In humans, when it comes to parenting, anything goes. Family structures have come a long way since “nuclear family or bust”. Now, we raise children as single parents, adoptive parents, in multigenerational families, and in same-sex couples to name just a few. But what about the rest of the animal kingdom?
As with humans, the answer is varied and complicated – there are many different ways in which animals raise their young. But is same-sex parenting among them? We know plenty of same-sex behavior, mating, and pair-bonding occurs in thousands of species but which, if any, animals of the same sex take the next step and tackle parenthood together?
Same-sex parenting in penguins
In short, yes, some animal species have been found to parent in same-sex pairs. In fact, you might be familiar with a certain couple who hit the headlines just last month.
Elmer and Lima, a pair of male penguins from New York, became the first same-sex penguin parents at Rosamond Gifford Zoo in Syracuse. The duo are Humboldt penguins (Spheniscus humboldti), a vulnerable species, and were given an egg to incubate as part of the zoo’s internationally renowned Humboldt penguin program. Foster parents, such as Elmer and Lima, are tasked with sitting on, hatching, and raising the chicks of breeding pairs who may not be best equipped for the task, according to NBC. And, it seems, the new penguin parents are doing a fine job.
“Elmer and Lima were exemplary in every aspect of egg care,” Zoo Director Ted Fox told NBC.
Elmer and Lima are not alone. Same-sex parenting in penguins in zoos and aquariums is fairly well documented, and judging by the number of stories we’ve written on the topic, it’s also fairly popular. Pairs of male penguins of various species have incubated eggs, hatched and/or raised chicks all over the place, including gentoos in Australia, Humboldts in England, and African penguins in the Netherlands. There was even a pair of king penguins in Denmark caught chick-napping an abandoned baby.
However, other examples in the animal kingdom are less well known, possibly for this reason: While same-sex behavior is commonplace – at least 1,500 species have exhibited it – biparental care (when both parents jointly provide care for their offspring) is not de rigueur among non-human animals, it turns out.
“There aren’t very many animals that have that kind of parental care,” Professor Marlene Zuk, an evolutionary biologist at the University of Minnesota, told IFLScience. “There’s a tiny tiny tiny fraction of all animals that even do that. Period. Whether it's males and females or members of the same sex.”
But those that do are often birds, Zuk explains.
“Among vertebrates, it’s likely to be a bird because [in] mammals, what’s a male going to do? There aren’t very many cases of biparental care in mammals to begin with. Because the females are giving birth to the offspring and nursing them and males can’t do that part.”
“In birds, except for laying the egg, a male can do everything a female can do. He can incubate, he can feed the chicks, and he can protect the nest from predators.”
Same-sex parenting in birds
Penguins famously, and sometimes scandalously, form pair bonds, making them ideal candidates for same-sex biparental care. But they are not the only birds to choose this path to raise their little ones.
“In birds, actually, it’s thought to be quite common,” Vincent Savolainen, Professor of Organismic Biology at Imperial College London, told IFLScience.
“There were studies in Australia with swans and, in fact, when they same-sex parent the chance of the young to succeed and to develop well … and fledge was higher than when they compared to opposite-sex parenting.”
Male-male pairs of black swans (Cygnus atratus) mate with a female, who then leaves her eggs behind. Some particularly lawless swans might even chase off the breeding pair, so desperate are they for an egg of their own to raise. Which they do, with 80 percent success, compared to just 30 percent for opposite-sex couples.
Though it's an old study, circa 1981, which may need updating, Savolainen caveats.
Flamingos (Phoenicopterus roseus) have also been observed in same-sex parenting.
“[It is] common in captivity (fairly) when unequal sex ratios in captive flocks mean unpaired females or males that cannot find a partner of the opposite sex redirect their breeding activities to an unpaired bird of the same sex and go through the motions of trying to nest and raise a chick,” Dr Paul Rose, a zoologist at the University of Exeter, told IFLScience.
“Such same-sex pairs are normally very disruptive to the stability of the colony, trying to monopolise nesting sites or the nests of other flamingos.”
Two female-female pairs of flamingos were the focus of one study, which found their parenting behaviors were basically identical to those of an opposite-sex pair. The egg layer spent more time away from the nest, while the non-egg layer was involved in more agonistic behavior than other females. Overall, the time spent on the nest was the same for same-sex and opposite-sex couples.
Despite the flamingos seeming natural inclination, same-sex parenting is not an adaptive behavior, Rose says. “It is generally an artefact of the captive environment."
Outside of captivity, same-sex parenting between males has not been commonly observed. As Zuk points out: “where are they going to get the egg?”
“In nature, there aren’t people going around with eggs saying, ‘would you like an egg?’”
In captivity, however, there are. The aforementioned penguins, of course, but a similar foster scheme has also been employed in vultures. In 2017, a pair of male griffon vultures (Gyps fulvus) successfully hatched an abandoned egg for the first time at a zoo in Amsterdam.
"As in some penguin species, vultures do everything the same, they alternate all the jobs. Females lay the eggs, but they breed together, they forage for food together. Males are programmed to have that duty of care," zookeeper Job Van Tol told BBC News at the time.
In the wild, same-sex parenting can arise in response to a sex ratio skew. In a colony of Laysan albatross (Phoebastria immutabilis) in Oahu, Hawaii, for example, 59 percent of the population are female, and consequently, 31 percent of pairs are female-female.
“Because it takes two Albatross parents to raise a chick, if these females didn’t pair with each other, they would not be able to raise any chicks. So this increases their fitness by allowing them to raise chicks in a situation where they normally would not be able to,” Dr Lindsay Young, executive director of Pacific Rim Conservation, told IFLScience.
Young’s research in Laysan albatross has demonstrated how same-sex parenting can be an adaptive advantage in that particular colony. While same-sex pairs raise significantly fewer chicks – 80 percent fewer than male-female pairs – and the survival of those chicks is lower, it is still better than not breeding at all. Female albatross may be “making the best of a bad job,” the authors write.
Evidently, plenty of species raise young in same-sex pairs. But, as heartwarming as it might be to imagine a big happy “gay” bird family, we cannot make that discrimination. Co-parenting can occur in same-sex bonded, or "homosexual" mated pairs, but “We need to be careful with anthropomorphic statements around sexuality and gender. This is indeed a defined characteristic of the human animal,” Rose told IFLScience.
“People are fluid in their sexuality and there is no heteronormatic scale. But in the animal kingdom, the examples of same-sex pairing cannot be feasibly considered hardwired by DNA or formed by an individual’s attractions and desires (we simply cannot measure this).”
Instead, environmental pressures and other factors beyond the animal’s control might push them into same-sex parenting, he says.
Despite the many documented occurrences of male pair-bonded penguins taking on fatherhood together, same-sex parenting in animals might not always be a choice governed by love or desire – in male-female pairings this is rarely the case either – but it demonstrates the fascinating complexities of the animal world. Unlike penguins, animal parenting is not black and white. And it’s definitely not always a husband and wife situation – just ask Leslie Knope.