Whales (this term applies to all whales, dolphins, porpoises, etc.) are air breathing mammals, but have perfected the ability to live entirely in water over the past 50 to 60 million years. They belong to the order Cetacea, and are often simply referred to as cetaceans. Like the seals, they evolved from terrestrial carnivores, but they have taken their adaptations to living in a marine environment much further than have the seals. The hind legs have completely degenerated; they have developed fluked tails for propulsion; the front limbs have been transformed into stiff pectoral flippers; the nostrils have moved to the top of the head; they have lost their fur and instead opted for a thick layer of oil-rich blubber with which to insulate themselves from the cold waters; the vertebrae have lost their interlocking processes because their mass is essentially weightless in the buoyancy of water (this has allowed the gigantism of many species).
Aquatic life creates numerous problems for air breathing animals, but the whales have overcome them through many physiological adaptations. Muscle cells can survive several hours of oxygen deprivation, but nerve cells sustain damage within minutes from lack of oxygen. Whales have developed blood circulatory shunts which keep the oxygen-rich blood moving through those organs which need a constant oxygen supply while they are diving and "holding their breath". They inhale before diving (seals exhale before diving), but the tremendous pressure exerted by water causes the lungs to collapse thereby compressing the retained air into cartilaginous supply tubes in the bronchial system. Because they must return to the surface every time they breathe, whales live in a vertical world, and unlike fish, their tails are flattened horizontally which facilitates up and down movements. They have large lungs by comparison to most other mammals, and they typically exchange up to 85% of the air in the lungs at each breath (compared with the 15-20% exchange that occurs during normal breathing in humans). Most of the larger species produce a visible vaporous "blow" when they exhale at the surface. This blow forms mostly from instant condensation when the warm, moist air in the lungs is suddenly depressurized upon exhalation. The thick layer of blubber not only insulates them from the cold, it also aids in buoyancy because fat is lighter than water, and it is used as stored food during times of migration and fasting.
There are two basic types of whales, those which have no teeth and those which possess teeth. The toothless whales belong to the suborder Mysticeti, and include all the filter-feeding whales. These animals, including right whales and the rorqual whales, possess rows of horny baleen, or whalebone, which hang down vertically on both sides from the roof of the mouth. The inside edge of each plate has a frayed appearance of dense bristles, and the plates overlap one another so the frayed edges form a very efficient sieve. As the whale moves through the water it opens its huge jaws (most species also have expandable throats which increase the efficiency of this method of feeding) and takes a large quantity of water into the mouth. The water is squeezed out between the baleen plates thereby trapping any small prey animals, such as krill, tiny schooling fishes, etc., inside the mouth. This food is then pushed back to the throat by the huge muscular tongue and swallowed. This process enables the baleen whales to take advantage of the almost limitless resource of krill and the secondary level of organisms near the base of the food chain. Different species of baleen whales have different sizes of baleen filter plates that allow them to coexist and yet feed on different prey. Baleen whales typically feed in the upper layers of water because the zooplankton which makes up most of their diet is dependent upon phytoplankton which in turn is dependent upon sunlight. Therefore, they are not normally deep divers like some of the toothed whales, and seldom dive to more than 90 m (300 ft) below the surface.
The Antarctic baleen whales live in an annual cycle of breeding in the warm waters of low latitudes in the Winter, and feeding in cold Antarctic waters in the Summer. Baby baleen whales, especially the larger species, must undergo an accelerated rate of growth in order to be weaned at the feeding grounds in mid-Summer. Cetacean milk has a high fat content and a thick consistency, which keeps it from mixing readily with sea water. This helps the baby whale avoid swallowing too much water when it nurses. The rich, highly nutritious milk understandably produces rapid weight gain and growth within the babies. The extreme example of this rapid growth is the blue whale whose offspring may gain weight at the rate of 4.5 kg (10 lbs) per hour, or 900 kg (1 ton) in 9 days. There are seven species of baleen whales that we often see in Antarctic and SubAntarctic waters…
The great right whale is a very large whale found in the polar waters of both the Arctic and Antarctica. These two populations are completely separated, however, and never intermingle. Because it is a slow-moving species and its body is so rich in oil that it floats even after death, it was the "right" whale to hunt (hence the name). Both males and females average about 15 m (50 ft) in length, with a maximum of 18 m (60 ft), and average about 54,500 kg (60 tons) in weight, with a maximum of 96,000 kg (106 tons). The coloring is pure black with some mottling of brown, as well as white callosities above the eyes, near the tip of the snout and on the chin, and sometimes a white marking on the belly. Its body is very rotund, extremely broad, and smooth. There is no dorsal fin, which precludes it being mistaken for any other large whale in Antarctic waters. The right whale has two widely separated blowholes which produce a distinctive V-shaped double spout. The tail of this species, which is broad with very pointed tips and a deep notch, is usually raised above the surface when the animal dives. The head is very large, about 25% of the total body length, and there are no throat grooves. Therefore, the animal cannot expand its throat significantly when feeding, like most baleen whales. Instead, it has a narrow and highly arched upper jaw which holds baleen plates more than 2 m (7 ft) long. The right whale simply swims through the water with its mouth open and passively filters food items through its very long baleen plates as it moves along….a feeding strategy known as ‘skimming’.
