Relationships can be complicated, especially in nature. There are dozens of ways creatures mate, from microscopic bacteria to huge jungle mammals. But as is the case with humans, there is no one-size-fits-all solution in the animal kingdom and there is no shortage of breeding and parenting habits.
In the act of promoting their species, male and female animals assume distinct sexual roles. The term does not just refer to their role in copulation, but to the specific tasks they perform in mating and parenthood. A common theme in the world of nature courtship is a female choosing a mate from competing male suitors and then raising her young, mostly alone.
Male humpback whales, for example, compete for females and leave care of the calves to the mother. Other animals, such as elephant seals, will form a harem: a group of females led by a male who has a mating monopoly and interacts little with his offspring. Both scenarios fall under polygyny, where a male mates with multiple females.
Alternatively, in monogamous animals, such as the albatross, a breeding pair mates for life. These are considered conventional sex roles.
However, reproductive relationships like matriarchies or female-headed harems that fall outside traditional polygamy or monogamy are considered role reversals.
The reversal of roles in the sea, the sky and the subsoil highlights the diversity of courtship displays in the animal kingdom and the wonderful variety of life on Earth.
In the subterranean colonies of naked mole-rats, a powerful queen rules over hundreds of blind and hairless subjects. As in colonies of bees or ants, naked mole-rat queens are the only females that mate and give birth. She is joined by one or sometimes a few breeding males, to whom she has granted the right to sire the next generation. The rest of the colony is responsible for caring for the babies, in addition to enlarging the burrows with their sturdy teeth and feeding the queen. Biologists call this “extreme cooperative breeding.”
“Naked mole-rats are the most extreme example of this among mammals,” says Melissa Holmes, a behavioral neuroscientist at the University of Toronto. “It’s extremely rare.”
The queen reigns supreme by suppressing reproductive behaviors in the colony. Researchers suspect that she does this with dominant behavior, pushing and shoving colony members. When the queen dies, another female can peacefully take her place, beginning to mate and procreate. But sometimes, before her death, subordinate women stage a coup, attacking the queen and fighting to the death for a chance to ascend to the throne. Due to their exceptionally long lifespans – over 30 years – queens can rule for decades if not overthrown.
Above ground in the floodplains and savannahs of Africa, female topi antelopes also take control of breeding situations. Instead of the males fighting for mates, it is the female topis that aggressively attack their competitors – some even ambush couples in the midst of copulation. The competition is justified: female topis are only fertile one day a year. By mating with around four other males a day, they increase their chances of conception. Meanwhile, male topis play their own love games, rejecting females they have already mated with and allowing more advances from potential new mates.
Under the sea
Similar to naked mole rats, groups of clownfish are also led by a female who is “very responsible”, says a senior aquarist Savannah Dodd at the Oregon Coast Aquarium. A male companion swims beside her, the only fish allowed to fertilize her eggs. Together they care for their developing eggs until they hatch. But if the female dies, a reversal of another kind occurs: her companion turns into a female and takes her place.
All clownfish are hermaphroditic, which means they are equipped with both sets of reproductive gear, but they are all born male. The now female clownfish begins spawning and the largest male in the school takes on the role of father fish.
The sea dragons lurking in the swaying kelp off the Australian coast take the role reversal one step further: the males are the ones who carry and give birth to the babies. Like their seahorse relatives, Seadragon males receive unfertilized eggs from females, which leave their future young in a special pouch under the males’ tail. If a male is unimpressed by a female – who attempts to seduce him with an elaborate dance – he rejects the eggs.
But if he is well courted, he guards the eggs and fertilizes them. The eggs develop in their father’s lap for the next six weeks before emerging. Once born, babies must face the dangers of the ocean and changing currents on their own. Only about five percent of these unique baby sea dragons survive, Dodds says, and the International Union for Conservation of Nature considers some species to be near-threatened.
In mainland Australia, male emus also take on daddy duty. When the breeding season begins, the male emus win over the females with a slow, flailing neck display. But after mating, instead of incubating the eggs she lays, the mother emu leaves them with her mate and wanders off to repeat the process with someone else – a mating pattern called polyandry. The father emu is left with a clutch of massive eggs and must sit in his nest for the next two months. During this time, he will give up food and lose up to a third of his body weight. After hatching, the devoted daddy raises his chicks for about a year, teaching them to survive in the rugged backcountry.
Meanwhile, in the tropical trees of New Guinea, Australia and neighboring islands, colorful parrots are challenging the idea that females should be the dullest of a pair. In a stunning display of reverse sex dichromatism, where females are more vibrant than males, female eclectus parrots stand out like gems against their nesting hollows with bright red and blue plumage. Their male counterparts mostly sport green feathers, which they rely on to blend in with the tree canopy.
Although sex appeal plays a role in the bold palette-swapping, the females’ coloration likely appeared to advertise their claim to territory, says Rob Heinsohnevolutionary biologist at the Australian National University.
“It’s a very strong signal of hollow ownership: ‘Don’t come here; I will fight you,” he said.
Hollows inhabited by eclectus parrots are in high demand and the birds defend them at all costs against other marauding mothers. Their dazzling coloration announces that a tree is occupied, but some females still kill each other at a prized nesting site. Because they keep their hollows around the clock, females rely on their mates to bring them food. And the more companions they have, the more food they get.
Although they only lay two eggs per clutch, the females mate with many males, leading them all to believe that they might be the father. Males, seeking the chance to advance their lineage, also mate with multiple females. The males will help take care of all their chicks by carrying fruit from tree to tree, which the females eat and regurgitate for their young. This is a type of cooperative breeding called cooperative polyandry, a behavior that combines the parenting methods of naked mole-rats and the multi-mate habit of emus.
A handful of other birds display inverted color schemes, but “nothing is as bold or obvious as the eclectus parrot,” says Heinsohn. Glistening in the bright sunlight of the canopy, “there is probably nothing more beautiful in the whole world.”