habitat_narrative
Marine
The Dusky Dolphin is a resident coastal species, most commonly located over the continental slope and shelf (Jefferson et al. 1993; Aguayo et al. 1998). Along the west coast of southern Africa, its distribution is associated with the continental shelf and cool waters of the Benguela Current. Research indicates that they favour sea surface temperatures between 10°C and 18°C (Brownell & Cipriano 1999). They use a wide range of habitats within the Benguela Current depending partly on age and reproductive status, from extreme nearshore to shelf edge, with corresponding flexibility in prey usage. Dusky Dolphins usually rest and socialise in shallow waters, but utilise deeper marine habitats when feeding (Wursig & Wursig 1980).Dusky Dolphins take a wide variety of prey, mainly Piscine and Cephalopods. Food remains from 36 dolphins from South Africa included Horse Mackerel Trachurus p. (34.7% by mass), Hake Merluccius sp (22.9%) and Lantern Fish Lampanyctus sp. (12.8%) with Sardine (Sardina pilchardus), Arrow Squid (Nototodarus sloanii) and Chokka Squid (Loligo reynaudii) also taken occasionally (Best & Meÿer 2010). Stomach contents tend to either consist of prey associated with the epipelagic zone (surface schooling fish such as Sardine, Anchovy (Engraulidae sp.) and Horse Mackerel or even such nearshore inhabitants as Mullet, Liza richardsoni) or mesopelagic prey (those associated with the deep scattering layer such as myctophids, Lampanyctys and Diaphus or Hatchet Fish Maurolicus), suggesting that Dusky Dolphins use at least two foraging strategies.
Group sizes within South Africa have been recorded from 2 to 800 (mean 35.3, Best 2007), although the vast majority of groups encountered consist of fewer than 20 individuals (Best & Meÿer 2010). The species is known to form nursery groups consisting entirely of mother-calf pairs. These nursery groups are most common in late summer with peak occurrence of 38% in February (Best & Meÿer 2010), coinciding with a birth season in January to early February, estimated from the reproductive status of dead females and stranded neonates (Best & Meÿer 2010). Calf size at birth has been recorded at approximately 0.86 m, and strandings data revealed highest calf percentage in January and February (Skinner & Chimimba 2005).
Ecosystem and cultural services: This species is a flagship species for conservation and ecotourism on the west coast of South Africa.
