It is normal for birds to swoop down and catch fish from water. But, since 1940s, stories about a meter-long-demonic-African-fish leaping out of water to catch birds in mid-air have been told. They were only stories; no one had seen the actual occurrence…Until now.
Recently, a video of it happening was captured by a team of researchers from North-West University in Potchefstroom, South Africa, and was posted on YouTube. As expected, the video went viral. Who wouldn’t love watching a fish-eating a bird! I put it on repeat and must have watched it 10 times already.
In the video you see a Tiger fish (Hydrocynus vittatus – literally means a ‘spotted water dog’) that lives in African fresh waters. It is one of the largest predators there and lives with a larger cousin, the Giant Tiger fish (Hydrocynus goliath). The Tiger fish can measure as much as 1 meter in length. On the other hand, giant tiger fish (not seen here) can reach up to 1.5 meters in length.
Taking shots around the South African lake in the Mapungubwe National Park, they were not really expecting to record a video in which a fish would fly out of the water and catch a swallow. Rather they were there to study migration and habitat at the lake. The team was surprised to see this. The director said:
“The whole action of jumping and catching the swallow in flight happens so incredibly quickly that after we first saw it, it took all of us a while to really fully comprehend what we had just seen.”
Given that a fish in water, or even human beings for that matter, cannot see beyond a specific window (The Underwater Optical Man-hole), this fish does an amazing job of tracking and striking a bird in mid-flight with so much precision. Cheers for that Mr. Tiger Fish.
Agreed the video isn’t clear, but it the first of its kind. Soon, I hope, we’ll see HD, NatGeo quality videos. Watch it on video here: [Video]
Scientific name: Alticus arnoldorum
After having seen animals that live on for centuries, fish that have legs and several others, another fascinating animal joins the list at AweSci today. The Pacific Leaping Blenny – A fish that, unlike every other extant specie of fish, lives on land.
The Pacific Leaping Blenny is a 2-4 inches long fish that is found on reefs in Samoa, Marianas, Society, and Cook Islands, in the western and southern Pacific Ocean. For all its life, this fish stays on land. It breathes through its gills and partly through its skin.
During the few hours when the tide is at a normal level, such that the waves are just strong enough to reach them and not enough to pull them back into water, these fish take care of their business on land. They need the water to hit them because it keeps their skin wet. Which in turn, lets them breathe through their gills and skin. As long as their skin is moist, they can live out of water indefinitely. So much that they have been officially classified as a terrestrial specie. They would suffocate if their skin dries off completely.
Their fascinating camouflage
It is fascinating to see an existing example of how ancient sea dwelling creatures must have first evolved. At these times when we have great predators waiting on land to immediately end this transitional specie, this fish does a great job of hiding itself from them. And given their poor speed on land, that is how they survive on these rocky shores. They have developed a specialized kind of camouflage that makes it difficult for a predator to find and kill them. As you can see in the picture above, they have a skin color that matches very well with the surrounding reefs/rocks.
How do they move on land?
Since they don’t have legs, that is exactly the question that hit my mind when I first read about these creatures. Turns out, for movement on land, they have developed a very peculiar kind of a movement style. They twist their tails, load up the tension and then release to leap. This sequence happens too quickly to notice easily through naked eyes. So, picked off directly from the Wikipedia page, here we have a slow motion video of this fish leaping off.
Agreed, sometimes, when you find yourself being interrogated in a room covered with one-way mirrors, you can’t see the people who are observing you; Instead, you see yourself in the mirrors. Otherwise, If you can see something, it seems normal to assume that the thing can see you too.
A trout’s window to the outside world is something similar to what a person in the interrogation room experiences. However, unlike the person, a fish can actually see things that are out of the water, but the view is very limited.
The Snell’s Window
When a fish looks up from water, it sees only a circular window of light, from under the water surface. Everything that lies outside of this circle is darker. This darker area of vision is replaced by the reflection of the sea/lake bed (where there is no source of light to illuminate it). This effect isn’t due to any limitations of a fish’s eye. In fact, even human divers see only a circle of light when they are under water. This circle is called the Snell’s Window or the optical man-hole.
Irrespective of the fish’s visual acuity, some physical properties of water and air get together and have a great effects on what a fish can see. It sees a circle with diameter calculated by the Snell’s equation.
In short, the window is about 2.3 times as wide as the fish’s depth. So, a fish can see more if it goes deeper. At a depth of 1 meter, it can clearly see things on a circle that is 2.3 m wide on the surface of water.
So, even if you can see a fish in water, it will be foolish to assume that the fish can see you too. Some times it can’t. It looks something like this from under water:
In Wikipedia’s words:
Snell’s window is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees.
Why does it happen?
It happens due to a simple optical phenomenon called the total internal reflection.
The physics behind this phenomenon can be read here. [Read here]