General Hannibal Barca riding an elephant, painted by 17th-century French artist Nicolas Poussin. Mel22/Wikimedia provided
General Hannibal Barca of the Carthaginian Empire, which rivaled ancient Rome, drove dozens of elephants in the Second Punic War that began in 218 BCE, marching through what is now Spain and France, crossing the Alps to attack the Italian Peninsula where Rome was located and driving it to the brink of collapse. The exact route by which the elephant corps that pushed Rome to the verge of destruction crossed the Alps remains unclear.
A research team from the German Centre for Integrative Biodiversity Research (iDiv) calculated the energy expenditure of Hannibal’s army while crossing the Alps and reported on the 6th (local time) in the Proceedings of the National Academy of Sciences (PNAS) that the route over the Col de la Traversette was likely the most efficient.
Hannibal is said to have crossed the Alps in 15 days with 46,000 soldiers and 37 war elephants. Historians and geologists continue to debate the precise line of march. The Col de la Traversette, a rugged pass in the Western Alps reaching up to 2,947 m above sea level, is currently considered the most plausible actual route.
The team compared the direct movement costs of four candidate routes using a calculation model that incorporated elevation and travel distance as well as the body weight and locomotion-related metabolic rates of humans, horses, and elephants.
Total energy expenditure along the Traversette route was 5.42 terajoules (TJ, a unit of energy), which was 11%, 16%, and 19% lower than the 6.02 TJ for the Col de Montgenèvre, 6.28 TJ for the Col du Clapier, and 6.45 TJ for the Col du Mont Cenis, respectively.
Assuming carbohydrates were the soldiers’ main energy source, the food required to cross the Col de la Traversette was about 232.7 tons, or 25.8–44 tons less than on the other three routes.
According to the calculations, each elephant, excluding its basal metabolic rate on level ground, consumed an additional 1.53 gigajoules (GJ, a unit of energy where 1,000 GJ equal 1 TJ) over 15 days while crossing the Col de la Traversette. To maintain body weight, it is estimated that each elephant would have needed to spend an extra 5–6 hours a day feeding.
Given that securing sufficient fodder was likely difficult, the proportion of body fat depleted at the Col de la Traversette was estimated at 4% for elephants, 11% for horses, and 19% for soldiers, suggesting that elephants may actually have withstood the Alpine crossing better than humans.
The researchers concluded that elephants had an advantage in crossing the Alps thanks to their large fat reserves and leg structures suited to rough terrain, but once they arrived in Italy, replenishing and maintaining energy through the winter would have posed a much greater challenge.
In fact, about 30 elephants are thought to have crossed the Alps and been deployed at the Battle of the Trebia, but by the following winter all had reportedly died except for “Surus,” the elephant Hannibal rode.
This study is a model-based analysis that excludes the costs of foraging, transport, distribution of fodder, and non-combat personnel such as elephant handlers, and thus does not constitute direct historical or archaeological evidence that Hannibal actually chose the Col de la Traversette.
The team stated, “Our findings offer insights not only into Hannibal’s route of march, but also into logistics and supply systems, as well as the psychological aspects of warfare that employed war elephants.”
– doi.org/10.1073/pnas.2612764123
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