Sixteen years later: Occurrence, group size, and habitat use of humpback dolphins (Sousa plumbea) in Algoa Bay, South Africa. Issue 2 (23rd October 2015)

• Record Type: Journal Article
• Authors: Koper, Renée P.; Karczmarski, Leszek; du Preez, Derek; Plön, Stephanie
• Is Part Of: Marine mammal science. Volume 32:Issue 2(2016)
• Page Start: 490
• Page End: 507
• Publication Date: 2015-10-23
• Subjects: Sousa plumbea -- group size -- occurrence -- behavior -- habitat use -- anthropogenic disturbance -- environmental change -- South Africa -- Algoa Bay; Marine mammals -- Congresses; Marine mammals -- Periodicals; Marine mammals, Fossil -- Periodicals; Mammifères marins -- Périodiques; 599.5
• DOI: 10.1111/mms.12279
• Languages: English
• ISSNs: 0824-0469

Abstract

Abstract: Coastal dolphins are more prone to cumulative impacts of environmental and anthropogenic changes than pelagic species. However, few studies use historical comparisons to evaluate those impacts across a temporal scale. The study presented here describes the pattern of occurrence, group size, behavior, and habitat use of humpback dolphins in Algoa Bay and compares these to a similar study conducted in the early 1990s. Results indicate a considerable change in the frequency of occurrence. Furthermore, the mean group size has decreased from six to three individuals, mainly due to an increase in occurrence of solitary individuals (36.3% vs . 15.4%). Foraging, which was previously the predominant activity (64%), has now been replaced by traveling (49%). Moreover, dolphins showed a negative reaction towards a variety of watercrafts and swimmers. These observed differences could be due to a change in prey abundance, direct anthropogenic disturbance, and/or population decline. We emphasize the need for long‐term environmental and biological data series and long‐term monitoring of the demographics of this population to accurately assess any changes observed in future.