Fanfin anglerfish demonstrate one of the strangest mating behaviours in the animal kingdom. In the depths of the ocean, where almost no light reaches, encounters between these usually solitary fish are rare. When they do occur, the male angerflish, which is several orders of magnitude smaller than his mate, bites into her skin, latching onto her permanently - even fusing his blood vessels with hers - and now exists solely to fertilise her eggs until she dies.
These anglerfish were filmed in 2016 with help from the Rebikoff-Niggeler Foundation in a deep-sea submersible at a depth of 800 metres off São Jorge Island in the Azores . Footage from this dive can be seen on Youtube  [Link 1][Link 2]
Toad-headed agama sp.
Toad-headed agama males entice potential mates by maintaining burrows among sand dunes in Russia. They face two problems however: first, leaving his burrow to search for a mate risks losing it to a rival male; second, the strong winds on the dunes can blow his burrow away entirely, so he must be fast! One male displays out on the sand by wagging their black-tipped tails high above his head, hoping to be seen by a female in the vicinity. When he returns to his unguarded burrow, he finds a rival male in his place and the circle each other, attempting to intimidate one another by tilting their bodies off the ground so as to appear bigger.
The species of toad-headed agama that occur in Russia are Phrynocephalus guttatus, P. helioscopus, P. kulagini and P. mystaceus.
Albatrosses circumvent the recurring problem of finding a mate by pairing for life. A couple will return to their breeding grounds after spending months apart and renew their bonds with a courtship dance. But some Laysan albatross males abandon their female after mating. These females have adapted remarkably by forming same-sex pairs and sharing the responsibilities of incubating an egg. Another problem arises however, when both females have laid an egg. Each female has an overwhelming drive to incubate her own egg but, since one partner is always out feeding at sea, only one egg can be raised and the chick within the other, neglected, dies. Still, these females are still able to form successful partnership by alternating each breeding season which of their eggs will be incubated, for decades to come.
Sonoran Desert, USA
Rio Grande wild Turkey
Meleagris gallopavo intermedia
Of the three Brood X 17-year periodical cicada species (Magicicada septendecim, M. cassini and M. septendecula), only M. septendecim have the "broad orange stripes on the underside of the abdomen, and with orange coloration on the sides of the thorax behind each eye and in front of the forewings"  that we see on almost every close-up shot of the cicadas in this sequence. They are also distinguishable by the specific calls they make. [Link 1]
National Black-footed Ferret Conservation Center, Colorado, USA
Elizabeth Ann, the star of this sequence, was born at the National Black-footed Ferret Conservation Center in Wellington, Colorado . The shots of the ferret searching for a mate at night may have been shot elsewhere. [Link 1]
Ailuropoda melanoleuca melanoleuca
Wolong National Nature Reserve, China
According to an article on China Daily , this sequence was filmed at the Wolong Panda Centre: "The fifth and final episode visits the Wolong Panda Center in China and features giant pandas, commonly regarded as being some of nature's worst breeders". [Link 1]