Marine scientists have definitively confirmed the existence of the 'Sharktober' phenomenon, with a comprehensive new study revealing a pronounced spike in tiger shark attacks during the month of October in Hawaiian waters.
Decades of Data Reveal Clear Pattern
Researchers have analysed bite incident data spanning from 1995 to 2024, providing conclusive evidence for a seasonal trend that was previously supported mainly by anecdotal reports. The analysis shows October accounts for as much as one-fifth of all recorded tiger shark bites in the region, establishing a statistically significant pattern.
Biological Drivers, Not Human Behaviour
The study, published in the journal Frontiers in Marine Science, demonstrates that this seasonal increase is driven primarily by tiger shark biology rather than fluctuations in human water activity. "The October spike is real and statistically significant, but the overall risk remains very low," stated lead author Carl G Meyer, a marine biologist from the University of Hawaii at Manoa.
Dr Meyer emphasised: "This pattern appears to be driven by tiger shark biology, not by more people being in the water." The research indicates tiger sharks are more likely to be present in the nearshore waters surrounding Hawaii's main islands during October, directly linked to their reproductive cycle.
Reproductive Cycle Explains Seasonal Presence
Tiger sharks give birth to large litters during September and October, a period when adult females become abundant in coastal habitats. This timeframe also coincides with a partial migration of mature females from the Northwestern Hawaiian Islands to the main Hawaiian Islands.
The physiological demands of reproduction play a crucial role. Giving birth to substantial litters is energetically taxing, leaving postpartum females with heightened motivation to forage actively. This increased foraging activity, combined with their seasonal presence in nearshore waters, elevates the potential for human encounters.
Aligning Observations with Data
Scientists noted that this seasonal trend aligns with peak tiger shark sightings at ecotourism locations. The study authors wrote: "The temporary influx of late-term females into the main Hawaiian Island insular shelf waters during the pupping season could heighten the likelihood of human encounters and bite incidents, particularly if these individuals exhibit heightened foraging activity."
Tiger sharks are responsible for at least two-thirds of all shark attacks recorded during October in the studied region, underscoring their central role in the observed pattern.
Implications for Safety and Future Research
The researchers advocate for further studies to investigate the primary drivers of this phenomenon more thoroughly, aiming to refine risk mitigation strategies. They propose using non-invasive ultrasound techniques to determine the pregnancy status of nearshore sharks, providing a direct test of whether reproductive state is a key driver of seasonal bite patterns.
"These findings provide ecological insight into seasonal shark bite risk and highlight potential biological drivers warranting further investigation," the scientists concluded in their paper.
Promoting Informed Coexistence
The research team hopes their findings will help visitors to Hawaii's shores make informed decisions, supporting awareness and peaceful coexistence. They advise increased caution during October while stressing that the absolute risk remains low.
Dr Meyer explained the practical application: "Understanding when risk is slightly elevated helps people make informed choices, not fearful ones." This approach encourages precaution without promoting unnecessary alarm, balancing safety education with ecological understanding of these marine predators.
