LIVE: Greatest Fights In The Animal Kingdom: Part 7 | BBC Earth

And weigh up to five kilos. These prize fish have monstrous appetites and surprisingly bloodthirsty tastes. So some fly fishermen opt for something a little more substantial. Here the insect imitations have been replaced with fluffy imitation mice. House mice first arrived in New Zealand as stowaways on European boats. This youngster is looking for his next meal. New Zealand is a modern paradise for newcomers from around the world. A sally lightfoot crab. One of thousands of shore crabs just waiting for their moment. Every day they gather on the tropical shores of Brazil. Waiting for the tide to go out, which exposes their feeding grounds. Seaweed covered rocks a hundred meters from the shore. Getting there is a race against the tide. They leap from rock to rock. These crabs seem to be afraid of the water. Its blunt teeth can easily grip and crush a crab's shell. It's the crab's deadliest enemy. But the crab's feeding grounds are still a long way off. Crossing the land. Reset the ambush. To feed, the crabs must keep going. Made it. Risking life and limb to graze on these seaweed pastures. But in two hours' time, when the tide starts to turn, they will have to run the gauntlet all over again. Back in the Australian rainforest, this weaver ant fortress sits at the heart of a rich territory. Hunting parties go out to gather food to fuel their growing numbers. Some canopy caterpillars are not killed, but farmed by the ants. They exude a sugary secretion that the ants collect. In return, the ants mount a guard to protect the caterpillar wherever it goes. But a successful colony inevitably attracts enemies. This jumping spider's body shape resembles that of an ant. A disguise good enough to fool these nursery guards. It's after one of the colony's most valuable assets, the grubs. In a colony numbering tens of thousands, a single grub is an insignificant loss. But the rich territory of a successful colony draws more destructive enemies. Raiders from a neighboring weaver ant colony looking to expand their own empire. Invaders are quickly spotted. The guard releases pheromones to alert the rest of the colony. They stream out of the nest to defend their home. If the home defenses fail, the colony will be wiped out. Some of the defenders deploy their most potent weapon. They squirt formic acid. The stinging liquid halts the invaders in their tracks. And now the home guard can go on the offensive. Home and territory are secure once again. A colony may lose many workers in defense of its home. But their sacrifice helps safeguard the next generation. It's now midsummer and the sun is shining at full strength. The increasing warmth is the cue for an Atlantic lobster to start on a long journey. She spent the winter 250 meters down, far beyond the reach of the storms. But it was cold down there and now she needs to find warmer water. So she's marching towards the shallows. They, however, are 150 kilometers away. After a month of walking, she finally arrives at her favorite sandbank. But she's not the first here. Dozens of other lobsters have already dug themselves homes in the sand and they don't intend to surrender them to newcomers. Size counts for everything in these battles. The new arrival is in urgent need of a pit. And since she weighs a hefty seven kilos, she stands a good chance of getting one. She's won. These battles continue for the next two months and they're crucial. For the females must have both shelter and warm water if they're to raise their young. For the last seven months, each of these females has been carrying around about 20,000 fertilized eggs. But their task is approaching its end. The warmth of the shallows is speeding the eggs development. Two more months and the eggs are ready to hatch. At first, they're not very good at swimming. But within a few minutes, the babies are able to set off in a purposeful way. Danger passed. And that's just as well. Because he is a father. And he's guarding some very precious eggs. For the last few weeks, females one after the other have visited him and entrusted him with their offspring. Some are now almost ready to hatch. There are several clutches on the leaf and those at the top, the most recently laid, are barely a day old. But in the jungle, there's always someone out to get you. This wasp is a specialist hunter of frog's eggs. It's noticed the wriggling tadpoles at the bottom of the leaf. He mustn't move. The youngest eggs are the most vulnerable and he can't guard them all. But these tadpoles are not as helpless as they might appear. Incredibly, the unhatched tadpoles can sense danger and the oldest and strongest wriggle free and drop into the stream below. The eggs at the top of the leaf, however, are still too young to hatch. And now the wasps know they're there. But the male's back looks very like the youngest cluster of eggs. That seems to confuse the wasps. Using his own body as a decoy is a huge risk. The wasp's stings could kill him. He's managed to save most of his young. He'll have to remain on guard for another two