Effect of mine discharge on the pattern of riverine habitat use of elephants Elephas maximus and other mammals in Singhbhum forests, Bihar, India

The aim of this paper is to assess the influence of water quality both on the occurrence of, and utilization by, elephants (Elephas maximus) in a riverine habitat. Mining operations and other anthropogenic changes to natural river systems have caused degradation of the ecosystem for elephants. A decline in their numbers has been seen throughout the Singhbhum Forests, India due to fragmentation and loss of habitat. The need to preserve and restore the habitat of the elephant is accepted, but until the factors that influence their distribution are known and understood, suitable management plans cannot be implemented. The study area was the catchment of the river Koina where waste discharge from an iron ore mine and processing plant impact upon water quality. The study period from April 1995 to March 1996 looked at sections of the river where unregulated mine discharge was made, and where regulation through tailing ponds controlled total suspended solids (TSS) output from the mine waste water to the river system. Various physico-chemical parameters recorded at seven sampling stations were quantified. Principal Component Analysis (PCA) segregated the key parameters in determining the discharge levels of both regulated and unregulated discharge at various sites. The main contrasts between regulated and unregulated sites were turbidity and TSS, which were higher in unregulated reaches of the rivers. Patterns of elephant and other mammal use of a river valley in Bihar, India, were recorded using dung dispersion to estimate the distribution and occupancy of elephants. Dung dispersion was employed as a surrogate for habitat use, in an attempt to identify the factors that influence the distribution and occupancy of elephants. Riverine woodlands are seen to be very important for elephants in the summer because they provide shady dense forest and water, needed primarily for behavioural thermoregulation to avoid heat stress during the daytime. The increase in riverine habitat use by elephants throughout the catchment of regulated river sections in 1996 identified the special value of this habitat during summer for such mammals. The regulated river sectors showed an increase of 300% use by elephants, and 600% by other mammals over the unregulated mine discharge situation (P<0·001). While habitat use remained unchanged (P>0·05), throughout the study period in the control stations. These findings suggest that river-water quality has a significant influence on mammal use of the riverine habitat. Results suggest the need to regulate mine discharge and restore the ecosystem health by maintaining waste levels below the TSS and turbidity levels of 200 mg l−1and 60 NTU, respectively.