Flipping a shark upside down, also known as tonic immobility, induces a trance-like state in the shark. This is done by gently turning the shark over onto its back, which puts the shark into a natural state of paralysis. The reasons for this reaction and the effects on the shark vary depending on how the technique is applied.
Why Do Sharks Go Into Tonic Immobility When Flipped Upside Down?
There are a few theories as to why sharks exhibit tonic immobility when flipped upside down:
- Natural defense mechanism – By entering a paralyzed state, the shark is less likely to be seen as a threat and attacked further by predators. It’s essentially playing dead.
- Reduced stress response – The immobility may be a way for the shark to cope with the stress of being caught or restrained. It enters an inhibited state to conserve energy.
- Brain chemistry – The change in position may alter blood flow or oxygen to the brain, essentially putting the shark into a trance.
The most widely accepted explanation is that tonic immobility is an inherent defense mechanism, similar to feigning death. By remaining motionless, sharks can wait out danger and then make an escape when the threat recedes.
How Long Does Tonic Immobility Last in Sharks?
The length of tonic immobility varies by shark species and depends on how the state is induced. Some factors that influence duration include:
- Method of induction – Forced inversion lasts longer than gentle handling.
- Temperature – Colder temperatures prolong immobility.
- Repeated induction – Immobility lasts longer with repeated tries.
- Shark size – Larger sharks tend to stay immobilized for longer periods.
On average, tonic immobility lasts from 5-15 minutes in most shark species. However, it can persist for over an hour, particularly in larger species like tiger and great white sharks. The immobility state will also wear off more quickly if the shark is stimulated, such as by moving water.
What Happens to a Shark’s Body When Flipped Upside Down?
Here are some of the physiological effects seen when a shark enters tonic immobility:
- Reduced respiratory rate – The shark’s breathing slows down significantly.
- Decreased muscle and fin movements – The shark remains still with minimal body movements.
- No response to stimuli – The shark will not react to stimuli that would normally cause a response.
- Altered blood flow – Blood flow to the gills may be reduced, slowing oxygen exchange.
- Lowered heart rate – The heart rate decreases by up to 50% of normal levels.
These effects demonstrate that tonic immobility deeply alters the shark’s normal body functions and reflexes. It enters a profoundly inhibited state both physically and mentally.
Is Tonic Immobility Harmful to Sharks?
Brief tonic immobility induced by trained handlers does not appear to cause lasting harm or stress to sharks. However, there are some concerns around harm based on these factors:
- Length of immobility – Long or repeated episodes could potentially cause oxygen debt or even brain damage.
- Rough handling – Forcibly holding sharks still instead of turning them over gently is more likely to cause injury or added stress.
- Predator threat – Immobilized sharks are vulnerable to predator attack, especially in open water.
There are also ethical concerns around deliberately inducing an unnatural state in wildlife. But research indicates short-term tonic immobility does not negatively impact shark health or survival. Proper training helps handlers use this approach safely.
Which Shark Species Exhibit Tonic Immobility?
Most shark species will exhibit varying degrees of tonic immobility when inverted. Some species known to display this reflex include:
- Great white shark
- Tiger shark
- Hammerhead shark
- Blacktip reef shark
- Nurse shark
- Lemon shark
- Bull shark
- Sand tiger shark
- Spiny dogfish
In general, larger shark species seem most strongly affected, staying immobile for longer periods. Smaller shark species may resist inversion or recover more quickly. Tonic immobility appears to be near universal in sharks as an innate survival reflex.
Are Sharks the Only Marine Animals That Exhibit Tonic Immobility?
No, sharks are not the only marine creatures to display tonic immobility. Other ocean animals also appear to have this defense mechanism, such as:
- Rays – Relatives of sharks that also go into paralysis when inverted, like stingrays.
- Tilefish – These bottom dwellers enter a trance when caught and handled.
- Frogfish – Invert these anglerfish cousins and they’ll play dead.
- Octopus – Flipping octopuses upside down induces paralysis for some period.
