Complex sentence: Dukes had been reported by Seaworld staff to have "dived" with other sea mammals, earlier that year he had to be removed from the manatee tank, which is warmer and hosts much more docile creatures.
Split into simpler sentences: Dukes had been reported by Seaworld staff to have "dived" with other sea mammals. Earlier that year he was removed from the manatee tank, which is warmer and hosts much more docile creatures.