Where in the World?

Happy World Tapir Day!  (Giraffes get a day, penguins get a day, everyone gets a day, it seems).  Today, the world - or at least the very tiny percentage of it that cares - celebrates the world's five (or four - still some argument) species of tapir - solitary forest-dwelling ungulates from Central and South America... oh, yeah, and Southeast Asia.

Hmmm... about that one.

One of the most fascinating aspects of animals' natural history is the question of what animals end up where.  Why are all the tapirs in Latin America, except a single species - the Malayan tapir - found clear on the other side of the world?  For that matter, if you have tapirs in South American rainforests and Asian rainforests, why not in African rainforests?  Then again, why do the African and Asian rainforests have apes, but not the South American?  One species of alligator is found in the southeastern United States and is very common; the only other one in the world is found in China, and is critically endangered.  What gives?

The science of the distribution of animals around the world is called zoogeography.  It tries to answer these questions, and sometimes it succeeds.  Sometimes it's a story of ancient geology - seas rising and falling, mountain ranges and canyons appearing, continents drifting - for the later, consider North and South America, which were once entirely separate land masses before they collided together, allowing animals to cross between the two.  In other cases, more active exploration leads to animals appearing in strange places - consider the various island animals, carried out to sea on floating rafts and colonizing new islands.  Sometimes, a species was once widespread around the globe, and then disappeared as conditions changed, leaving only a few remnant populations.  And sometimes we have no idea... yet.

Part of it may have to do with chance, too.  Perhaps tapirs would do very well if they were introduced to the Congo.  Maybe gorillas or orangutans would thrive in the Amazon - plenty of other species do just fine when they are introduced (often by human intervention these days) into a new environment.  And maybe not - maybe they wouldn't be able to find appropriate food items, or maybe there is some other variable that would prevent them from establishing themselves.  There have been plenty of experiments - some disastrous, some harmless, some bizarre - in introducing animals around the globe.

Tapirs probably aren't destined to be added to that list any time soon.