So while most well-known in sharks, tonic immobility occurs across diverse marine species. It likely evolved independently to help different sea creatures handle capture or restraint by predators.
Do Fish Also Exhibit Tonic Immobility?
Some fish species do display physiological and behavioral responses similar to tonic immobility when flipped upside down or restrained. Fish known to exhibit this include:
- Parrotfish
- Cod
- Flounder
- Yellowfin tuna
- Rainbow trout
However, immobility may not be as deep or lasting in fish compared to sharks. Righting reflexes that allow fish to reposition themselves may counteract full paralysis. More research is still needed on tonic immobility in different fish species.
Can Tonic Immobility Be Induced in Whales and Dolphins?
There is no scientific evidence that cetaceans like whales and dolphins can be put into tonic immobility. Their anatomy as air-breathing mammals does not allow for safe inversion or restraint to induce an immobility response.
While dolphins can exhibit trance-like states, this is voluntary and facilitated by their own relaxed floating posture. Deliberately trying to paralyze whales or dolphins by inversion could cause significant harm and would be unethical.
Are There Any Other Animals That Exhibit Tonic Immobility?
Beyond marine life, tonic immobility has been observed in a diverse array of animal species, including:
- Chickens
- Rabbits
- Rodents
- Lizards
- Frogs and toads
- Insects like cockroaches
- Dogs
- Cats
Most animals have some capacity for an immobility response when handled, though it manifests differently across species. Even humans can experience forms of tonic immobility in response to extreme fear or stress.
How Is Tonic Immobility Used in Shark Research?
Inducing tonic immobility is a common technique in shark research and allows scientists to:
- Measure sharks up close safely – Immobility lets researchers examine size, injuries, parasites, etc.
- Tag sharks – Allows attachment of tracking devices with minimal handling stress.
- Draw blood samples – Provides ability to collect fluids without restraint.
- Transport sharks – Keeps sharks calm when being moved for studies.
Proper training ensures the technique is used only briefly and ethically for research. The data gained contributes greatly to understanding shark biology, behavior and conservation.
Is Tonic Immobility Used to Train Whale Sharks in Captivity?
No, tonic immobility is not used in training captive whale sharks. As filter-feeding elasmobranchs, whale sharks do not display the same tonic immobility reflex seen in predatory sharks. Handling techniques focus more on positive reinforcement training.
Additionally, very few aquariums house whale sharks. Their massive size makes transport and care prohibitively difficult. Public display of whale sharks is extremely rare and does not involve any form of tonic immobility in training.
Can Tonic Immobility Be Used to Stop Shark Attacks?
Intentionally inducing tonic immobility is not a feasible or reliable strategy to stop a shark attack. While an inverted shark may exhibit immobility, attempting this during an attack would be nearly impossible and also extremely dangerous.
Better strategies for deterring sharks include:
- Staying calm and maintaining eye contact
- Backing away slowly if approached
- Grouping together with others
- Hitting shark’s snout or gills if attacked
While tonic immobility can be induced in sharks for research, intentionally immobilizing an attacking shark would be unrealistic and inadvisable.
Can Humans Enter a State Similar to Tonic Immobility?
There are situations in which humans can enter states resembling tonic immobility as an extreme reaction to trauma, stress or fear. These include:
- Rape victims experiencing paralysis during assault
- Soldiers developing immobility in combat
- People remaining still during crimes due to fear
- Feigning death as an involuntary defense mechanism
This human response likely stems from primal survival instincts and involves override of normal physical and psychological control. It highlights the universal nature of tonic immobility across species when faced with threats.
Conclusion
Tonic immobility is a natural state of temporary paralysis seen in sharks and many other animals species when inverted or restrained. While an unusual reaction, it likely evolved across diverse taxa as an adaptive defense mechanism. Inducing short-term immobility in sharks can be safe when done properly and helps provide valuable scientific data. But deliberately paralyzing any animal in distress or attacking would be unethical. Understanding this phenomenon provides insight into both shark biology and primal survival responses.