Ecological and Life History Factors Influence Habitat and Tool Use in Wild Bottlenose Dolphins (Tursiops sp.)

Abstract

While it has long been known that individual animals behave quite distinctively from other conspecifics, only recently has this intraspecific behavioral variation itself been the subject of investigation rather than a nuisance in statistical analyses. As research amounts, it is becoming ever more apparent that the ecology of individuals can have real and measurable biological consequences. Previous studies have documented pronounced inter-individual variation in foraging behaviors in Shark Bay wild bottlenose dolphins, which often coincide with individual specialization. In this dissertation I examine how individuals' phenotypic characteristics relate to their foraging behavior, habitat use, and ranging.

In Chapter 1 I explore habitat and ranging for adult male and female bottlenose dolphins. Dolphins show marked intraspecific variation in both habitat use and ranging, which partially relates to foraging tactic, sex, and season. However, some variation cannot be explained by any obvious phenotypic or ecological factors, highlighting the importance of individual level analyses, especially for conservation and management.

In Chapter 2 I examine the underlying basis of one foraging tactic involving tool use: sponge foraging. By mimicking dolphin sponging behavior, I found that dolphins that sponge forage (spongers) target prey that are difficult to detect with their echolocation, and dolphins have to use sponge tools to access this resource. Spongers appear to hunt an easy to catch, reliable food source that non-spongers cannot access, thereby minimizing feeding competition and providing them access to an empty niche.

Finally, Chapter 3 explores life-long learning of the sponge foraging. Like humans, and many other animals, dolphins improve upon their skills with age, reaching a peak in sponging efficiency in midlife and declining thereafter. Dolphins also improved in their ability to locate sponges with age, and both this and efficiency likely help females meet the energetic demands of lactation.

In all, this dissertation increases our knowledge concerning how a species ecology and life history relates to intraspecific behavioral variation and has implications for conservation, tool-use, innovation, social learning, culture, and ultimately fitness and evolution.