She might have grown to be a full-fledged howler, adding her voice to that of the louder families in Washington.

But Loki, a young black howler monkey, a member of a species named for its sonic output, never came into her full vocal inheritance. Loki, who was born at the National Zoo this year, became ill and was euthanized Sunday, the zoo said.

According to the zoo, Loki, not yet 7 months old, suffered complications of a metabolic bone disease, an imbalance of vitamin D, calcium and phosphorus.

It was another loss for the zoo, where the recent death of a newborn giant panda cub remains fresh in memory.

Although lacking the allure of the panda, howler monkeys, denizens of South and Central American forests, have attracted attention through the power of their sound-producing apparatus. The sound, particularly that of the alpha males, has been likened to a blend of roaring, barking and braying.

Although many may be skeptical, a recent edition of the Guinness Book of World Records listed the howler monkey as the “noisiest land animal.” (Some whales are said to be louder.)

Males, in full voice, can be heard up to three miles away, the record book said. The sounds are said to be used to mark territory.

Females play a subordinate role in the howler chorus, said Greg Budney, curator of audio at the Macaulay Library at Cornell University, which collects animal sounds.

The zoo said Loki’s ailment often stems from from a lack of ultraviolet light, dietary problems and/or metabolic failures.

Zoo officials said Loki was treated at the zoo hospital with injectable vitamins, iron and calcium. She received a blood transfusion, was exposed to direct sunlight and was given 24-hour-a-day nursing care. Glass skylights in the small-mammal house transmit the sun’s ultraviolet radiation, which helps produce vitamin D. But despite the efforts, the zoo said, Loki grew weaker.

Two pairs of howler monkeys are on exhibit, the zoo said.