TAIPEI (Taiwan News) – A visitor at the Taipei Zoo alerted guards to the death of a white rhino, reports said Saturday.

The dead rhino was “Xihui” (犀慧), a 38-year-old female animal born at the zoo, the Liberty Times reported. An autopsy will help determine the cause of death.

At 12:40 p.m. Saturday, a visitor alerted staff that one of the white rhinos did not look well. Experts rushed to the scene to find the animal immobile.

The witness told them the rhino had been rolling around and twitching before collapsing. A team from National Taiwan University would come in to perform an autopsy, the zoo said.

In March and April, staff had noticed Xihui had trouble digesting long dry grass, leading to a decision to cut the grass before handing it to the animal. The rhino maintained a weight of around 1,640 kilograms, but sometimes spat out the grass. Saturday morning, guards had noticed the animal had been slow to respond to the calling of its name.

White rhinos usually weigh between 1,700 kg and 2,400 kg, per CNA. They can reach an age between 40 and 50.

The animals are listed as near threatened, with a declining number of about 15,000 living mostly in southern Africa, according to the International Rhino Foundation.