Social and Behavioral Responses to Environmental Stressors in Bottlenose Dolphins in Shark Bay, Australia
Miketa, Madison Layne
Animals experience a variety of natural and anthropogenic environmental stressors, and responses to such stressors can impact fitness. Bottlenose dolphins are long-lived, socially complex, and behaviorally flexible. I examined how individuals behaviorally adjust in response to such stressors and whether long-term bonds might be a mitigating factor.One such stressor for dolphins and whales is maternal care, where the mother must dive to find food, leaving her less able calf at the surface. Chapter 1 investigates mother-calf diving behavior in wild bottlenose dolphins, showing that while calves increased their dive durations with age, mothers modified their behavior according to calf sex and distance from their calves in a way that favored female calves. This is consistent with sex-specific socio-ecological strategies, where vertical learning is more important for female than male calves. Mothers are affording daughters more direct experience of her foraging behavior than sons.Another stressor is human impacts, especially fishing gear entanglement. In a rare observation, Chapter 2 shows how a dolphin behaved before, during entanglement and after she was free from the fishing line. During entanglement, the dolphin decreased association and social behavior with others, decreased foraging and increased in traveling and erratic behavior.Chapter 3 quantifies the paradoxical impact of a major seagrass die-off on dolphin behavior, where dolphins increased their use of seagrass habitat following the die-off. Seagrass specialists shifted habitat use and foraging from their preferred seagrass species to the less preferred, but less damaged species. Calf survival and birthrate did not decrease post-die-off, but there may longer-term impacts if prey abundance decreases.In the first detailed examination of female-female bonds, Chapter 4 explores the temporal dynamics and factors driving such bonds. Most females maintained strong long-term bonds for 4-18 years, and was associated with calving success. Partner similarity, degree of alter, and bond strength were important for the maintenance of ties, while friends-of-friends and age difference were important for the creation of ties.Long-term datasets on long-lived, socially complex mammals are rare, but invaluable for understanding how individuals respond to a changing environment and stressful events.
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Age Determination, Life History and Juvenile Behavior in Bottlenose Dolphins (Tursiops sp.) in Shark Bay, Australia Krzyszczyk, Ewa Beata (Georgetown University, 2013)Although of theoretical interest, the juvenile period in mammals is a relatively neglected area of research. In large-brained and social mammals, such as bottlenose dolphins, where juvenile periods are prolonged, life ...