Oliver Jewell, Movement patterns and habitat use of an apex predator
Channel: African Campus
Date: 2013-06-13

Oral Presentation

Oliver Jewell
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
Dyer Island Conservation Trust, Great White House, Geelbek St, Kleinbaai, Gansbaai 7220, South Africa

White shark habitat use has been well defined through various studies using acoustic telemetry in Mossel Bay. We examined habitat use of white sharks at a different location, Geyser Rock, Gansbaai, using manual acoustic tracking and compared the results to the previous studies in Mossel Bay. Traditional home range estimates were difficult to use in this area as heterogeneous structures are prominent and shark movements were shaped around them. To counter this we adapted a Movement-based Kernel Density Estimate (MKDE) which can account for structures, barriers and movements, outperforming location-based methods. Daytime habitat use of white sharks at Geyser Rock was confined to small areas close to the seal colony or kelp reefs adjacent to it. There were no peaks in rate of movement (ROM) or linearity (LI) at dawn or dusk and no preference for movement close to the seal colony was observed during this time -- contradictory to previous studies in Mossel Bay. Instead movement close to the colony took place during day and moonlight and once the moon set, or if there was cloud coverage at night sharks moved to distant reefs or further out to sea. Activity areas were smaller than recorded at Mossel Bay and independent of body size. The prime prey species is presumed to be the same at both locations (Cape fur seal), yet the significant differences in movement patterns suggest white sharks are able to adapt their habitat use to better suit the location they are utilising.