National Zoo Mourns the Death of Black Howler Monkey

The Smithsonian’s National Zoo euthanized a young black howler monkey, Loki, Sunday, Oct. 7, because she was ill from complications of metabolic bone disease. This disease is a vitamin D, calcium and phosphorus imbalance. It is most often caused by lack of sunlight (ultraviolet light), lack of dietary intake of vitamin D and/or the body’s inability to properly metabolize these compounds.

For five days, Loki was treated in the hospital with injectable vitamins, iron, calcium and exposed to direct sunlight while receiving around-the-clock nursing care. A blood transfusion was provided from the father as well. Despite the combined efforts of keepers, nutritionists, technicians and veterinarians, the monkey grew weaker. The consensus decision was made to humanely euthanize Loki on Sunday morning.

The skylights in the Small Mammal House are made of UV-transmissible glass, which allows the UV to penetrate the animal enclosures in order to provide sunlight. This is important for young animals especially as they wean. This monkey was in the weaning process as she was entirely dam-reared and just starting to eat solid foods. Because the amount of UV light penetration can vary depending on many factors, staff regularly use light meters to measure the intensity of the UV light. Zoo experts are now examining the accuracy of the light meters used. Staff are implementing immediate husbandry changes, where appropriate, such as rotating animals to outdoor enclosures to allow direct sunlight exposure and evaluating diets for at-risk animals.

Loki was born March 22 to first-time parents Chula (mother) and Pele (father). The Zoo has two pairs of howler monkeys on exhibit.

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