weeks. But in the jungle, just surviving the day can count as a success. This is one of them. From the purposeful way in which he's walking, it's clear that the search for prey has started. The other members of the team are not far away. They've been steadily following the monkeys for about 20 minutes, looking for an opportunity. The technique they'll almost certainly use is that one of them will be driving the colobus ahead of him and there will be others that go up on either side, blockers who won't make any attempt to catch the monkeys, and then there are chasers who go and grab at the monkey if they can. And finally, there's one male who will go up ahead and ambush it, so bringing the whole trap closed. The monkeys are now getting alarmed. A driver's going up to prevent the group from settling and to drive them towards an area where they're more easily trapped. The blocker says, now, quietly come ahead of the colobus. He's halfway up the tree now. He's deliberately making himself conspicuous. Now it looks as though they're all in position. The driver's gone up, the blockers have gone up, and now the one who's going to make the ambush and close the ring, he's gone up too. The colobus will be very lucky if they escape now. They've got one. The hunters are tearing it apart. Everyone, the hunters in the trees and the spectators on the ground, are screaming with excitement. And now the kill is brought down so that the females and others can share it. And there's the reward for that long chase, the divided body of a colobus monkey. These blood-stained faces may well horrify us, but we might also see in them the face of our long-distant hunting ancestors. And if we are appalled by that mob violence and bloodlust, we might also see in that too, perhaps, the origins of the teamwork that have, in the end, brought human beings many of their greatest triumphs. In only a few months' time, the water here will cease to flow. 8,000 square kilometres of swamp will dry and disappear. And all the hippos of the Okavango will face real hardship. Water is the hippo's sanctuary. It keeps them cool in the baking heat and provides the vegetation on which they depend. And safety away from predators. But with all of this slowly evaporating, everyone will need to be prepared. The calf is now several weeks old and has built up his strength. It's time for him to meet the family. Returning to the pod with a new baby is inevitably risky. A mother has to re-establish that she's a member of the pod. And in the excitement, a clumsy adult could crush her calf. The dominant bull is right in her path. If she stands her ground with him, half her battle could be won. But the real problem comes from an unexpected place. Her previous calf is showing an unhealthy interest. She's battle-scarred and appears to have a quarrelsome nature. Genesis or curiosity? Whichever it is, it's dangerous. Her calf is far too young to be pushed around like this. He's frightened and stays close to his mother. This has turned into an attack and the mother must put a stop to it. The pair remain on the periphery of the pod. But the rest of the family can still hear them. Hippos are thought to be the closest living relatives of whales. And they too make most of their vocalisations underwater. Their head and jawbones capture vibrations and transmit them directly into the ear. Vibrations become sound. And in these quiet waters, these can carry up to a mile. They're setting off on the greatest overland trek made by any animal. Wherever grass-eaters travel, predators are on the move. Here they are. Arctic wolves. They must seize their chance while the caribou pass through their territory. The wolf runs at the herd, trying to flesh out the weak or the slow. A calf is separated. At full tilt, 60 kilometres an hour, the wolf is just faster. The calf has stamina. Only a few weeks old and this calf's will to survive is remarkable. And it needs to be. For these young caribou have now started a journey that will last a lifetime. Forever chasing the seasonal growth of the grass on which they depend. Like all grassland creatures, they are at the mercy of these unpredictable but ultimately bountiful lands. Grass can survive some of the harshest conditions on Earth. Flood, fire and frost, and still flourish. So it is that grasslands provide a stage for the greatest gatherings of wildlife on planet Earth. St Andrew's Beach is one of the most crowded on the planet and so holding a territory here is a constant battle. This bull elephant seal holds the mating rights to 60 females. For two months, he's guarded this stretch of beach. Unable to feed, he's losing 10 kilos a day and he's exhausted. But other bulls are lying around, waiting their chance. Blubber, 15 centimeters thick, is protection against the cold, but not from the impact of a four-ton opponent. He holds his ground and forces the intruder back out to sea. Life in the Antarctic is harsh indeed, but all these creatures come here because the Southern Ocean is one of the richest on Earth. Trout were first introduced to these pristine rivers for sport in the late 1800s.