Evolutionary Mash-up: Coconut Crab

Let’s play a game. You are stranded on an island. You have circled the perimeter of the island and have climbed to the highest point on the island. In your exploration, you find that there are no people on the island and not a single sign of animal life anywhere. Birds do not travel to the island and you haven’t noticed a fish in the ocean for days. The only living things on the island are palm trees filled with coconuts. You would like to eat the coconuts so you could survive, but the island is completely void of rocks to help you bust them open. The coconuts fall from the trees onto soft sand and never have a chance to break open. Just as you are about to resort to eating your own arm for survival purposes, you come across a magic lamp deep in the center of the island. The magic lamp is gold in color, glinting in the sun, and has the name “Charles Darwin” etched in the metal. You rub the lamp, expecting a large, blue, floating genie to appear. Nothing. You quickly drop the lamp as your hands begin to tingle and mutate right before your eyes. Here’s the game: what do your hands need to transform into in order for you to survive on the deserted island? If you guessed “cheese burgers” you are wrong for that will only bring you brief satisfaction. If you guessed “coconut crab claws” you are correct for that will give you the ability to crack open all the coconuts on the island.

low angle photography of palm trees under clear blue sky
Photo by Mwabonje on Pexels.com

The coconut crab is known as the world’s strongest crustacean. These crabs live in islands near the Indian and Pacific oceans. For a crustacean, they can get pretty big measuring at about 3.5 feet and weighing about 10 pounds. Scientists have measured the grip strength of these armored monsters by using a steel rod complete with force measuring sensors. The largest coconut crabs clocked in a grip strength of 3300 Newtons–That is more than 10 times the average human grip strength and slightly under the strength of a lion’s jaw!

So why did this crab develop such strong claws? Well, much like our stranded island game above, the crab’s main food source was coconuts and in order to eat these coconuts they needed strong claws to break them open. These crabs have been known to drop the coconuts onto hard surfaces, whack them with their claws, and even crack them wide open with their incredible grip strength. Recent studies show that these crabs are also interested in bird meat. Coconut crabs have been spotted sneaking up on birds while they roost on low-hanging branches and, once in reach, they grip their wings with their powerful claws and break their wings. This causes the bird to fall to the ground where the crab can feast without fear of the bird flying away. Some scientists hypothesize that these dominant crabs will invoke fear in other ground nesting species on the islands and perhaps, over a long period of time, cause evolution to change the shape or behavior of these coconut crab prey. For this is the dance of evolution, beneficial traits survive and pass on their desired traits to the next generations while the others die.

coconut fruit sliced into two
Photo by Pixabay on Pexels.com

Now, back to our evolutionary mash-up of the Northern Lampfish. Last time, we left our lampfish with an extended body lined with electrocytes (the electricity forming cells found in electric eels). Now we will give our vulnerable prey the claws of a coconut crab! This new trait will give the crab an added defensive and offensive strategy. Predators that try to sneak attack it might find themselves in the powerful grasp of its coconut crab claws. Plus, these armored claws give the predators less vulnerable surface area to exploit and attack on the lampfish. The lampfish will now also have an effective way to snatch prey of its own. Certain birds were once predators of the lampfish, but now that it has large claws, maybe it will tear a page out of the coconut crab’s book and eat bird meat. As the lampfish develops more defensive and offensive traits, other species within the oceanic ecosystem will surely change with time as well. Some predators will be forced to seek out other sources of food while others might find themselves on the lampfish’s menu. But in order for our lampfish to shift from ultimate prey to untouchable prey, we need to give it a better adaptation to deter the massive predators like sharks and whales. A Great White Shark’s jaw can produce a force of about 17000 Newtons, much larger than the coconut crab claw force of 3300 Newtons. The lampfish is still outmatched when put head-to-head with large predators. Stay tuned as next week I give our Northern Lampfish one final adaptation that will make it the ultimate untouchable prey of the ocean.

beach foam landscape nature
Photo by Pixabay on Pexels.com

 

If you read this whole blog post, you are my hero! Thanks for reading. Please feel free to leave me a comment and feedback below. Also, let me know if there is any particular science topic you would like me to look at “through green tinted glasses” and I will write about it. *Also, stay tuned as next week I unveil the full evolutionary mash-up of the Northern Lampfish complete with beautiful artistic interpretations by some skilled artists. 

Work cited:

https://blog.nationalgeographic.org/2017/11/01/meet-the-coconut-crab-the-worlds-largest-land-crab-with-a-powerful-grip-and-an-appetite-for-coconut-rats-and-birds/

https://www.britannica.com/animal/robber-crab

Scholastic. Science World Current Science Magazine. March 6, 2017. Volume 73, Number 9, Page 5.

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