Rare Sumatran Tiger Cubs Emerge from Zoo Den for the First Time: 'Still a Little Shy'

Two mischievous zoo tiger cubs have braved leaving their den for the first time, emerging into their outdoor habitat to wrestle each other and play with their mom.

The Sumatran tiger cubs were born in January at Chester Zoo in the U.K. and have been named Alif, a popular name in Indonesia, and Raya after Mount Raya in Sumatra.

Until recently, the tiger sisters had been inside their den with their mother, Kasarna.

Dayna Thain, who is the carnivore keeper at the zoo, said the birth of the two girls was "wonderful news" because the endangered species is "hanging on to survival by a thread in Sumatra."

"They're one of the world's rarest tiger subspecies and so to see these two cubs thriving here is absolutely wonderful. It's a real joy to get a glimpse of the cubs exploring and enjoying some playful rough and tumble together," Thain said.

"The cubs are still a little shy and pop in and out of the den with mum Kasarna, but it's going to be a real privilege to watch as they grow in confidence and their feisty personalities really start to show through," the zookeeper added. "Crucially, with so few Sumatran tigers left on the planet, Kasarna's girls are vitally important additions to the conservation breeding program, which is working tirelessly to prevent the species from becoming extinct."

Raya and Alif's vivid markings already show the white spots on their ears, which act as false eyes and give the impression of being alert when viewed from behind. Sumatran tigers' stripe patterns are closer together than other tiger subspecies, and the big cats are the smallest of all tigers.

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The species is listed as critically endangered, and there are only believed to be about 350 living in the wild, in small patches of forest on the Indonesian island of Sumatra.

The International Union for the Conservation of Nature said habitat loss and hunting were significant factors in the dwindling Sumatran tiger populations. The species is also heavily poached for its skin, bones, and teeth, which are sold illegally in some traditional medicine markets.

Chester Zoo is part of an international conservation breeding program to protect the species. The zoo's 128-acre site is home to more than 27,000 animals and more than 500 species.