep in their roosts.

284
00:29:34,574 --> 00:29:38,249
Soon it'll get dark,
and the birds will go to roost

285
00:29:38,414 --> 00:29:42,009
and the bats will come out to claim their share.

286
00:29:53,854 --> 00:30:00,009
At night, there are even more
flying insects than during the day,

287
00:30:00,174 --> 00:30:04,372
and by the mill stream there's
a colony of Daubenton's bats

288
00:30:04,534 --> 00:30:07,128
that are already stirring.

289
00:30:18,174 --> 00:30:21,450
Their little faces are so like a shrew's

290
00:30:21,614 --> 00:30:24,970
it's easy to imagine shrew-like
ancestors in the trees,

291
00:30:25,134 --> 00:30:28,763
jumping from branch to branch, chasing insects.

292
00:30:28,934 --> 00:30:32,006
Ever larger flaps of skin between their fingers

293
00:30:32,174 --> 00:30:38,170
helped to extend those jumps,
until eventually they could fly.

294
00:30:40,454 --> 00:30:43,014
And how they can fly!

295
00:30:43,174 --> 00:30:48,089
The change from a scurrying shrew
to a fluttering bat

296
00:30:48,254 --> 00:30:53,248
is the most magical
in the whole history of mammals.

297
00:31:11,574 --> 00:31:14,964
The bats' mastery of flight is so complete

298
00:31:15,134 --> 00:31:18,410
that few insects can
out-manoeuvre them in the air.

299
00:31:20,734 --> 00:31:24,966
The bat scoops up the moth
with the membrane around its tail,

300
00:31:25,134 --> 00:31:28,365
then passes it forward to the mouth.

301
00:31:35,694 --> 00:31:39,403
Their ground-living ancestors
probably used sound

302
00:31:39,574 --> 00:31:43,613
to find their way in the night-time forest,
as shrews still do.

303
00:31:43,774 --> 00:31:46,732
Bats then perfected that technique,

304
00:31:46,894 --> 00:31:49,852
using sound frequencies beyond our hearing.

305
00:31:50,014 --> 00:31:54,053
A bat detector makes those calls audible to us.

306
00:31:55,054 --> 00:31:58,683
Bats emit high-intensity pulses of sound,

307
00:31:58,854 --> 00:32:01,209
then listen to the echoes that bounce back.

308
00:32:01,374 --> 00:32:05,253
Their brains then process these reflections

309
00:32:05,414 --> 00:32:08,884
to give a three-dimensional image
to their surroundings

310
00:32:09,054 --> 00:32:11,329
and their prey.

311
00:32:11,494 --> 00:32:14,327
(SQUEAKS AND CLICKS)

312
00:32:16,734 --> 00:32:19,328
Moths, with their rather laborious flight,

313
00:32:19,494 --> 00:32:21,849
are relatively easy to catch.

314
00:32:27,694 --> 00:32:30,447
Some evolved a defence, a simple ear,

315
00:32:30,614 --> 00:32:34,129
so when they hear the sonar
of a bat approaching,

316
00:32:34,294 --> 00:32:36,524
they can swerve out of the way.

317
00:32:39,054 --> 00:32:42,285
So one bat changed tactics.

318
00:32:43,614 --> 00:32:46,606
The long-ear doesn't hunt with sonar,

319
00:32:46,774 --> 00:32:50,562
it uses its enormous ears to listen for prey.

320
00:32:53,774 --> 00:32:57,244
It can even filter the faint sound
of a moth's wing-beats

321
00:32:57,414 --> 00:32:59,928
through the noise of the rushing water.

322
00:33:08,654 --> 00:33:11,771
Its sonar guides it through the branches,

323
00:33:11,934 --> 00:33:17,645
but as it approaches the moth,
it enters ''stealth mode''.

324
00:33:23,374 --> 00:33:27,811
Now it's guided solely
by the noise of the moth's wing-beats.

325
00:33:27,974 --> 00:33:29,965
But the system isn't perfect.

326
00:33:30,134 --> 00:33:32,602
The bat can hear the moth through the leaf,

327
00:33:32,774 --> 00:33:36,164
and it's approaching it from the wrong side.

328
00:33:45,334 --> 00:33:47,973
A lucky escape for the moth.

329
00:33:48,934 --> 00:33:52,893
But now the bat has come round
to the other side.

