Relationship Between Behaviors and Group Sizes Common Bottlenose Dolphins (Tursiops truncatus) in the Galveston Ship Channel, Texas.

Abstract

Galveston Bay is an inlet from the Gulf of Mexico that connects to the Galveston Ship Channel where common bottlenose dolphins (Tursiops truncatus) are regularly observed. These dolphins live in fission-fusion societies where group structure changes frequently and individuals associate in different ways. Group size may facilitate foraging efficiency or reduce predation risk and therefore may be influenced by behavioral states. For this study, we examined bottlenose dolphin group sizes and behaviors in the Galveston Ship Channel and surrounding coastal waters. Group size and predominant group behavior were recorded during each survey. Data were collected from boat- and land-based platforms from September through December 2012. Vessel-based research was conducted for 9 days and shore-based research was conducted for 41 days. Previous studies in this area found socializing dolphins to have the highest mean group size. This study’s results were similar to the previous study. We also found that foraging was the most frequently recorded behavior. Resting dolphins were observed in groups on average of two to three individuals and were not often observed, which may be influenced by high vessel traffic within the area.