Sanctuary Data Helps Reveal Why Tiger Sharks Converge Near Maui's Humpback Whale Nurseries

February 19, 2026

Each winter, Hawaiian Islands Humpback Whale National Marine Sanctuary protects shallow coastal waters where humpback whales (koholā) breed, give birth, and nurse calves. A new University of Hawaiʻi-led study published in Scientific Reports, co-authored by sanctuary Research Ecologist Dr. Marc Lammers, suggests those same seasonal whale nurseries may also help shape when and where tiger sharks appear around Maui.

The research analyzed long-term acoustic telemetry from the Hawaiian Archipelago to better understand tiger shark movements and a behavior rarely documented for this typically solitary predator: seasonal aggregation. The team found that mature tiger sharks tagged around Oʻahu migrated seasonally to Maui, with timing aligned to Hawaiʻi's mid-winter mating season, while sharks tagged around Maui showed year-round residency. The clearest seasonal pattern occurred at Olowalu, Maui, where males and females overlapped in space and time and some sharks displayed physical signs consistent with recent mating activity—evidence that Olowalu may function as a diffuse, seasonal mating area.

The sanctuary's contribution strengthened a key ecological question in the study: whether whale-related factors might also influence shark presence. Dr. Lammers and the sanctuary provided humpback whale survey and acoustic datasets that helped researchers compare shark detections with indicators of whale presence and calf abundance near Olowalu. The analysis showed tiger shark detections were positively related to humpback whale acoustic activity and moderately associated with whale calf counts—patterns that suggest foraging opportunities could help shape the timing of shark aggregations, even as the paper's primary focus remains the mating-aggregation hypothesis.

Importantly, the most likely "attraction" is not adult whales as prey. Tiger sharks are opportunistic scavengers, and a predictable pulse of nutrient-rich resources—such as placentas produced during humpback births, or material from sick or dying whales—could offer an energetic-free meal during the same season sharks are gathering to mate. Some predation on compromised calves may occur, but scavenging is thought to be the more common pathway.

For the sanctuary, the study underscores the broader ecosystem value of humpback whales: their seasonal return can influence food-web dynamics across Maui and beyond, linking protected whale habitat with the movement ecology of an apex predator. It also highlights the power of long-term sanctuary monitoring to reveal hidden connections that inform conservation and management in Hawaiʻi's living seascape.

This work was funded by the Hawaiʻi Department of Land and Natural Resources and the Pacific Islands Ocean Observing System.

Rachel Plunkett is the content manager and senior writer/editor for NOAA's Office of National Marine Sanctuaries