Throughout their global range Dusky Dolphins are associated with the continental shelf and shelf edge, ranging from the coastline to more than 100 km from shore and more than 2,000 m deep, although in all areas where they have been reported, the majority of animals are observed in water less than 500 m deep (Findlay et al 1992, Cipriano and Webber 2010). The species has been recorded to occur in cool temperate waters between 10 and 18°C (Brownell and Cipriano 1999, Würsig and Würsig 1980). Dusky Dolphin distribution is strongly associated with highly productive upwelling cells on either side of South America (Humboldt and Falkland) and off southern Africa (Benguela), with various cold-water currents around New Zealand (Brownell and Cipriano 1999) and in higher latitudes with several sub-Antarctic Islands. Although southeastern Australia is commonly reported as part of the species range, sightings there are very rare given the amount of survey effort in the region (Gill et al. 2000), suggesting that the species should be considered an occasional transient rather than resident, as noted by Cipriano and Webber (2010).

Dusky Dolphins consume a wide variety of fish and cephalopod prey, including schooling fishes such as anchovy, Sardine (Sardina pilchardus) and Horse Mackerel (Trachurus sp.), and more benthic species associated with the deep scattering layer such as hake (Merluccius sp.), lantern fish (Lampanyctus sp.), hatchet fish and a number of squid species. In Peru, analysis of stomach content for 72 individuals reported Peruvian Anchoveta as the main prey, followed by Slimtail Lanternfish Lampanyctus parvicauda and Inca Scad Trachurus murphyi (Garcia-Godos et al., 2007). On the basis of stomach contents and stable isotope methods, Dusky Dolphins in northern and central Patagonia feed on Argentine Anchovy (Engraulis anchoita), Argentine Hake (Merluccius hubbsi), Butterfish (Stromateus brasiliensis), and squids (Illex argentinus, Loligo gahi) together with few benthic prey (Koen Alonso et al. 1998; Romero et al. 2012; Loizaga de Castro et al. 2015). In southern Africa, analysis of stranded, caught and bycaught dolphins showed stomach contents to consist of 34.7% Horse Mackerel, 22.9% Hake, and 12.8% lantern fish with Sardine, Arrow Squid (Nototodarus sloanii) and Chokka Squid (Loligo reynaudii) also taken occasionally (Best and Meÿer 2010). In New Zealand, Dusky Dolphins near Kaikoura primarily feed on deep scattering layer-associated species, including squids (especially Nototodarus/Todaroides spp.) and lanternfish (Cipriano 1992). In winter, Dusky Dolphins in Admiralty Bay, New Zealand feed on Pilchard (Sardinops neopilchardus), Yellow-eyed Mullet (Aldrichetta forsteri), and Sprat (Sprattus antipodum; Markowitz et al. 2004).

To catch their prey, Dusky Dolphins use at least two different foraging strategies: forming large groups to herd and attack surface-schooling fish such as anchovies and sardines in ‘bait balls’ (Markowitz et al. 2004, Best and Meÿer 2010, Degrati et al. 2012) or predominantly nocturnal foraging on species associated with the deep scattering layer, which migrate closer to the surface at night (Benoit-Bird et al. 2004, Best and Meÿer 2010, Bernasconi et al. 2011). In the latter case, Dusky Dolphins appear to engage in a clearly diurnal movement pattern, returning close to shore during daylight hours when prey are too deep to access, probably to reduce the threat of predation from deep-water predators such as sharks and Killer Whales (Orcinus orca). Dusky Dolphins appear to modify their foraging strategy to adapt to the most abundant prey available and foraging strategy may vary over space and time. For instance, at Península Valdés, Argentina, Dusky Dolphins predominantly engage in coordinated diving during winter months (9.5% of the time) but engage in surface feeding on bait balls (diving drops to 0.1% of the time) during summer (Degrati et al. 2012). In both seasons, most of the groups observed diving were small (less than 10 dolphins). Similarly, in New Zealand, Dusky Dolphins predominantly forage nocturnally off Kaikoura on deep scattering layer-associated species (Cipriano 1992, Benoit-Bird et al. 2004), while the same animals also engage in shallow-water bait-ball feeding in the Marlborough Sounds (Markowitz 2004, Markowitz et al. 2004).

Dusky Dolphins have a discontinuous distribution in the Southern Hemisphere associated with cool temperate coastal and shelf waters (Brownell and Cipriano 1999, Van Waerebeek 1992, Cipriano and Webber 2010). They occur in apparently disjunct populations in the waters off New Zealand (including the Chatham and Campbell Islands), central and southern South America (including the Falkland Islands) (Van Waerebeek 1993b, Van Waerebeek et al. 1995, Crespo et al. 1997), and southwestern Africa (Best 2007). These populations have been assigned to four separate subspecies. Dusky Dolphins also occur around some oceanic island groups (e.g., Tristan da Cunha, Prince Edward, Amsterdam, and St. Paul Islands). The subspecies affinities of these groups are uncertain.

The species is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES).

Population structure and abundance has been little studied in most areas, and intensive photo-identification, genetic and survey studies are recommended.

Bycatch in gillnets occurs at high levels in south America and needs to be investigated and monitored. Pingers were tested as a mitigation measure for a small-scale gillnet fishery in Peru and showed a 37% reduction of combined dolphin and porpoise bycatch in gillnet fisheries (Mangel et al. 2013).