For two years, Barbara J. King, a professor of anthropology at the College of William and Mary, has studied how animals react to death. In her new book, “How Animals Grieve” (University of Chicago Press), she argues that a wide variety of creatures including dogs and cats feel the pain of losing a loved one. Here, she explains why grief may be an emotion many animals share.

Wild elephants sometimes stand silently at the bodies of dead companions and, later, stroke their sun-bleached bones as if embracing a memory.

Dolphin mothers may refuse to part with the bodies of their babies who die, forgoing food and tirelessly keeping their child buoyant in the water day after day.

Jane Goodall famously reported that a chimpanzee juvenile, even though mature enough to feed on his own, could not recover emotionally from the death of his mother, and soon passed on himself.

Scientists have known for years that big-brained mammals may grieve when a family member or close friend dies. But after two years of research, I have discovered something unexpected: Mourning is found more widely than science has recognized before in animals, extending to horses, cats, dogs, rabbits and birds.

It’s not only the animals in the wilderness who grieve, it’s often animals right here on our farms, or in our back yards, or cuddling next to us every night as we go to sleep.

Separated by how we think, we are united in how we feel.

Vigil for a thoroughbred

Take Storm Warning, a dressage horse who fractured his hind leg in an accident on the farm where he lived. In the same field where he had been so often turned out, he was put down and then buried. That evening, the woman who rode him and cared for him, walked alone to his grave. She placed flowers there in remembrance. She was grieving — and saw that she wasn’t alone.

Six geldings, all horses who had bonded with Storm Warning during his life, grouped themselves in a circle around the mound of fresh earth. They stopped grazing, showed no interest in the flowers, and simply looked, with a heads-down gaze, straight at the grave. Other horses, nearby but not part of Storm Warning’s herd, did not join in. The next morning, the horses were still there, standing vigil.

Two Siamese cat sisters named Willa and Carson who lived in Virginia were inseparable for 14 years. They ate, slept and relaxed together, at times fitting their bodies tightly into a circle to soak up the sun’s warmth.

As she aged, Carson developed some health problems. One day, new symptoms appeared, and her human family took her to the veterinarian. Kept in an incubator for warmth, Carson died that night in her sleep. At first, Willa acted mildly upset at her sister’s absence. Within two or three days, however, she started to wail, searching the house for her sister. It took Willa many months to resume taking her old interest in life again.

Skeptics may raise questions in each of these two cases. Could Willa have just been stressed by the change in her environment, or might her distress have been triggered by her owners’ own visible sadness at losing Carson? Could the geldings who stood vigil at Storm Warning’s grave have acted that way for a similar reason?

But consider: Willa repeatedly searched specific spots in the house that she had shared with her sister. The horses involved were friends of Storm Warning’s, and their response, while not as prolonged as Willa’s, was far from momentary.

And one fact is inescapable, from all that scientists and animal caretakers know now to a certainty: Animals feel their lives. They experience joy and sorrow. Why wouldn’t they grieve?

A gorilla’s mourning

A question less easy to answer is whether animals can recognize death as death. When they respond with sorrow to a lifeless body, do they really grasp that death has occurred?

A hint comes from one of our closest living relatives, the gorilla. At Boston’s Franklin Park Zoo, the gorilla female Bebe was euthanized to spare her the pain that accompanied advanced cancer. Her friend of many years, Bobby, was allowed to spend some time with her body. At first, Bobby tried to revive Bebe, by touching her and placing celery — a favorite food of hers — in her hand. It is clear that, at this point, Bobby knew something was amiss, but had no comprehension of the permanent loss he faced.

Then something changed. Bobby seemed to come to a sudden realization and both his mood and his behavior shifted. He began to wail and bang on the bars of his cage. Whether Bobby actually had a concept of death in his mind is impossible to know, but the sequence of his actions strongly suggests that he did recognize death in some way.

The story of Bobby and Bebe tells us something else, too. Franklin Park workers encouraged not only Bobby but also Bebe’s entire social group to approach the body. The other three gorillas touched Bebe as if to rouse her from sleep, but they never erupted into sadness the way Bobby had. Perhaps they didn’t make the cognitive leap that Bobby did. Or maybe their relationship with Bebe just wasn’t as close, or of the same nature. Individual animals of the same species may grieve quite differently from each other, just as is the case with humans.

Elephants are the gold standard of animal-grief research, because we have meticulous observations from the wild.

