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• Tiger sharks gather around Hawaii’s French Frigate Shoals in summer to prey on newly fledged seabirds, a new study has revealed.
• The influx of tiger sharks pushes smaller shark species to change where and how they hunt.
• Seasonal seabird movements strongly influence the balance of the entire local shark ecosystem.

When seabirds fledge, northwestern Hawaii shark ecosystems are disrupted

There are several shark species that patrol the waters of the French Frigate Shoals atoll in northwestern Hawaii. In December 2025, scientists reported that the population of tiger sharks surges during the summer in some areas of the atoll. That’s because those sharks are opportunistically preying on newly fledged seabirds, primarily albatross chicks. Moreover, that high seasonal influx of tiger sharks forces smaller sharks in those waters to change the way they use their habitat.

Chloé Blandino, at the Hawaii Institute of Marine Biology Shark Lab, is the lead author of the paper on this study. She said in a statement:

We discovered that tiger sharks gather around small islands in summer to hunt fledgling seabirds, which, in turn, forces other smaller sharks to adjust their habitat use. It’s a clear example of how a seasonal food source can influence habitat use by an entire predator community.

The researchers published their findings in the peer-reviewed journal Ecosphere on December 2, 2025.

Tiger sharks go after young seabirds

The French Frigate Shoals in northwestern Hawaii is a crescent-shaped barrier reef with small sandy islands. These tiny islands provide critical habitat for seabirds, green sea turtles, and Hawaiian monk seals. The seabirds include species like albatrosses, tropicbirds and terns.

During the summer, tiger sharks converge in the atoll waters to prey on fledgling seabirds. These young birds, which hatched just months earlier, are just learning to fly. As a result, they have not yet become adept at avoiding predators.

Tracking shark behavior

The researchers targeted three species known to frequent the atoll waters: tiger sharks (Galeocerdo cuvier), Galapagos sharks (Carcharhinus galapagensis), and gray reef sharks (Carcharhinus amblyrhynchos).

They surgically inserted acoustic transmitters in the sharks, each one emitting a unique coded signal. Their work followed careful animal handling protocols that University of Hawaii researchers developed to minimize harm to the sharks.

In addition, the researchers installed underwater receivers to pick up sounds from each shark’s transmitter. These receivers were placed in habitats occupied by the sharks: near coral reefs, as well as in deep and shallow lagoon areas. As a result, when a shark swam near a receiver, the signal from its transmitter was picked up, recording a timestamped location for the animal. This allowed the scientists to track each shark’s movement.

Extra influx of tiger sharks affects other sharks

For two years, the scientists tracked 128 sharks at the French Frigate Shoals. Their data revealed interesting information about the sharks’ movements.

They found that tiger sharks are more abundant in the shallow lagoon of the atoll in summer, around the time that albatross chicks are fledging. They were taking advantage of easy prey since the chicks were not yet adept fliers.

Moreover, the summer influx of tiger sharks also affected the dynamics of the atoll’s shark community. Grey reef sharks, which are smaller than tiger sharks, moved out of the lagoon areas occupied by tiger sharks. They retreated to waters near the reef to primarily hunt fish. Meanwhile, Galapagos sharks changed the timing of their hunts in some places. They also preyed on monk seal pups, avoiding albatross chicks.

Towards the end of summer, surviving fledgling seabirds, along with their parents, dispersed farther out to sea. With no more easy prey to take down, most tiger sharks moved out of the shallow lagoon, and the other sharks returned to their usual ecological niches.

Seabirds have a big impact on shark population

Carl Meyer, also at the Hawaii Institute of Marine Biology Shark Lab, is a paper co-author. He and his colleagues noted that if the birds lost their habitat to adverse weather, it would have a significant effect on the shark community, the Hawaiian monk seals, and of course, the seabirds themselves.

Meyer commented:

This study highlights the far-reaching impact of seabirds, showing they can shape the movements of top predators like tiger sharks, which then ripple through the entire food web. Understanding these predator-prey links is crucial for managing Hawaii’s marine ecosystems.

Bottom line: When seabirds fledge at the French Frigate Shoals atoll of northwestern Hawaii, tiger sharks move in to prey on the fledgling seabirds, disrupting shark populations in the area.

Source: Seabirds mediate intraguild and competitive interactions in a shark community

Via University of Hawaii Manoa

Read more: Teenage Greenland sharks’ hangout spot revealed in new study

KAILUA-KONA, Hawaii — Throngs of feral cats emerge from the shade of parked trucks and bushes as soon as the familiar Subaru Forester pulls into a dump on Hawaii’s Big Island. They run after the vehicle to a certain meal — a gravy train that might not be around much longer.

A Hawaii County law set to take effect at the start of the new year bans feeding feral animals on county property. It’s an effort to protect native species, such as an endangered goose called the nene, from a super predator introduced to the islands by Europeans in the 18th century.

But the measure doesn’t sit well with many cat lovers, including the driver of the Subaru, Liz Swan, who has been feeding feral felines on the Big Island for 33 years.

“I don’t believe the cats should be exterminated at the expense of the nene,” Swan said. “They’re both living creatures.”

It’s unclear how many feral cats — abandoned pets and their descendants — live on the Big Island. Estimates range well into the tens of thousands, with pockets of dense colonies supported by people. Opponents of the ban say it will hamper their efforts to contain the population by trapping and neutering the animals — and that hungry cats will then have to hunt for food.

