Although Alexander and his troops first encountered elephants at Gaugamela, scholars believe those 15-20 animals were not a major factor in the fight. That would come later, in India, at the battle of the Hydaspes.
Horses, not accustomed to the sight of elephants and unfamiliar with their scent, can panic when they see such huge creatures. Such was also true of the Macedonian cavalry and their mounts. On the other hand, elephants - as the largest animals on earth - have no significant natural enemy except man.
What type of elephant did Alexander and his army encounter during their time in India? Then, as now, there were two types of elephants: Asian (Elephas Maximus) and African (Loxodonta Africana). Asian elephants - like those faced by Alexander - are slightly smaller than African elephants. Both species can run as fast as 25 miles (40 km) per hour for short distances. Charging elephants (click on the top-left button and be patient as this video link loads) are an unbelievable sight.
The Asian elephant (don't miss this link with nineteen different movies of Asian elephants in natural habitats), like its African relative, has a life span of about seventy years. But it is distinguished from the African elephant (there are thirty-two movie clips in this link, including a running herd on the third page) in that Elephas Maximus has much smaller ears, a flat forehead with two humps, and more toes and toenails on both its fore and hind feet. The highest point of an Asian elephant is its head; the highest point of an African elephant is its shoulders. Male and female African elephants have tusks, while female Asian elephants have none.
Because elephants eat so much, their teeth wear out. Over its lifetime, an adult typically has six different sets of teeth. When the last set wears out, the elephant could starve to death.
The population of Asian elephants today is estimated between 35,000 and 50,000 in the wild with an additional 15,000 in captivity. They are endangered and a charging Elephas Maximus has been known to trample people to death - especially when humans move near the elephants' natural environment.
It was a different story, however, on the day in 326 B.C. that Alexander and his men encountered elephants on an Indian battlefield. On that day, the animals would face a horde of fearless men intent on killing them.