Besides ice that may trap them in the fall, belugas have few natural enemies. The one they fear most is the killer whale. Polar bears may occasionally succeed in killing one trapped by ice in shallow water. Humans, however, have had the greatest impact on the whales. Europeans used to kill large numbers of them, but now in North America only Eskimos are allowed to hunt them for their oil, meat, bones, and skin.
Humans also affect the beluga populations in other ways.
Pollution in the St. Lawrence River has caused a significant increase in the amounts of mercury and DDT found in the belugas of that area. Noise pollution also causes a problem for these highly adapted marine mammals who depend on sound information to live in their environment. All of these sounds are formed when air is forced between two air sacs. The sacs lie beneath the blowhole of the animal and are controlled with muscles. Echoes that bounce off of objects in the water are received by the whale to form a kind of sound picture.