330
00:33:53,054 --> 00:33:57,093
If the moth stays still,
it doesn't make any noise at all,

331
00:33:57,254 --> 00:33:59,404
so the bat can't locate it.

332
00:34:09,174 --> 00:34:13,087
But sooner or later,
the moth will have to move.

333
00:34:16,814 --> 00:34:19,931
And that is its undoing.

334
00:34:24,774 --> 00:34:28,449
How can a bat catch prey that is silent

335
00:34:28,614 --> 00:34:31,526
in a place like this,
so cluttered with vegetation

336
00:34:31,694 --> 00:34:35,164
that echolocation shouldn't work?

337
00:34:36,454 --> 00:34:41,005
These places are difficult to navigate
but are full of food.

338
00:34:41,174 --> 00:34:43,290
Spiders are more nutritious than moths,

339
00:34:43,454 --> 00:34:45,365
but they're silent, venomous

340
00:34:45,534 --> 00:34:48,173
and construct webs that are so strong

341
00:34:48,334 --> 00:34:52,122
that a bat could become fatally
entangled in the sticky silk.

342
00:34:54,534 --> 00:34:56,729
Here comes Natterer's bat.

343
00:34:56,894 --> 00:35:01,172
It seems aware of the almost
microscopically thin threads,

344
00:35:01,334 --> 00:35:05,725
and with surgical precision,
removes the spider from its web.

345
00:35:26,214 --> 00:35:30,412
It even reverses away from the web
to avoid getting entangled.

346
00:35:30,574 --> 00:35:36,012
To detect the threads and recognise
on which side the spider is sitting

347
00:35:36,174 --> 00:35:39,166
must be the ultimate refinement of sonar.

348
00:36:01,174 --> 00:36:03,529
Mexican free-tailed bats.

349
00:36:03,694 --> 00:36:08,324
They form some of the biggest
and densest assemblages of mammals

350
00:36:08,494 --> 00:36:10,928
found anywhere on the planet.

351
00:36:11,094 --> 00:36:13,847
There are 12 million of them in this cave alone.

352
00:36:14,014 --> 00:36:18,166
Where does such a vast number
find enough food,

353
00:36:18,334 --> 00:36:20,973
within flying distance of where they roost?

354
00:36:21,134 --> 00:36:24,922
That puzzle baffled people for a long time.

355
00:36:25,094 --> 00:36:29,007
Now we're discovering what they feed on

356
00:36:29,174 --> 00:36:32,883
and where they find it -
and it's very surprising.

357
00:37:02,094 --> 00:37:05,643
A few years ago, pilots flying above Texas

358
00:37:05,814 --> 00:37:09,250
reported seeing bats at high altitude.

359
00:37:09,414 --> 00:37:14,249
Scientists investigated and made
an extraordinary discovery.

360
00:37:37,774 --> 00:37:42,894
As I climb into the evening sky,
the weather conditions seem good.

361
00:37:45,934 --> 00:37:49,813
But the local weather radar
shows a storm nearby,

362
00:37:49,974 --> 00:37:51,965
growing with alarming speed.

363
00:37:52,134 --> 00:37:56,685
However, I needn't worry. This is not a storm.

364
00:37:56,854 --> 00:37:59,846
It's the bats we just left, leaving their roost.

365
00:38:00,014 --> 00:38:04,530
Starting from a number of points,
each is the mouth of a cave.

366
00:38:04,694 --> 00:38:09,404
Swarms are vast, with up to
20 million bats leaving each entrance.

367
00:38:09,574 --> 00:38:15,171
Some fly low over Texas,
but, curiously, most start to climb.

368
00:38:19,454 --> 00:38:23,732
At 10,000 feet up,
bats are so widely dispersed

369
00:38:23,894 --> 00:38:25,885
that it's difficult to see them.

370
00:38:26,054 --> 00:38:29,012
I've got with me my bat detector.

371
00:38:29,454 --> 00:38:31,843
(HIGH-PITCHED BUZZ)

372
00:38:32,014 --> 00:38:36,530
There's one, and that is a feeding buzz.

373
00:38:36,694 --> 00:38:40,209
They're eating something, but what?

374
00:38:49,094 --> 00:38:53,804
Already a kilometre above the ground,
most are still climbing.