The other half dozen species are called rorqual whales and they share the characteristic of having many throat grooves, which allows the throat to be expanded when feeding, thereby enlarging the mouth’s carrying capacity many times. Unlike the right whales, they engulf a single, huge mouthful of water (hopefully with suitable prey within) and then close their jaws and squeeze the water out through the short baleen plates which filter out their prey inside the mouth…enabling it to be swallowed. This feeding strategy is called ‘gulping’. The advantage to this method is that when the throat area is constricted, they take on a surprisingly long and streamlined shape which allows some species to swim at speeds of over 16 knots. There are five species of rorqual whales found in Antarctic waters. Four of them, of the genus Balaenoptera, are closely related and differ primarily in size and coloration. Even so, it takes a trained eye to identify them when they are encountered at sea. It is interesting to note that among almost all the rorqual whales, the females grow to a slightly larger size than the males.
The blue whale is the largest of the rorqual whales, and is in fact the largest of all the living cetaceans. It averages 25 m (82 ft) in length, but several individuals longer than 30 m (100 ft) have been captured by whalers. The normal range of weight varies between 80,000 and 130,000 kg (90-144 tons), but the maximum recorded weight was 178,000 kg (196 tons). Because of the animal's speed and sleek grace it is easy to underestimate its size. The color is hard to evaluate unless one is fairly close, but is marine blue-gray, mottled with small spots of white or light gray. It has a tiny triangular dorsal fin which becomes exposed long after the blow, and often the flukes are exposed as the animal dives. The rostrum is broad and flat with a single prominent ridge running lengthwise down the center. Its blow is typical of all the species in this genus, a high powerful thin column, but it is comparatively bigger than all others. In Antarctic waters, blue whales feed almost entirely upon krill, and a large whale may eat 4,000 kg (over 4 tons) of these tiny animals in a day (this amounts to about 4 million krill). The krill season lasts about 120 days, after which the whales basically fast until the next Antarctic krill season.
The fin whale is the second largest cetacean, with lengths averaging around 21 m (70 ft) and a maximum of 27 m (89 ft). The weight varies from 35,000 to 45,000 kg (40-50 tons) with a maximum of 69,500 kg (76 tons). It is relatively easy to identify since it is a very large species and has a large falcate dorsal fin (hence the name) which quickly separates it from the blue whale. The fin whale is unique among the rorqual whales in that it is counter-shaded like an aggressive predator, that is, a black or dark brown back and a white or light-colored underside. However, a close look will show that the fin whale's coloration is somewhat asymmetrical, especially in the head region…the lower right lip is white and the lower left lip is dark. The fin whale is probably the fastest swimmer of the great whales, and is a generalist feeder meaning it eats not only krill, but also various schooling fishes such as sardines, anchovies, capelin, and pollack, as well as squids and many other small species of animals which form dense groupings. Because much of its food consists of fast and relatively intelligent prey, it needs the predatory counter shading to help surprise and confuse its prey, and it needs speed to overtake it. As a fin whale feeds it often rolls over onto its right side and arches its back and swims in a tight circle, which actually increases the speed experienced at the mouth region. When the animal rolls onto its right side the countershading about the head is dark on top and light underneath, precisely what is needed for a predatory lifestyle.
The sei whale generally avoids the coldest waters closest to the ice, so it is rarely seen near the continent. This species is quite large, averaging about 15 m (50 ft) in length with a maximum of 20 m (66 ft), and 12,000 to 15,000 kg (14-17 tons) in weight with a maximum of 29,000 kg (32 tons). The coloration is mostly dark, steely gray, but with a lighter throat and belly. There is usually light mottling on the flanks and belly. It has a high, vertical dorsal fin, rather like that of the fin whale, but it does not arch its back high out of the water like the fin whale when at the surface. The sei whale is a generalist feeder, specializing in planktonic crustaceans, but will also eat small schooling fishes when the opportunity presents itself. It is interesting to note that this species often rolls onto its side when feeding, like the fin whale, but will roll first onto one side and then the other side continuously. It does not have asymmetrical coloration like the fin whale.
