Animal navigation systems
Eels are one well-known example. The European eel inhabits rivers. Adult eels migrate thousands of miles in order to reproduce in the Sargasso Sea. The very young animals then migrate back to the rivers in Europe. There they grow to reproductive maturity, and then return to the Sargasso Sea.
Bar-tailed Godwits also migrate over enormous distances: from Alaska to New Zealand and back again. The female bar-tailed Godwit holds the record for the longest nonstop migration: 11,500 kilometres in nine days. Other bird species are also known to cover huge distances in migration.
Distance, of course, is relative. An ant species in the Sahara goes searching for food as much as half a kilometre away. The ants run in all directions, yet can still find their way back to the nest according to how many steps they have taken, and by navigating on polarised sunlight. Finding their way back to the nest is essential, as ants that stay out too long under the hot sun get roasted.
The National Geographic website contains more examples, as well as links to videos.