The great hammerhead shark (Sphyrna mokarran) opts for high risk and high reward when hunting. While many shark species prefer to hunt smaller, more common prey, the great hammerhead deliberately targets large animals—including other sharks like blacktips. New research, published in the journal Oecologia, shows that this strategy offers energetic advantages: by hunting large fish, rays, or other sharks, the hammerhead can meet its energy needs much more efficiently.
Mathematics of survival
Erin Spencer from Florida International University, lead author of the study, explains: If the great hammerhead eats an entire blacktip shark every three weeks during the period when blacktips are abundant, it has enough energy to survive phases of low prey density—up to two months—without starving. Newly deployed biologging technology—including sensors for speed, sonar, and video—allowed researchers to precisely record the sharks’ swimming speeds, metabolism, and prey encounters.
A model shows that an approximately 110 kg hammerhead shark would only need to consume a roughly 25 kg blacktip shark every three weeks to meet its energy requirements. In contrast, it would have to catch one to two reef fish weighing about 1 kg each daily to reach the same energy level.
Decisions under energy constraints
Yannis Papastamatiou, a behavioural ecologist at Florida International University, sums up the dilemma: “Do we hunt large but elusive prey—with high reward? Or do we take every prey that comes our way?” The study provides important insights into why the great hammerhead prefers larger prey such as sharks or rays—more energy-efficient and effective.
Conservation strategy for the endangered hunter
The study is not only scientifically groundbreaking but also a key component in protecting the species. The great hammerhead shark is globally endangered or even critically endangered according to the IUCN. Only by understanding its biological needs and preferred hunting grounds can we develop effective conservation measures. Additionally, the study demonstrates the power of modern biologging and modelling techniques, especially for hard-to-observe marine giants.
Biological background to the hunting strategy
The distinctively shaped head, known as the cephalofoil, gives the great hammerhead shark special advantages: nearly 360-degree vision, particularly precise depth perception, and an expanded electromagnetic sensory field through the ampullae of Lorenzini. This allows it to precisely locate hidden prey such as rays buried in the sand. These senses not only enable targeted hunting of large prey but also increase the efficiency of feeding—a further piece of evidence supporting the optimal foraging model.
