Deaths in annual gray migration leave scientists wondering

Last week, in a tragedy broadcast across the world, three adult gray whales washed up dead at the Magdalena Bay breeding lagoon in northwestern Mexico.

Mexican television stations showed footage of biologists at the port of San Carlos in the southern reaches of the Magdalena lagoon hacking into the whales' giant bodies for post-mortem examinations, otherwise known as necropsies. Scientists did not know what caused the deaths, nor did they know whether any pregnant females were among the dead.

Magdalena Bay is one of three major lagoons traditionally used by the whales for breeding in Baja California. These whales bring this year's total of dead grays to nearly ten; cases of beaching or outright deaths have been reported this year in Sonora, Baja California and Nayarit states, all states on the western edge of central Mexico.

Some whales die during every migration, but more whales have died this year than in any year this decade. Biologists say they are concerned that too many whales are being found beached in shallow waters or dying during the crucial breeding period of their life cycle.

"This is not normal," Homero Aridjis has been quoted as saying. Aridjis is a poet and president of the Group of 100, a leading ecological body in Mexico. "In general you don't see them dead, and this implies something is disturbing them, possibly climate change or changes in [water] temperature or pollution in their waters."

Each year the majority of the world's remaining gray whale population sets off on a 10,000-kilometer migration from Arctic seas to a handful of warm water lagoons on Mexico's Baja California peninsula to breed and give birth. Scientists believe it to be the longest migration of any species on earth.

There are three things we can expect to see every year around this time - spring training in Florida, snow in Northern California, and gray whales in the lagoons of Mexico. Down south, these whales birth and rear their young. The lagoons are so shallow that gray cows don't have to worry about killer whales or other predators bothering their young. What's more, the pools are perfect for baby grays to learn what it takes to become adult whales.

The whales arrived late in Mexico this year, their departure from the northern Bering Sea, between Alaska and Siberia, delayed possibly by climatic factors, ecologists say. They blame the El Nino and La Nina weather cycles for slowing the whales down. Only a handful of the barnacle-encrusted gray whales had arrived in December, when normally hundreds are found in Mexico's warm water lagoons. Most arrived during January instead.

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