A few years ago, right whales began washing up on the shores of Argentina's Patagonian coast. So far, researchers have counted a total of 308 dead whales since 2005.

These right whales in the waters around Peninsula Valdés are amidst the largest die-off of great whales ever recorded. Whatever is killing them remains unknown.

About 88 percent of the whale deaths were calves that were less than three months old. Curiously, many of the corpses had unusually thin layers of blubber. The deceased calves found comprise almost a third of all right whale calve sightings in the last 5 years. In 2009, the Scientific Committee of the IWC identified the die-off as a management priority.

"Península Valdés is one of the most important calving and nursing grounds for the species found throughout the Southern Hemisphere," said Dr. Howard Rosenbaum, director of the WCS's Ocean Giants Program and a member of the IWC's Scientific Committee. "By working with the government of Argentina, the Province of Chubut, the IWC, and our diverse team of experts and specialists, we can increase our chances of solving this mystery, the critical next step to ensuring a future for this population of southern right whales."

This week a team of whale and health experts from the Wildlife Conservation Society joined experts from other organizations at a workshop to try to solve this perplexing problem. The International Whaling Commission sponsored the workshop, which convened in Puerto Madryn.

"We need to critically examine possible causes for this increase in calf mortality so we can begin to explore possible solutions," said Dr. Marcela Uhart, associate director of WCS's Global Health Program and one of the early founders of the program that discovered the whale deaths. "Finding the cause may require an expansion of monitoring activities to include the vast feeding grounds for the species."

Around one-third of the estimated population of right whales in the Southern Hemisphere use the protected bays of Península Valdés (a World Heritage Site) as a calving and nursing habitat between the months of June and December.

The southern right whale is one of the world's great conservation success stories. Unlike the North Atlantic and North Pacific right whales (both of which number in the low hundreds), southern rights have managed to rebound from centuries of commercial whaling, with populations growing at approximately 7 percent annually since 1970. Growing up to 55 feet in length and weighing up to 60 tons, the southern right whale is now the most abundant species of right whale in the world.

But ensuring their long-term survival may require solving this issue quickly. These charismatic animals are also the focus of a thriving eco-tourism industry along Argentina's Patagonian coast.

The workshop participants will consider many hypotheses on the cause or causes of the calf deaths. Possible explanations might include biotoxins, disease, environmental factors at their nursing grounds, and potential variations in prey availability at the whales' distant feeding grounds.