The National Zoo’s elderly Tammar Wallaby, which had suffered the indignities of old age as well as chronic fear of its new neighbors, two Abyssinian ground hornbills, was euthanized Thursday, the zoo announced Friday.

The animal, a kind of miniature kangaroo, had long suffered from dental problems, and lately was caught up in the controversy over the zoo’s Cheetah Conservation Station complex, where it lived.

The wallaby was a female named Maji. She was 18. Most wallabies, which are native to Australia, only live to be 10, the zoo said.

The zoo had been in the process of shipping out its wallabies to make way for the African hornbills as it shifted the focus of the exhibit to species from Africa. But Maji, the last wallaby, was too old and infirm to be moved out, the zoo said.

And the recent arrival of the large, loud, and long-beaked hornbills so upset her that she bloodied her nose running into a wall to get away from them, according to a worried volunteer who voiced concerns to zoo officials. The wallaby had been at the zoo for seven years. The zoo at one time had four wallabies.

Maji was subsequently given her own holding area where she didn’t have to look at the hornbills, according to a zoo report that detailed a series of animal deaths and other serious mishaps in the Cheetah complex.

The zoo said that Maji had several teeth pulled in recent years, and was on medication for infections and pain. Recently she had lost weight and her appetite.