Elephants are highly intelligent and long-lived animals; Asian elephants may live as long as 70 years (5). They are extremely sociable and occur in groups of related females, led by the oldest female known as the 'matriarch'. Groups of Asian elephants average six to seven individuals, and will occasionally join with other groups to form herds; although these are more transient than those of African savanna elephants (2). Males leave their natal group when then reach sexual maturity at around six to seven years of age, after which time they are predominantly solitary (2). When males reach 20 years old they start coming into 'musth', an extreme state of arousal when levels of testosterone in the blood may increase 20 times (2). This state lasts about three weeks and during this time the individual will become aggressive and wander widely in search of females (2). Musth may cause males to fight for access to females and also increases their attractiveness to females. Cows only reach sexual maturity at ten years of age (6), and the interval between births may be as long as four years owing to the long gestation time and infant dependency (4). The single calf may suckle from other females in the group as well as their own mother (4). Elephants use their dextrous trunk to pluck at grasses and pass them into their mouths; the average daily intake of food is 150 kilograms of vegetation a day (5). Grasses make up the mainstay of the Asian elephant's diet but scrub and bark are also eaten, and calves may eat their mothers dung to obtain nutrients (2). Where elephants occur near plantations they will readily feed on banana or rice crops. Asian elephants have had a close relationship with man over the centuries; they are still used to clear timber particularly in some of the more inaccessible forests of the continent, and play an important role in the religious and cultural history of the region (2).