Hundreds of small cetaceans were stranded along Peru's northern coast earlier this year. While the event is under investigation, Peru's government should be setting up programmes to monitor marine pollution and taking precautions to protect the coastal ecosystem.
The dead animals comprised mainly long-beaked common dolphins (Delphinus capensis) and Burmeister's porpoises (Phocoena spinipinnis). They had internal trauma and lesions that could have been caused by underwater noise effects (see http://go.nature.com/tbfi7n). Although military sonar is known to induce cetacean strandings, no naval exercises had been reported in the area. Neither had there been any seismic testing associated with gas and oil exploration, which can also be a contributor.
Persistent pollutants that accumulate in cetaceans could be a factor. These weaken cetacean immune systems, making them more susceptible to infection (P. Ross Hum. Ecol. Risk Assess. 8, 277–292; 2002), exacerbated by food shortages during El Niño episodes and harmful algal blooms.