Relationships can be complicated, especially in the wild. There are dozens of ways that creatures can pair up, be it microscopic bacteria or huge jungle mammals. But as with humans, there is no one-size-fits-all in the animal kingdom — and no lack of variety in reproductive and parental habits.
In promoting their species, male and female animals take on different gender roles. The term refers not only to their part in copulation, but also to the specific tasks they perform in mating and rearing. A common theme in the courtship world of nature is that a woman chooses a mate from competing male suitors and raises her young, mainly alone.
Male humpback whales, for example, compete for females and leave the care of the calves to the mother. Other animals, such as elephant seals, will form a harem: a group of females led by one male who has a mating monopoly and has little interaction with his offspring. Both scenarios fall under the umbrella of polygyny, where one male mates with multiple females.
Alternatively, in monogamous animals, such as the albatross, a breeding pair mate for life. These are considered conventional gender roles.
However, breeding relationships such as matriarchies or female-led harems that fall outside of traditional polygyny or monogamy are considered role reversals.
Role reversals in the sea, air and underground highlight the diversity of courtship in the animal kingdom – and the amazing variety of life on Earth.
In underground colonies of naked mole rats, a mighty queen rules over hundreds of blind, hairless subjects. As in bee or ant colonies, naked mole rat queens are the only females to mate and give birth. She is accompanied by one – or sometimes a few – breeding males, to whom she has given the right to sire the next generation. The rest of the colony is in charge of baby care, in addition to expanding burrows with their robust teeth and feeding the queen. Biologists call this ‘extreme cooperative breeding’.
“Naked mole rats are the most extreme example of this among mammals,” said Melissa Holmes, a behavioral neuroscientist at the University of Toronto. “It’s extremely rare.”
The queen reigns supreme by suppressing breeding behavior in the colony. Researchers suspect she does this with dominant behavior, pushing and pushing colony members around. When the queen dies, another female can peacefully take her place by mating and producing offspring. But sometimes, before her death, subordinate women stage a coup, attacking the queen and fighting to the death for a chance at the throne. Because of their unusually long lifespan – more than 30 years – queens can rule, if not overthrown, for decades.
Above ground in the floodplains and savannas of Africa, female topi antelopes also take control of breeding situations. Instead of males fighting each other for a mate, it’s the female topis aggressively attacking their competitors – some even ambush mates mid-mating. The competition is justified: female topis are fertile only one day a year. By mating with about four other males in a day, they increase their chances of conception. Meanwhile, male topis play their own love games, rejecting females they’ve already mated with and allowing more advances from new potential mates.
under the sea
Like naked mole rats, groups of clownfish are also led by a female who is “very much in charge,” says senior aquarist Savannah Dodds of the Oregon Coast Aquarium. Next to her swims a male partner, the only fish with permission to fertilize her eggs. Together they care for their developing eggs until they hatch. But when the female dies, a reversal of a different kind happens: her mate turns into a female and takes her place.
All clownfish are hermaphrodites, meaning they are equipped with both sets of reproductive equipment, but they are all born male. The now female clownfish begins to lay eggs and the largest male in the school takes on the role of fish father.
Sea dragons hiding in the swaying kelp off the coast of Australia take role reversals one step further: The males are the ones who carry and give birth to babies. Like their seahorse relatives, sea dragon males receive unfertilized eggs from females, who leave their expectant young in a special sac under the tails of the males. When a man is not impressed by a woman – who tries to seduce him with an intricate dance – he rejects the eggs.
But if properly provoked, he keeps the eggs and fertilizes them. The eggs develop in their father’s fold for the next six weeks before emerging. Once born, the babies must face the dangers of the ocean and the changing currents for themselves. Only about five percent of these unique sea dragon babies make it, Dodds says, and the International Union for Conservation of Nature lists some species as near threatened.
In mainland Australia, male emus also take on the father duty. When the breeding season begins, male emus win over females with a slow, neck-swinging display. But after mating, the mother emu doesn’t incubate the eggs she lays, but leaves them with her mate and saunters off to repeat the process with someone else — a mating pattern called polyandry. The emu father is left with a group of huge eggs and must remain in his nest for the next two months. During that time, he will refrain from eating and lose up to a third of his body weight. After hatching, the devoted daddy raises his chicks for about a year and teaches them how to survive in the rugged outback.
Meanwhile, in the tropical trees of New Guinea, Australia and neighboring islands, colorful parrots challenge the idea that females must be the dull in a pair. In a stunning display of reverse sexual dichromatism, where females are more lively than males, female eclectus parrots stand out like gems against their nest cavities with bright red and blue plumage. Their male counterparts usually have green feathers, which they rely on to blend in with the canopy.
While sex appeal plays a part in the bold palette change, the females’ coloration likely evolved to announce their claim to territory, says Rob Heinsohn, an evolutionary biologist at the Australian National University.
“It’s a very loud signal of cavernous property: ‘Don’t come here; I will fight you,” he says.
The cavities in which eclectus parrots live are in high demand, and the birds defend them at all costs from other marauding mothers. Their dazzling color announces that a tree is occupied, but some females will still kill each other over a prized nest site. Since they guard their burrows around the clock, females rely on their mates to bring them food. And the more partners they have, the more food they get.
Although they only lay two eggs per clutch, females mate with many males, making them all think they could be the father. The males, pursuing the opportunity to continue their lineage, also mate with several females. Males will help care for all their chicks by bringing fruit from tree to tree, which females eat and spit out for their young. This is a type of cooperative breeding called cooperative polyandry, a behavior that combines the nude mole rats’ rearing methods and the multi-partner habit of emus.
A handful of other birds display inverted color schemes, but “nothing is as bold or obvious as the eclectus parrot,” Heinsohn says. Glistening in the bright sunlight of the canopy, “there is probably nothing more beautiful in all the world.”