habitat_narrative
Marine
The Heavisideâs Dolphin is strongly associated with the cold, northward-flowing Benguela ecosystem off the west coast of southern Africa. This is a shelf-dwelling dolphin, seen mainly in waters less than 100 m deep, where more than 85% of sightings occur in waters with surface temperatures of 9â15 °C (Best & Abernethy 1994). Evidence from photographic mark-recapture (Elwen 2008) and satellite telemetry (Elwen et al. 2006; Davis et al. 2014) suggest individuals maintain small home ranges, extending approximately 50â80 km along the shore, resulting in total home range sizes of between 300 and 2,300 km2, depending on the measure used.The diet of Heavisideâs Dolphins, as ascertained from caught, stranded and bycaught animals, consists mainly of juvenile hake Merluccius spp. (49% by modified volume) as well as juvenile goby, Sufflogobius bibarbatus (13.6%), kingklip Ophiphidae spp. (8.5%) and a range of other predominantly demersal fish and cephalopods, including Cape Gurnard (Chelidonichthys capensis), octopus, and Chokka Squid (Best 2007). Most fish caught by Heavisideâs Dolphins are well below the modal length of commercially caught fish (Sekiguchi et al. 1992), and there is little spatial overlap in fishing effort and dolphin habitat (Fairweather et al. 2006). In South African waters, Heavisideâs Dolphins mainly feed nocturnally on prey associated with the deep scattering layer, which migrates closer to the surface at night (Sekiguchi et al. 1992; Elwen et al. 2006, 2009a). By day the majority of dolphins rest and socialise close to shore (Elwen et al. 2006, 2009a). This feeding habit results in a strong diurnal movement pattern, with animals being closest to shore between 06h00 and noon and farthest offshore between 15h00 and 05h00 (Elwen et al. 2006). Although the species similarly exhibits a strong diurnal movement pattern in Namibia, the pattern appears to be reversed with acoustic detections in coastal habitat higher during the night than day (Leeney et al. 2011). This is likely driven by differences in prey habitat use and behaviour.
They reach a maximum age of 26, and become sexually mature at 7.5 years. Calving is thought to occur seasonally in summer, and females are able to be simultaneously pregnant and lactating (Skinner & Chimimba 2005).
Ecosystem and cultural services: This is South Africaâs only near endemic cetacean species and a flagship species for the West Coast.
