Blue Whales

The Blue Whale has a long tapering body that appears stretched in comparison with the stockier build of other whales. The flippers are three to four meters (10 to 13 ft) long. The upper sides are grey with a thin white border. The lower sides are white. The head and tail fluke are generally uniformly grey. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey colour all over, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled. The Blue Whale also incidentally consumes small fish, crustaceans and squid caught up with krill.

Blue Whales most commonly live alone or with one other individual. It is not known whether those that travel in pairs stay together over long periods or form more loose relationships. The whale's upper parts, and sometimes the flippers, are usually mottled. In locations where there is a high concentration of food, as many as 50 Blue Whales have been seen scattered over a small area.

With global warming causing glaciers and permafrost to rapidly melt and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point there will be a disruption in the thermohaline circulation. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. Considering the Blue Whale's migratory patterns are based on ocean temperature, a disruption in this circulation which moves warm and cold water around the world would be likely to have an effect on their migration. The whales summer in the cool, high latitudes, where they feed in krill-abundant waters; they winter in warmer, low latitudes, where they mate and give birth. However, they do not form the large close-knit groups seen in other baleen species.

The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kg (8,000 lb) of krill in a single day. This means that they typically feed at depths of more than 100 m (330 ft) during the day, and only surface feed at night. The longest recorded dive is 36 minutes. Blue whales have twin blowholes, shielded by a large splash guard  The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed.