Ranging and Spacing Behaviour of Asian Elephant (Elephas maximus Linnaeus) in the Tropical Forests of Southern India

Abstract

Larger body mass and associated life history traits of large mammals pose high risks of anthropogenic extinction. Given the wide ranging nature and the synergistic impacts of habitat loss and fragmentation, the living elephants are among the most threatened mammals in the world. Therefore, information on ranging and space use pattern are extremely important for conservation planning, especially in the case of long-ranging species. We studied the ranging and spacing behaviours of Asian elephant (Elephas maximus) radio-collaring three clans and two bulls between 1991 and 1995 in Nilgiri Biosphere Reserve, southern India, to understand their implications for conservation. Home-range size varied considerably among the clans (range 562–800 km2), bulls (range 211–375 km2), and between them. Clans ranged over larger areas (mean 677 ± 69 km2) compared to bulls (293 ± 82 km2). Clan ranged in degraded, poor quality habitat with low annual rainfall had larger home range (800 km2) than those ranged in high rainfall optimal habitats (562 km2). The smaller home ranges of bulls were possibly due to nonrepresentation of musth during the study period. The dry season movements of the clans and the bulls were restricted around the perennial water sources, while the wet season movements were extended to areas with temporary water sources. Seasonal home ranges of clans were large during wet seasons (401 ± 64 km2) than in the dry season (308 ± 20 km2). On the other hand, bulls ranged over larger areas during the dry season (231 ± 47 km2) than in the wet seasons (141 ± 35 km2). All the clans (excepting one) and bulls showed strong fidelity to their home and seasonal ranges. One of the clans shifted its range during the second year of the study. This clan had a major part of the range in the reserved and revenue forests areas, which continued to experience severe biotic pressure resulting in devoid of access to perennial water source. Therefore, the home-range shift of this clan could be attributed to habitat loss and degradation of major parts of its original range. Clans, unlike bulls, appeared to space themselves out and mostly avoided meeting each other, despite extensive overlap in space. Observations on interclan interactions further suggest that there is hierarchy among clans in space use. Such a hierarchy and its resultant spacing among the overlapping clans influence the seasonal habitat use pattern, which in turn could result in dominant clans having priority access to good quality habitat and food, thereby show better survival and reproductive success.