Population trends and conservation status of the Northern Rockhopper Penguin Eudyptes moseleyi at Tristan da Cunha and Gough Island

Populations of the recently split Northern Rockhopper Penguin Eudyptes moseleyi are restricted to Tristan da Cunha and Gough Island in the South Atlantic, and Amsterdam and St Paul in the Indian Ocean. The majority of the population is in the Atlantic (> 80%), but population trends at Tristan da Cunha and Gough are uncertain. Early records indicate “millions” of penguins used to occur at Tristan da Cunha and Gough Island. The most recent estimates indicate declines in excess of 90% for both Gough and the main island of Tristan that have occurred over at least 45 and 130 years, respectively. Numbers breeding at Inaccessible and Nightingale islands (TDC) also may have declined since the 1970s, albeit modestly, whereas numbers on Tristan appear stable over the last few decades. Current population estimates are 32,000–65,000 pairs at Gough, 18–27,000 at Inaccessible, 19,500 at Nightingale, and 3,200–4,500 at Tristan. Numbers and trends at Middle Island (TDC) are unknown. Middle Island supported an estimated 100,000 pairs in 1973, and recent observations suggest this colony is being impacted by competition for space with recently recolonising Subantarctic Fur Seals Arctocephalus tropicalis. Past human exploitation and the impact of introduced predators may be responsible for the historical decline in numbers at Tristan, but these factors cannot explain the sharp decrease (since the 1950s) at Gough Island. Overall, declines at Gough, Tristan, Nightingale and Inaccessible islands indicate a three-generation decline of > 50%. Taken in combination with recent decreases in Indian Ocean populations, the Northern Rockhopper Penguins is now categorised as globally ‘Endangered’. Determining the causal factors responsible for these recent declines is an urgent priority.