2,000-pound Great White Shark Unama'ki May Have Swum Hundreds of Miles Into Open Ocean to Avoid Male Mating Attempts

A great white shark that is being tracked by researchers, dubbed Unama'ki, is currently way out in the open ocean, more than 700 miles of east of Cape Cod, Massachusetts. Scientists think the shark may be pregnant—and that it is possible the journey may be an attempt to avoid further mating attempts by males.

Marine research organization OCEARCH has fitted the female shark, which is more-than-15-foot-long and 2,000 pounds, with a satellite tracking device that "pings" when her dorsal fin breaches the surface of the water.

Pings from just over a week ago indicated that the shark was moving northwards fast, although subsequent pings over the past few days show that the animal has turned back on itself, appearing to hang around in one region of the mid-Atlantic.

At the beginning of April, Unama'ki turned away from the waters off the eastern U.S. coast and started heading deeper into the ocean, in what researchers call a "pelagic journey." The word "pelagic" refers to things related to the open ocean.

The only white sharks that OCEARCH has observed making these big pelagic loops—in which the animals move away from the North American coast into the deep ocean before returning again—are large adult females. And these females do not tend to make these journeys every year.

OCEARCH said these movements suggest that Unama'ki and other large female sharks may be pregnant when they make them. In the case of Unama'ki, this is intriguing because it could lead researchers to a great white shark nursery.

"We have tracked at least one big mature female returning from one of these journeys by heading straight back to the New York Bight, which is a white shark nursery. This is further indirect evidence that they may be gestating while in the open ocean," OCEARCH's founding chairman and expedition leader Chris Fischer told Newsweek.

According to Fischer, there are three possible reasons why these females would make these offshore loops while pregnant.

"One, they could be avoiding further attempts to mate by the males; two, they could be taking advantage of temperature regimes offshore that are favorable for gestation of their young; and three, they might be exploiting food sources offshore also favorable for gestation. These are all hypotheses that we are testing with our research," he said.

OCEARCH has been conducting research since 2007, and the data it has collected in the subsequent years has revealed fascinating details about where white sharks spend their lives—something that was once a mystery.

"We've observed time and time again that white sharks demonstrate very predictable migration loops," Fischer said. "Males especially have very routine migrations and we frequently see them visit pretty much the exact same spots at the same exact time year after year.

"Mature females like Unama'ki are a little bit more irregular because they do make the big offshore swings on some years and skip them on other years, again suggesting that the years they make big pelagic journeys are the years they are gestating. But once we've mapped several years of a female's life, their migration becomes quite predictable."

great white shark
The female great white shark known as Unama’ki that has been tagged with a monitoring device by OCEARCH researchers. OCEARCH/R. Snow

Based on this knowledge, OCEARCH researchers think that Unama'ki may eventually make her way back to the waters off Nova Scotia, Canada, where the team tagged her in September, 2019. The organization thinks that there may be two sub-populations of white sharks in the Northwest Atlantic, one of which gathers near Nova Scotia.

"The two sub-populations are distinguished by which late summer and fall feeding aggregation site they utilize," Fischer said. "One sub-population aggregates during the late summer and fall in Cape Cod and the other population aggregates in Atlantic Canada. We suspect Unama'ki is part of the sub-population that aggregates in Nova Scotia/Atlantic Canada.

"We've observed that white sharks aggregate in either Cape Cod or Atlantic Canada to feed, with only a very small portion of the population utilizing both. These feeding aggregations sites offer a change in diet compared to where they spend the rest of the year off the Southeast Coast. Both Cape Cod and Atlantic Canada offer a chance to feed on prey such as seals, which are not available on the Southeast Coast."

OCEARCH has also observed this pattern of distinct late summer and fall aggregation sites in their work along the Pacific Coast as well.

"During our early work on the West Coast we observed sub-populations of white sharks utilizing distinct late summer and fall feeding aggregation sites," Fischer said. "Just like we are seeing sharks in the Northwest Atlantic utilize either Cape Cod or Atlantic Canada, on the west coast we saw white sharks aggregate either at Guadalupe Island, Mexico or at the Farallon Islands."