At the National Zoo and its associated research facility, births provide frequent cause for celebration, but this month four poignant deaths have occurred, including the loss of a sloth bear that had been hand-raised.

The zoo said Remi was euthanized May 2 at the age of 6, well short of the 17-year median life expectancy for sloth bears in captivity.

In a statement last week, the zoo ascribed the decision to end her life to a foot wound that was not healing, despite treatment. Remi’s loss may have been particularly painful to zoo staff considering the efforts made to save her shortly after her birth.

Remi was one of three cubs delivered by their mother, Khali, at the Smithsonian Institution’s zoo on Dec. 29, 2013. It was after Khali ingested the other two and did not seem appropriately attentive to Remi that the staff intervened, according to the zoo.

At one point, Remi was bottle-fed eight times a day. Keepers carried her around in a sling, to provide the social interaction of which she was deprived.

In the zoo’s statement, Michael Brown-Palsgrove, curator of the zoo’s Asia Trail, called Remi’s care and treatment “a testament to the passion and commitment of our dedicated team to do what was best for this sloth bear.”

Another death this month among the 2,700 animals at the zoo was that of Mook, a clouded leopard that at the age of 18 was elderly. In the care of humans, clouded leopards can expect to live about 12 years, the zoo said.

Mook came here in 2006 from a zoo in Ohio and was the oldest clouded leopard in North America, the National Zoo said Friday.

Shy and reserved, the zoo said, Mook was not easy for keepers to get to know, but to those who did, she offered a friendly vocalization as a “good morning.”

Mook had suffered an “irreversible decline in health,” the zoo said, and was “humanely euthanized” on Wednesday.

Finally, the Smithsonian Conservation Biology Institute in Front Royal, Va., reported the loss of two animals that to many of us, embodied the romance and history of the American West.

The two bison, often called buffalo, were Ten Bears, a male, and Kicking Bird, a female. They were humanely euthanized May 14, the zoo said. Both 22, the zoo said, they were old and ill and after years together, the death of one was expected to place undue stress on the other.