A rancid stench in the meat of some gray whales has made them inedible to Russian aboriginal hunters, according to a new report.

Chemical contamination or disease may be causing the increasing phenomenon of so-called stinky whales, experts say.

A similar stink is also being noticed in the meat of ringed and bearded seals, walruses, and cod, the report by the International Whaling Commission (IWC) adds.

Something Fishy

Aboriginal whalers in Russia's northeastern province of Chukotka first began sensing there was something wrong with the whales in the 1990s.

Since then, many of the mammals they tow ashore from a hunt end up having a foul medicinal odor.

People who eat the meat have reported temporary problems such as numbness in the mouth, skin rashes, and stomach aches. Such whales are of no other use to locals.

"Even dogs will not eat the meat," said Gennady Inankeuyas, a whaling captain and chairman of the Association of Traditional Marine Mammal Hunters of Chukotka. The organization looks after the interests of whale hunters and their families.

Some experienced whalers have learned to recognize stinky whales just from the mammals' breath.

Talks with other older hunters reveal that the smelly whales have probably been around since the late 1960s and early '70s.

Chemical Brew

Spurred by reports of the odorous whales, U.S. and Russian toxicologists began testing tissue samples of stinky whales in 2003.

They looked for traces of heavy metals and other harmful compounds, such as organochlorines and polyaromatic hydrocarbons, which are products of industrial processes.

The samples show a slew of more than a hundred volatile compounds, including hydrocarbons, sulfur and nitrogen compounds, and various odorants. Yet the results are still unclear and do not appear to implicate human activity, said Wendy Elliott, a program officer at the nonprofit WWF-International.

But she thinks that perhaps the whales' diet might provide a clue.

Strangely enough, hunters have found that the stomachs of stinky whales are packed with seaweed.

"We are not fully sure, but it is possible that a change in prey abundance due to climate change is forcing the whales to change their diet," Elliott said, "and this is causing certain biochemical reactions within them."

The IWC report hints at the same conclusion, stating that gray whales appear to have reached carrying capacity.

Simply put, there are either too many Eastern North Pacific gray whales competing for the same food supply, or the food supply is fast drying up.

Biotoxin at Play?

But the report adds that the stink could also be caused by an unidentified biotoxin.

Lorenzo Rojas Bracho is coordinator of the National Marine Mammal Program at Mexico's National Institute of Ecology.

He said the stink could not be due to the whales approaching carrying capacity, because in that scenario a large number of whales would be affected.

Instead, he said there could one agent that might be causing the stink, and another agent causing the numbness in people who eat the meat.

Rojas points to various compounds such as aldehydes and ketones in the whales.

The whales might be suffering from a metabolic disorder from feeding in certain locations near Russia that are awash in odiferous compounds.

It is probably a regional, ecosystem issue, he adds, noting that the stinky smell has also been reported in other mammals and birds of the region.

"Maybe certain bacteria, fungi, and biotoxins are the cause of the stinky whale. This could explain the numbing, and is a more plausible explanation," he said.

Rojas said scientists from U.S and Mexico are working on a project to check the chemical composition of the blowhole breath of free-swimming whales in the breeding lagoons of Mexico. After breeding there in the winter, the whales move north.

If researchers find the problem that is causing the whales to become stinky, these whales could possibly be worked into a revised aboriginal whaling management procedure, to be put in place by 2009.

Quotas Renewed

At the recent IWC meeting in Anchorage, Alaska, the Russian government announced that it did not consider the stinky whales to count against the quota, adding the whales do not fulfill the aboriginal subsistence needs. At the same time, the government recognized it could not make that determination unilaterally.

Russian aboriginal hunters maintain that at least 10 percent of the whales they hunt turn out to be stinky.

The IWC also upheld a shared catch limit of 280 bowhead whales until 2012 for U.S. and Russia indigenous peoples, and renewed the quotas for gray whales.

"We did not gain anything, since our cultural and nutritional needs for whales exists with or without the quotas," whaling captain Inankeuyas said.

"The international community recognized our right to hunt, use, and eat whales. We feel very fortunate."