Planet Earth II

Male three-toed sloths living on in the mangroves on the island of Escudo in Panama have a problem when it comes to finding a mate. Even though the sloth can hear the call of a female, following it to its source requires overcoming the body of water surrounding his tree. Luckily, sloths are excellent swimmers; the male, determined in his quest, clambers from branch to branch, before dropping into the water and beginning his passage to a neighbouring thicket of mangroves. The sloth he does find here, however, is already carrying a baby and will not be ready to mate for another 6 months while its infant is still dependent on its mother.

At 3-metres long, Komodo dragons are the largest lizards on Earth but, being cold-blooded, they don't need to feed as often as an similarly sized mammal would to sustain their great size; a single meal can last a dragon a month. As the apex predators on the islands of Komodo and Rinca in Indonesia on which they live, their only competition is each other. When female dragons become ready to breed once a year, rival males fight to earn the right to mate. Using their tails for support, they stand up on two legs to wrestle with each other, each trying to topple the other. Back on all fours, the males bite with jaws lined with serrated teeth and lash at each other with their muscular tails. Eventually, one dragon is bested and falls to the ground.

Madagascar's size and length of isolation from neighbouring Africa have made it a hotbed for endemic species, notably lemurs, occupying every concieveable niche. The indri, the largest of the group, spends almost all of its time in the trees.

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Madagascar's size and length of isolation from neighbouring Africa have made it a hotbed for endemic species, notably lemurs, occupying every concieveable niche. Among them are ring-tailed lemurs which travel in search of fruit across the forest floor, rather than through the tree-tops like some of their more aboreal cousins.

Madagascar's size and length of isolation from neighbouring Africa have made it a hotbed for endemic species, notably lemurs, occupying every concieveable niche. Among them is the bamboo lemur, which has specialised to only eat bamboo.

The spiny forests of Madagascar are the home of Verreaux's sifaka. No predators can navigate the treacherous spines of the Didierea on which they forage. A mother with a tiny infant clinging to her back feeds on the small green shoots lining the edges of the Didierea branch. The youngster follows her suit, taking care to place its hands and feed around the spines. The mother leaps down from a tree onto the ground, hopping along in a sideways motion with her infant still clinging to her back, towards another tree, where the pair resume feeding.

Fernandina Island in the Galápagos is still volcanically active and, as such, doesn't support much plant life - certainly not enough to support the 7,000 or os marine iguanas that gather here. These reptiles instead head out to the sea each day where they can dive down 30 metres to spend up to half an hour grazing on the algae growing on the sea floor on a single breath. Back on land, they have mutualistic relationships with several smaller animals. Sally Lightfoot crabs eat dead skin that they pick off from the iguanas' bodies as they rest on the rocks, while Gálapagos laval izards clamber atop their hosts to hunt for small flies that pester the colony.

Sally Lightfoot crabs perform a cleaning service for marine iguanas on Fernandina Island in return for a meal, using their claws to exfoliate dead skin off their sunbathing hosts.

Galápagos lava lizards engage in a mutualistic relationship with marine iguanas on Fernandina Island. The iguanas permit the lizards to clamber atop their heads and bodies, where they can easily hunt the many flies that pester the larger reptiles.

Flies are an annoyance for the sunbathing marine iguanas on Fernandina Island in the Galápagos. The iguanas rely on the local lava lizards to handle the pests, allowing them to clamber atop their heads to reach the insects.

Baby marine iguanas burrow out from beneath the sands in which their eggs were laid, some distance the adults that gather on the black lava rocks at the edge of the sea. As the iguanas embark across the stretch of sand to join them, hordes of racer snakes emerge from between the nooks and crannies of the surrounding rocks and give chase. Some unlucky hatchlings are caught and are quickly engulfed in a ball of snakes. Others attempt to lay completely still to avoid giving away their presence to the snakes, which are now swarming dangerously close out on the sand. One hatchling decides to drop its guise and make a frantic break for it, even as more snakes emerge from seemingly every direction. It leaps from rock to rock, narrowly avoiding each predator, and manages to make it to the colony shaken but unharmed.

