Sharks are jaw-some
They’re at the top of the food chain, they can’t get cancer, and they’re out to eat us – or maybe not. UQ alumnus and adjunct fellow marine biologist Dr Blake Chapman takes the bite out of 10 shark myths.
1. Sharks ‘attack’ people all the time
There were only 15 confirmed cases of unprovoked shark bites in Australia in 2017. Of these, one was fatal and nine resulted in injuries. In five cases, the person involved was uninjured. Worldwide, there were 88 confirmed unprovoked bites recorded in 2017, and five fatalities.
2. Sharks are ‘man-eaters’
Although very infrequent, shark bite fatalities do occur. Yet, it is very rare that a shark will actually consume a human. In fact, even extremely serious bites that result in great amounts of damage generally are not characterised by large losses of flesh.
3. Sharks do not get cancer
Sharks can get cancer, but sharks and their cartilaginous fish relatives have incredible immune systems. Interestingly, the myth that sharks do not get cancer did spark interest in elasmobranch immunology (investigation into the immune system of sharks and their relatives).
Shark-derived compounds exhibit broad spectrum antibiotic/antimicrobial properties and are being investigated after showing promising preliminary results for treating Parkinson’s disease and the currently untreatable condition of idiopathic pulmonary fibrosis (a type of chronic lung disease).
4. All shark bites are fatal
Over the past few years, the percentage of unprovoked shark bites that have ended in fatality has dropped to just less than six per cent.
5. All shark encounters are negative
Sharks occupy aquatic environments, so it should be no surprise for people who commonly also use these environments that they may occasionally encounter sharks. However, one study found that less than five per cent of respondents who had encountered sharks in the wild (in various parts of the world) described their encounters as negative.
6. Shark nets prevent sharks from getting to the beach
The beach mesh nets used in traditional shark control programs in no way form a barrier. In fact, around 40 per cent of sharks are caught on the beach side of the net, having come in to the beach, only to get caught on their way back out to sea – so it is not much more than chance as to whether a shark will be on the ‘right’ side or the ‘wrong’ side of these nets.
7. Sharks are apex predators
Very few species of sharks are true apex predators; most have natural predators (often other sharks). We are realising that even adult white sharks can be killed by orca whales, so could not be classified as true apex predators. Most sharks are more accurately termed ‘mesopredators’, meaning they occupy middle tropic levels and predate on other animals, but also have natural predators in their environment.
8. Sharks target humans
Sharks have been in existence for an exceptionally long time (about 400-450 million years), so humans cannot be considered to be a prey item that their successful evolutionary history has trained them to rely on.
Sharks have the biological and physiological capacity to locate, capture and kill large, highly mobile, heavily defended and intelligent animals in their aquatic environments; environments where humans are awkward and inefficient. Given the amount of time humans spend in the water, if sharks really were targeting us, we would know about it.
9. Sharks are stupid
Although sharks have relatively small brains, they have a demonstrated capacity for learning, with a rapidity in line with that of other vertebrates, and a memory span of at least several months.
Tiger sharks, for example, rely on orientation and navigation for their movements; both of which involve neural processing of sensory inputs for directional and distance determination. These abilities are dependent on the formation, storage and retrieval of spatial memories.
Tiger shark movement patterns suggest that they may be using cognitive maps to navigate among distant foraging areas (with ranges of hundreds of thousands of kilometres) based on experiential exploration and learning.
10. Sharks are large, streamlined and have big teeth.
While this is the stereotypical image of sharks, there is immense diversity in shark size, body shape, and just about every other feature of these animals. There are about 509 species of sharks currently described, and they range from maximum total body lengths of around 20 cm to more than 12 m. Sharks can be flat, round, or torpedo-shaped. Some have exceptionally long tails, while others have long fins. All sharks have teeth, but three of the largest shark species are actually filter feeders, with only tiny, rudimentary teeth.
Want to learn more? Dr Chapman’s book Shark Attacks: Myths, Misunderstandings and Human Fear (CSIRO Publishing) is available now. It covers topics including shark biology and basics; deconstructing shark attacks; the role of media; human psychology; lessening the risks of shark attacks; first aid and trauma medicine; human-wildlife conflict; mitigation measures; and legislation. It includes first-hand accounts from survivors.
Media: Dr Blake Chapman email@example.com, +61 (0)403 552 016.
Images 1-6 and 8-9 by Denice Askebrink.
Image seven by Blake Chapman.
source: The University of Queensland