[4] 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.

More than 99% of northern rockhoppers breed during late spring or early summer on Tristan da Cunha and Gough Island in the south Atlantic Ocean.

[9] Proof that the three subspecies were truly different, in terms of more than reproductive isolation and some morphological features, was found in the mitochondrial sequences of the three species.

[12] The northern rockhopper penguin feeds on krill and other sea life such as crustaceans, squid, octopus and fish.

They are monophyletic; meaning they have a split in the mitochondria DNA trees which forms two subspecies: the northern and southern rockhopper penguin.

During breeding season the adults eat zooplankton and then transition to fish, showing they favor future reproduction.

[17] Other possible factors in the decline include disturbance and pollution from ecotourism and fishing, egg-harvesting, and predation and competition from subantarctic fur seals (Arctophoca tropicalis).

The crew was rescued, but the ship broke up, leaving an oil slick that surrounded the island, threatening its population of rockhopper penguins.

[21][22] Nightingale Island has no fresh water, so the penguins were transported to Tristan da Cunha for cleaning.