Two Amur tiger cubs had their first public outing Thursday at Cologne Zoo in Germany, one of several zoos that has sought to help keep up the numbers of the rare big cats.

The cubs – a female named Tochka and a male named Timur – were born in mid-April and now weigh about 13 kilos (28.7 pounds) each. The pair explored their enclosure together with their mother, 13-year-old Katinka.

“They are well fed, alert and awake,” the zoo said in a social media post, noting that the cubs still consume almost exclusively milk, but their interest in meat is “increasing.”

Amur tigers, also known as Siberian tigers, are found in the far east of Russia and northeastern China and are considered endangered.

“We are very happy and proud of the offspring of this highly threatened species,” zoo curator Alexander Sliwa said in a statement, which said that 240 Amur tigers in zoos are currently part of a European program to help conserve and breed the animals.

Katinka was brought from the zoo in Nuremberg last summer in exchange for Cologne tiger Akina after the existing pairs at both zoos had long failed to produce offspring. She quickly hit it off with 9-year-old Sergan, the cubs’ father, the zoo said.

According to the Amur Tiger Center, Siberian tigers are the “largest living cat on the planet.” Males weigh 400-700 pounds and are 9-12 feet long, including their tail, according to the Denver Zoo. Fewer than 500 Siberian tigers remain in the wild although there are several hundred in captivity.

Earlier this month, eight rare tiger cubs, including Siberian tigers, were born in a Russian zoo.