 During peak sexual activity , males engage in combat . This starts with one male rubbing its chin along the back of the other . The second male will then raise its head as high as possible . As they both do the same , the necks intertwine . When the heads are level , they turn towards each other and push . Their bodies intertwine as they switch positions . They become oblivious to everything else , continuing even after they fall off a surface or into water . Sometimes they intertwine and <unk> so tightly that their scales stand out from the pressure . They have also been observed to strike at each other with mouths closed . Occasionally , the combatants will tire and break off the fight by " mutual consent " , resting for a while before resuming once more . The event is settled when one of the two succeeds in pushing the other 's head to the ground and raising its own by 20 – 30 cm . In captivity , combat may occur four or five times a week until courtship and copulation ends . 
