Lessons Learnt from post-release monitoring of oiled-penguins: New Zealand C/V Rena

Abstract

Abstract The value of rehabilitating oiled wildlife is an on-going global debate. On October 5, 2011, the cargo vessel C/V Rena grounded on Astrolabe Reef, New Zealand (NZ), spilling over 300 tonnes of heavy fuel oil. As part of the Rena oil spill response, 383 little blue penguins (LBP, Eudyptula minor) were captured, cleaned, rehabilitated and released back into a cleaned environment. Over the last four years, since the C/V Rena spill, we have undertaken survival, diving behaviour, diet and stress hormone response research on these and non-rehabilitated LBPs from the spill area to assess the success of the rehabilitation process, determine what lessons could still be learnt and to help determine if the environment has returned back to its natural state. Findings from this research showed that the survival was reduced for both rehabilitated and non-rehabilitated groups in the first six months following the spill and clean-up process however, the survival probabilities of both groups increased thereafter and remained high and stable over a two year period directly after the spill. The foraging behaviour and diet studies showed there were no foraging behaviour differences between rehabilitated and non-rehabilitated LBPs and the overall diving behaviour of these LBPs were similar, if not less energetic, than other LBPs in NZ, indicating that the environment appeared to have also returned to pre-oiling state. Concurrently, the stress hormone response study showed no differences between groups, suggesting the rehabilitation process for LBP did not affect their long term physiological responses to humans, meaning no habituation or excessively stress caused by humans over the long term. Together these results suggest the rehabilitation process and clean-up undertaken after the C/V Rena appears effective and helps validate the rehabilitation of oiled wildlife.