Great White Sharks Like to Hang Out With Each Other When Feasting on Baby Seals, Scientists Find

Great white sharks are normally thought of as being largely solitary animals. However, research has revealed for the first time that the predators may purposefully form "communities" and consistently spend time with certain groups, according to a study published in the journal Behavioral Ecology and Sociobiology.

While they are mostly solitary, the animals do sometimes congregate in some locations. For example, scientists already knew that large numbers of great whites periodically flock to certain areas, depending on the season, to hunt baby seals in their colonies.

"White sharks are unlikely to 'gather together'—aside for mating—but they can be found at the same location at the same time, for example, around seal colonies," Charlie Huveneers, an author of the study from Flinders University, Australia, told Newsweek. "In the case of white sharks, the aggregations form as a result of different individuals being attracted to a common resource, i.e. food."

Previously, researchers explained the gatherings by saying they are random in nature, that the sharks only came for the food and not because they wanted to interact with other individuals from their species.

For the study, a team of scientists led by Stephan Leu from Macquarie University in New South Wales, Australia, examined white sharks that frequently gather in large numbers at a site in the Neptune Islands—located off Australia's southern coast. This area, near a seal nursery, lays claim to hosting the largest aggregation of great whites in the country.

Over the course of four-and-a-half years, between June 2010 and November 2014, the researchers monitored nearly 300 sharks that visited the site using by taking pictures so that they could identify individuals. They also conducted a network analysis to determine whether or not sharks were gathering in specific groups.

Their observations revealed that many of the sharks were spotted next to others more frequently than would be expected by chance. This led the researchers to conclude, for the first time, that many of the sharks like to hang out in certain groups, and that these relationships can last for several years.

"Rather than just being around randomly, the sharks formed four distinct communities, which showed that some sharks were more likely to use the site simultaneously than expected by chance," Leu said in a statement.

Huveneers said that while white sharks gather at the Neptune Islands site all year round, the same individuals do not remain there throughout the year.

"Different sharks come at different times of the year even though seal abundance typically peak in summer and seal pups are weaned and venture in the water around late autumn, early winter," he said. "For example, some sharks are sighted at the Neptune Islands during summer, while other sharks are mostly sighted in winter."

"Broadly, you'd expect all white sharks to match their presence with prey availability, but for some reason not all white sharks visits to, and use of, the Neptune Islands correspond to periods when seals are most abundant," he said. "Some individuals consistently occur when seal abundance is low and are often sighted on the same day, suggesting that these individuals respond to external drivers in the same way."

In light of the latest findings, the team is still unsure of the reason behind the sharks forming these persistent communities.

"We still don't know why some individuals prefer summer and some individuals prefer winter, or why some sharks like to hang out at the Neptune Islands together, but now we have empirical data to show that some sharks have non-random co-occurrences," Huveneers said.

"We already knew that white sharks temporarily aggregate at seal colonies to feed, so our study hasn't told us that sharks are more or less solitary," he said. "However, our study shows that white sharks can prefer some individuals and selectively spend more time with some sharks than others. The reasons for such preferences is unknown, but might be related to what attracts them to seal colonies."

great white shark
Stock photo: A great white shark. iStock

This is not the first evidence that has emerged recently of white sharks interacting. Earlier this year, researchers captured fascinating footage of two great white sharks interacting with each other in an unusual display in the waters off Cape Cod, Massachusetts.

Greg Skomal from the Massachusetts Division of Marine Fisheries (DMF) previously told Newsweek that this video was the first time anyone from his organization had seen social interaction between white sharks. Researchers have since been analyzing the video to see whether it demonstrates aggressive/defensive behavior, or if it is related to mating in some way.

Researchers from non-profit OCEARCH—which tracks great whites with tags—have suggested that there are two sub-populations of white sharks in the Northwest Atlantic: one that aggregates in the Cape Cod area in the late summer and early fall and another that aggregates in Canada.

"So in the study of the white shark in the northwest Atlantic, we're tracking these big animals all the way from Atlantic Canada to all the way down in the Florida peninsula," Robert Hunter, OCEARCH's chief science adviser, said in a video on the organization's Facebook page.

"Something fascinating that we've noticed is that there are some animals that go to the Cape Cod area in the summertime to feed. And then there are others, that have bypassed cape cod and come up Nova Scotia to feed," he said. "So right now we are looking at the possibility of two distinct groups or subpopulations of white sharks in the northwest Atlantic."

There is even a place in the Pacific Ocean known as the "White Shark Café"— a 160-mile wide stretch of seemingly barren ocean where white sharks that normally live off the North American West Coast travel to every year during the winter. This unusual migration has puzzled scientists for decades.

Great White Sharks Like to Hang Out With Each Other When Feasting on Baby Seals, Scientists Find | Tech & Science