Capstone Title

Comparative Study on Behavior Of Common Bottlenose (Tursiops truncatus) and Short-Beaked Common Dolphin (Delphinus delphis) in the Inner Ionian Sea Archipelago, Greece

Defense Date


Document Type


Degree Name

M.S. Marine Biology

First Advisor

Nick Funicelli

Second Advisor

Joan Gonzalvo


Bottlenose and short-beaked common dolphins have coexisted in the Inner Ionian Sea archipelago as long as can be remembered. Between 1997 and 2007, the common dolphin population declined significantly, concurrent with an increase in fishery activity, while the bottlenose dolphin population remained stable. This study describes the behavior of bottlenose and common dolphins in the archipelago and searches for differences between the two species. The data included in this capstone was collected by the Ionian Dolphin Project between 2002 and 2015 during 303 boat based surveys. Data was collected during morning and early afternoon hours, in good weather conditions, at six minute intervals. Behavioral budgets were produced to assess the behavior of the two species and were derived from five categories: Aerial behavior, Percussive behavior, Social Interactions, Stationary behavior and Surface Foraging. Within each category, the frequency at which the dolphins were observed performing the behavior was recorded as No, Occasional, Regular and Uncertainty. Bottlenose dolphins had the highest budget for occasional-aerial (4.1%) followed by occasional-percussive (2.1%), occasional-social (2.0%), regular-social (1.0%), occasional-stationary (0.8%), regular-aerial (0.7%), regular-percussive (0.1%), occasional-foraging (0.1%), regular stationary (0.1%), and regular foraging (0.0%). Common dolphins had the highest budget for occasional-aerial (7.0%) followed by occasional-percussive (5.4%), occasional-social (5.2%), occasional-stationary (3.4%), regular-social and regular-stationary (1.0%), regular aerial (0.8%), occasional-foraging (0.4%), regular-percussive (0.3%) and regular-foraging (0.1%). A high percentage of No was recorded for bottlenose and common dolphins (89.1% and 75.6% respectively) emphasizing the need to reconsider categories. Common dolphins showed significantly more behaviors, especially active surfacing displays, than bottlenose dolphins for most years of the study. Implications of the behavioral differences between the two dolphin species we’re discussed in relation to conservation. Recommendations were made to encourage the return of the common dolphin to the archipelago.

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