Striped marlin demonstrate the advantages of group hunting

Have you ever wondered why animals engage in group hunting only to divide the spoils later? Turns out, there’s more to it than just the thrill of the chase.

A research team from the Cluster of Excellence Science of Intelligence (SCIoI) embarked on an aquatic adventure to answer this question.

In collaboration with experts at Humboldt-Universität zu Berlin (HU Berlin) and the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), the team dived into the ocean off the coast of Mexico to observe the striped marlin’s hunting strategies in nature’s wildest theater.

What’s the catch?

Interestingly enough, it all boils down to the speed of the prey. The faster the prey school flees, the higher the capture rate.

Why? Because as the school scurries away at a high pace, individual fish are more likely to break away from the pack. And these lonesome fish are nothing less than easy pickings for the non-attacking marlins.

Advantage of group hunting

On dry land, there is evidence showing that predators have a higher success rate when they chase groups of prey – targeting the slower, weaker animals that fall behind. The question was whether this strategy applies to the open ocean.

“Little is known on this topic for predators that hunt in groups in the open sea, as it is difficult to record the attack and capture rates of several predators together with the positions of predators and prey,” explained Professor Jens Krause, a behavioral ecologist and co-first author of the study.

Need for speed in group hunting

Meet the striped marlin (Kajikia audax), one of the ocean’s most epic hunters. These behemoths, armed with spear-like mouth appendages, are renowned for their cooperative hunting strategy to round up schools of small fish.

Using intricate underwater and aerial photography, the research team took to the seas, observing the marlins’ movements while hunting approximately 30 kilometers off the coast of northern Mexico.

The experts collected data on the attack and capture rates during different states of the prey school’s movements.

The researchers found that chasing schools of prey at high speed resulted in a greater number of isolated targets for the marlins. The likelihood of a fish breaking away from the school was directly associated with the speed of the school.

An increase of just 0.1 meters per second in the school’s speed boosted the probability of isolation by a whopping 18 percent.

Group cohesion among prey

Understanding the dynamics of group cohesion among prey is crucial to comprehending the hunting success of predators like the striped marlin.

In schools of fish, cohesion serves as a defense mechanism, decreasing the likelihood of any individual being singled out. This collective movement disrupts predator-promoting strategies, creating a bewildering spectacle of flashes and turns.

However, as marlins capitalized on disorder within the ranks, it raises intriguing questions about the nexus of cooperation and competition within both predator and prey communities.

The marlin’s ability to exploit breaks in cohesion demonstrates nature’s intricate checks and balances, where equilibrium often dictates survival and success.

Implications for ecosystems

The work led by SCIoI, HU Berlin, and IGB delivers vital implications for understanding marine ecosystems and the role of apex predators like the striped marlin.

By highlighting the importance of water dynamics and prey behavior in shaping predator-prey interactions, this research sheds light on the delicate balance of aquatic food webs.

The findings emphasize the interconnectedness within marine ecosystems and highlight the potential impacts of environmental changes on predator efficacy and prey vulnerability.

As climate change alters ocean temperatures and currents, continued exploration of these dynamics is essential to predict and mitigate future ecological shifts, ensuring the health and resilience of marine biodiversity.

Advantage of rapid group hunting

The marlins’ group hunting strategy doesn’t necessarily mean every marlin has to actively chase the school. Fish that become isolated from the school are quickly snapped up by nearby marlins.

According to Korbinian Pacher, a behavioral biologist and co-first author of the study, the research clearly shows the advantage of rapid group hunting for predatory fish.

“The rapid movement of the swarm of prey makes it easier to isolate and catch individual fish. This significantly increases the hunting success of the group of marlins,” noted Pacher.

Dr Matthew J. Hansen, who led the study, said that another interesting aspect of group hunting at high speed is that in this form of hunting, prey also falls to the animals that are not actively attacking the prey school.

“This effect probably favors group hunting in striped marlins and may be a principle that applies to many large predatory fish in the open sea that join together to hunt schooling fish,” concluded Dr. Hansen.

The study is published in the journal Functional Ecology.

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