A 2-year-old female addax named Terri has died at Smithsonian’s National Zoo in D.C.

The addax was found dead June 12 near a fence that separates the addax and ostrich habitats. Necropsy reports showed evidence of a cervical fracture, which the zoo said indicates something may have spooked Terri and caused her to run and collide with the fence.

Terri and her two herd mates, Jack and Janet, arrived at the zoo in November of 2021. Their species is native to the African countries of Chad and Niger and is considered critically endangered in the wild.

The zoo said the life span of an addax is unknown in the wild, but in human care, males have lived up to 11 years and females have lived up to 14 years.