Northern rockhopper penguin colonies in a range of locations from sea level or on cliff sides, to sometimes inland. The Northern form, found in Amsterdam and Gough island, is reproductively isolated from the Crozet and Kerguelen islands. They are monophyletic; meaning they have a split in the mitochondria DNA trees which forms two subspecies: the northern and southern rockhopper penguin. Another interesting difference between the two subspecies is their mating ritual. They both use different songs and head ornaments in their mating signals. The reproductive isolation has led to not only physical difference but also behavioral. The adults feed their chicks lower trophic
Rockhopper Exploration viable rates. In July 2012, Rockhopper announced that it had entered into a conditional farm out agreement with Premier Oil plc whereby Premier will acquire 60% of Rockhopper's interests in its North Falkland Basin licences in exchange for an upfront cash payment of $231m, a contribution of $722m to Rockhopper's share of the Sea Lion development costs and a net exploration carry of $48m. Rockhopper will be fully funded on its share of the Sea Lion development through the contribution to costs and standby financing provided by Premier. First oil from Sea Lion is expected in 2020. Rockhopper holds interests