A Sumatran tiger cub is seen with its mum at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen with its mum at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

Visitors are seen at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen with its mum at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen with its mum at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

A Sumatran tiger cub is seen with its mum at ZSL (the Zoological Society of London) London Zoo in London, Britain, on Jan. 27, 2022. A Sumatran tiger cub was born here last month. The Sumatran tiger is classified as critically endangered on the International Union for Conservation of Nature's red list of threatened species. (Xinhua/Han Yan)

来源：Xinhua