Lemon Shark in black and white

Sharks

Sharks can see very well
Sharks can see very well

What are sharks aware of?

Sharks have a very different set of senses than we do, yet the eyesight of the free swimming species is good, so when they look at you, they are seeing you. But you may have the impression that they are using senses other than their eyes most often, and indeed, apart from our shared good eyesight, it is impossible for us to imagine how sharks experience their liquid realm.

Australian researchers found that the embryos could identify electric fields simulating a nearby predator, despite being confined to a tiny egg case.
Australian researchers found that the embryos could identify electric fields simulating a nearby predator, despite being confined to a tiny egg case.

Embryonic sharks play dead to evade predators

Brown-banded bamboo sharks can sense electrical fields even before they've hatched from their egg cases.

Despite being confined to the small space within the egg case, where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response.

Normally, an embryo pulses its gills actively. But when researchers turned on electrodes to produce an electric field near the egg cases, the unhatched sharks froze and stilled their gills for several seconds.

Bull shark.
Bull shark.

Bull sharks have strongest bite of any shark

Research has revealed that bull sharks bite with almost 6,000N, a force that is greater than what is required to kill and eat prey. In a study published in the journal Zoology, Maria Habegger from Tampa’s University of South Florida, along with colleagues in the US and Germany, examined bite forces produced by 13 shark species and their close relatives, ranging from 1m-long ratfish to the great white shark.

Wobbegongs spend most of their time on the sea floor and hunt mostly at night using an unusual sit-and-wait ambush strategy
Wobbegongs spend most of their time on the sea floor and hunt mostly at night using an unusual sit-and-wait ambush strategy

Many sharks are colour blind

The PhD study bt Dr. Susan Theiss showed that the wobbegong visual system contains only a single class of cone photoreceptor. Cone photoreceptors are the retinal cells that are used for vision under bright light conditions, whereas as rod photoreceptors are used in dim light.

These previous studies looked at opsins, which are light-sensitive proteins found in the photoreceptor cells of the retina. Rod opsins are used in low light and produce a black and white image, while cone opsins are used in bright light, and often to see colours.

Unlocking the secrets of the Greenland Shark

One of the dreams of any naturalist is to be the first to find and detail the life of a hidden or unknown animal first hand. Since 2003, scientific divers with the Greenland Shark and Elasmobranch Education and Research Group (GEERG) have begun to unravel the mysterious life of the Greenland shark, which at over seven meters in maximum body length and exceeding a ton in weight, is the second largest carnivorous shark after the great white.

Do's and Don't's of Responsible Shark Diving

Divers with lemon sharks. Photo by Andy Murch
Divers with lemon sharks. Photo by Andy Murch

Maybe the concept of ‘responsible shark diving’ sounds a little oxymoronic, but there are many things that you can do to protect yourself and the sharks during your interaction. First and foremost, I can’t stress enough the need to gain as much knowledge as possible about the animals and their environment. To go into the water without at least a basic idea of how the sharks are likely to react is foolhardy to say the least.