375
00:38:53,974 --> 00:38:58,365
The radar picks up another front
blowing in from New Mexico,

376
00:38:58,534 --> 00:39:01,048
and the bats are flying towards it.

377
00:39:01,214 --> 00:39:05,287
What could there be to attract them
to these great heights?

378
00:39:05,454 --> 00:39:10,289
Scientists find out
what's flying high in the sky at night

379
00:39:10,454 --> 00:39:13,048
with a device like this.

380
00:39:16,614 --> 00:39:20,812
And in it...moths.

381
00:39:22,174 --> 00:39:24,210
Vast numbers of these insects

382
00:39:24,374 --> 00:39:29,129
use the prevailing winds at altitude
to travel from the tropics to feed,

383
00:39:29,294 --> 00:39:34,846
and bats travel up to three kilometres
into the night sky to catch them.

384
00:39:40,574 --> 00:39:43,725
Bats are so numerous and so voracious

385
00:39:43,894 --> 00:39:47,330
that the individuals in this one cave below me

386
00:39:47,494 --> 00:39:52,170
eat 120 tonnes of insects every night.

387
00:40:02,654 --> 00:40:06,567
If bats have such ravenous appetites,

388
00:40:06,734 --> 00:40:11,091
how do they survive winter
when there are no insects around?

389
00:40:11,254 --> 00:40:13,484
In Texas they migrate.

390
00:40:13,654 --> 00:40:18,887
Here in Canada they have
a truly radical solution.

391
00:40:39,654 --> 00:40:43,044
(WHISPERING)
Outside, it's 20 degrees below freezing.

392
00:40:43,214 --> 00:40:45,808
Inside, icicles hang from the ceiling.

393
00:40:45,974 --> 00:40:49,887
Yet these little brown bats

394
00:40:50,054 --> 00:40:55,367
can survive throughout the winter
without a single meal.

395
00:40:56,494 --> 00:40:58,530
How do they do it?

396
00:41:00,734 --> 00:41:02,725
The thermal imaging camera

397
00:41:02,894 --> 00:41:07,649
is showing my face as red and orange.

398
00:41:07,814 --> 00:41:11,284
That's because it's warm. I'm a mammal.

399
00:41:11,454 --> 00:41:15,845
More precisely, I'm losing energy as heat.

400
00:41:16,014 --> 00:41:21,884
These little bats are blue because they are cold,

401
00:41:22,054 --> 00:41:25,763
as cold as the rock to which they're clinging.

402
00:41:25,934 --> 00:41:30,405
As the bats are no longer losing
any heat to their surroundings,

403
00:41:30,574 --> 00:41:33,566
they're using hardly any energy at all

404
00:41:33,734 --> 00:41:38,250
and their metabolism
has slowed down almost to a stop.

405
00:41:39,694 --> 00:41:42,333
Although they're in the deepest hibernation,

406
00:41:42,494 --> 00:41:46,282
they have to wake up
every now and then to drink.

407
00:41:46,454 --> 00:41:49,127
As they fire up their body chemistry,

408
00:41:49,294 --> 00:41:53,970
their image on the thermal camera
glows like a furnace.

409
00:42:19,254 --> 00:42:22,849
Once awake, a male seeks out
the slumbering females.

410
00:42:23,014 --> 00:42:25,209
This one won't get a warm reception,

411
00:42:25,374 --> 00:42:28,810
but he won't meet with much resistance either.

412
00:42:42,934 --> 00:42:47,007
He'll mate with several more
and then, after a drink,

413
00:42:47,174 --> 00:42:50,405
he will return to sleep until the spring.

414
00:43:01,534 --> 00:43:06,210
The power of flight not only enabled
bats to catch insects in the air,

415
00:43:06,374 --> 00:43:09,207
it also allowed them to extend their range

416
00:43:09,374 --> 00:43:12,366
far beyond that of any other mammal.

417
00:43:27,414 --> 00:43:32,568
Bats were the first mammals
to find their way to fragments of land

418
00:43:32,734 --> 00:43:36,283
that were isolated
in the South Pacific - New Zealand.

419
00:43:36,454 --> 00:43:41,448
Here there were no cats, no rats,
but lots of insects.

420
00:43:41,614 --> 00:43:44,811
It was paradise for any insect-hunter.

