This discovery about dolphins is not entirely shocking

Such signals can help the dolphins find prey hiding on the seabed. Bottlenose dolphins engage in so-called crater feeding, says Denise Herzing, a marine mammal expert with the Wild Dolphin Project in Florida, who was not involved in the study. “They dig,” she said. “They stick their beaks into the sand, almost up to the eyeballs, and pull the eels out.” Sand can make it harder for dolphins to detect buried fish via echolocation, she said.

Other researchers urge caution. The study used two dolphins, and “we don’t know if this ability is actually used in the wild,” said Juliana López-Marulanda, a marine biologist at the University of Paris Nanterre.

Dolphins can also use electrosensitivity to navigate. Dr. López-Marulanda and others have observed that dolphins can sense magnetic fields. Because they have bits of magnetic material in their bodies, the electrical sense can allow them to sense changes in the Earth’s magnetic field and use something like a magnetic map.

Dr. Dehnhardt wonders whether electrosensors can explain the mass strandings of healthy whales and dolphins. Researchers have noted on the left between shifts in the magnetic field, such as during solar storms, and mass strandings. “This may explain for the first time on a sensory basis how this actually happens,” he said. Such strandings don’t occur in baleen whales, which — unlike their toothed cousins ​​— use the whiskers they were born with all their lives, he noted.

A better understanding of dolphins’ senses could help protect the animals, Dr. López-Marulanda said. For example, when sharks’ electrosensitivity was discovered, some fishing fleets added electromagnetic devices to nets to keep sharks at bay. Perhaps something similar is possible with dolphins, although they are much less sensitive, she said.

For an animal that has received a lot of research attention, discovering a new sense is exciting.

“Everything about this species has been worked on,” said Dr. Dehnhardt. “And there is still something new we can discover.”