Island gigantism is a biological phenomenon where the size of animals isolated on an island increases dramatically over generations. It is an apparent counterexample to Bergmann's Rule, which states that creatures near the equator tend to be smaller; smaller size in herbivores usually makes it easier to escape or hide from predators, but on islands, these are often lacking. Thus, island gigantism is not an evolutionary trend due to fundamentally new parameters determining fitness (as in the complementary phenomenon island dwarfing), but rather the removal of constraints. With the arrival of humans and associated predators (dogs, cats, rats, pigs), many giant island endemics have become extinct. As opposed to island dwarfing, island gigantism is found in most major vertebrate groups and in invertebrates.