The Mating Game

As fresh rains create pools of water in South Africa, male African bullfrogs emerge en masse to breed. Each male yearns to occupy the centre of the breeding pool and will engage in sometimes-deadly clashes to do so. Once in position, the males will call out for females. Arriving females will swim underwater, avoiding the rest of the males, and emerge in the centre where they mate with the strongest. The pool will soon dry up, so latecomers have likely missed their chance to mate.

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The critically endangered hooded grebe gathers on lakes on the high plateaus of Patagonia to perform elaborate courtship routines with potential partners. As a pair begin to dance, the male grebe reveals to the female his experience through the precision of his moves. In a final act of courting, the female grebe dives down to pluck a strand of milfoil and presents it to its mate.

Sockeye salmon only breed once in their lives. To do so, they undertake a lengthy journey from Pacific Ocean off the coast of Alaska and then 160 miles upriver to reach lakes such as Iliamna. This is the largest salmon run in the world and it attracts hordes of predators such as grizzly bears and freshwater seals. Female salmon that survive the journey to the spawning grounds use their remaining reserves of energy to dig a nest, protect it from rival females, and attract a male to fertilise them; at the end of it all, she and her mate die.

Grizzly bears in Alaska await the annual salmon run as 3.5 million sockeye salmon attempt to reach their spawning grounds upstream from the coast. The bears feed extremely well but still vast numbers of the fish survive the onslaught.

Freshwater seals inhabiting Iliamna Lake in Alaska benefit from the annual Sockeye salmon run, in which 3.5 million fish travel upstream to reach their spawning grounds.

Hellbender salamanders are found in rivers and streams of the Appalachian Mountains in the eastern United States. Each autumn, male Hellbenders compete with each other to find and secure a suitable den to nest in. When the females arrive, the male in possession of a suitable den greets her with a "courtship kiss" before the female lays her eggs in the den. Surprisingly, other males and females are then allowed to enter the den where the first male will now protect a communal clutch of eggs as they develop.

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Splash tetra fish breed during the rainy season, when the water level in their river basin habitats rises. This is key because these fish breed out of water! The male tetra first splashes water onto leaves hanging close to the water's surface. Then, the male and female leap out of the water in unison to land on the leaf where the female lays her eggs and the male immediately fertilises them. The surface tension of the water on the leaf helps to hold the fishes up just long enough for this to happen. The male will then continue to regularly splash water onto the eggs as they develop over the following days so that they don't dry out.

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The breeding behaviour of Lesser flamingos begins with feeding. They flock to caustic lakes as such Lake Logipi, Kenya, in their millions to feed on the microscopic algae that develop in the lake's salty waters. The toxins from the algae are stored in their plumage, which turns them pinker, and thus more attractive to potential mates. During courtship, they dance in groups before couples pair off. They appear to be selecting partners based on how closely their shades of pink match.

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The conditions of East Africa's Lake Tanganyika have remained largely unchanged for millions of years, and this has allowed highly specialised mating behaviours to develop, such as that of the callipterus cichlid. Dominant male cichlids maintain a "castle" of empty snail shells in which his harem of 20 females lay their eggs for him to fertilise. He spends his time adding to this collection, chasing off predatory eels and defending his territory from marauding bachelor males. Some male cichlids exhibit dwarfism, a surprising adaptation but one that allows them to sneak into the large male's territory and mate with one of the females inside a shell.

Eels in Lake Tanganyika would make quick work of cichlid eggs, but are hingered by territorial male callipterus cichlids who quickly remove any predators that threaten his brood.

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Zambia's Busanga Plains are home to herds of red lechwe, an antelope with a particular penchant for water. During the dry season, a female lechwe will leave the safety of its herd and travel overland to find a mate. Groups of male lechwe attempt to show off to her, stabbing the ground with their horns and rutting with each other to demonstrate their strength. After a brief union, she returns to the safety of the swamp to begin her pregnancy.

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Lions are among the predators that pose a danger to female red lechwes that leave the Zambia's swamplands to find a mate.

As their pools dry up during the Pantanal's dry season, Yacare caiman travel overland to reach places which have water year-round. Thousands of caiman congregate here but all remain relatively tolerant of each other... until dawn. Now, the males compete for patches of water where they will mate. To attract females, the male caiman makes a deep rumbling call, at a frequency that is too low for us to hear, but one that produces a mesmerising pattern of water droplets that dance on the reptile's back.