Sharks can become formidable predators, but when turned upside down, many species enter a trance-like state known as tonic immobilization, and are powerless like beetles on their backs.
The immobility of tonics is “close to hypnotizing sharks as much as you can get!” Joel Gayford, a doctoral candidate in marine ecology at James Cook University in Australia, told Live Science in an email. “The animal stops swimming completely, and the only movement it makes is slow, rhythmic breathing.”
But what happens when a shark enters this state? And why do sharks freeze when you get mad?
You might like it
During the immobilization of tonics, sharks experience reduced sensory reactivity, heart rate, blood pressure, and pain relief. This means reduced sensitivity to pain.
For shark species that become immobilized by tonics, such as the Great White Shark (Carcharodon Cacharias), Lemon Shark (Negaprio Brevillostris), and Grainer Shark (also known as Sand Tiger Shark, or Cultureriasurus), this freeze response can induce this freeze response when the shark stimulates electricity, when it becomes cheerful in the amp. Jillian Morris, founder of Sharks4Kids, a Florida-based nonprofit organization, told Live Science in an email.
By placing sharks in this dozing state, scientists can safely conduct research while reducing stress on animals.
“We can make small incisions and insert acoustic tags safely and humanly, without the need for special equipment,” Morris said. “It’s always done very quickly and the sharks get turned over.”
Related: Can turtles really breathe through their asses?
How does tonic immobilities help sharks survive?
However, sharks did not evolve this property to help scientists take samples.
There are several major theories. A 2023 study in the Journal of Environmental Biology of Fish shows that immobilization of tonics may be for self-defense, courtship, or protection from sensory overload. “The consensus among the scientific community is that tonic immobilization is a passive defensive response,” says Miranda Paes, co-author of the study.
In other species, it is useful to die and play. Dice snakes and ants pretend to stop clogging when predators attack, but female dragonflies and ordinary European frogs fake their own death to avoid sex.
However, not everyone is convinced that paralysis is an effective protection for sharks. “This explanation doesn’t work well for sharks,” Gayford said. “Most shark predators are not blocked by immobilized targets.”
In some cases, that is a clear disadvantage. Orca believes it can overwhelm sharks and neutralize them as they devour their nutritious liver.
When the shark enters this state during sex, Morris said, who observed the nurse’s shark mating. “The man flips the woman over and she enters the tonic immobilization before mating.” However, men are also affected. “So the reason why this phenomenon occurs is not fully explained,” she added.
A 2025 study in the Journal Review of Fish Biology and Fisheries suggests that tonic immobilities have no purpose and merely an evolutionary hangover. “We have actually discovered that tonic immobilities have been independently lost several times throughout the evolutionary history of sharks and rays,” says Gayford, co-author of the study.
Many of the species that don’t have this response probably lost it for a reason, Gayford said. Usually, sharks who live in small corals spend a lot of time searching for food in small spaces. “If these species enter tonics in this situation, they can have fatal consequences,” Gayford said.
For now, scientists don’t have enough data to ultimately say what purpose tonic immobilization can serve. “There are a lot of theories, but none of them are fully understood or fully supported,” Morris said.
Shark Quiz: How much do you know about these iconic ocean superstars?
Source link
