Occurrence of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) off the Wild Coast of South Africa using photographic identification

Abstract

The present study represents the first reported boat-based photographic identification study of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off the Wild Coast of southeast South Africa. This area is known for the annual sardine run, which attracts apex predators to the region during the austral winter. Dedicated photo-identification surveys were conducted along this coast at three different study sites in February, June, and November of each year from 2014 to 2016. During 47 surveys, 136 bottlenose dolphin groups were encountered, an estimated 4,474 dolphins observed, and 2,149 individuals were identified. Although most individuals (N = 1,770, 82.4%) were only observed once, some were resighted 2-7 times (N = 379, 17.6%), with an average of 305 days (range: 88-705 days) between resightings. The majority of bottlenose dolphins were resighted within the same study site (N = 192), indicating some degree of residency. However, 65 individuals were observed at two different study sites, indicating individual movements along the coast. Our findings contrast earlier suggestions that bottlenose dolphins only use the Wild Coast during the sardine run, as we found large number of animals year-round with some level of site fidelity. This highlights the importance of the Wild Coast to bottlenose dolphins and provides further information on their status off southeastern South Africa.

Rostrum abnormalities in the endangered Indian Ocean humpback dolphin (Sousa plumbea) in South Africa

“…The south coast population of bottlenose dolphins in South Africa are almost completely sympatric with humpback dolphins and highly abundant (Reisinger & Karczmarski 2010; Caputo et al. 2021), including having among the largest group sizes for the species seen anywhere globally (Bouveroux et al. 2018b).…”

“…There is much to suggest that bottlenose dolphins are violent toward other species of dolphins and that they inflict trauma that is characterized by multiple skeletal fractures, though the species involved are generally smaller than humpback dolphins (Ross & Wilson 1996;Wedekin et al 2004;Coscarella & Crespo 2009). The south coast population of bottlenose dolphins in South Africa are almost completely sympatric with humpback dolphins and highly abundant (Reisinger & Karczmarski 2010;Caputo et al 2021), including having among the largest group sizes for the species seen anywhere globally (Bouveroux et al 2018b). At least, one aggressive interaction between humpback dolphins and bottlenose dolphins has been recorded in the country (Saayman & Tayler 1979).…”

Cetacean Research and Citizen Science in Kenya

“…comm. ), Réunion (Dulau-Drouot et al, 2008), Mozambique Bay (Guissamulo, 2008) and South Africa (Caputo et al, 2021). In southern Kenya, a small population size was estimated with a mean of 65 dolphins (SE: 7.06), with seasonal fluctuations ranging from 20 (95% CI 11-36) to a maximum of 102 individuals 95% CI 77-138) (Pérez-Jorge et al, 2016).…”