Sunday, October 28, 2012

Great white sharks are one of the most well adapted and adept predators on earth. They have remained virtually unchanged in shape or size for 16 million years. As an apex predator, or a predator at the top of the food chain, white sharks play a crucial role in food webs throughout the world. They are mainly found in temperate waters with temperatures ranging from 12-25 degrees Celsius. The map below depicts common ranges for white sharks, however it excludes migratory routes which are one of the main focuses of this blog.

In particular, this blog will examine how climate change forecasts might alter the predator-prey dynamic between white sharks and cape fur seals in southern Africa through changes in white shark migration. With respect to climate change, an area of research I was involved in is monitoring and predicting the effects of rising ocean temperatures on white shark migrations as well as trophic interactions between these predators and their prey. Through Oceans Research in Mossel Bay, South Africa, I was able to participate in shark tagging studies to monitor migrational patterns and durations. White sharks are endothermic, but are only observed regularly in habitats with water temperatures below 25 degrees Celsius (Carlisle et. al, 2012). The migratory patterns of white sharks are irregular and their environmental cue is unknown. For these reasons, little is known about the complexities of white shark migration, which yields effects of sea warming on these behaviors even harder to predict than in other species. Ocean temperature appears to have a large impact on white shark migratory patterns, and a shift towards warmer ocean temperature will likely alter the global distribution of white sharks.

White sharks not only serve as an iconic predator in cultures around the world, but have very real economic impacts to humans in all oceans. Regardless of predation effects on tuna and other fish populations, white sharks are responsible for large streams of revenue through tourism in South Africa and are the topic of large research grants in waters near California and Australia. Trying to grasp how climate change may effect these ecological and economic processes is an important area of research in contemporary conservational biology.

Here is a short clip I shot while studying white sharks in Mossel Bay, South Africa, demonstrating some predatory techniques only observed in South African white shark populations.