The Honolulu Zoo announced that it recently euthanized two Sumatran tigers, both of which had suffered from kidney disease.

The City and County of Honolulu today said that it had euthanized Seattle, a 15-year-old male, on Jan. 5 and Chrissie, a 23-year-old female, on Tuesday.

“It was a very trying and emotional week for our staff as we have lost two of our beloved Sumatran tigers. We are happy that Chrissie lived a very long and full life, and Seattle lived to a good age of 15 and a half,” said Honolulu Zoo Director Linda Santos in a statement. “Chronic kidney disease is common in feline species including tigers, and I am very proud of our staff who have worked together and with other zoos and animal care professionals to provide the best welfare, husbandry, and medical care for both Chrissie and Seattle.”

Seattle became ill with Bartonella infection last month, the city said, prompting zoo staff to euthanize the tiger. Despite treatment, the infection resulted in “significant worsening” of a previously diagnosed kidney disease, and he went into acute renal failure. He was euthanized under anesthesia.

Chrissie had been treated for her kidney disease for over 12 years. Her activity and appetite had slowed recently, and the decision was made to euthanize her before she declined further.

Seattle was born on June 3, 2007, at the Los Angeles Zoo and brought to the Honolulu Zoo from Baton Rouge Zoo on June 9 last year despite his advanced age and evidence of ongoing renal insufficiency, the city said.

He was brought to Honolulu to breed with Anala, a female tiger at the zoo and one of Chrissie’s biological granddaughters.

Chrissie was born on June 24, 1999, at the Smithsonian’s National Zoo. She had three cubs, including Anala’s father, in 2008 at the Honolulu Zoo. The cubs were transferred to other zoos. Anala was transferred to the Honolulu Zoo in July of last year.

The zoo is working to identify breeding opportunities for Anala.

The Sumatran tiger is one of the smallest species of tiger and is listed as critically endangered under the International Union for Conservation of Nature. Their average lifespan ranges from 15-20 years under care.