There are scant inevitabilities in life. One of them (with very few exceptions) is death. Unless you’re a particular type of freshwater polyp or a weirdo jellyfish, birth is a guarantee of death. Humans have developed our own intricate coping strategies for managing this bleak biological reality–stretching back millenia. Some archaeological findings even indicate that human death rituals predate Homo sapiens, with evidence of burials and funeral practices found among Neanderthals and other extinct, archaic hominins. But what about the rest of the animal kingdom–how do non-human animals understand and respond to death?
The answer depends on species, individual, and circumstance. “There’s a wide variety of animal responses to a dead companion or group member,” says Barbara J. King, an emerita professor of anthropology at William and Mary and author of the book How Animals Grieve. From what King describes as heartbreaking and apparent emotional displays to the pragmatic and pre-programmed, scientists have documented all sorts of animal reactions to mortality.
Evolutionary or comparative thanatology is “the scientific study of death and dying in non-human animals,” says André Gonçalves, a primatologist and anthropologist at the University of Kyoto in Japan. As far back as Aristotle, people have theorized about how animals conceive of death, he explains–but formal study has been limited. Slowly, that’s starting to change through the emergence of the young discipline. Each new thanatological observation sheds light on where our own behaviors may have come from and prompts new questions.
Reluctant to let go
Alecia Carter, an associate professor of evolutionary anthropology at the University College London, has spent years studying baboons at the same field site in Namibia. Repeatedly, she and her colleagues there have witnessed instances of mother baboons carrying the corpses of their deceased infants. Initially, she didn’t find the behavior surprising. “It just made sense,” she says–that is, until she observed an orphaned, deceased infant being carried by other members of the group. “I didn’t really understand what would motivate an individual who hadn’t bonded to that infant to carry that infant.” So, she began to take a closer look.
In her research, she’s discovered just how common this “infant corpse carrying” behavior is among primates. “There’s only a couple of groups of species where this hasn’t been reported happening,” and usually there are clear physiological reasons why, she says, as in lemurs who aren’t well-adapted to carry their offspring, because their living babies do a good job of clinging on their own.
Corpse carrying is most prevalent in great apes and larger primates and most often observed when infants die non-violent deaths (like from disease), according to a 2021 study co-authored by Carter. Length of time for carrying bouts varies widely based on species, age of infant, and other factors, but in some cases, chimpanzees will continue carrying deceased infants for more than 100 days. And it’s not just primates. Infant corpse carrying has also been documented in elephants, dingoes, and even cetaceans–as in the 2018 instance of an orca mother who supported and held on to her dead calf for 17 days across nearly 1,000 miles of ocean.
It’s not yet known why, exactly, animals do this, though there are theories. One idea is that animal parents are unaware that their offspring are dead. However, both King and Carter say that’s an unlikely explanation. Often, transporting a body takes considerable effort beyond the normal, and so it’s not as if the behavior is a continuation of the regular routine, King explains. Plus, mothers seem to “treat the corpse very differently” from a living infant “rather quickly,” adds Carter.
In Carter’s view, infant corpse carrying is likely the result of the intensely close bonds that mothers and offspring form. That attachment, once it’s been made “is really hard to break,” she says, and there may be an innate or cognitive response at play that compels mothers to keep even dead offspring close. From King’s perspective, the explanation varies, but in cases where corpse carrying constitutes a big behavioral shift, it probably comes down to some familiar emotions. “Grief is not just a human thing–nor is joy or sorrow or fear,” King says. A mother carrying her dead offspring may simply be grieving. “We humans are surrounded by other species who think and feel,” which should prompt us to reconsider how we treat animals and their habitats, she says.
Yet neither close bonds nor maternal grief necessarily explain that orphan baboon carried by the group. “Observational studies can only get us so far,” says Carter, and there’s lots of still-unanswered questions. “We’re at the very beginning of the field,” she adds.
Guarding, tending, and vigils
Carrying a body isn’t the only expression of seeming care that animals display. In many species, animals have been observed staying near a familiar corpse for an extended period of time or even guarding it from would-be scavengers in something of a zoological vigil. “Sometimes surviving group members go to great lengths to defend a carcass,” says King.
Giraffe mothers have been documented standing over or near their deceased offspring for days at a time. Peccaries, pig-like pack animals found throughout the Americas, have been caught on camera visiting and protecting the corpse of a dead group-member for 10 days after the peccary perished. The troupe warded off coyotes and also intermittently nuzzled and pushed at the body of their fallen herd-mate. Researchers have additionally witnessed chimpanzees grooming and even cleaning the teeth of corpses.
African elephants are well known for their “funerals,” documented instances wherein many individuals, even those unrelated to the deceased, will visit a corpse over a long period. In some cases elephants may even bury their dead, says Gonçalves, “but these have been very rarely reported,” he adds–disputing that elephants’ death response meets the criteria for formal ritual, at the level of what humans engage in.
