What do blue whales eat, how long can they live, and is the orca their natural enemy?
The blue whale is a marine mammal belonging to the suborder Mysticeti. There are four subspecies in total. The blue whale is considered the largest animal known to have ever lived on Earth, reaching up to 33 m in length and weighing up to 181 tonnes. So what does the blue whale mainly eat? How long can it generally live? Does it have natural enemies? Will it be eaten by orcas?
What does the blue whale eat?
Like other baleen whales, the blue whale feeds mainly on small crustaceans (such as krill) and small fish, and sometimes squid as well. Krill is the most abundant animal in the world, widely distributed in the sea areas of the Arctic and Antarctic. It is precisely because of such abundant food, and because living in water removes the limit of supporting body weight, that the blue whale has been able to grow so enormous. The blue whale's stomach is divided into four chambers; the first stomach is formed by an enlargement of the oesophageal section, so its appetite is extremely large. It can swallow about 2 million krill at one time, and eats 4000-8000 kg per day. If the food in its belly is less than 2000 kg, it will feel hungry.
How long can a blue whale live?
Its lifespan is generally over 50 years, and at most it can live to 90—100 years.
Blue whales breed in winter. The female generally gives birth once every 2 years, with a gestation period of 10—12 months, and only 1 calf per birth. This “sea monster” also produces astonishingly large calves: at birth the calf is already 6—8 m long and weighs about 6000 kg. To prevent it from suffocating to death, the female must lift the calf out of the water to breathe its first breath of air; after that it can breathe on its own. The nutrients in blue whale milk are extremely rich, and its fat content is 10 times that of cow's milk, while the calf suckles more than 1000 kg of milk per day, so it grows very quickly. After 8 months it can increase to 15 m and its weight can grow to 23,000 kg, and it can open its mouth on its own to eat various kinds of plankton. By the age of 2 and a half to 3 years, its body length can exceed 20 m. The age of sexual maturity is about 8 to 10.
Will blue whales be eaten by orcas?
According to one statistic, 25% of blue whales were recorded as having been bitten by orcas in their youth. Even subadult blue whales may be preyed upon by groups of orcas. But the prerequisite is that the orca pod must be very large, for example 20-30 orcas, to be able to prey on one juvenile blue whale. As for adult blue whales, apart from whaling ships and large human vessels at sea, they have no natural enemies. So if the question is whether blue whales can be eaten by orcas, then the answer is yes. But if one says that orcas are the natural enemy of blue whales, that is a bit too far-fetched. It is just like the orca being the tiger of the sea and the blue whale being the elephant of the sea. Under extreme circumstances, a tiger may also go and prey on juvenile elephants that have lost their mother's protection and on solitary subadult elephants. But one cannot say that the tiger is the natural enemy of the elephant. So under extreme circumstances orcas will indeed prey on juvenile blue whales, but orcas cannot become the natural enemy of blue whales.