Starvation may be impeding the recovery of the Pacific gray whale population. This population was thought to have recovered from commercial whaling, but now a new genetic study suggests the marine mammals once numbered between three and five times the 22,000 population estimated today.

If true, the findings could imply that the world's oceans are no longer able to support the same number of whales that they once could. Previously, it had been thought that thin, starving whales – as have been observed recently in Mexico – were a consequence of the population exceeding its historical ecological limits, rather than the oceans running out of food. Earlier this month the National Marine Fisheries Service reported that at least 10 percent of gray whales returning to one of their four main calving and breeding lagoons off Baja California showed signs of being underfed. Some of the whales even had bony shoulder blades.

DNA samples taken from 42 gray whales determined that the gray whale populations would have averaged between 78,000 and 118,000 over the past tens of thousands of years – rather than the current estimated population of 22,000. Most of the existing population roams the eastern Pacific – there are only about 100 gray whales left in the western region, making them some of the most endangered whales on the planet. However, even if historically, the whales were evenly distributed between the American and Asian Pacific coasts, with 48,000 on either side on average, this would still mean that the current eastern Gray whale population is now half of what it was.

The researchers say that the logical conclusion is that the oceans are no longer able to feed as many gray whales as they once did and could be any number of reasons for this, ranging from natural variation of the ocean’s food supply, to human effects on the oceans. A 2006 study showed that warming seas in the Arctic are displacing crustaceans on which the whales feed. Depleted numbers of the whales can also be bad news for other species too as when gray whales feed, they stir up sediment by "bulldozing" the ocean floor for food – this feeds animals throughout the marine food chain. Decades ago, whales were the first creatures to tell us that we were over-fishing the oceans. Maybe now they trying to tell us the oceans are in deeper trouble. Gray whales were the first marine mammal to bounce back and get off the endangered species list in 1994 but the researchers that led the study are now recommending that the eastern gray whales still be considered depleted.