Hobbies And Interests
Orcas
Some populations of orcas, also known as killer whales, target whales such as humpbacks as their main prey. The orcas work together to kill juveniles; they probably wouldn't be able to bring down an adult whale unless it was very ill. The pods of orcas are often successful in their hunts, even when the mother whales, which are several times larger than the orcas, are defending their offspring.
Sharks
Sharks are not as social as orcas and do not work as a well-organized team. This means they are less of a threat to whales. However, large sharks can and do attack young or sick whales.
Polar Bears
The beluga, a small Arctic whale, is also vulnerable to predation from land predators. These whales swim underneath the ice sheets, coming up to holes in the ice to breathe. At this point they are vulnerable to attacks from land carnivores. Polar bears have been known to successfully attack and kill individuals, especially young ones.
Humans
Humans have been, and still are, more of a threat to whales than all their natural predators put together. The large-scale commercial whaling of the 20th century drove many species, including the blue, fin, southern right and gray whales, to the edge of extinction. An international moratorium on the practice allowed whale populations to recover to a certain extent. However, whaling still takes place. Japan, Iceland and Norway all conduct whaling operations on a commercial scale as of the time of publication.
Other Threats
Humans also endanger whales accidentally. Over-fishing, water pollution, ocean acidification and fishing waste all threaten the survival of the most endangered species of whale. Accidental collisions with ships kill or seriously injure a number of whales every year.