Predator!

December 7th, 2024| Topic: RaMbLeS | 0

Australia is known for having a number of shark “incidents” every year. Most victims are what they call “surface recreationists”—those victims atop a body of water through the use of a board or flotation device, engaging in surfing, water skiing, windsurfing, boogie boarding, rafting, or floating on inflatables at the time of attack.

Well, we may be closer to a prevention of such “incidents,” report a group of Australian scientist collaborating with some in South Africa (another country whose waters are known for shark “incidents”): “Counterillumination Reduces Bites by Great White Sharks,” published recently in Current Biology.

In the open ocean, achieving camouflage is complicated by the fact that any object, even if its underside surface is white due to countershading, will appear as a dark silhouette when viewed from below, particularly by predators with poor visual acuity and lack color vision, like the Great White shark. In fact, to overcome this, many marine species employ counterillumination, whereby light is emitted from cells on their undersurface to replace the downwelling light blocked by their body (that makes them appear with a dark silhouette when viewed from below).

Of course, surfboards or kayaks, and even surface swimmers, look like seals to these apex predators looking up.

So these enterprising researchers decided to take inspiration from nature and attempt counterillumination.

We explored the efficiency of different light configurations on the deterrence effect, showing that visual shape and motion cues are critical for prey recognition by Great White sharks. Counterillumination that is brighter than the background is most effective in deterring sharks. Our results reveal the importance of a dark silhouette against a lighter background in predatory behavior in Great White sharks and that altering the silhouette may form the basis of new non-invasive shark deterrent technology to protect human life.”

Yup, LED lights the underside of surfboards and kayaks!

Lead author, Dr Laura Ryan of Macquarie University in Sydney:

Great white shark attacks on humans may be case of mistaken identity. If you flip that dark silhouetted human to a light and bright object, then it doesn’t seem to be something they recognize as prey.”

The new study, conducted in Mossel Bay, South Africa, involved towing decoys behind a boat for dozens of hours. The researchers initially found success by covering the underside of the decoy entirely in lights.

Ryan again:

But if you’re actually going to come up with something to protect people, entirely covering a surfboard is just not practical because it’s a huge amount of lighting, which needs a huge amount of battery power. Besides, surfers are picky about their boards.”

The researchers experimented with more sparse lighting options, finding that horizontal stripes of LED lights had a similar deterrent effect.

All that to say: Light deters predators!

It does!

Yahweh is my light and my deliverance—whom shall I fear?
Yahweh is the stronghold of my life—whom shall I dread?
When evildoers came upon me to devour my flesh,
my adversaries and my enemies against me—
they—they stumbled and they fell.
If an army camp encamp against me, my heart will not fear;
though war rise against me, [even] in this I am trustful.
One thing I have asked from Yahweh—that I shall seek:
for me to dwell in the house of Yahweh all the days of my life,
to behold the beauty of Yahweh, and to contemplate in His temple.
For He will conceal me in His shelter in the day of evil;
He will hide me in the hiding place of His tent;
on a rock He will lift me high.
Psalm 27:1–5

Safe. From predators.

SOURCE: Guardian