In the week after welcoming the surprise birth of an Angolan colobus monkey, the Lake Superior Zoo is now mourning the loss of its 15-year-old Amur tiger, Lana.

Lana was euthanized Wednesday afternoon after undergoing treatment for a liver disease since September.

Among zoo staff and the greater community, Lana's presence will be missed, said the zoo's director of animal management, Dave Thompson.

"Above all I want to commend my staff for all their efforts to ensure that Lana's quality of life was maintained at the highest possible level," Thompson said in a news conference Thursday. "Lana was very charismatic and a very valued member of our zoo family. She was also a great ambassador of her species."

Lana has been touching lives in the community since she arrived at the Lake Superior Zoo in 2015. She was born at the Minnesota Zoo in Apple Valley.

"She was rejected by her mom and one of our keepers actually helped raise Lana when she was a young kitten," Thompson said.

In the upcoming months, the zoo hopes to have another Amur tiger, whether it's one or two, to represent the species. Until then, Lana's former exhibit will remain closed. She was the only Amur tiger at the zoo.

Before Lana died, the Lake Superior Zoo was one of 47 facilities in North America to have an Amur tiger.

Lana died at an age typical for her species. The lifespan for the Amur tiger is usually between 10 and 15 years in a natural environment or 15 to 20 years in a zoological facility, Thompson said.

Dr. Louise Beyea, veterinarian at the zoo, said Lana's body was taken to the University of Minnesota veterinary diagnostic lab, meaning that in a month the zoo will get further results on the disease Lana had.

In late August, zookeepers first noticed that Lana's behavior was off, Beyea said. Although Lana had received her routine physical exam in May and everything appeared normal, zoo staff decided to check up on her health again and found that she had an infection and inflammation in her liver and bile ducts.

Since then, Lana was given medication every day and her blood work was showing signs of improvement.

"However, yesterday things took a sudden turn for the worse," Beyea said on Thursday. "Yesterday morning she was extremely depressed and was refusing all interactions with her food or treats or toys and clearly was showing symptoms that something was really wrong."

Emergency blood work showed that Lana's liver values were increasing rapidly.

In a group discussion, caretakers decided to euthanize Lana before her suffering became worse, a decision that Beyea said doesn't come easy when toying with hope that more medication or trying different therapies will work.

"The reality is none of us get off the planet alive including our beloved pets and zoo animals," Beyea said. "So there does come a point where it's necessary to alleviate the suffering because animals don't understand their disease, animals don't have hope, all they know is they hurt."

Beyea referred to Lana as the most enthusiastic tiger she's ever worked with.

"She was just an absolute joy," Beyea said. "She really has a special place in our hearts ... whenever I'd go to a meeting or church people would always say, 'How's the tiger doing?' She was really special to a lot of people."

It's estimated that there are between 350 and 500 Amur tigers currently in the wild, due to deforestation, poaching and illegal hunting, Thompson said.