Elephant Seals Dive Deep with 'Smoker's Blood'

Elephant seals have surprisingly high levels of naturally produced carbon monoxide — a noxious gas that is deadly at high concentrations — in their blood, a new study finds. In fact, the amount of carbon monoxide found in the blood of these large mammals is roughly the same as that in people who smoke 40 or more cigarettes each day, researchers say. Carbon monoxide is an odorless and colorless gas that is naturally produced in small quantities in humans and animals. The scientists are unsure why elephant seals have such unexpectedly high levels of the gas in their blood, but the researchers suggest it could protect the animals from injury when they dive to extreme depths in search of food.