Why Animals Don’t Cross This Invisible Border in the South Pacific

GeoGlobeTales shared a very interesting tidbit about the Wallace Line, an invisible boundary between Bali and the south Philippines in the South Pacific that animals, including birds and fish, will not cross despite the relatively short distance between the two points. What's even more fascinating is that the animals on either sides of the line are vastly different from one another.

The western side of the line is home to animals like rhinos, elephants, tigers and woodpeckers which are typical of Asia. But once you cross the line you enter a completely different world with kangaroos, monitor, lizards, dingos and koalas despite the extremely short distance between the islands.

The Wallace Line was formed due to the shifting of tectonic plates that formed a deep strait, separating the land masses. This caused very disparate evolutionary ecosystems to thrive on both sides.

This strait prevented animals from migrating and as a result evolution took its own path on opposite sidesof this line therefore even birds and fish that can cross long distances almost never crossed this line as they have adapted to survive only within their own ecosystems.