How did sharks survive the extinction disaster?

Having existed on Earth for more than 400 million years, sharks have learned to deal with natural disasters.

Not only survived natural disasters, sharks also survived the Big Five, a series of five mass extinction events that wiped out animal and plant species over millions of years.

Feel the disaster

The Big Five includes the Ordovician-Silurian extinction (444 million years ago), the Late Devonian extinction (383 - 359 million years ago), the Permian-Triassic extinction (252 million years ago), the Jurassic-Triassic (201 million years ago) and Cretaceous - Paleogene extinction (66 million years ago).

 Sharks move to deep water if they feel unsafe.

Among them, the most terrible disaster for sharks was probably the late Permian-Triassic extinction that wiped out 90% of marine life and 70% of land wildlife. Also, our planet takes 10 million years to recover. But the shark still survived this 'massacre'.

While studying sites that were once the ocean floor during the Cretaceous period, paleontologists discovered fossilized teeth of Cladodontomorph sharks.

Up to this point, scientists still believe that this shark was a victim of the Permian-Triassic extinction event. But they still survive by leaving the natural shallow water to hide in the deep seabed environment.

Sharks today still possess this innate instinct. Researchers at the Center for Shark Research (CRS) recorded the process of 13 young blackhead sharks leaving the familiar waters of Terra Ceia Bay, Florida, USA, and disappearing before the storm. Tropical Gabrielle appeared in 2001.

Natural disasters profoundly affect the seas in which they make landfall. Storms cause desalination or mineral removal in aquatic environments; also cause a decrease in oxygen concentration.

Storms stir up the seafloor, destroy coral reefs, increase pollution from inshore runoff, and create pollution by dumping debris from land into the sea. Storms can also hurt sharks due to high winds and high currents.

Evacuating near-shore areas can make the difference between life and death, according to a Florida International University (FIU) study of calf sharks during Hurricane Irma. They believe that three sharks were killed because they stayed in shallow water for too long. Maybe they're scared if they have to swim out into the open water.

Research by the University of Massachusetts Amherst also shows that tiger sharks left the area affected by Hurricane Maria two hours before the disaster struck. The FIU study also recorded three bull sharks leaving a week before the storm.

Similarly, research by the University of Miami's School of Atmospheric and Marine Sciences (UM) shows that sharks, and many other marine life, are very sensitive to atmospheric pressure. This pressure drops when a hurricane-like storm hits.

As such, sharks can sense pressure changes during a disaster and swim to where they feel safer. In most cases, the safer places are usually in the waters deep in the ocean.

Catch the storms

Sharks have 'sensitivity' to barometric pressure.

By exploring the behavior of sharks today, researchers can explain how their ancestors survived. CRS observed the environmental factors of Tropical Storm Gabrielle and found very small differences in precipitation, wind speed, tidal levels and tidal currents.

In fact, before the storm hit, the wind speed did not change much, the salinity of the sea water had not decreased to an alarming level.

Instead, a drop in barometric pressure should be a warning sign. Many sharks have a special sensory organ, which runs all the way through the body, connecting from the tail to the head and jaw, called the 'lateral line'.

This organ contains nerves that help pick up the slightest vibrations and changes in pressure in the water. According to an experiment by the University of Aberdeen, as long as the pressure is reduced by 0.005 bar, the shark immediately reacts 10 seconds later.

Thanks to this special warning system, sharks can detect Earth's magnetic field or tectonic movements. They can sense vibrations in the water or detect some of the sounds made before a volcano erupts.

However, shark species react differently. According to research by the University of Miami, some sharks like tiger sharks like to 'hunt storms'. This species is attracted to places with rapidly changing temperatures, often where the intensity and frequency of storms are high.

They remained in nearshore waters throughout the storm, even spawning during this time. They seem to have adapted to live with extreme weather conditions and thrived afterwards.

Similarly, near the Solomon Islands, where the Kavachi volcano is active, many shark species such as hammerhead sharks, silky sharks live. The water here contains sulfur, carbon dioxide and methane that are dangerous to humans. But sharks have adapted to live in toxic waters and away from humans.

While most sharks gradually returned to shallow water following the Permian-Triassic extinction, some species permanently adapted to conditions in deep water and have remained there to this day.

As such, sharks also quickly adapt to a variety of living conditions and find ways to reproduce.

However, sharks now face a sixth mass extinction event, the Holocene, caused by humans. Dealing with this disaster, sharks will need more than instinctive senses to survive.