Does this drone image show a newborn white shark? Shark experts aren’t sure

Does this drone image show a newborn white shark? Shark experts aren’t sure



In late January, the internet went all “Baby shark, doo doo doo.”

Video of a purported newborn white shark, taken by a drone off the coast of California, went viral, garnering over a million views and a spate of somewhat breathless news coverage. The shark measured an estimated 1.5 meters long and appeared to be shedding a whitish film, possibly from recent birth, Carlos Gauna and Phillip Sternes described January 29 in Environmental Biology of Fishes.

If confirmed, it would be the first sighting of such a young white shark (Carcharodon carcharias) possibly just hours after birth. Plus, it could provide clues to where these enigmatic and endangered sharks’ breeding grounds are located.

Gauna, an independent wildlife videographer, spotted the unusual-looking young white shark in July along the coast near Santa Barbara with Sternes, a marine biologist at the University of California, Riverside. While adult white sharks have a grayish upper side and whitish underbelly, this shark appeared to be pure white. Besides its estimated size, other clues to its age became apparent upon reviewing the video, Gauna says: It appeared to be shedding some mucus layer and its fins appeared underdeveloped.

But while tantalizing, it’s too early to go goochie goo over the evidence, shark experts say. “It’s an interesting observation,” says Chris Lowe, an ichthyologist at California State University, Long Beach. But “I do think it’s a little overblown.” For starters, there’s only a drone shot as potential proof. Testable samples or other similar observations would be needed to confirm if the young shark was, in fact, a newborn.

The researchers themselves are careful to couch their finding with words like “possible” and to provide an alternative explanation for the milky film: It could be a skin condition. And they agree more sightings are needed.

Whether or not the images capture a newborn, the sighting has thrown a new spotlight on these cryptic creatures (SN: 6/30/14). Here’s what we know about white sharks, and what this new evidence can — and can’t — tell us.

Where do young white sharks live?

The aerial video was shot 400 meters off the coast of California. The spot is near one of four coastal sites along southern California where young white sharks are already known to congregate, thanks to fishing records, some going back decades, and increasingly more high-tech surveillance.

“Back in the day, I remember filling up helium balloons with cameras underneath to try to observe what was happening to these sharks,” says Michelle Jewell, a marine biologist at the Michigan State University Museum in East Lansing. Now drones, tagging and satellite tracking are often the tools of choice.

Lowe and his team use drones to spot white sharks. Then the team drives up alongside them in boats to attach tracking tags. Satellite data have shown that young and juvenile sharks frequently visit the four coastal sites, sometimes migrating between them, and stay there for days to months. Juveniles tagged by Lowe’s team have turned up at a fifth site in Baja, Mexico, the data show. “In a year, they have migrated down to Mexico, and back to California,” Lowe says.

Unlike many animals, mother great whites show no parental care (SN: 02/09/2023). “They drop and run, and the [pups] are on their own,” Lowe says. These coastal sites are nurseries, experts say, a safe haven that provides the young sharks protection from larger predators and also easy access to food sources such as fishes and squids.

Where are white sharks born?

That’s still a mystery.

 “Personally, I don’t think that those young ones have to travel very far,” Gauna says. “They have to be born nearby to get to these nurseries.” Pups born farther offshore would have to make a perilous journey through deep, predator-infested water to reach the safer coastal waters, he and Sternes say.

Other experts disagree, saying all the evidence to date doesn’t hold for coastal births. If a female gave birth recently and nearby, some experts say it would be unusual to see just one pup. That’s because white sharks, which have two uteruses running the length of their body, give birth to 10 pups on average at a time, each about 1.5 meters long. That’s 15 meters of white shark pups tucked inside of gravid females.

“California is the most heavily flown-over coastline in the world,” Lowe says. “Between helicopters and fixed-wing planes, if 18-foot big females were coming in and dropping pups along our beaches, somebody would see it.”

Satellite tracking data (SN: 01/04/2019) have also shown that “around every three years, large female white sharks go far from their regular home range, stay there for a while and leave,” Jewell says. That suggests that the reproductive cycle for female great white is three years. But the tracking data alone do not have enough information to say what white sharks do in these far-flung remote places.

Researchers filmed a young great white shark off the California coast near Santa Barbara, that appeared to be sloughing off its skin layer. The sighting might give clues to where white sharks are born.

What does a newborn white shark look like?

That’s a mystery too — because no one has witnessed a white shark giving birth.

But there is a way to visually estimate a young shark’s approximate age: Look at the color and texture of the yolk scar present between its pectoral fins. “It is like a belly button, where the baby shark used to have its yolk sac,” Lowe says. The yolk sac, which nourishes the embryo, gets used up inside the mother’s uterus, leaving a mark where it was once attached to the pup. The scar appears red and raw-looking in the smallest white sharks Lowe’s team has caught. As the white shark grows, the scar turns white and becomes raised, disappearing by about the time the shark is a year and a half old.

Gauna and Sternes couldn’t spot the underbelly yolk scar from a drone shot. But they say there is another visual clue to the shark’s age: Both the dorsal fin and pectoral fins of this shark seemed underdeveloped and rounded.

“Why would the fins be rounded?” Gauna asks. “Well, to exit the [womb of the] mother.” That rounded shape has been documented in embryonic sharks found inside pregnant females that have died.  By the time the sharks are a year old, the fins take on a sharper, more defined shape, Sternes says.

But with a drone shot alone, it is hard to gauge the depth of the shark’s location, making it difficult to estimate its true shape and size because water can distort an image, Lowe says.

Another clue to the shark’s age is the white material that seemed to be sloughing off its body in the video, Gauna and Sternes say. It could be a film of substances from the womb that coated the pup during birth and still clung to it. An autopsy of a pregnant shark in 2016 revealed that her uteri contained a lot of “yellowish viscous uterine fluid.” While it’s unknown how long the sharks produce this “uterine milk,” that’s what could be covering the young shark, the researchers suggest.

An unknown skin condition is another possible explanation, the team and other experts say. When sharks visit coastal sites, “they are in areas that have a lot of pollution and human runoff,” Jewell says, which could cause a skin infection (SN: 08/01/2012).

While experts agree that the team have spotted something unusual, they say it is too early to jump to conclusions on whether it is a newborn.

“We need to add a layer of science and go and repeat and try [to] see the same thing over again and collect samples to whatever it is that’s coming off of that shark,” Jewell says. “What that something is, will then help us answer the rest of it.”


Source link

Leave a Reply

Your email address will not be published. Required fields are marked *