The rutting (or mating) season usually occurs during periods of high rainfall, as females come in heat in the second half of the rainy season. During the mating season, bull (male) elephants produce large amounts of a hormone known as 'musth', which makes them more aggressive as well as sexually active.
New calves are born 22 months after mating - in time for the beginning of a rainy season, when there is plenty of food available. An expectant mother is often given protection by a second cow elephant during birth and for a while afterwards, because elephant calves are sometimes attacked by lions, tigers and hyenas.
A new born Asian elephant weighs about 100kg, and grows rapidly for the first few years. They continue to grow throughout their lives, though after 15 years, the growth rate slows. Bull elephants have a further growth spurt between 20 and 30 years. The largest animal in a group of elephants is usually the oldest. Elephants are able to regulate their population without interference from humans. If habitat is lost, they are able to reach puberty later, and extend the period between births.
Only 50% of Asian elephants survive beyond 15 years, and only 20% reach 30. Younger elephants are now being killed by hunters, so their chance of survival is growing slimmer. The surviving population of Asian elephants is estimated between 30,000–50,000, one-tenth of the population of African elephants and they are now regarded as endangered throughout most of their natural habitat.Read More: Behaviour