Eastern rockhopper penguin genetic divergence with the southern rockhopper penguin may have been caused by a vicariant event caused by a shift in the position of the Subtropical Front during the mid-Pleistocene climate transition. Analysis of a part of a mitochondrial control region from a northern rockhopper penguin found on the Kerguelen Islands showed that it may have come from Gough Island, 6,000 km away, and that the southern and northern rockhoppers are genetically separate, though some individuals may disperse from their breeding colonies. Many taxonomists have yet to recognize the split, although some are beginning to do so. "E. c. filholi" breeds
Rockhopper Exploration in production licences PL023, PL024, PL032 and PL033 covering approximately 3800 km. In 2005 it farmed into licences PL003 and PL004 operated by Desire Petroleum plc. In 2011, Rockhopper increased its share of PL004b from 7.5% to 60.0% and in PL004c from 7.5% to 25.0%. Licence PL004b contains an extension to the Sea Lion field as well as the Beverley, Casper and Casper South discoveries. The Rockhopper board comprises eight directors; a non-executive chairman, three executive directors and four non-executive directors, one of whom acts as senior independent director. Four of the non-executive directors are considered to be independent. The