A young trio of Amur tigers celebrated their first birthday at the Yorkshire Wildlife Park in style on Tuesday. Hector, Harley and Hope were filmed on their journey from adorable cubs to adorable ferocious predators and, to mark the landmark occasion, the park released an adorable video showcasing how they’ve grown.

The park posted the video on YouTube on Tuesday with the message “Happy 1st birthday to our very special (not so little anymore) tiger cubs, Harley, Hector and Hope!” And indeed from helpless newborns, totally dependent on their mother Tschuna, the trio grew into fearsome cats.

Since their birth in March of 2015, the cubs have been one of the park’s greatest hit with visitors, as “they are always up to mischief,” Yorkshire Wildlife Park’s website reads. The cubs live alongside their mother, Vladimir their father and another tiger named Sayan. And as much as it saddens me to see animals in zoos, it might be for the best.

I say this because Amur (or Siberian) tigers are a dangerously endangered species, threatened by poachers, illegal wildlife trade and habitat destruction from illegal loggers, conservation nonprofit World Wildlife Fund for Nature reports. There are only an estimated 540 of the regal beasts still living in the wild, in their native forests of the Russian Far East.

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