Amboseli ecosystem experienced a dry and hot period in September. Vegetation dried off and most grasses, except for stumps of Elephant grass ( Pennisetum purpureum ), were completely degraded or removed. Weak, old, and young animals were significantly affected by these harsh conditions, and many died of exhaustion and thirst. Forage was very scarce for herbivores, a good number of these animals had to rely on the little vegetation left within the swamps for sustenance.