Each June on Fernandina Island, racer snakes await the emergence of marine iguana hatchlings. When the iguanas begin to journey acrosss the sand to get to the rest of the colony at the edge of the sea, the snakes give chase, shooting out from the nooks and crannies of the surrounding rocks. The snakes' eyesight is poor so they rely on movement to detect their prey, something which some baby iguanas exploit by lying very still to avoid giving away their presence. Others are more easily caught and quickly engulfed by a ball of several snakes as each vies to swallow the prey for itself.

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Summer in the Snares Islands off New Zealand sees the arrival of Snares penguins looking to pair up, breed and raise chicks before the season ends.

With no predators, the Snares Islands off New Zealand are an ideal place for seabirds to breed and raise their young. Among those that do are sooty shearwaters, which arrive each summer and dig burrows in the ground to use as nests. The shearwater parents head out to sea each day to collect food for their chicks.

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Among the many seabirds that come to the Snares Islands off New Zealand during the sumer to breed are Buller's albatrosses. Like other albatrosses, these birds mate for life. A male albatross has arrived early and eagerly waits for the arrival of his mate atop a nest. When she finally arrives, the first order of business is to renew their bonds after spending the past 6 months apart. They perform a special dance, complete with an assortment of head bobs and beak taps, before they begin to mate.

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The minimal seasonal variations in the tropics means that islands here often host seabirds year around. One such permanent resident, in the Seychelles, is the white tern, which lays its egg rather precariously in the crooks of tree branches, rather than building a nest. This is, as you'd expect, is a dangerous strategy. Other birds, such as the Seychelles fody, target unattended eggs to feed on the yolk inside. One tern mother returning to her egg to find it damaged and leaking yolk continues to sit atop it, driven by an overriding instinct to incubate. The luckier hatchlings are fed on a diet of small fish sourced from the surrounding waters by their mother.

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A Seychelles fody cracks into an unattended white tern egg, nestled simply and dangerously in the crook of a tree branch, and feeds on the yolk that drips out.

Lesser noddies come to the Seychelles to make nests in Pisonia trees. As they grow, the noddy chicks pick up the sticky seeds of the Pisonia, which they carry with them when they are fully fledged, dispersing the seeds to neighbouring islands.

Brown noddies come to the Seychelles to make nests in Pisonia trees, whose seeds latch onto noddy chicks as they grow. When the chicks fledge and fly to neighbouring islands, the Pisonia's seeds are dispersed. Sometimes, however, a fledgling that drops to the ground may become covered and completely encumbered by sticky seeds, and will be unable to free itself, eventually starving to death.

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Island inhabitants have often evolved in very specific conditions for millions of years. For these animals, a sudden change, such as the introduction of an invasive species, can be devastating. Such is the case for the red crabs of Christmas Island, whose population has been decimated by yellow crazy ants that were inadvertently introduced by humans arriving on ships. The crabs are defenseless against the tiny ants, which squirt debilitating acid into the crabs' eyes and mouth, rendering them blind. The crabs eventually die and are quickly dismembered by the ants. As a result, the number of crabs making their annual migration to the sea to breed and release their eggs has declined by several million in recent years.

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Yellow crazy ants were inadvertently introduced to Christmas Island by human visitors to the island. Here, they have devastated the population of endemic Christmas Island red crabs by millions. The ants attack the crabs, squirting debilitating acid into their prey's eyes and mouth and rendering them blind. Then, teams of ants work together to dismember the corpses and feed on the remains.

Zavodovski Island's chinstrap penguins form the largest penguni colony in the world. The seas surrounding the island are incredibly rich in food, but to live and raise chicks here, the penguins have to brave the extremely rough seas, an arduous 3-kilometre commute between the coast and the nest site, and the constant presence of predatory skuas.

Gangs of brown skuas on Zavodovski Island harass its colony of chinstrap penguins, looking snatch a vulnerable chick.