In 218 BCE, Hannibal crossed the Alps with 37 war elephants, 7,000 horses and 40,000 men. 2,244 years later, models show the elephants may have lost just 4% of their fat reserves on the most efficient route

More than 2,000 years after Hannibal led his army across the Alps, researchers have used modern route and energy models to estimate how demanding the journey may have been for the people and animals who made it.

The Carthaginian general crossed the mountains in 218 BCE with about 40,000 men, 7,000 horses, and 37 war elephants during the Second Punic War. The exact route remains uncertain, but a new study suggests the Col de la Traversette was the most energy-efficient option among the routes examined, as per a report.

The modelling offers an unexpected detail: while Hannibal's men could have lost around 19% of their body fat reserves during the crossing, the elephants may have lost only about 4%, as per a Popular Science report.

The route Hannibal may have taken

Hannibal needed to reach Italy without relying on Rome's powerful naval presence in the Mediterranean or its army garrisons on land.

Crossing the Alps was a difficult alternative. His army had to move through steep terrain, snow and ice while dealing with mountain passes controlled by local tribesmen who could attack from above.

Only two primary sources of the crossing survive, and they were written decades after the event. With no archaeological evidence available, modern theories rely on interpreting ancient place names and comparing them with the geography of the Alps today.

One route previously considered likely was the Col du Clapier, a pass about 8,127 feet high between Savoy in France and Piedmont in Italy.

How researchers compared the routes

Researchers from the University of Oxford, the German Centre for Integrative Biodiversity Research and Friedrich Schiller University Jena compared several possible Alpine routes.

They combined route modelling and elevation data with information on how much energy modern African elephants use when moving across different types of terrain.

The results pointed to the Col de la Traversette, a pass reaching 9,669 feet on the border between France and Italy.

Compared with the Traversette route, travelling through the Col de Montgenèvre would have required about 11% more energy. The Col du Clapier would have required 16% more, while the Col du Mont Cenis would have required 19% more.

The soldiers may have paid the bigger price

The models suggest that the journey would have placed a substantial physical burden on Hannibal's soldiers.

If the army travelled through the Col de la Traversette, the men could have lost around 19% of their body fat reserves during the crossing.

Hannibal's campaign ultimately cost roughly 20,000 men, although the study does not establish that the energy lost during the Alpine crossing directly caused those later losses, as per the Popular Science report.

The elephants appear to have faced a smaller energy deficit. The models estimate that they would have lost only about 4% of their fat reserves on the Traversette route. Their larger energy reserves may help explain why many, if not most, of the elephants survived the crossing.

Why Hannibal brought elephants remains unclear

The study does not determine why Hannibal brought 37 war elephants across such difficult terrain.

One possibility is that he intended to use them as a tactical surprise in his first battles against the Romans. Another is that he hoped the animals would impress the Celts of Northern Italy and encourage them to join his side.

According to Livy's account, Hannibal's army crossed the Alps in 16 days. His wider military campaign lasted roughly two months and ended with heavy losses, according to the Popular Science report.

The route is still not proven

The new analysis does not establish that Hannibal definitely used the Col de la Traversette.

Instead, it provides another way to compare the competing theories by examining the physical demands of moving a large army, thousands of horses, and dozens of elephants through difficult Alpine terrain.

The exact route remains unresolved more than two millennia later, but the modelling strengthens the case for the Traversette route by showing how its terrain would have affected the army's energy requirements.