A variety of threats

About 200 cats live at the Kealakehe Transfer Station and Recycling Center, not far from the bustling tourist district of Kona. Swan shows up every late afternoon with water and kibble, and says she’s never seen a nene anywhere near the dump. Despite living amid trash, the cats there generally appear robust, most of them missing the tip of an ear, indicating they’ve been spayed or neutered.

The cats threaten the native species directly — by killing them — and indirectly, biologists say. Food left out for the cats can attract native animals, bringing them into closer contact with humans. Cat feces can also spread a parasite that causes toxoplasmosis, a disease that has killed endangered Hawaiian monk seals and native birds.

Last year, a male nene — pronounced “neh-neh” — was struck and killed by a car as it crossed a road in Hilo, on the eastern side of the island, to reach a cat feeding station. The goose’s surviving mate, which also had a gosling die of toxoplasmosis in 2024, has recently taken on another partner and is nesting in a Hilo park, the state Department of Land and Natural Resources announced this month.

The county’s feeding ban will help protect them, the department said.

A Hawaiian biologist’s view

State wildlife biologist Raymond McGuire recently checked for nene nesting sites among the barren black-rock fields near a shopping center at the Waikoloa resort. It’s not their traditional habitat, but he has seen the geese fly in to grab food — risking getting hit by cars — and last year some nested there.

As he approached, a pair of feline eyes peered out of a crack in the lava rock. Cats emerged from their nooks, perhaps mistaking him for someone who might offer food.

McGuire was relieved to see there were no nene nearby — but frustrated with evidence the cats are being fed: empty water bowls and aluminum pans.

He’s a cat owner — “my favorite animal is a cat” — but as a Hawaiian whose love of nature inspired him to pursue conservation work, he believes there is no room for them where native species are struggling to survive.

“There’s so many birds that my kids will never see, that I got to see,” he said, referring to native forest birds. “I think about my ancestors and I do wonder: Are we honoring them well in what we do? Because they did take steps to protect them.”

Feral cats are a problem in many places, but Hawaii’s sensitive ecosystem is full of species that evolved without mammalian predators, making them especially vulnerable, McGuire said.

‘I felt bad for the cats’

Hawaiian culture is closely tied to Hawaii’s animals; aumakua, or ancestral spirit guides, can take animal form, noted Big Island Mayor Kimo Alameda. His family’s aumakua is the shark, he said.

After the county council passed the measure with a veto-proof 6-2 vote, Alameda decided to let it take effect without his signature. Opponents persuaded him it would harm the cats.

“I had a soft spot for that,” he said. “I felt bad for the cats.”

The debate was so contentious that some opponents sent him hate messages, Alameda said.

The mayor said he hopes police consider enforcement a low priority. Violations carry fines of up to $50 for a first offense and up to $500 for subsequent offenses.

Will the ban prompt feeders to work in secret?

The answer is simple to Makaʻala Kaʻaumoana, a cultural practitioner — someone who works to preserve Hawaiian cultural traditions — on the island of Kauai.

Trapping, neutering and releasing cats makes no difference because they can still hunt, she said.

“The cats have to be removed,” she said.

Debbie Cravatta, who feeds cats in her West Hawaii neighborhood, questioned why.

“It’s a native species — why does that reign over a domestic cat that somebody dumped out pregnant and that had six kittens out in the wild?” Cravatta said. “Why is that life more valuable than this life?”

Opponents also argue the ban might only push feeding efforts underground.

“I’m not going to let them starve,” Swan said.

The Hawaii Rainbow Warriors’ comeback win in the Hawaii Bowl over the California Golden Bears on Wednesday night was marred by a fight near the end of the game.

Golden Bears quarterback Jaron-Keawe Sagapolutele tried to answer Hawaii’s go-ahead score with one second left in the game. He fired a pass to wide receiver Trond Grizzell, who tried to pitch the ball back to a teammate but lost the ball. 

Cal’s Jacob De Jesus picked up the loose ball and tried to lateral the ball to another teammate, but Hawaii defender Virdel Edwards II recovered the bouncing ball to end the game.

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Behind the recovery, California’s QuaRon Adams and Hawaii’s Brandon White began to mix it up. A fracas began as Hawaii players and coaches rushed onto the field to celebrate the win. It took a few minutes for the brouhaha to end.

Hawaii won the game, 35-31, coming back from a 21-point deficit.

Backup quarterback Luke Weaver threw a 22-yard touchdown pass to Nick Cenacle with 10 seconds left to take the lead. He entered the game after Micah Alejado took a hard hit on the previous play.

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Alejado was 32 of 46 for 274 yards and three touchdowns. Hawaii wide receiver Pofele Ashlock had 14 catches for 123 yards for two touchdowns. The Rainbow Warriors scored 22 points in the fourth quarter.

“These boys just keep continuing to fight through adversity and I love them for that. They learn the hard way, but they learn how to do it and that’s what’s important,” Hawaii head coach Timmy Chang said.

Cal’s Sagapolutele was 28-for-39 for 343 passing yards, a touchdown pass to De Jesus and a rushing touchdown. Kendrick Raphael and Anthony League each had rushing touchdowns.

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Hawaii finishes the season 9-4, and Cal dropped to 7-6.

The Associated Press contributed to this report.

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