Humpback Whales: A Seemingly Socially Simple Whale with Communicative Complexity

Abstract

AbstractHumpback whales (Megaptera novaeangliae) occur in all major oceans. Given this worldwide distribution, and since they tend to migrate along coastlines, they are one of the best known of the baleen whales. Humpbacks are relatively easy to find and easy to observe. This, along with their surface behaviors and attraction to vessels, makes them popular with whale-watching businesses. In the scientific world, their song and behaviors have been studied since the 1970s, producing hundreds of scientific papers. Despite this, there are still many unsolved mysteries. Why do humpbacks sing (Chaps. 8 and 11), how do they locate their prey (Chap. 5), and how do they navigate when migrating (Chap. 4)? In this chapter, we focus on the mysteries of their social communication. Communication and social complexities often go hand in hand. Animals with more complex social structures tend to have more complex vocal repertoires, perhaps peaking, with humans. Within the baleen whales, humpback whales are considered an exception. Present knowledge indicates that humpbacks have a relatively complex acoustic repertoire but work on their breeding social system has considered them to be socially simple. Animals regarded as having a simple social structure tend to have small group sizes and a lack of repeat associations between individuals over time. Humpback whales meet this criteria in that they form temporary associations between a small number of individuals, and these associations are not repeated over time, leading to the conclusion that their social structure is simple and individually based. Why then do humpbacks have what could be considered a complex acoustic repertoire? Is the conclusion that they possess a simple social structure supported by best available scientific evidence? This chapter illustrates that humpbacks may in fact have a complex social structure, with complexity defined differently than traditional definitions of complexity (number in a group, number of repeat associations). Rather than forming large permanent groups with repeated interactions between individuals, humpback whales during the breeding season form networks that encompass multiple groups. These groups are frequently changing membership, and animals are constantly moving into, and out of this network. Whales must therefore continuously assess, and respond to, a changing social environment. Given that humpbacks likely rely on acoustic communication to manage these interactions, this added layer of social complexity may go toward explaining their large and varied vocal repertoire. Perhaps communicative and social complexities do go hand in hand for the humpback whale.KeywordsBaleen whaleBreeding behaviorCommunication repertoireSocial complexitySocial behaviorVocal repertoireVocal complexity