Asian Elephant - Ecology of a Social animal
Asian elephants are very social animals. They live in family groups consisting of related females and their offspring that are led by the oldest female, the ‘matriarch’. The social bond between group members is very strong, and co-operative behaviour is common, particularly in the protection and guidance of the young.
The average group size is around six or seven. There is no evidence of territoriality, and groups occasionally coalesce to form herds when food is plentiful. Males leave the natal group when they reach sexual maturity, at around 6-7 years.
After this time they tend to live alone or in small temporary all-male groups. At around 20 years males first come into ‘musth’, an extreme state of arousal in which highly elevated testosterone levels cause aggressive behaviour, pronounced secretions from the temporal gland, and an increase in sexual activity. Musth occurs annually and usually lasts two or three months. During this time males will wander widely in search of receptive females.
Females become sexually mature at around 10 years and generally first give birth at around 15-16 years. When habitat conditions are favourable, they are capable of giving birth every 3-4 years. Elephants can live as long as 70 years, although the period of greatest female fecundity is between 25 and 45 years of age. The gestation period lasts 18-22 months, and usually results in the birth of a single calf, weighing an average of 100 kg. The calf may continue nursing for up to 18 months, and can suckle from its mother or from other lactating females in the group.
The species feeds during the morning and evening and at night, and rests in the shade during the heat of the day. The diet consists mostly of grasses, but bark, roots, stems, and the leaves of trees, vines and shrubs are also eaten.
Cultivated crops such as bananas, rice and sugarcane are also favoured foods, bringing the species into conflict with local farmers. Calves often feed on their mother’s dung for extra nutrients. Elephants must drink frequently, as they require 70-90 litres of water each day.
Elephants play a vital role in the ecosystems they inhabit. They modify their habitat by converting areas of forest to grassland, and are important seed dispersers. They can provide water for other species by digging holes in dry riverbeds, and the wide paths they create as they wander through the forests act as firebreaks. Given their physiology and energy requirements, elephants need to consume large quantities of food per day. They are generalists and browse and graze on a variety of plants. The proportions of the different plant types in their diet vary depending upon the habitat and season.
During dry season in southern India, Sukumar (1992) observed that 70% of the elephant's diet was browse, while in wet season, grasses make up about 55%. However, in an adjoining area, observed that browse formed only 15% of the diet in dry deciduous forest and 47% of the diet in the thorn forest in the dry season, while the annual diet was dominated by grass (84%). In Sri Lanka, elephants may feed on more than 60 species of plants belonging to 30 families (McKay, 1973).
In southern India, recorded that elephants fed on 82 species of plants (59 woody plant species and 23 grass species). Elephants may spend up to 14–19 hrs a day feeding, during which they may consume up to 150 kg of wet weight They defecate about 16–18 times a day, producing about 100 kg of dung. Dung also helps disperse germinating seeds.
Elephants range over large areas and home ranges in excess of 600 km² have been recorded for females in south India. In north India, female home ranges of 184–326 km² and male home ranges of 188–407 km² have been recorded (Williams, 2002). Smaller home range sizes, 30–160 km² for females and 53–345 km² for males, have been recorded in Sri Lanka. Given their requirements for large areas, elephants are regarded as an “umbrella species” because their conservation will also protect a large number of other species occupying the same area.
They are also a premier “flagship species” and are sometimes regarded as a “keystone species” because of their important ecological role and impact on the environment.