421
00:43:44,974 --> 00:43:47,329
So the bats flourished,

422
00:43:47,494 --> 00:43:51,453
and their descendants
are still here, somewhere.

423
00:43:59,054 --> 00:44:02,649
To see them, I must wait for darkness.

424
00:44:05,254 --> 00:44:07,370
(CREATURES CALLING)

425
00:44:17,534 --> 00:44:21,004
This is the species I've been waiting for.

426
00:44:22,854 --> 00:44:27,325
These bats look normal enough,
but bats are aerial predators

427
00:44:27,494 --> 00:44:30,770
and much of the uneaten prey
in New Zealand is on the ground.

428
00:44:32,974 --> 00:44:36,728
They can fly all right,
but our infra-red camera reveals

429
00:44:36,894 --> 00:44:41,604
they also have
a very un-bat-like way of hunting.

430
00:44:42,454 --> 00:44:46,413
They land on the ground
and forage through the leaf litter,

431
00:44:46,574 --> 00:44:48,724
just like shrews.

432
00:44:57,694 --> 00:45:01,972
They walk on their wrists
with the finger bones pointing upwards

433
00:45:02,134 --> 00:45:05,092
and slotted into a groove along the upper arm.

434
00:45:07,494 --> 00:45:10,213
Now they're hunting as a pack.

435
00:45:10,374 --> 00:45:15,084
Insects and small creatures
fleeing from the jaws of one

436
00:45:15,254 --> 00:45:17,973
run straight into those of another.

437
00:45:25,414 --> 00:45:27,291
Worms are a favourite.

438
00:45:27,454 --> 00:45:31,413
So much more satisfying
than several hundred mosquitoes.

439
00:45:31,574 --> 00:45:35,567
They don't want to share them
with one another either.

440
00:45:53,734 --> 00:45:57,010
They complete their meal
with a drink of nectar

441
00:45:57,174 --> 00:46:00,689
from the Hades plant
that bloom flat on the ground.

442
00:46:00,854 --> 00:46:03,926
They're this plant's pollinators.

443
00:46:04,094 --> 00:46:07,052
Relationships between a plant and its pollinator

444
00:46:07,214 --> 00:46:09,409
take a long time to evolve, so these bats

445
00:46:09,574 --> 00:46:12,805
must have been scuttling over
the New Zealand forest floor

446
00:46:12,974 --> 00:46:15,727
for many millions of years.

447
00:46:17,694 --> 00:46:21,892
Worms and nectar are easy prey,
but what about this?

448
00:46:22,054 --> 00:46:26,809
It's a weta, a giant flightless cricket,

449
00:46:26,974 --> 00:46:29,807
with spiny legs and ferocious jaws.

450
00:46:29,974 --> 00:46:35,287
How could bats, whose ancestors
ate mosquitoes, tackle this?

451
00:46:42,814 --> 00:46:47,763
The weta can flick its back legs forward
with surprising force.

452
00:46:48,374 --> 00:46:50,444
Even if you dodge that,

453
00:46:50,614 --> 00:46:53,765
you still have to contend
with its powerful jaws.

454
00:47:08,334 --> 00:47:11,167
The giant insect gains the upper hand...

455
00:47:16,094 --> 00:47:19,609
..but it's soon overwhelmed by numbers.

456
00:47:19,774 --> 00:47:24,006
These extraordinary bats
now fight one another over its remains

457
00:47:24,174 --> 00:47:26,483
with equal ferocity.

458
00:47:32,814 --> 00:47:36,523
Evolution doesn't often go into reverse,

459
00:47:36,694 --> 00:47:39,049
but it seems to have done so here.

460
00:47:39,214 --> 00:47:42,843
After several million years of aerial combat,

461
00:47:43,014 --> 00:47:45,847
these bats are reverting
to the hunting techniques

462
00:47:46,014 --> 00:47:48,244
of their shrew-like ancestors.

463
00:48:01,974 --> 00:48:06,013
Mammals have pursued insects
to the far corners of the earth.

464
00:48:06,174 --> 00:48:10,565
They chased them up to the skies
and back to the ground again.

465
00:48:10,734 --> 00:48:14,124
The insect-eaters were there
right at the beginning

466
00:48:14,294 --> 00:48:17,730
of the rise of mammals,
and they're still here today.

467
00:48:17,894 --> 00:48:22,888
They're one of the great success
stories in the life of mammals.