As a group, the Balaenopteridae are the largest creatures ever to inhabit the earth. They are also the most modern — that is, the most recently evolved — of all whales. Until the advent of modern whaling it appeared the Balaenopteridae’s evolutionary path was highly successful. Not only did these whales grow to prodigious size, they also flourished in great abundance throughout the world’s temperate seas. Giant among whales, the blue whale (Balaenoptera musculus) formerly reached 100 ft (30.5 m) in length and had a worldwide population in excess of 400,000 animals. The fin whale (Balaenoptera physalus) reached more than 80 ft (24.5 m) with a worldwide population of more than 900,000 individuals. But over the past 100 years whalers have reduced the number of blue whales in the world to fewer than 25,000 and the number of fins to fewer than 150,000. Moreover, because whalers take large specimens by preference, the largest have been removed from the herds methodically; now, blue whales rarely grow larger than 80 ft (24.5 m) and fins as long as 60 ft (18.5 m) are exceedingly uncommon.
The modern history of the humpback whale (Megaptera novaeangliae) is even more depressing, although the few remaining herds have been afforded protection by most countries and seem to be holding their own.
Because they are smaller animals with less material to offer the whaler, the sei whale (Balaenoptera borealis), Bryde’s whale (Balaenoptera edeni), and the minke whale (Balaenoptera acutorostrata) were not hunted as heavily as their larger cousins in the past. Recently, however, as the larger whales have become increasingly scarce, the smaller Balaenopteridae also have been exploited to varying degrees by whalers.
The Balaenopteridae are distinguished from other baleen whales by pleated grooves that expand when the whales feed, permitting them to engorge great mouthfuls of food and water in a single gulp. In addition to this anatomical adaptation, evidence suggests that these animals can conceptualize their feeding approach — that they can perceive a desired result and organize a method for accomplishing it that goes beyond grasping and swallowing a single prey, or straining a soup of plankton through baleen plates. The fin whale, for example, swims in rapid, clockwise circles around a school of food fish. When the school balls up, or compacts, to avoid the flashing white color on the right side of the whale’s head, the fin lunges through the dense mass with its parachute-sized mouth agape, engulfing the prey it has corralled.
The humpback’s feeding behavior is even more remarkable than that of the fin. Once the humpback locates a school of small fish or plankton, it swims in a slow spiral beneath the school exhaling as it rises. In this way the whale builds a net, or screen, of bubbles around its prey. As the school tightens ranks in the center of the bubble net, the humpback swims up the bubble column with its mouth open, taking at a single gulp virtually the entire school. In Alaskan waters, this feeding strategy has been observed where three humpbacks act collectively as a synchronous team with each playing a particular and dedicated role.
We know little about the intricacies of these whales’ social lives, but what we have been able to observe so far suggests that feeding is not the only realm in which the Balaenopteridae exhibit sophisticated behavior. It appears that specific groups of whales live together for most of their lives. Some researchers think they may mate for life, although this thesis cannot be proven on the basis of existing information. The maternal bond is known to be intense even in the face of mortal danger. And while mother Balaenopteridae surely guide their young through the rigors of juvenile life and teach them the necessary survival skills for life in the sea, whale calves just as surely have the ability to learn from their mothers, from other whales of their species, and from their own experiences.