Social Organization of Baleen Whales

Baleen whalesBaleen whales are specialized to find and exploit preyPrey that form dense patches seasonally within broad ocean areas. Most populations have an annual reproductive cycleAnnual reproductive cycle that separates their breeding seasonBreeding season from their feeding seasonFeeding season, often with long-distance migrationsMigrations between feedingFeeding and breedingBreeding areas. The longest bond we know of for most baleen whale species is the mother-calf bondMother-calf bond. CalvesCalve suckle for five to seven months in most species and wean by the next feeding seasonFeeding season. The species whose social behavior has been most studied is the humpback whaleHumpback whale, enabled by their distribution, which often is near shore, and their individually distinctive natural markings. Some humpback whalesHumpback whale feedingFeeding on mobile prey form stable groupsStable group where each individual learnsLearn specific roles to perform coordinated group foragingGroup foraging. Aside from these groups, which may last for many years, most baleen whale groups are reported to be fluid with few strong associations between individuals other than mother and calfCalf. However, most researchers define whale groups in terms of the number of whales that are close enough to be sighted within a certain distance of one another. Sound propagates so well underwater that whale sounds can be heardHeard at distances of tens to hundreds of kilometers away. This means that whales may be able to maintain contact over much greater ranges than are usually assessed by human observers—they may form long-range “heards”Heard in addition to shorter range “herdsHerd.” The social organization of whales during the breeding seasonBreeding season is structured in part by songsSong—acoustic reproductive advertisement displays. The potential scale of “heards”Heard is indicated by the ability of scientists to track one singingSinging blue whaleBlue whale for 43 days as it swam > 1700 km. Scientists will start to develop a fuller understanding of the social organization of baleen whales when they apply methods that can make observations and test hypotheses over the temporal and spatial scales at which baleen whales move and communicate.