Hannibal's enigma: how elephants' metabolism defined the route to Rome

BarcelonaIn 218 BC, the Carthaginian general Hannibal undertook a daring action to surprise his bitter enemy, Rome: he crossed the Alps with 40,000 soldiers, 7,000 horses, and 37 war elephants with the intention of invading Italy. For centuries, historians and archaeologists have debated which mountain pass the Carthaginian army used. An interdisciplinary study published in the journal Proceedings of the National Academy of Sciences (PNAS) has launched a new theory with a highly innovative approach: bioenergetics. The research, led by the University of Oxford and Friedrich Schiller University Jena, indicates that the Col de la Traversette, located at an altitude of 2,914 meters on the current border between France and Italy, was the chosen route because it required less energy consumption, especially for the elephants.

The Carthaginian pachyderms were the weapon the Romans feared most and the pride of the Carthaginian general. To develop the study, data from contemporary African elephants – from the Samburu reserve in Kenya – were used, and the energy costs of movement were estimated based on body mass and terrain slope. The results suggest that the Montgenevre pass would have been the second most efficient route, and the Col de Clapier would have been third. Crossing the Alps in extreme cold, to which the Carthaginians were not accustomed, became a true odyssey that many books have described. Now, the energy expenditure can even be quantified. On the Traversette route, men would have lost 19% of their body fat reserves during the crossing, which could explain the high mortality. Surprisingly, according to the model developed by the teams from the British and German universities, the war elephants would have endured better and lost only 4% of their reserves.

It cannot be stated with certainty that the Traversette was Hannibal's chosen route. "Nevertheless, it reinforces the arguments in favor of the Traversette route, because it is shown that it adapted better to the demands of moving a large army in extremely hostile terrain," assures Emilio Berti, co-author of the research. Beyond logistics, the reason why Hannibal insisted on attacking by land with elephants, and not by sea, continues to fascinate historians. It is believed that he was seeking an element of psychological surprise and to intimidate the Roman legions, but also to impress and recruit the tribes opposed to Rome. The plan, initially, worked. Hannibal strung together legendary victories: at Cannae, he surrounded and massacred an army of 60,000 men. Despite everything, the general, who was a great military strategist, never received the necessary reinforcements from Carthage, and Rome had time to recover. General Scipio Africanus brought the war back to Carthage and finally defeated Hannibal at the Battle of Zama (202 BC). Abandoned and pursued, to prevent the Romans from capturing him, in 183 BC Hannibal committed suicide in Bithynia.