Common bottlenose dolphin (Tursiops truncatus) behavior in an active narrow seaport

Area of Science:

• Marine biology
• Wildlife behavior
• Conservation science

Background:

• The Galveston Ship Channel (GSC) is a critical habitat where human activities like shipping and tourism overlap with common bottlenose dolphin (Tursiops truncatus) presence.
• This overlap raises concerns about the potential negative impacts of human activity on dolphin behavior and well-being.

Purpose of the Study:

• To investigate the behavioral responses of dolphins to vessel traffic within the GSC.
• To analyze dolphin movement patterns and social interactions in relation to vessel presence and other environmental factors.

Main Methods:

• Land-based tracking and behavioral observations of dolphins and vessels using a digital theodolite.
• Analysis of positional data to calculate dolphin movement patterns and proximity to vessels.
• Statistical tests (log-likelihood ratio, Chi-square) and generalized additive models to assess behavioral states and movement patterns.

Main Results:

• Dolphins primarily use the GSC for foraging (57%) and socializing (27%), not as a travel corridor.
• Dolphin behavior, including foraging and socializing, was significantly reduced in the presence of boats.
• Dolphin swimming speed and reorientation rates increased significantly with the presence of various vessel types, including recreational boats, tour boats, and shrimp trawlers.

Conclusions:

• Vessel presence significantly alters dolphin behavior in the GSC, leading to reduced foraging and socializing opportunities.
• Increased swimming speeds and reorientation rates in response to vessels may indicate stress and disrupted activity, potentially leading to decreased energy consumption.
• Management strategies are needed to mitigate the negative impacts of vessel traffic on dolphin health, energy balance, and long-term survivorship in this busy waterway.