Tiger sharks may disappear from some Hawaiian waters for months, but that does not mean they are gone for good. New research shows that some tiger sharks make seasonal trips between the Hawaiian islands, with mature sharks from Oahu moving toward Maui during the winter. Scientists have now found a likely reason for this pattern: the sharks may be gathering to mate, while also taking advantage of seasonal food.
The discovery gives researchers a better look at where these large predators go and why they return. It also helps explain why shark sightings around Hawaii can vary from one season to the next.
Scientists tracked the sharks for years
Researchers from the University of Hawaii studied tiger shark movements using acoustic tags and underwater listening stations. The team followed sharks around Oahu and Maui over six years, looking for changes in where the animals appeared during different parts of the year.
The results showed a clear pattern among sharks tagged around Oahu. Their numbers around Maui rose during the winter and were highest around February, while sightings became much lower during the summer. Sharks tagged around Maui were different because they stayed in the area throughout the year.
Some sharks travel between islands
The research shows that tiger sharks do not all follow the same travel plan. Of the 21 Oahu tagged sharks later detected around Maui, 14 were later detected back around Oahu at least once.
Some individual sharks made the trip more than once. One shark was recorded making as many as four round trips between Oahu and Maui, showing how far these animals can travel even within the Hawaiian island chain.
Maui may be a mating area
One of the biggest findings came from waters near Olowalu on Maui. Researchers found mature male and female tiger sharks appearing in the same area during January and February, the known mating season for tiger sharks in Hawaii.
The sharks did not form one tight group. Instead, they spread across several miles of ocean and stayed in the area for weeks. Signs of possible mating were also found on some sharks, giving researchers strong clues that Olowalu may be a seasonal mating area.
Food may also bring them back
Mating may not be the only reason tiger sharks return to Maui. The seasonal arrival of the sharks also lines up with Hawaii’s humpback whale season, when mothers and calves move through Maui waters.
Scientists found that shark numbers were linked with the presence of humpback whale calves. This does not prove that the whales cause the sharks to arrive, but it suggests that food may help shape the sharks’ seasonal movements along with their need to reproduce.
Tiger sharks are not all seasonal
The phrase “tiger sharks return” can be misleading if it sounds like every tiger shark leaves Hawaii. Research shows that some sharks stay in Hawaiian waters all year, while others make seasonal trips between islands.
Older studies also found that adult female tiger sharks can move from the Northwestern Hawaiian Islands toward the main Hawaiian Islands during the fall. These movements are linked to the sharks’ reproductive cycle, which includes mating and the birth of young.
What the discovery means
The new findings help explain why tiger shark sightings can change during the year. Scientists now have evidence that at least some mature sharks make regular seasonal movements, rather than simply appearing in new places by chance.
The discovery also gives researchers a better way to study tiger shark behavior and protect both sharks and people. Hawaii’s waters remain home to tiger sharks throughout the year, so a seasonal return does not mean the animals were completely absent before.
Featured Image: Photo by Michael Worden on Unsplash
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