The rare Asian gray whales are picky about where they breed, and for centuries have been going to one spot every summer, off the northwest tip of Sakhalin Island in Russia's Far East.
This is most unfortunate, say environmentalists, because there are plans to drill for oil on the very spot where the whales carry out their reproductive activities.
"I think there is definitely a threat for the whales," says Masha Vorontsova, Russia director of the International Fund for Animal Welfare. "They could die out. Whales always go to the same place to breed. This is exactly where the Sakhalin 2 oil field is," she says.
Scientists estimate there are between 60 and 80 West Pacific gray whales left. Their numbers are low because of hunting that supplies meat to Japanese restaurants and feeds arctic foxes on Russian fur farms.
These whales are related to the East Pacific gray, which breeds off California and whose numbers are estimated at a more comfortable 20,000 becasue of stringent protection measures.
The company developing the oil field - Sakhalin Energy Investment Co. - has agreed to support scientific investigations into the whales' habitat by international experts. A company spokesman believes there will be "very little impact" on the habitat, but nothing has been proved so far.
Aside from potential disruption to the whales' breeding activities, environmentalists worry about the possibility of a major oil spill. The impact on the whales - and vital crab- and salmon-fishing waters nearby - would be disastrous.
But local authorities say it is a calculated risk to develop the poor island.
Oil would create 10 times more revenue for the local economy than fishing does. Fishing, however, would employ four times as many people.