This Is Why Crabs Hate Stingrays

in 1970 port phillip bay was under the protection of sharks spider crabs could gather there once a year knowing they had nothing to be scared of but the ocean started to change and over 50 years more than 71 percent of sharks have simply disappeared dark times came for crabs take a closer look this is a giant cemetery can a few stingrays really do something like this every year a fantastic event happens in the bay near melbourne tens of thousands of giant spider crabs gather together and march along the bottom not for the sake of a spectacular show of course although it does look impressive usually spider crabs are not so easy to spot they blend in with their surroundings using camouflage but when an entire horde of such crabs is moving towards you becomes hard to miss this the crabs have music festivals or is it an australian underwater comic con the explanation is simple crabs gather in the bay to shed their old skin to grow they need to get rid of old exoskeletons but the new exoskeleton will take several days to harden in addition crabs are so weak after molting that some cannot even stand up and this is where the stingrays come into play they are well aware that crabs will not be able to fight back and without a hard shell they'll be easy prey stingrays literally suck them into their mouths like spaghetti but wait how do stingrays understand who they need to eat and where the prey is i'm not questioning their hunting skills but crabs are well how do i put it below the mouth of the stingray is underneath the body but its eyes are at the top after all stingrays can't keep turning over to check whether the prey is escaped imagine having to do somersaults before you bite into a sandwich not very convenient huh the stingrays found a way out using a special organ they can detect tiny electric currents coming from other animals this organ is called the ampolae of lorenzini and it's something like tubes inside the body of the fish in short those are extra nostrils they help detect the smallest changes in the electric field so no eyes are needed you can just open your mouth and no wonder hiding from a hungry stingray is simply impossible if it wants to eat a crab it will get a crab especially when there are thousands of them around you can eat so much you won't even be able to look at crabs all year long such veracity inevitably affects the population sometimes only a couple of hundred crabs survive molting can you imagine that several thousand of them came to the bay to shed old skin and almost none of them survived but that couldn't have been nature's plan all along it's too merciless even for natural selection crabs should somehow fight back maybe smarter species are shedding their old exoskeletons elsewhere alas crabs have no choice there's nothing they can do when natural mechanisms are activated as strange as it may sound port phillip bay is the safest place to do this when thousands of crabs band together like small fish in huge schools individuals are less likely to get eaten yes there's no guarantee the one to survive will be you and not the guy on the left but at least there's a chance perhaps sometimes crabs try to scare predators away well how else can you explain the huge pyramids they build at the bottom scientists still haven't figured out the meaning of this structure but i think it's a defense mechanism you know when an animal gets on its hind legs to appear bigger and scarier it's the same here i doubt it helps though most likely stingrays see a pile of crabs just like we see a pile of cheeseburgers are you scared of cheeseburgers that's what i thought i want an american cheeseburger hogan drive four cheeseburger first the crabs outnumber the stingrays they have claws why not fight back the predator well looks like the crabs are only brave enough to fight cameramen who are you filming come at me okay everything is clear with crabs they just can't do anything about their fate they are unfortunate victims of natural selection but how did the stingrays realize molting season was the perfect time for a sumptuous dinner well although stingrays are fish i'll give you a second to process this so although they are fish they leveled up their intellect this is especially true for manta rays manta rays are the largest stingrays existing today and they can grow up to 23 feet in a diameter wingspan it's hard to measure a creature with such a strange shape manta rays are like whales and the stingray world they even feed on plankton but the most unusual feature about them is their intelligence some researchers claim that manta rays even know how to recognize their reflection only a few species can do this including humans i would not be surprised to find out manta rays are our very distant and very flat relatives well other stingrays have even learned to use tools it might get hard though when you're a stingray you don't have that many limbs so there's nothing to hold the stick with but you can create a stream of water to extract food stuck somewhere under the stone when it comes to hunting techniques stingrays can get very creative for example this stingray decided to have a fish in this tank for lunch pressed it against the glass and tried to suck it into its mouth don't panic the fish was saved the story ended well they ask you how you are you just have to say that you're fine when you're not really fine but you just can't get into it because they would never but perhaps the coolest way to hunt was invented by manta rays yes they feed on plankton it's not so spectacular blah blah blah you just didn't see how manta rays move around they migrate in search of food and it looks like shots from some kind of science fiction movie if so many stingrays were in port phillip there would be no crabs left in australian waters but back to hunting stingrays approach each other creating a funnel with swarms of plankton in the middle all that's left is close in and have a feast on the go when stingrays feed near the surface of the water they use a different tactic simultaneously making wave-like movements and diving deeper one after another row by row and sometimes they jump out of the water perhaps to alert others they've found food or maybe to attract females come on you have to admit it's hard not to admire it and i'm not even a stingray however manta rays are harmless creatures who will not attack a person even if they want to what are they going to do suck them in with the water electric rays are a different story evolution gave them special electrical organs located on both sides of their heads those are a kind of battery that generates 50 to 220 volts enough to knock an adult man down but not enough to kill unless of course the stingray victim has heart issues in addition a single electrical discharge lasts about .03 seconds but rays tend to generate a whole series of them till the victory yet the most common stingray weapon is the venomous barb on its tail not all species have it but it was this barb that killed a famous naturalist steve irwin the scared stingray pierced the chest and stabbed him in the heart if the barb hit anywhere else irwin would have survived because this venom is not fatal to humans but as i said this stingray only attacked the naturalist because it got scared there's simply no other reason for them to attack humans we're not on their menu and they are not as curious as sharks to bite people for research purposes and yet the number of stingray attacks is growing seems like their population is increasing which means that people are more and more likely to accidentally step on a stingray somewhere in shallow waters our planet simply does not have enough sharks no really for millions of years they've suppressed the stingray population in the simplest way possible by hunting them it's difficult to grow in numbers when you can be eaten anytime but times have changed there are a lot of stingrays and this turned out to be a problem and not only for spider crabs but let's be honest the poor fellows gathering in port phillip bay are not only eaten by stingrays this is a real smorgasbord for all local animals seagulls seals dolphins even other spider crabs after molting each of them is too weak which means they urgently need to restore strength to eat why make an effort when you can go for cannibalism well no love for thy neighbor do you know who comes off second best in eating crabs in port phillip after stingrays of course starfish seriously what's next aggressive corals amur starfish aren't supposed to live that far in the south but this species was brought to local waters and they felt like this was a resort especially when there is so much food around that can't fight back scientists are already seriously concerned that together with the stingrays they could eat all the spider crabs wait hold on a sec turns out we have creatures that comes on top of the crab slaying competition humans it is probably very difficult to resist and not start catching crabs when there are tens of thousands of them around there's currently a limit of 30 crabs per human per day but no one seems to follow this rule in fact people not only destroy spider crabs but also cut off the food source of animals who feed on them and most importantly these crabs are actually inedible for humans so what's the point just why why why why after all for a long time the migration of spider crabs was the secret known only to melbourne and avid scuba divers who explored the bay if they had stayed this way perhaps the crabs would not have suffered but the famous tv presenter and naturalist david attenborough released the movie blue planet 2 where he talked about the crab migration he of course could not imagine what this could lead to the news was picked up by social media it spread around the world and the crabs began to disappear to preserve them these spider crabs alliance was formed today there's a petition urging to stop catching spider crabs during migration and generally treat them with care if you want you can sign it now see you later [Music]

Channel: WATOP

Views: 3,636,699

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Id: RW4s2WtwoUY

Length: 10min 0sec (600 seconds)

Published: Sat May 29 2021