PORTLAND, Ore. - A black rhinoceros has died while in transit from Kansas City to Portland.

Zookeepers had planned for the 8-year-old rhino named Kipenzi to breed with the Oregon Zoo's male.

Zoo deputy director Mike Keele says black rhinos are among the world's most endangered animals. He called Kipenzi's death "devastating."

Keele says the rhino became agitated early Monday about 20 miles outside Phoenix. Zoo staff immediately stopped the truck to check on the rhino, and then headed to the city's zoo to seek care.

The Phoenix staff had a crane delivered and the rhino was unloaded into their elephant barn. The rhino died Monday night.

A necropsy is being performed to determine the cause of death. Preliminary results should be available within three weeks.