The National Zoo’s elderly tammar wallaby, which had suffered the indignities of old age as well as tensions with her 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 she lived.

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

The zoo had shipped out its other wallabies to make way for the African hornbills as it shifted the exhibit’s focus to species from Africa. But Maji was too old and infirm to be moved, the zoo said.

The recent arrival of the long-beaked hornbills apparently upset her. A worried volunteer told zoo officials that she’d heard the wallaby had injured herself running from the hornbills, which are large birds.

The zoo denies that happened. The birds are in a separate enclosure. But it erected a barrier so Maji didn’t have to look at the hornbills.

Maji had been at the zoo for seven years and had been the lone wallaby for about two. The zoo at one point had four wallabies. The hornbills arrived last year.

The wallaby-hornbill relationship was reviewed in a recent report.

The zoo said it has addressed the lapses. It added that Maji had several teeth pulled in recent years and was on medication for infections and pain. Recently, she had lost weight and had no appetite.

A recently released internal zoo detailed the deaths of two animals — a lesser kudu, a type of antelope, and a female red river hog — and a series of other mishaps in the cheetah exhibit as the zoo brought in new African species.

Additionally, a Dama gazelle died Nov. 18 at the zoo and a Przewalski’s horse died Dec. 11 at the zoo’s Conservation Biology Institute in Front Royal, Va.