The Minke, or piked, whale is the smallest rorqual whale. It averages about 8 m (26 ft) in length with a maximum of 10 m (33 ft), and 5,800 to 7,250 kg (6-8 tons) in weight with a maximum of 9,000 kg (10 tons). The rostrum is very distinctive in that it is narrow and very pointed, which is what gives the species one of its common names, i.e. piked. The coloration is dark blue-gray above and light gray underneath, and there are usually two pale bracket marks above the flipper extending across the back. In some populations there is a diagnostic bright white patch on each flipper. It has a relatively large, high dorsal fin located far back on the body. The Minke whale does not always produce a distinctive high spout, because it often begins to exhale before it breaks surface. It often leaps clear of the water, usually two or three times in succession, and has the peculiar habit, for a baleen whale anyway, of approaching boats. This species is a very fast swimmer, and in places where krill are not readily available it often eats small schooling fishes and squids. It tends to be a rambunctious feeder with a lot of leaping and splashing accompanying what may be described as a feeding frenzy. Minke whales seem to be enjoying a population growth in Antarctic waters since the near eradication of the blue whales, because they have taken advantage of the increased food resource (krill).
The humpback whale is the only rorqual whale not in the genus Balaenoptera. It has the same general life history as the aforementioned rorquals, but does not have the same long and sleek body shape. The humpback whale is comparatively more broad and massive, and averages about 15 m (50 ft) in length with a maximum of 19 m (62 ft), and weighs about 30,000 to 40,000 kg (34-45 tons) with a maximum of 48,000 kg (53 tons). The body characteristics and behavior make this the easiest great whale to identify. Its coloration is basically black or dark gray with a white throat area. The ventral surface of the tail is also usually white, as well as most of the flippers (which are nearly one third the length of the body). The humpback whale's broad bushy spout is distinctive, as is its dorsal fin which is small, but mounted on a fleshy hump. It often leaps completely out of the water to land on its back in a tremendous splash. Besides breaching, the humpback whale waves and slaps its enormous flippers upon the surface of the water to make a loud sound rather like a gun shot, and almost always exposes its great tail when it dives. This species is amazingly acrobatic and energetic, and never fails to create excitement among its observers. In Antarctic waters, the humpback whale feeds primarily upon krill and other planktonic crustaceans, but in other areas they sometimes feed upon small schooling fishes. The normal feeding method is to lunge forward near the surface, but on occasion it may swim in a tight circle below its prey and blow a continuous stream of bubbles, which has the effect of corralling the prey into a concentrated mass, and then swimming straight up through the mass with its mouth open. Humpback whales are famous for producing the longest and most varied songs in the animal kingdom, and much research has been done in recent years upon these songs.
Whales with teeth belong to the suborder Odontoceti, and include the dolphins, porpoises, beaked whales, killer whales, sperm whales, and others. These animals actively pursue motile and relatively large prey such as squids, fishes, birds, seals, and other whales. The toothed whales have developed very useful sonar (underwater echolocation) systems with which they can locate and capture prey or avoid obstacles and predators, even in dark or turbid waters. The echolocation system works by focusing sound waves (produced in the nasal passages) through an oil-filled lens, or melon, which is set in a cradle on the front of the skull. The reflected sound waves are thought to be sensed primarily through the lower jaw upon return and transmitted through fat to the ossicles of the inner ear. A rule of thumb is – the larger the melon, the better developed the sonar system, and the more time spent in deep and/or turbid waters.
The killer whale is probably the most easily recognized of all cetaceans. It is a medium-sized whale averaging 8 m (27 ft) in length for males and 7 m (23 ft) for females. Killer whales are heavy-bodied animals and average 700 kg/m for males, with a maximum of 7,200 kg (8 tons), and 500 kg/m for females. Generally speaking, they are mostly dark to black, except for a white belly extending to a white process on the flank, a white patch just behind each eye, and a faint gray saddle mark behind the dorsal fin. This design of a black dorsal region and white ventral region is a very common form of countershading found among marine predators. In addition, the flippers are relatively large and rounded, and the most diagnostic characteristic is the enormous dorsal fin grown by adult males which is the longer and more pointed than that of any other cetacean. In older males it grows erect and may measure 2 m (6 ft) in height, while in females and immature males it is curved and shark-like. Killer whales normally travel in very cohesive pods made up of 5 to 20 individuals, which usually consist of members within an extended family. As the name suggests, they are highly predaceous and often exhibit a high degree of cooperation in hunting prey, which includes squids, fishes, sea birds, seals, and even other whales. Scientists have identified three distinctive types of killer whales in Antarctic waters, but whether or not they are separate species is still debatable. Type A is very striking with a mostly glossy black coloration contrasted by bright white markings…similar to the well-known populations in the Northern Hemisphere and of movie fame. It apparently migrates to Antarctic waters in the Summer and specializes in preying upon Minke whales. Types B and C probably stay in Antarctic waters year ‘round and are similar in appearance since they both exhibit a yellow-greenish tinge during the Summer, which is probably caused by diatoms adhering to skin. They both also have a distinctive lighter dorsal cape marking in front of the dorsal fin. Types B and C differ from each other in that Type B has very large eye patches and Type C has small, forward slanting eye patches. Type B specializes in preying upon seals, but also is known to occasionally kill whales. Type C apparently feeds almost exclusively upon the Antarctic toothfish.