By Stephen Beech
Shark attacks are most likely to happen around when the deadly predators are giving birth, according to new research.
Incidents are so frequent in seas around Hawaii in October that it has been dubbed “Sharktober”.
Now a new study has confirmed a statistically “significant” spike in shark bite incidents in Hawaiian waters every October.
University of Hawaii researchers analyzed 30 years of data from 1995 to 2024.
Their findings, published in the journal Frontiers in Marine Science, showed that around 20% of all recorded bites occurred in that single month, a frequency far exceeding any other time of the year.
The research determined that the “Sharktober” pattern is primarily driven by the seasonal movements and biological needs of tiger sharks, which account for at least 63% of the incidents during that month.
Study leader Professor Carl Meyer said: “The October spike is real and statistically significant, but the overall risk remains very low.
“This pattern appears to be driven by tiger shark biology, not by more people being in the water.”
He says the findings suggest a “strong link” between the October spike and the tiger shark’s reproductive cycle, specifically giving birth – known as pupping season, which occurs during the September–October window.
Meyer explained that the evidence indicates two primary mechanisms acting together.
He said: “First, there is a temporary increase in the abundance of large adult females in nearshore habitats, including a partial migration of mature females from the Northwestern Hawaiian Islands to the Main Hawaiian Islands.
“Second, giving birth to a large litter is energetically taxing, likely leaving postpartum females in a state of poor nutritional condition and increasing their motivation to forage actively to recover energy reserves.
“This conclusion is supported by multiple independent lines of evidence, including the peak in tiger shark sightings at ecotourism sites that aligns precisely with the pupping season.”
Meyer says the study provides science-based information that allows Hawaii residents and visitors to make informed decisions about ocean use during that time of year.
He added: “Understanding when risk is slightly elevated helps people make informed choices, not fearful ones.”
Meyer advised people to be aware that large tiger sharks are more likely to be present in the nearshore waters of the Main Hawaiian Islands during October, and extra caution is advisable, particularly for high-risk, solo activities such as surfing or swimming in coastal areas.
He said future research will focus on directly studying adult female tiger sharks during the pupping season, including tracking their movements and using non-invasive tools to assess their reproductive status and body condition.
