Observations of a Benthic Foraging Behavior Used by Common Bottlenose Dolphins (Tursiops truncatus) in Barataria Basin, Louisiana, USA

Across their worldwide distribution, bottlenose long-term, multifaceted study. Over the course of dolphins (Tursiops spp.) use a variety of techniques this study, dolphins were observed engaging in a to detect, pursue, and capture prey. Dolphins may previously undescribed behavior, which we term hunt independently or in groups, and specialized drilling (or drill feeding), in which a single dolforaging behaviors have been identified at both the phin positions itself almost vertically in shallow individual and population levels. These behaviors water and thrashes its flukes/tailstock across the can involve tool use (Patterson & Mann, 2011), surface, presumably to forage for prey in the subcoordinated herding of prey (Engleby & Powell, strate below. Herein, we report on observations of 2019), benthic foraging techniques (Rossbach & this behavior and discuss its significance for the Herzing, 1997), and even cooperative interac- BBES Stock. tions with fishermen (Daura-Jorge et al., 2012). In The Barataria Basin is a large estuarine-wetland many bay, sound, and estuary populations along system in southeastern Louisiana (USA), extendthe U.S. coast, dolphins have developed foraging ing from Bayou Lafourche in the west to the strategies that incorporate local habitat features Mississippi River in the east (Figure 1). The south(Wells, 2019). For example, along the southeast ern boundary consists of a series of barrier islands coast of the U.S., strand-feeding dolphins utilize that separate the estuary from the Gulf of Mexico. exposed mud and sand banks to drive prey onto The estuarine waters are turbid and shallow, with a shore (Hoese, 1971; Fox & Young, 2012). Other mean depth of -2 m and salinities that range from strategies are more specifically adapted to target tidally influenced saline waters (-25%0) in the and handle individual prey species. For instance, south to freshwater lakes (-0%0) in the north (U.S. populations have developed a technique to remove 1999; Das et al., 2012). The substrate is soft and the spiny heads from catfish (Ariidae), consuming muddy, primarily composed of silty clay sediment