But his rescuers were unable to simply reintroduce Owen to another pod of hippopotamuses, because the oldest male would see him as a threat and kill him.
Conservationists therefore decided to transport Owen to Haller Park, about 50 miles (80 kilometers) away.
There the hippo immediately ran to Mzee, a 130-year-old Aldabran tortoise who resides at the Haller Park sanctuary. The park is a restored ecosystem that also serves as an orphanage for abandoned wildlife.
At first the tortoise wanted nothing to do with the hippo, but Owen persisted. Some conservationists suggest that Owen, in search of a mother figure, may have been attracted to Mzee's round shape and gray color, which resemble an adult hippo.
The first night at the sanctuary, Owen fell asleep next to Mzee. The following morning photographer Peter Greste took a picture of the pair, which was subsequently published in newspapers around the world.
Hans Klingel is a zoology professor at the University of Braunschweig in Germany and an authority on hippopotamus behavior. He said given hippos' social nature, Owen's attraction to Mzee makes sense.
"They are social animals," he said in an email. "In that sense, they join whoever is available."
In the year since the tsunami struck, the bond between hippo and tortoise has strengthened, and now the two are inseparable. They rouse each other for meals, spend hours wallowing in the pond together, and snuggle up side by side each night.
According to Haller Park staff, Owen behaves more like a tortoise than a hippo. He eats tortoise food, such as leaves and carrots, and ignores the grasses that hippos normally consume. He sleeps at night, not during the day as wild hippos do. And he doesn't respond to hippo calls.
While Owen's attraction to Mzee may be explained by a baby's need for a mother figure, tortoises are not known for affectionate or social behavior, Kahumbu said.
Nevertheless, Mzee follows Owen around, nudges him to go for walks, initiates play in the water, and even stretches his neck out so Owen can give him a lick.
There has been growing evidence of physical communication between the pair, with Owen nibbling Mzee's back feet to get him to walk in a desired direction. The two have even developed a sort of vocal communication of their own, Kahumbu said.
The vocalizations are not the honking of hippos or the grunts and hisses of tortoises, but rather a soft whimpering that emanates from one and is mimicked by the other.
"It's very high pitched; definitely not a stomach sound, as some had suggested," Kahumbu said. "They're vocalizing towards each other."
What the animals are trying to communicate is not yet understood, but researchers think it is a contact call made to get the other's attention.
Concerned that Owen's affection for Mzee may lead to an unintended injury, Kahumbu and colleagues are constructing a new enclosure at the sanctuary for Owen and the female hippo, Cleo.
The researchers hope Owen and Cleo will bond and take to their new grounds, which will be in the public view. They are also trying to accustom Owen to the presence of humans.
The move is expected to take place this April or May. At that time Mzee will be moved with Owen to the new enclosure to help keep the young hippo calm.
Once the two hippos are comfortable with each other, Mzee will be returned to his original grounds with other tortoises.
"We hope Mzee will not be too traumatized by being separated from Owen," Kahumbu said.
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