One of the Amur tiger cubs born earlier this month at the Magnetic Hill Zoo in Moncton, N.B., died Sunday.
The zoo said the cub, a female, was the smallest of the four tigers born at the zoo on May 11.
"She was just not reaching those same milestones that the other ones were, so we continued to support but unfortunately we couldn't cure whatever happened or whatever was going on with her," said the zoo's director Jill Marvin.
Marvin said the cub had been given "extra support" — like extra fluids and warming — by the zoo's veterinary team in addition to her mother's care.
Marvin said it's not clear what the cause of her death was, but said the zoo will do a full necropsy to find out.
Amur tigers, commonly known as Siberian tigers, or Panthera tigris altaica, are endangered. These cubs are the second litter born to Anya and Alik, who were both brought to the zoo in 2014.
Marvin said the other cubs are "thriving, they're doing really well" and will remain away from the public exhibit with their mother for now.
"We've got some of the eyes gradually opening as well, they're milking, they're growing so we'll just keep our fingers crossed, but we certainly will keep them under watch," she said.