The first time Themba met Albert, he chased him round a watering hole until the sheep barricaded himself inside a shelter and refused to come out for twelve hours.

It was not, on the face of it, the start of a beautiful friendship.

But by the next morning Albert was venturing out, and Themba — a six-month-old elephant calf who had just lost his mother — would not leave his side. The two walked the enclosure together, the elephant's trunk resting on the sheep's woolly back, and they have stayed that way ever since.

The pair live at the Shamwari Wildlife Rehabilitation Centre in South Africa's Eastern Cape, one of the country's best-known sanctuaries for orphaned and injured wildlife. Themba arrived there after his mother fell down a cliff on the Sanbona reserve. Vets watched him for a week, hoping another cow would adopt the calf and let him suckle. None did. Without intervention, he would have starved.

Staff moved him to Shamwari and, casting around for a companion that might pull him out of a deep depression, tried something unconventional: they put a sheep in with him.

An unlikely herd of two

"At the first meeting, Themba made a dash for the sheep and chased him around his watering hole," filmmaker Lyndal Davies, who documented the pair, told the Mumbai Mirror. Albert retreated. Themba, undeterred, kept poking his trunk through the bars of the shelter and touching the sheep's back.

The truce, when it came, was total. "Ever since then, the two have been inseparable," Davies said.

Dr Johan Joubert, Shamwari's wildlife director, described Albert as "like a brother" to the calf and "definitely an important member of Themba's herd". The staff had worried they might end up with an elephant who thought he was a sheep. Instead, they got a sheep who thought he was an elephant.

"Albert copies everything Themba does," Joubert said. "In fact, they have almost the exact same diet. Albert is the first sheep I have ever seen eat a thorny acacia bush." The sheep had, he said, watched the elephant carefully and worked out how to angle his mouth past the spikes to reach the leaves.

Why animals reach across species

Stories like this one tend to be filed under "heartwarming" and left there, but they are also of genuine interest to ethologists. Interspecies bonds are most commonly observed in captivity or rehabilitation, where young animals have been separated from their own kind and are under acute stress. Researchers who study the phenomenon point to the same drivers that underpin friendships within a species: a need for social contact, shared routine, mutual benefit, and — in young mammals especially — the search for something to attach to when a mother is gone.

For an orphaned elephant, whose species forms some of the tightest family bonds in the animal kingdom, almost any steady presence is better than none. Albert, by all accounts, turned out to be a very steady presence.

The long game

Shamwari's stated aim was always to rehabilitate Themba for release into the wild, which would mean, eventually, separating the pair. Whether or not that worked out as planned, the image has stuck: a grieving baby elephant with his trunk draped across a sheep's back, picking his way through the scrub at dawn.

It is the kind of small, specific detail that outlasts the headlines — and a reminder that comfort, in the animal world as in ours, does not always arrive in the shape you expect.