Adoption is common among human beings and those who choose to take care of a child from another for various reasons, such as difficulties with fertility or the desire to provide a place for children in need.

However, why do animals adopt children from other animals? The act of caring for an infant that is unrelated to the parent may have resulted from some evolution advantage to the foster family member, said Michael Weiss, an ecologist specializing in behavioral ecology and director of research for the Center for Whale Research in Washington state. In particular, adoption could offer a beneficial experience as a caregiver for women who do not have offspring and may increase the likelihood of their youngsters’ chances of survival, Weiss told Live Science.

Adoptions can occur with the same species or in some very uncommon and baffling situations; it can occur between different species. In a study published in 2021 by the Journal eLife, researchers looked into the impact of the loss of a mother on young mountain gorillas ( Gorilla beringei beringei) and discovered that orphans older than 2, formed bonds with other members of the group, particularly dominant males.

“A young gorilla would usually share its nest at night with its mother, but if the mother dies or leaves the group, then it will share a nest with the dominant male,” the study’s lead researcher Robin Morrison who is a behavioral scientist in the University of Zurich and an affiliate scientist for the Dian Fossey Gorilla Fund in Rwanda said on Live Science.

Mountain gorillas are social groups that are comprised comprising a dominating male as well as numerous females who have offspring. Whatever the case may be, regardless of whether one of them fathered children, the primary responsibility of Morrison is to guard the future generation against being killed by infanticide at the assault of males who are rivals. Morrison said that his capacity to protect his children could determine his reproduction success.

The mountain gorillas ( Gorilla beringei beringei) are part of social groups that take in orphaned children. (Image credit SIMON MAINA/AFP, via Getty Images)

“Males that are really good at caring for offspring and do this in front of females are the most popular,” she said. The care of the orphaned gorilla may bring a dominant male brownie point, increasing the chances of mating and passing his genes on to the next generation. “It’s part of demonstrating their reproductive quality,” Morrison stated.

The group’s females do not necessarily benefit from having an infant without a mother; this isn’t a huge physical cost, as infants above two years old can forage on alone, Morrison said. “It’s also good for the other young gorillas to have a playmate,” she added because it helps improve their social abilities.

Bonds with friends and babies are a huge part of the story.

Adoption is also prevalent in other primates and maybe a bridge between social classes; in a 2021 study by Scientific Reports, researchers discovered the first instances of great apes acquiring infants from another group. Researchers found two bonobos females ( Pan paniscus) who seemed to have taken in two infants from a different group. The team speculated that this behavior could boost the adult’s social standing.

“One possibility is that adoptees could become future allies of the adoptive mothers,” the researchers wrote in their study. “Both adoptees were females and female bonobos form strong social bonds and coalitions within their group and sometimes across groups.”

A different possibility would be just like women, female bonobos experience affection and empathy for infants, as revealed by the study. “Within primate species, some adults are really baby-obsessed,” Morrison stated, noting that this passion can cause kidnappings and even death if a baby is involved in a fight.

Certain species might adopt other baby animals because it is believed to invoke future blessings. (Image Credit: Eduard Figueres via Getty Images)

Researchers reported kidnapping of a three-week-old Tibetan macaque ( Macaca Tibetan) by a female from identical species. This was documented in the study 2023, written in Primate Research. The female was the mother of two children of her own when she took the baby off its mom and included an infant of 1 month who continued to nurse with the captive. The researchers suggested that the kidnapping-turned-adoption may have benefited the female by invoking future social support or favors, such as grooming.

The kidnapping of a five-day-old yellow baby baboon ( Papio cynocephalus) was reported in a study published in 1987 in The American Journal of Primatology. Sadly, The incident ended: The baby died of thirst or dehydration when a high-ranking female kidnapped the animal and carried it around forfor three days.

Adoption underwater

Nonhuman primates could have the same compassion instincts as humans when seeing a baby or a small animal. This could assist in understanding this behavior, Morrison said. Weiss says this isn’t just a matter of primates studying orcas ( Orcinus orca) in the Pacific Northwest and western Canada waters.

“All of the females, and especially the females who haven’t had a calf yet, are totally baby-obsessed,” he added. “The first year of a calf’s life is the absolute center of attention for everyone.”

In 2021, scientists from Iceland first observed an orca that appeared to have embraced an infant Pilot whale ( Globicephala). On June 20, 2023, researchers from the Icelandic Orca Project were baffled by another female exhibiting the same behavior. “We are trying to piece together what is happening, but we sure have a lot of questions,” they posted on Twitter.

Weiss said these incidents could be described as “a big mystery” because scientists haven’t seen any adult whales from both species interact, suggesting that the orcas might have abducted the whales’ babies. “The abduction case of a killer whale going into a pilot whale group and stealing a calf — while we don’t know that’s what happened — seems more likely to me,” He added.

There is a lot of debate about why this could be beneficial to orcas. As mothers tend to their calves for three years, Weiss said, producing milk is an enormous energy cost. In addition to dividing the attention of a female and draining her energy, adoptees may pose “a bit of an issue” for biological offspring, he said.

Adoptive, biological offspring and biological offspring can have to compete for attention, which could result in adverse outcomes. In a study from 2019 published by the Journal of the Journal Ethology, Researchers documented the story of a melon-headed whale calf ( Peponocephala electra) taken in by female bottlenose dolphins ( Tursiops truncatus) with a child that was hers. The adoptee repeatedly pulled the baby out of her mother’s abdomen, possibly leading to the biological calf’s disappearance soon afterward.

According to the research, the female dolphin might feel compelled to nurture the baby due to the recent birth of one of her own. “Both calves were approximately the same age, which could have enhanced the mother’s tolerance toward a newborn during a sensitive period for establishing mother-offspring bonding,” they said in their study. They wrote that other factors could contribute to the adoption, like the mother’s “curious and social personality” or lack of knowledge.

A female bottlenose dolphin ( Tursiops truncatus) adopted an emerald-headed whale calf ( Peponocephala Electra). (Image credit: JohnCarnemolla via Getty Images)

Inexperience could explain why orcas are interested in the calves of pilot whales. “It could be misplaced maternal instinct,” Weiss explained. He added that it could also be a “takeaway lunch” to eat later or to play with. “I wouldn’t be surprised if they saw a cute little baby whale and thought ‘Oh! I’ll pick that up for a while.'”

Also, moms who need to be better-versed can commit mistakes in nonmammal species. Cuckoos common ( Cuculus canorus) are brood parasites. Females lay eggs in the nests of other species’ nests to spare them the energy cost of raising the eggs. In a study in 1992, released in Behavior Ecology, Researchers discovered that the young Great Reed warbler ( Acrocephalus arundinaceus) females were more susceptible to being fooled with eggs laid by cuckoos than older breeders and suggested that their uncontrolled behavior could be due to lack of experience.

While evolutionary pressures may explain why animal adoptions started and persist, they cannot provide insight into individual cases. “One reason why that behavior might persist and keep getting passed down is because it helps build up the skills for taking care of a calf,” Weiss explained. “But the females are probably not doing it because they’re trying to build up experience.”

Orcas are mainly intelligent creatures that we might not fully comprehend. “They’ve got big, complex brains just like us, and they have instincts and impulses, which means that they’ll often do things that are really interesting and don’t have an immediate survival or reproductive advantage,” Weiss explained.