Unless you just connected your computer to the internet yesterday, you’ve probably seen this picture:
Your first reaction may be to think that this is the product of an unholy union between Photoshop and someone’s night terrors. However, I’m sorry to let you know that this image is probably genuine; at least partially. It’s hard to say for sure since the source has been lost to the aether of the web, but I can confirm that the animal in the photo is absolutely real.
Meet the worlds largest terrestrial arthropod, the coconut crab, Birgus latro. These crustaceans are related to hermit crabs, porcelain crabs, and squat lobsters in the Anomura infraorder. While they are young, their ecology is fairly similar to other terrestrial hermit crabs. At first, they use mollusk shells as mobile homes. However as they grow, they discard their shells and their carapace hardens. Eventually they reach a leg-span of over 3 feet and a weight of 10 pounds. Coconut crabs live on island beaches throughout the Indian and South Pacific Oceans. They live in dirt burrows and rock crevices, and scavenge for fruits and nuts, including coconuts, thus deriving their popular name. The Wikipedia entry for these crabs is pretty solid if you want more info.
Now back to the “trashcan crab” photograph. While the photograph has probably not been digitally altered, it nevertheless makes use of a cheap trick of mental association to give an inflated impression of the animal’s size. Let’s look at this helpful chart:
As you can see, the standard 32 gallon trash can is 51 inches, 4.25 feet, or 0.71 Ripleys in height. Coconut crabs typically reach a leg-span of about 3 feet, or 0.5 Ripleys. The coconut crab on a conventional trash can is not proportional with the “trashcan crab” photo. Instead, it is likely that the crab in the photo is climbing on a much smaller that usual can. Our brains see the shape of the trashcan and assume it is the large, 32 gallon size we are accustomed to.