A rhino calf celebrated his first birthday at a zoo in Portland, Oregon.

Weighing 1,040lbs (472kg), Tamu, the zoo's youngest black rhinoceros, marked the milestone on December 4.

Born to Jozi and King, Tamu is growing rapidly but still stays close to his 2,400lbs (1,089kg) mother.

Kelly Gomez, head of the zoo's Africa area, said: 'He's the only 1-year-old I know who weighs half a ton. We're thrilled with his growth and progress.'

Tamu and his family belong to the eastern black rhino subspecies, one of the most critically endangered species on Earth.

With the western subspecies declared extinct in 2011, Tamu's story offers hope for the survival of rhinos, who face severe threats from poaching for their horns.

The Oregon Zoo, in partnership with the International Rhino Foundation, has been working since 2013 to protect rhinos through anti-poaching efforts and local conservation programs.

Jozi and King were brought to the Oregon Zoo in 2021 as part of the Association of Zoos and Aquariums' Species Survival Plan, which aims to maintain genetically diverse populations of endangered species.

U.K. naturalist Steve Backshall said: 'We've gone from half a million to just a few thousand rhinos in the blink of an eye.

'The rhinos in zoos, born and bred there, are of disproportionate importance to the survival of their kind.'