Sex Difference in Bottlenose Dolphin Sightings during a Long-term Bridge Construction Project

• Main Author: Ann Weaver
• Format: Article
• Language: English
• Published: Animal Behavior and Cognition 2015-02-01
• Series: Animal Behavior and Cognition
• Subjects: Resident bottlenose dolphins; Coastal construction; Sighting patterns; Gender differences; Anthropogenic threats
• Online Access: http://www.animalbehaviorandcognition.org/uploads/journals/5/01.Weaver_FINAL.pdf
• ISSN: 2372-5052; 2372-4323

Almost nothing is known about the effect of long-term bridge construction on free-ranging bottlenose dolphins (Tursiops truncatus). The species’ natural history predicts that there should be sex differences in reaction to construction because bottlenose dolphins show sex differences in most of their behaviors. A 5-year bridge construction project over a narrow but important dolphin corridor at John’s Pass tidal inlet, St. Petersburg FL, brought chronic environmental changes. The purpose of this 8-year study was to determine if bridge construction was associated with changes in dolphin sightings. The sex difference hypothesis was tested with a comparison of sighting probabilities before, during and after bridge construction. Sighting probabilities were generated for 68 adults seen n = 6504 times during N = 951 small-boat surveys of the 6.5-mile estuarine study area, documented with photo identification June 2005-December 2012. The sex difference hypothesis was supported with a significant interaction between construction and gender. Female sightings showed a significant linear decline across construction. Male sightings did not change across construction. The main conclusion is that adult males and females may react differently to habitat changes associated with anthropogenic activities. Sex differences in environmental monitoring and vigilance associated with maternal behavior may have played a role. This is the first report on John’s Pass dolphins that evaluates changes in their behavior during a major construction project across a narrow but important dolphin corridor.