Hammerhead Sharks Use Breath-Holding to Manage Heat During Deep Dives
Researchers from the University of Hawaii at Manoa document a surprising adaptation in bronze hammerhead sharks: they appear to hold their breath to keep their bodies cooler while pursuing prey. This behavior emerges as these warm water swimmers dive into much colder depths during hunts.
Hammerhead sharks normally inhabit warmer waters, yet they feed at depths where the surrounding water sits around five degrees Celsius. For successful hunting and rapid movement, maintaining a warm core can be advantageous, creating a balance between heat and performance. One of the study authors, Mark Royer, described the finding as astonishing, noting that the sharks seem to mimic breath-holding in diving mammals as a way to regulate temperature.
The research team uncovered this pattern by outfitting the sharks with instruments that track muscle temperature, dive depth, body orientation, and activity levels simultaneously. The data showed that muscle warmth persisted during deep, cold dives but began to cool as the animals approached the surface.
Computer models suggested that the sharks regulate their gills, which function similarly to radiators in other vertebrates, to help keep muscles warm. In one video, a hammerhead glides along the seafloor at a depth of more than a thousand meters while its gill slits remain tightly closed. In contrast, footage captured near the surface reveals the gill slits opened wide, indicating renewed breathing as the shark transitions back into warmer, oxygen-rich water at the end of each dive.
The scientists observed that holding breath elevates muscle temperature enough to support efficient movement, but it also reduces available oxygen. Consequently, hammerheads typically hold their breath for roughly seventeen minutes, spending about four minutes at great depths, then return to warmer surface waters to resume breathing and replenish oxygen stores.
These insights complement earlier ideas about thermoregulation in large marine predators. Understanding how hammerheads manage heat during vertical migrations adds a piece to the puzzle of how these sharks optimize performance in environments with strong temperature gradients. The findings highlight the intricate relationship between respiration, temperature control, and hunting strategy in this distinctive shark species.
In summary, the bronze hammerhead showcases a refined balance between heat production and heat loss. By modulating breathing and gill activity during deep dives, these sharks maintain effective muscle function while adapting to the cooler depths they occasionally encounter in pursuit of prey.