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MIAMI — A new study of bonnethead sharks (Sphyrna tiburo) in Florida dispelled a previous hypothesis about how the distinctive head shapes of males and females develop, offering new insight into one of the species’ most unusual biological traits.
Researchers at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science and their collaborators found that the sharks’ shovel-shaped heads become rounder as both sexes mature — particularly in females. Previous research had suggested that the more pointed snout seen in males developed when they reached sexual maturity.
The study is the first in-depth assessment of bonnethead head shape and diet in Biscayne Bay. Sharks from Tampa Bay were included to determine whether the patterns were consistent across two populations on opposite coasts of Florida.
Bonnetheads are small members of the hammerhead shark family and the only shark known to have clear sex-based differences in head shape. Males typically have a more prominent point along the front of the head, while females have a smoother, more rounded profile. Scientists refer to this difference between the sexes as sexual dimorphism.
