SPERM WHALE BOTTLE-NOSE WHALE KILLER WHALE PILOT WHALE (BLACKFISH) CUVIER’S BEAKED WHALE FALSE KILLER WHALE TRUE’S BEAKED WHALE NARWAL WHITE WHALE (BELUGA) PYGMY SPERM WHALE BOTTLE-NOSE DOLPHIN COMMON DOLPHIN COMMON PORPOISE

Squid Eaters

The bottlenose whales are nearly toothless, feeding on squid like their close relatives, the sperm whales. Porpoises and dolphins possess many sharp conical teeth on both the upper and lower jaws, although the narwhal which is related to them, breaks the rule by being toothless save for the tusklike canine of the male. In this instance either the right or left tooth elongates to produce an 8-foot spear. The other tooth does not break the gum, and this is the condition found in the female where both are rudimentary and not evident. The bottlenose whales have but a single pair of teeth in the lower jaw, and their relatives, the sperm whales, have 18-28 conical teeth per side on the lower jaw, and these when fully grown may be 8 inches in length. Pockets are provided in the toothless gum of the upper jaw to accommodate the teeth when the mouth is closed.

The decline in the number of teeth in the sperm and bottlenose whales is thought to be the elimination of structures which are no longer useful. Whereas a porpoise’s long mouth, bristling with sharp teeth, insures the hooking and retention of a slippery active fish, a small mouth with a few teeth is adequate to crush and slurp down the squid and the weak-swimming fishes of the abyssal depths.

The sperm whale is the largest of the squid feeders, reaching 60 feet. There is a diminutive counterpart, the pygmy sperm whale, which reaches 13 feet. It is exceedingly rare, whereas the sperm whale is abundant in temperate and tropical seas. The beaked whales complete the groups specialized for feeding on squid. Besides the modification of the mouth, all these whales are noted for their ability to dive to great depths where their food abounds. Not only can they dive to great depths, but they can stay submerged for long periods—up to an hour? Sperm whales have been found entangled in the submarine cables which were known to be on the bottom at a depth of 3,000 feet. It is clear that such feeding habits have opened up vast areas of the oceans to these species.

Filter Whales

The whalebone whales seem to have undertaken two different lines of specialization in feeding: The right whales developed an enormous head with a very large filter plate, whereas the rorquals are much more streamlined with a small filter plate. The ability of the latter to gather food is insured by the pleated throat. The right whales lack a dorsal fin and are decidedly less streamlined. The rorquals have a dorsal fin. There are two species which do not exactly fit in either group. The humpback whale appears to be like the rorquals in that it has a pleated throat and a suggestion of a fin. It is however, a very bulky slow swimming species. The California gray whale, apparently, is intermediate between the two groups and may be thought to be a survivor of the ancestral stock from which both groups differentiated. It has neither a pleated throat nor a fin. The gray whale, like the right whale, has been slow to recover from whaling. It is likely that the populations were never very large. Only the rorquals seem to have the numbers needed for large whaling operations.

Significance of Blubber

Heat Conservation

As whales extended their operations into the icy waters of polar regions or into the cold waters of the ocean depths, they had to develop means of keeping warm. Anyone who has attempted to swim in cold water knows how quickly one loses his body heat and becomes chilled. Whales minimize the heat loss by accumulating a thick layer of fat just below the surface of the skin. The fatty layer, called blubber, not only keeps the whale warm, but it also provides for food storage. It has already been stressed how important it is for whales to survive long periods without eating, so it is likely that the two specializations arose together.