2 Answers

Testing needs to be done.  Are we polluting are oceans beyond the beyond?

The first place I would look is diet. 

30 April 2012 Last updated at 08:25

Peru's Deputy Minister for Natural Resource Development, Gabriel Quijandria Acosta, said a virus might have killed the dolphins.

A viral epidemic outbreak was linked to similar deaths of marine wildlife in Peru in the past, as well as in Mexico and the United States.

Analysis on the dolphins so far suggested they had contracted a morbillivirus, which belongs to the same group as the measles virus in humans, Stefan Austermuehle of a local NGO, Mundo Azul, told the BBC.

"We know that in other cases in the United States up to 50% of populations were killed by the virus," he said.

"What we also know...is that in previous cases animals that have higher loads of pollutants in their body will fall easier victims to these kind of diseases because their immune system is weakened."

Imarpe scientists said results of tests carried out on the dead dolphins would be released in the coming days.

Source: http://m.bbc.co.uk/news/world-latin-america-17890174