Diets of Coastal Bottlenose Dolphins From the U. S. Mid‐atlantic Coast Differ by Habitat

Abstract

We recorded 31 species in the stomachs of 146 coastal bottlenose dolphins (Tursiops truncatus) from North Carolina, U. S. A. Sciaenid fishes were the most common prey (frequency of occurrence = 95%). By mass, Atlantic croaker (Micropogonias undulatus) dominated the diet of dolphins that stranded inside estuaries, whereas weakfish (Cynosicon regalis) was most important for dolphins in the ocean. Inshore squid (Loligo sp.) was eaten commonly by dolphins in the ocean, but not by those in the estuaries. There was no significant pattern in prey size associated with dolphin demography, but the proportion of the diet represented by croaker was higher for males than for females, and mature dolphins ate more croaker than did juveniles. Dietary differences between dolphins that stranded in the estuaries and those that stranded on ocean beaches support the hypothesis that some members of the population inhabit the ocean primarily while others reside principally in estuaries. The overwhelming majority of prey were soniferous species (75% of numerical abundance), which is consistent with the hypothesis that bottlenose dolphins use passive listening to locate noise‐making fishes. However, spatiotemporal patterns in consumption of Sciaenid fishes did not coincide with their spawning, which is when peak sound production is thought to occur.

Association of an Unusual Marine Mammal Mortality Event With Pseudo-Nitzschia Spp. Blooms Along the Southern California Coastline

“…The relatively small number of individuals of bottlenose dolphins stranding during Pseudo-nitzschia bloom activity may reduce confidence that DA was involved, but may also give insight into the ecology of DA toxicity. Bottlenose dolphins tend to target less-efficient vector prey, feeding mainly on sciaenid, scombrid, and mugilid fish as well as cephalopods, and may therefore have less opportunity for exposure (Clarke, 1996;Walker et al, 1999;Gannon and Waples, 2004). Fewer short-beaked common dolphin than long-beaked common dolphin strandings were observed; their diets are thought to be similar and primarily consist of squid and anchovies, the latter being one of the better-known DA vector species (Evans, 1994).…”

Habitat structure and the dispersal of male and female bottlenose dolphins (Tursiops truncatus)

“…As reviewed in §1, local populations have been shown to favour specific habitat types (e.g. Barros & Wells 1998;Allen et al 2001;Gannon & Waples 2004). A comparative assessment of estimates of gene flow for mtDNA and bi-parental markers, together with the very similar pattern of F ST values for the two marker types (based on relative magnitude and the Mantel test), indicate that this pattern of movement is true for both sexes (with the exception of differential female movement at range margins).…”

“…For example, bottlenose dolphins in the Moray Firth, Scotland showed a clear relationship between feeding behaviours and submarine habitat characteristics (Hastie et al 2004). Bottlenose dolphins feeding in coastal habitat in the eastern North Atlantic also showed variation in diet according to habitat type (Gannon & Waples 2004), and dependence on specific habitat types such as estuaries and seagrass, which also correlated with group size and cohesion during foraging (Barros & Wells 1998;Allen et al 2001;Gannon & Waples 2004). The disposition of prey (shallow or deep in the water column, clumped or dispersed, etc.)…”

Thermal tolerance in bottlenose dolphins (Tursiops truncatus)

“…The relationship of prey distribution to dolphin distribution is also not as clearly determined (Barco et al, 1999;Wells et al, 1990); although prey distribution must to some extent affect habitat selection (e.g. Barros and Wells, 1998), the observed plasticity in prey selection (Young and Phillips, 2002;Gannon and Waples, 2004) may minimize the impact resulting from temporal and spatial variations in specific prey availability in the bottlenose dolphin.…”