The juvenile life stage is both fragile and formative for young marine mammals first learning to navigate their complex social and ecological environment independent of their mothers. While bottlenose dolphins are well-studied, virtually no prior work focused on understanding behavioral development between weaning and sexual maturity or determining factors influencing survivorship of independent juveniles. Because of the SDRP’s long-term research, the “natural laboratory” of Sarasota Bay has provided a unique opportunity to address these issues in my doctoral research.
To this end, the main objectives of my dissertation project are: 1) to develop a better understanding of social and behavioral development of juvenile bottlenose dolphins, and 2) to determine the major behavioral and ecological influences on survival of free-ranging juvenile dolphins. I have been investigating these questions by combining long-term sighting and mortality data from the resident dolphin community in Sarasota Bay with new information collected via focal animal observations on individually-identifiable juveniles in the community, providing both a longitudinal and cross-sectional perspective on juvenile behavior.
Fieldwork for this project began in summer 2005 and was completed in August 2008. In 2008, I spent most of my time in the field; carrying out my final winter and summer field seasons of behavioral observations and then finishing data entry and double checking data for all seasons this fall. Over the course of this project, I have collected over 585 hours of focal follow behavioral data on 27 individuals (14 females and 13 males) in the Sarasota community ranging in age from 2 to 13 years old. While a few of these animals have either died, gone missing, or had calves of their own since the project began, most were observed in each of my six seasons. It has been extremely interesting to watch their behavior and relationships change over the past three years, especially as several males have begun to form alliances and some females have gotten closer to becoming first-time mothers.
Now that data collection is complete, I have moved fully into analysis and writing mode. One of the main areas I’ve explored so far has been the effects of red tide on juvenile dolphin behavior. While not originally intended to be a focus of this study, my first two field seasons coincidentally took place during periods in 2005 and 2006 when red tide was a factor. Preliminary analysis from those seasons showed that both social behavior and activity budgets differed substantially during red tide, potentially as a consequence of underlying changes in relative prey availability and distribution (see Gannon, Berens, and Camilleri article in this edition). I am currently working on more extensive analysis of the changes in social behavior and social networks observed during red tide events and preparing a manuscript for publication from these results. Additionally, I am beginning to work on the major analyses for my dissertation, using focal follow data to explore sex, seasonal, and age-related differences in juvenile behavior (primarily looking at association and ranging patterns, habitat use, and activity budgets) and drawing on long-term data to investigate factors influencing age at independence for dolphin calves as well as behavioral and ecological effects on juvenile dolphin survivorship.
This research will reveal the range of variability in developmental trajectories of bottlenose dolphins and provide missing data on how juvenile dolphin behavior patterns vary by sex, age, season, and time since weaning. Such information will provide a more comprehensive understanding of dolphin life history and survival strategies, which may have implications for conservation and management of long-lived coastal cetaceans.
Support for this project has come from the Chicago Zoological Society, NOAA Fisheries, the UC Davis Graduate Scholars Fellowship in Animal Behavior, the Animal Behavior Society’s Cetacean Behavior and Conservation Award, and an NSF Graduate Research Fellowship.