It is widely believed that sharks are attracted to blood and have the ability to detect it through their senses, such as sight, taste, or smell. However, is it true that sharks can specifically distinguish between human blood and blood from other sources?

Various movies and shows, like the famous film “Jaws”, have perpetuated the idea that sharks are drawn to human blood. These predatory creatures of the ocean are often portrayed as always ready to devour a human being, as depicted in Hollywood. But is this phenomenon a reality in actual life, or is it merely a fabrication for the sake of entertainment?

Incidence of Shark Attacks on Humans

Although shark attacks receive a lot of media attention, they are actually quite rare. According to a global survey, shark attacks on humans result in approximately 10 deaths each year. Only about 7% of unprovoked shark bites worldwide between 2000 and 2009 were fatal. This means there are roughly 4.6 fatal bites per year.

The occurrence of lethal shark attacks on humans is less frequent than commonly believed. (Photo Credit: Cryptographer/Shutterstock)

Out of the 500 known shark species, it was discovered that three species—the great white shark, the bull shark, and the tiger shark—are responsible for the majority of attacks. These three species account for over 60% of all reported shark bites and 80% of the bites that result in casualties.

Can Sharks Detect Human Blood?

Contrary to what is portrayed in movies, sharks are not specifically attracted to human blood. It is not just blood, but any bodily fluid that may potentially attract sharks. However, they cannot detect a single drop of blood from miles away. Blood, along with other factors like disturbances in the water, can potentially attract sharks.

However, this applies not only to humans. A shark can also be attracted to the blood of a bleeding fish or sea lion, but there is a caveat. The likelihood of sharks being attracted to human blood or any other bodily fluid is much lower.

So, what would entice a shark to the source of blood from such a distance? The smell, right?

Sharks have a keen sense of smell and can detect odors. Taronga Zoo in Australia states, “Sharks may be attracted to one person more than others because that person is bleeding, has urinated in the water, or simply emits a stronger body odor or electromagnetic field.”

To detect odors from a distance, the fluid must be strong enough to resist dilution by the surrounding water. Even a small concentration of odor would be diluted to the point of being undetectable over a kilometer. Therefore, a large amount of blood is needed for a shark to detect it from miles away.

Some sharks have been observed swimming past others to target specific individuals or groups. This suggests that they may be attracted to the activities of these individuals rather than their bodily odors.

To test whether sharks prefer human blood, ex-NASA engineer Mark Rober conducted an experiment. He attached pumping devices filled with cow blood, fish blood, or seawater to three surfboards and released them into the ocean. A drone was used to observe the number of shark visits to each surfboard over an hour.

The results showed that the surfboard with seawater had no shark visits, the one with cow blood had 8 visits, and the one with fish blood had a whopping 134 visits. This experiment conclusively demonstrates that sharks are more attracted to fish blood than human blood.

However, it should be noted that this information is based on anecdotal evidence from academic sources and should not be considered a comprehensive analysis.

What About Menstrual Blood?

So, what happens when a person is menstruating? Does it attract sharks differently?

While sharks can detect menstrual blood, there is no solid evidence that it leads to shark attacks. Additionally, the chances of menstrual blood entering the water are low because the pressure of swimming or diving temporarily stops the flow.

Sharks do not show a preference for attacking males or females. Previous data may have suggested more attacks on males due to their higher involvement in water activities, but recent data shows that women are also attacked.

Can Sound Attract A Shark?

We have seen how smell can attract sharks, but what about sound?

Sound is the primary cue for a shark to move into an area. However, once a sound is detected, a shark relies more on sight than sound.

Sharks are attracted to low-frequency sounds, particularly in the range of 10-50Hz. This is the same frequency emitted by struggling or injured fish. Tests have shown that sharks are most sensitive to frequencies between 40 Hz and 800 Hz. They use their lateral line sense organ and inner ears to locate prey from distances of 250 meters or more.

A Final Word

As mentioned earlier, only a few shark species are known to attack humans. Sharks have been around for millions of years before humans, and their usual prey consists of marine animals like fish or seals. Humans are not a natural part of a shark’s diet, so it is logical to assume that they are not particularly interested in us.

Shark’s Diet: Small Fishes

When swimming or diving in the ocean, the possibility of being attacked and killed by a shark is extremely low, unless there is already excessive bleeding. However, it is important to be cautious of other animals. In the meantime, you can gain more knowledge about the unique characteristics of shark eggs compared to other types of eggs by clicking here!