A new study shows that dolphins already equipped with sonar systems have additional capabilities that develop as they mature in the area where their juvenile barbels were once located. Their senses can help them navigate and find hidden food sources.

Dolphins’ sonar ability, known as echolocation, is legendary in the animal world. This ability is so sensitive that mammals, technically whales, can use it to distinguish between a golf ball and a ping-pong ball underwater based on the density of the two objects. But that’s where the creatures’ impressive abilities end.

They also have eyes that allow them to see in two directions at once; skin secreting antibacterial gel to protect against parasites and molluscs; They can gain enough traction to reach speeds of 30 miles per hour; and they turn off half their brains to rest. A 2019 study also found that they have a super immune system that protects against antibiotic-resistant bacteria. Now, new research from the University of Rostock (UR) in Germany adds another impressive skill to the dolphin’s list of abilities: the ability to sense weak electrical fields.

Two RI researchers took a closer look at the tiny pits left behind after young bottlenose dolphins shed the thin whiskers they’re born with. They realized that the pits resembled structures that enable sharks to detect electrical fields, and designed a study to see if they worked the same way for dolphins.

For the first time, two dolphins at the Nuremberg Zoo were taught to rest their chins on a metal rod submerged in the pool. They then taught them to swim when they felt an electric current forming just above their faces. One dolphin could detect signals as small as 5.5 microvolts/cm, while another was even more sensitive and could detect currents as small as 2.4 microvolts/cm. A microvolt is equal to one millionth of a volt.

The dolphins also showed a high degree of responsiveness when the researchers applied pulses rather than keeping the electric current constant. They say this is more like the weak and irregular electric field emitted by the fish that dolphins hunt.

“Sensitivity to weak electric fields helps the dolphin search for fish hidden in the sediment in the last few centimeters before capture,” said study co-author Guido Denhardt. This is slightly different from using the sense of sharks, which can use it to detect the electric fields of fish up to 70 cm (2.3 ft) away.

Researchers also believe that an ability known as electrosensing may help dolphins navigate using the Earth’s magnetic field, which could explain the animals’ accidental beaching due to fluctuations in this field.