Coconut crabs (Birgus latro) are relatively mysterious (adding to the fear factor?). The International Union for Conservation of Nature classified this type of hermit crab as Data Deficient, meaning exactly what it seems. There are some things we do know, however: These crabs can grow up to 3 feet across and weigh as much as an Italian greyhound (up to 9 lbs). They burrow in the dirt or sand, hiding in their little crab caves until nighttime when they venture out for a midnight feast. Surprise—these omnivores eat coconuts (their huge claws are powerful enough to whack them open), but have also been known to eat chickens, kittens, and even fellow coconut crabs. Hey, with how big these things are, they need to eat everything they get their claws on.
Related: Lobsters Don't Age, But They Do Die
Let's get one thing straight: These things are big, but not that big. Occasionally, a viral photo like this one will go around to shock and awe. Biologist Michael Bok explains the coconut crab climbing into the trash can in that photo is normal sized, but the trash can is particularly small.
Related: The Smallest Scorpion On Earth