https://phys.org/news/2018-07-10th-endangered-rhino-dies-kenya.html

Preliminary investigations show the rhinos died from stress intensified by salt poisoning as the animals struggled to adjust to saltier water in their new home, Balala said.

"The animals were dehydrated, restless" and drinking more of the water only worsened the problem, said Peter Gathumbi, professor of veterinary pathology at the University of Nairobi.