White Shark Café – Are sharks eating or meeting down under?

Great white sharks congregate every spring in a deep area of the Pacific Ocean known as the white shark Café. Scientists are not sure what the sharks are doing while at the Café but because animals undertake extensive migrations for a number of reasons including escape, dispersal, foraging and reproduction, they cited this as a potential mating area. When the females arrive at the Café only briefly, the males were already patrolling the area in an increased rate of vertical movement.

Now, a new analysis of behavioural data collected from tagged great white sharks suggests that some sharks may be visiting the Café to participate in a lek-like mating system.

Leks are assembly areas where animals congregate to carry out complex courtship behaviours. Typically, males will gather together in an area to engage in endurance rivalry and females will visit the lek with the purpose of finding a mate. Leks are used for reproduction by many migratory species including birds, mammals, reptiles, insects and fish. Leks have not been observed in great white sharks before. In general, the mating system of white sharks remains somewhat of a mystery because these species are very difficult to observe in the vast expanse of the open ocean.

While at the Café, great white sharks displayed two different types of behavioural patterns. During one type of behaviour white sharks were observed diving to depths of up to 500 meters during the day and returning to shallower depths of roughly 250 meters during the night. Many marine prey species rise to the surface of the ocean at night to feed on algae and then retreat to darker depths during the day to avoid being seen and eaten by predators. This type of behaviour was thus associated with foraging.

The scientists also observed that white sharks engaged in the second type of behaviour while at the Café. White sharks were observed making repeated dives to depths of up to 200 meters. The scientific hypothesis was that this type of behaviour could be due to the formation of a lek-like mating system whereby the male sharks might be diving to either search for female pheromones in the water or to challenge each other in an endurance competition.

Bottom line:

A new analysis of behavioural data collected from tagged great white sharks suggests that some sharks may be visiting an open area of the Pacific Ocean known as the White Shark Café to participate in a lek-like mating system. The research was published on October 29, 2012, in the journal PLoS One.

Sources:

• Earth Sky
• Monterey Bay Aquarium
• University of Western Australia
• Plos One