When matriarch Eleanor weakened and died in Kenya’s Samburu National Reserve in 2003, other elephants’ responses provided a window into the elephant mind — and heart. Suffering with a swollen trunk and bruised body, Eleanor collapsed one evening on the ground. Two minutes later, Grace, a matriarch of a different family, used her tusks to lift Eleanor back onto her feet. It wasn’t long before Eleanor fell again — she was just too sick to go on.

Grace became quite distressed. While vocalizing, she continued to push Eleanor with her trunk. For at least another hour, she stayed with Eleanor even as her own family moved off.

By morning, Eleanor was dead. On that day, a female called Maui from a third family approached the body. With trunk extended, she sniffed and touched the body, then put her trunk into her mouth to assess the taste. She moved her right foot in order to hover over Eleanor, then pulled on the body with her left foot and trunk. When this failed to wake Eleanor, Maui stood over her, and rocked back and forth.

Was Maui’s rocking behavior evidence of a shift in her understanding, akin to Bobby the gorilla’s letting out a wail when he apparently realized that Bebe was dead? We just don’t know.

What we do know is that elephants came to Eleanor’s body, some to explore and some to grieve, for a full week after her death. Even though park rangers cut the tusks from Eleanor’s body to thwart poachers, and an array of predators ranging from lions to vultures came to feast on it, elephants were pulled to the body as to a magnet. Indeed, Grace returned to Eleanor, but unlike during her first approach, this time she made no attempt to lift Eleanor up and only stood quietly.

Members of Eleanor’s own family came, too. Eleanor’s youngest daughter, a calf of about five months, nuzzled her mother. In what must have been a sign of her confusion and upset, she tried to nurse from other calves. She kept returning to her mother’s body. Unfortunately, this baby was too young to survive on her own, and she died also.

What animals feel

What’s so remarkable here about Eleanor’s story — and a testament to the long-term scientific work by Iain Douglas-Hamilton and his team, who recorded the unfolding events — is that elephants from five different families responded to her death. Unlike the responses of horses, cats and gorillas that I’ve already described, there is a wider grief felt in elephants, beyond a small, tightly bonded group (or sibling pair).

One elephant has even become famous for expressing what scientists call cross-species grief. Tarra lives not in Africa but in the Elephant Sanctuary in Tennessee. Her eight-year friendship with the little stray dog Bella who appeared on sanctuary premises went viral on the Internet. It was fun to watch the great gray, bulky animal walk and play together with the much smaller, white, romping one. Then, Bella went missing. Sanctuary staff found that Tarra began to eat less, and appeared to be depressed.

Before long, Bella’s body was discovered; she had been attacked by a wild animal, most likely a coyote. Her caretakers offered Tarra a chance to attend her little friend’s burial, but she stayed about 100 yards away. The next morning, however, the caretakers noticed a footprint atop the grave. They believe the elephant had made a short solitary journey to visit her friend’s final resting place.

Though these stories of animal grief may evoke some sadness, I want to underscore how full they are of love and friendship. Storm Warning the horse had good horse friends, just as Bebe the gorilla had good gorilla friends and Eleanor the elephant had good elephant friends. And I believe that in her elephant way, Tarra loved the dog Bella, just as Willa the cat loved her sister Carson. There’s no inconsistency with the practice of rigorous science to say that the animals all around us may feel their lives quite deeply.

The roots of human grieving, then, go deep. It’s equally true, though, that we grieve in ways quite different from those of our fellow creatures. For one thing, we carry with us a heightened concept of death that goes far beyond the gorilla Bobby’s awareness of the loss of his friend Bebe.

It’s an awareness we come to gradually at some point in late childhood: all creatures, even those we love most, must die one day. Even we ourselves. That kind of consciousness is absent in other animals, at least as far as we know right now.

And we humans grieve for strangers. When we learn that families we will never know are suddenly steeped in painful loss, we empathize and feel their suffering. We may even make a pilgrimage to sites of public mourning in Manhattan or Oklahoma City, Auschwitz or Hiroshima. We pour our grief into creating and appreciating monumental architecture, and turn furious sorrow into great literature, music, film and dance. The scale of our mourning, and the creative outlet we pursue because of it, is unique to our species.

Yet what unites human grieving with that of other animals is more powerful than anything setting it apart. Grief can be a terrible weight for any creature to endure, and at the same time, it telegraphs to the world the power of a love once shared.

Adapted with permission from “How Animals Grieve” by Barbara J. King, barbarajking.com.