Elephants and the Carthaginian:

...The Numidians were followed on the way back to the Carthaginian camp which was almost empty at this point minus the elephants who Hannibal was to dedicate to sometime getting across. The scouts, seeing that Hannibal had not crossed with the whole of his force, raced back to the coast to alert the Consul. 

The Consul, upon learning this information marched his army up the river with boats, but it was too late. Upon arriving, Hannibal had long left the camp and crossed the elephants across the river...

*excerpt from Wikipedia on Hannibal's Crossing of the Alps.