Herds are usually led by cows, which are far more dangerous than bulls. They eat grass, leaves, bark, root, fruits, and twigs. A single calf is born and suckles for two years. In dry times elephants dig deep wells in river beds, their eyesight is poor but have an excellent sense of smell and hearing. Tusks can weigh up to 102 kg., and can reach up to 310 cm., shoulder height 320 cm., mass 4700 kg., lifespan 70 years.