Beyond mammals, some birds–particularly those that develop long-term bonds–are also known to stay with the bodies of their peers. Anecdotal evidence suggests ducks will spend time near or even on top of the bodies of their dead mates. King tells the story of two rescued ducks at an animal sanctuary “that were fast friends” who stayed bonded for years. When one of them died, she says, the survivor “draped himself” over the body and later became socially withdrawn.
Disposing of the body
Though there’s ample evidence that many types of animals do have emotional (and even stress hormone) responses to the death of kin, that’s not so for every species. In some animals, the reaction to death is much more practical.
Eusocial insects like ants, termites, and bees spring into action in the presence of the dead. In most cases, members of a hive or nest will quickly separate the corpse from the colony, either by moving it elsewhere, burying it, or in some cases cannibalizing it. Naked mole rats, which also live in matriarchal colonies, behave similarly–leaving bodies in sealed-off “refuse pile[s],” according to Gonçalves.
In these cases, scientists hypothesize that this “sanitation” practice helps to protect the rest of the colony from potential disease–it’s simply good hygiene to clean out the colony. Experiments on ants and termites indicate that smell is the primary driver of the behavior. Dead insects emit a chemical compound that triggers survivors to act. In fact, living insects spritzed with these deathly scents will be treated the same as a body would, and removed from the colony, says Carter.
Killer curiosity
In yet other instances, death seems to be a learning experience for some species. Corvids, the bird family including jays, ravens, and crows, are known to make alarm-calls and then gather around corpses of fellow birds in “cacophonous aggregations” that can last up to 30 minutes. Though sometimes described as “funerals,” researchers hypothesize that the purpose of these interactions is information gathering and self-defense more than mourning, says Carter. Birds may be looking to find and drive off a predator, or determine the source of danger so they can avoid it themselves. One fMRI study of crows indicated that the birds showed elevated brain activity in regions associated with higher order decision making, in response to exposure to a dead conspecific.
Other species, too, seem to display interest–though not necessarily grief–when faced with the dead. One camera trap study documented living wombats visiting and inspecting a corpse over the course of months.
Violent reactions
Of course, some animal behaviors are less palatable to us humans than others. Many animals have been known to copulate with corpses, in acts of necrocoitus or necrophilia. Scientists have observed this type of reaction in groups as varied as frogs, lizards, crows, penguins, seals, dolphins, macaques, and insects.
Cannibalism of the dead is also common among animals–even those we consider close relatives. Chimpanzees have been observed eating the bodies of their dead relatives. In instances where an infant dies, mothers will sometimes ingest parts of the corpse. Though this rare reaction is seemingly in contrast to the more commonly observed grief response of infant corpse carrying, it’s important to remember that animals don’t share our human taboos and we don’t know what motivates such actions.
Sometimes, it’s not clear if an animal is grieving, planning for cannibalism, or some mix of both. Predators and scavengers like bears and wolves often cache prey carcasses they find on the landscape–hiding the meat for later consumption. Both species have also been documented burying the bodies of their dead young in separate cases, notes Gonçalves. “When a carnivore encounters a dead conspecific [they] may bury it because the smell triggers their caching response,” he says. However some researchers have theorized this sort of action might amount to mourning.
To add to the confusion, aggression can be mixed in with other types of behaviors as well, says Carter. Additional research of chimpanzees has noted at least one instance where chimps intermittently beat, attacked, groomed, and inspected the body of a deceased adult female. One hypothesis for why the primates react in such a disjointed way is because they’re simply alarmed or unsettled by the presence of something that looks like a chimpanzee, but acts like an inanimate object, she explains. Perhaps, “it just freaks them out,” Carter suggests.
Inexplicable and unknown
Many animal responses to death are not so easily categorized, described, or detected. And often, our own assumptions can get in the way of true understanding. Remember those turkeys circling the dead cat that became a meme? Despite the fact that this looked like some sort of intricate ritual, it was likely a fear-motivated response to a perceived threat gone a little awry.
Humans have a tendency to see ourselves in animals, anthropomorphizing without evidence. In contrast, scientists can tend to overcorrect for this habit, by wrongly assuming that humans are exceptional in all of our cognitive faculties, says King. Neither approach is accurate. But further observations and studies, conducted with an open mind, may offer clues to persistent mortality mysteries.
“There remain many unanswered questions,” says Gonçalves. For instance, it’s not yet clear which species (if any) have a concept of death and its permanence–nor how animals recognize death in many cases. “Humans often perceive the line between dead and alive as very sharp,” Gonçalves says. “For other animals it may be more like a blurred, wide brushstroke, where states such as sleeping or wounded become intertwined in an uncertain middle ground.”