Description of a Unique Solitary Feeding Strategy Observed in Bottlenose Dolphins (Tursiops truncatus) in the Biloxi Marsh, Louisiana

Mystera M Samuelson,Ashley Millan Ambert,Cristina Díaz Clark,Moby Solangi

doi:10.26451/abc.07.04.03.2020

Abstract

Bottlenose dolphins’ (Tursiops truncatus) foraging strategies in the Biloxi Marsh have received little attention when compared with other comparable habitats in the southeastern United States. Previous reports of dolphin foraging in this region have included sophisticated strategies such as strand feeding but have not included a detailed analysis of the observed behavior. Dolphins were observed performing a unique solitary foraging strategy, termed marsh bank feeding. Although this behavior was observed to occasionally result in stranding upon the marsh bank, it is argued here that the observed behavior is fundamentally different than the definitions for strand feeding, as well as other prominent shallow water foraging strategies. Video footage resulting from observations made between 2013 and 2019 were analyzed in order to establish the components of the behavior, enabling a detailed comparison to other dolphin foraging strategies.

Highlights

The numerous and variable feeding strategies of bottlenose dolphins (Tursiops truncatus) are a distinguishing credit to their adaptive nature (Würsig, 1986), which allows this species to thrive in a wide variety of ecosystems, including marsh environments (Silber & Fertl, 1995)
In this paper we describe a unique solitary feeding style, heretofore referred to as marsh bank feeding (MBF), observed in the Biloxi Marsh, Louisiana
Behavioral coding confirmed that the MBF behavior occurred in four distinct stages: 1) An individual dolphin swam slowly parallel to and within less than one body length, or 2.5-3 m (Bearzi et al, 1997) from the marsh bank (Figure 2a); 2) When the animal identified a target prey item, an individual fish chase was initiated (Figure 2b, 2c & 2d); 3) The dolphin herded a single fish toward the marsh bank (Figure 2e) in an attempt to capture the prey (Figure 2f)

Summary

Introduction

The numerous and variable feeding strategies of bottlenose dolphins (Tursiops truncatus) are a distinguishing credit to their adaptive nature (Würsig, 1986), which allows this species to thrive in a wide variety of ecosystems, including marsh environments (Silber & Fertl, 1995). The organized and cooperative circle feeding behavior is characterized by the trapping of prey within vortices and mud plumes produced by one or more animals rapidly swimming in a circle, trapping the prey inside Both shallow water feeding and circle feeding are known to occur year-round and predominantly at low tide, when mud flats are exposed (Rigley et al, 1981). Beach feeding has been described as the “intentional beaching to capture fish chased onto shore” and has been observed along sand beaches and muddy marsh banks on the eastern coast of the United States It excludes the use of a dolphin-induced bow wave to move prey fish onto a bank, as was reported in strand feeding, and specifies the dolphins’ intention to beach, and is not qualified as an exclusive group behavior (Silber & Fertl, 1995)

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Results

Conclusion