Little blue penguins on the mend after oil spill

When an oil spill hits the news, the images of environmental devastation are often soon followed by more optimistic pictures of people cleaning and rehabilitating wildlife. But some critics have called the effectiveness of these recovery efforts into question.

To find out whether the cost justifies the conservation value, researchers need to know how well rehabilitated animals fare after release. In a recent study, a team in New Zealand found that penguins cleaned up after a 2011 oil spill now appear to be diving normally — a hopeful sign for their long-term recovery.

The spill released more than 300 tonnes of oil at Astrolabe Reef off the coast of New Zealand. In response, people rehabilitated 383 little blue penguins — diminutive birds that measure less than 1.5 feet tall — and released 347 with implanted microchips back into the wild. Follow-up research showed that the treated penguins had survival rates similar to those of other penguins in the area that had not been oiled or rehabilitated.

In the new study, the researchers wanted to investigate the birds’ foraging behavior. The team caught 10 rehabilitated penguins, as well as 10 that had not been oiled or rehabilitated, and fitted them with tracking devices. The devices could detect how frequently the animals dived, how deep, and whether the shapes of the dives resembled a V, U, or W.

The team managed to gather data on 24,508 dives from 14 of the penguins. A typical foraging trip was about 13 hours long, and the birds dived an average of 131 times per hour. The rehabilitated and non-rehabilitated penguins showed similar diving patterns.

The researchers also collected six feathers from each penguin and analyzed the carbon and nitrogen content. The rehabilitated and non-rehabilitated birds’ feathers had similar chemical signatures, suggesting that the two groups of penguins were eating the same types of prey. So the clean-up effort “appears effective,” the authors write, “and helps justify the rehabilitation of oiled wildlife across the world.” Roberta Kwok | 15 October 2015

Source: Chilvers, B.L. et al. 2015. Diving behaviour of wildlife impacted by an oil spill: A clean-up and rehabilitation success? Marine Pollution Bulletin doi: 10.1016/j.marpolbul.2015.09.019.

Image © Stanislav Fosenbauer | Shutterstock