Recent studies from the University of Miami Rosenstiel School of Marine and Atmospheric Science and ongoing research by the University of Delaware and Rutgers University are shedding new light on how large sharks respond to hurricanes and their potential utility in predicting these powerful storms. While some shark species flee from approaching hurricanes, others, like tiger sharks, exhibit unexpected behavior, even increasing in number after a storm passes, likely due to increased scavenging opportunities. This newfound understanding of shark behavior, coupled with the development of "mobile marine monitors" using tagged sharks, offers a promising, albeit complementary, method for gathering crucial oceanographic data to improve hurricane forecasting, especially as climate change is expected to increase storm intensity.
II. Shark Behavior During Hurricanes
Sharks possess unique biological capabilities that allow them to detect and react to approaching storms, though their responses vary significantly by species.
A. Shark Sensory Abilities for Storm Detection
- Barometric Pressure Changes: Sharks can "feel changes in atmospheric pressure through a sensitive inner ear and organ unique to many fish called lateral lines" ("Are sharks scared of hurricanes?", p. 6). The lateral line system is a "tube of sensory cells used to detect pressure changes in the surrounding waters" ("Sharks Can Sense Storms", p. 4). This allows them to anticipate a storm well before its arrival.
- Water Condition Changes: Hurricanes cause "massive waves (as high as 60 feet!) and powerful surges of underwater currents (as deep as 300 feet!), not to mention changes in oxygen levels and salinity (or saltiness) as the ocean’s deep and surface waters mix—all of which can be deadly for marine life" ("Sharks Can Sense Storms", p. 3). Sharks must respond quickly to these changing conditions to survive.
B. Species-Specific Responses
- Fleeing Behavior: Some shark species exhibit a clear avoidance response to hurricanes.
- Nurse, Bull, and Hammerhead Sharks: These species "fled the area before the storm arrived" when Hurricane Irma approached Biscayne Bay, Florida, in 2017 ("Are sharks scared of hurricanes?", p. 6). This "fleeing behavior...wasn't surprising" to researchers ("Are sharks scared of hurricanes?", p. 7). Juvenile blacktip sharks have also been observed moving to deeper waters before tropical storms and hurricanes ("Sharks Can Sense Storms", p. 5).
- "Swarming" or Remaining Behavior: Conversely, some larger, more robust species remain in storm-affected areas, and their numbers may even increase afterward.
- Tiger Sharks: During Hurricane Matthew (a Category 5 storm in 2016), "the Tiger sharks didn't flinch." The study showed that "during the storm, the number of sharks remained steady." Even more surprisingly, "In the days after landfall, the number of Tiger sharks doubled" ("Are sharks scared of hurricanes?", p. 5).
- Scavenging Opportunities: Experts hypothesize that this doubling was due to "the increase of scavenging opportunities from the storm killing marine life" ("Are sharks scared of hurricanes?", p. 5). This is the "opposite of what happened in previous studies involving small sharks" ("Are sharks scared of hurricanes?", p. 5).
- Unanswered Questions: Researchers are still exploring whether "some shark species are attracted to areas recently hit by a hurricane?" and if "they can track the storm with their lateral lines and inner ear?" ("Are sharks scared of hurricanes?", p. 7).
