Dusky Dolphins Foraging in Daylight

Diving for food: a switch of foraging strategy of dusky dolphins in Argentina

“…During milling, dolphins swim erratically possibly searching for prey, and once they find them, they dive to catch them. This could represent an alternative foraging tactic different to the foraging sequences that have been described previously (Vaughn et al 2010;Degrati 2011), where feeding bouts alternate with traveling bouts in long sequences. In the present study, prey were not surveyed at the same time that dolphins dived.…”

“…Dolphin groups join up, and large prey schools may attract up to 300 dolphins and over 1,000 birds. In Golfo Nuevo, surface feeding bouts alternate with traveling bouts in long sequences (Vaughn et al 2010). This would be a foraging strategy related to prey distribution, where dolphins find a prey patch, feed on it, and then move to the next patch (Degrati 2011).…”

Characterizing dusky dolphin sounds from Argentina and New Zealand

“…Studying how dusky dolphins use click trains and burst pulses to communicate and to coordinate foraging behaviors potentially provides insights into the mechanisms of coordinated foraging. Dusky dolphins exhibit two broad foraging tactics: feeding at night on a deep scattering layer (e.g., in Kaikoura: Dahood and Benoit-Bird, 2010) and feeding during the day in shallow bays on small schooling fishes [e.g., in Argentina and in the Marlborough Sounds, New Zealand (NZ): Vaughn et al, 2010a]. They exhibit coordination during both tactics, and often form larger groups during foraging to contain or capture prey more effectively (Pearson, 2009;Würsig and Würsig, 1980).…”

“…The sound repertoire of dusky dolphins was not been characterized, and burst pulses were not previously examined. The characterization presented here represents an opportunity to do so for a (probably) nonwhistling dolphin that exhibits coordination during foraging (Vaughn et al, 2010a). Studying how dusky dolphins use click trains and burst pulses to communicate and to coordinate foraging behaviors potentially provides insights into the mechanisms of coordinated foraging.…”

“…In both locations, dusky dolphins at times coordinate behaviors to herd and capture schooling fish, and they feed with diverse associated predators including seabirds, pinnipeds, and sharks (Vaughn et al, 2007); however, in Argentina, dusky dolphins feed in much larger groups and for longer durations (Vaughn et al, 2007;Würsig and Würsig, 1980). These behavioral differences may relate to differences in bay sizes and consequent sizes of fish schools (Vaughn et al, 2010a), or they could be due to differences in fish species or their behaviors, or to dolphin genetic or cultural factors.…”