The Peruvian government claims that nearly 900 dolphins died of natural causes between February and April of this year. A separate dolphin necropsy disagrees with this statement and lays the blame on bursts of high-pressure compressed air used to look for oil deposits beneath the ocean.

The government’s report didn’t say what killed the dolphins or why so many died at one time. Blaming natural causes doesn’t specify any particular culprit. And it seems odd that 800 individuals all died at once, especially considering they were of different ages and species. It would be as if everyone at a shopping mall just suddenly died and the coroner said it was perfectly natural. But the government claims it has happened before.

BRIEF: Are Dolphins Doomed?

“It happens periodically, it isn’t the first time. It has happened in New Zealand, Australia, and other countries. There is no need to find other reasons that are not it,” said Gladys Triveño, Peru’s Minister of Production in EuropaPress.

No data was provided as to when these earlier events occurred.

The Organization for Research and Conservation of Aquatic Animals (ORCA) has a more precise explanation of what caused the mass dolphin death.

A necropsy on the dolphins by ORCA, along with other international organizations, found fractures and hemorrhages in the dolphin’s middle ear. They also found gas build ups in mammals’ internal organs. The necropsy concluded that severe acoustic trauma and gaseous embolism led to decompression syndrome and killed the dolphins.

ANALYSIS: Thousands of Dolphins Dying in Gulf Waters

In a press release, ORCA stated that these symptoms could have been caused by the compressed air bursts used to observe the ocean floor in search of oil deposits.

IMAGE: A dead dolphin on a beach of Caleta San Jose, Peru. (CREDIT: Corbis)

Fractured middle ear bones found by the ORCA necropsy (CREDIT: The Organization for Research and Conservation of Aquatic Animals)