Written by Jason Bittel
Although they do not have limbs, dolphins' predatory abilities should not be underestimated, and their skills such as mud ring predation and sponge predation are eye-catching, and they are the astute foragers of the underwater world.
Bottlenose dolphins swim in the Ponta do oro Marine Reserve in Mozambique. Bottlenose dolphins are one of the dolphin species that have been studied in depth. Photographed by Thomas P. Peschak, nat geo image collection
Dolphins are very intelligent species, there's no doubt about that. Even so, marine biologists marvel at their survival intelligence, and these animals exhibit new fascinating behaviors every year.
So how exactly do the 36 known species of dolphins, from the 50-kilogram Maui dolphin to the car-sized killer whale, catch food without limbs?
The common bottlenose dolphin is one of the most studied species, and it has evolved an impressive set of hunting strategies, such as mud ring predation. The predators wag their tails violently and then make a circular motion, trapping a swarm of fish in a mud whirlwind. To the fish, such a stream is like an impenetrable wall that will make them panic and try to jump over the barrier from the surface of the water. Unfortunately, hungry dolphins are waiting for them with their mouths wide open.
Previously, mud ring predation was thought to be unique to Florida's few bottlenose dolphins. But a recent study published in the journal Marine Mammal Science notes that mud ring predation is more prevalent than previously thought, as confirmed in bottlenose dolphins in Belize and Mexico, said Eric Ramos, a marine biologist at City University of New York.
In general, dolphins that rely on mud rings to prey on may have brought this behavior from Florida to the Caribbean, or vice versa, but Ramos thinks this explanation is too far-fetched. He thinks different populations of dolphins living in similar habitats may have independently created the same strategy.
Ramos said, "Anyway, it's really cool." This is just one of the many witty ways dolphins learn to survive.
Stranded Predation: The Most Dangerous Game
For marine mammals, being too close to the coast is very dangerous and may be at risk of stranding and death. However, some species of dolphins are willing to risk blocking the fish on the beach, swallowing them, and then turning their heads back into the sea.
"It's too dangerous," said Janet Mann, a behavioral ecologist at Georgetown University in Washington, D.C., who studies the behavior of eastern bottlenose dolphins in Shark Bay, Australia.
In fact, the most famous "beach catcher" Jamaica (a female dolphin) had sunburn marks a few years ago, probably due to the prolonged exposure to the sun after being trapped on the shore.
Stranded predation is a rare strategy that is only available in a few places, such as South Carolina and Shark Bay. "It's a very interesting behavior because only a few animals do that," Mann said.
Flutter: Play with prey
When a dolphin flaps its tail on the surface of the water, you might think it's just playing, but it's actually an extremely serious hunting act.
Dolphins in different habitats have different hunting moves, and some may stun the fish with a nice tail flick, or even throw them into the air before killing. This is called "kicking the fish" or "pounding the fish".
Some bottlenose dolphins in Australia will shoot octopuses off the water before swallowing them, which can relieve the suction of octopus brachiopods.
Other times, the dolphins' flapping may have a different purpose. In Shark Bay, Australia, some dolphins forage for food in the seagrass on the ocean floor with their noses will slam into the water, perhaps to scare out the fish hiding in it. Scientists nicknamed this behavior "kerplunking."
Cooperative foraging: one pot end
Many animals will work together to deal with their prey, just as dolphins do when they hunt in mud rings. But few animals cooperate with humans in hunting.
In Laguna, bottlenose dolphins herd the fish to shore. The fishermen were standing there, the water had reached their chests, and they were waiting for the right moment to cast their nets as soon as the dolphins approached and sweep them away.
"For fishermen, when they follow the dolphins' instructions, they harvest more, sometimes even bigger mullet," mauricio cantor said. "The waters near the shore can be very turbid, and you can't see where the fish are, which highlights the importance of dolphins."
Of course, dolphins do not have unseen situations. They can use the sonar in the body, or echolocation capability, to "see" them. Dolphins also benefit, Cantor said, because fishermen and nets act as a barrier to catch schools of fish that they drive away. It's a win-win model of cooperation, as Recorded in Brazil about 120 years ago.
Another dolphin species also uses cooperative foraging, the Yi River dolphins in Myanmar.
Sponges and shelling: predatory tools
Since the 1980s, researchers have been tracking dozens of dolphins in Shark Bay who practice "sponge predation," a classic example of animal use of tools.
When dolphins search for fish on the rocky seabed, it tears a sponge from the seabed and pushes the soft animal onto its nose as protection. Sponges can also help dolphins catch small fish that can hide from their natural sonar.
According to Mann, using sponges is more than just a hobby, which, according to her research, can make dolphins culturally different from their neighbors.
"Dolphins that use sponges are really more independent and less sociable," she says. When they socialize, they tend to form small groups with dolphins that also like to use sponges. Most interestingly, sponges seem to have been passed from mother to daughter. "A female dolphin discovered in 1984 still uses sponges today," she says. "She's 37 years old."
More common is a behavior known as "shelling," in which dolphins drive fish into an empty conch shell.
"The dolphin sticks its mouth into the opening of the conch shell, brings it to the surface of the water, and then starts rocking so that the fish basically falls into its open mouth," said Sonja Wild, a behavioral ecologist at the University of Konstanz in Germany, who led a study on the shelling behavior of dolphins in Shark Bay in 2020.
Curiously, the act of shelling is transverse, while the use of sponges can only be learned vertically. In other words, dolphins can learn the technique of shelling from their friends, but sponge predation can only be passed down within the family.
Ramos of the City University of New York says that with the popularity of satellite imagery, drones and smartphone cameras, scientists are likely to make new discoveries on the already long list of dolphin foraging behaviors.
"Technology gives us access to things we've never seen before."
(Translator: Strange Flowers Blossom)