Time dependent activity pattern of Ganges river dolphin Platanista gangetica gangetica and its response to human presence in upper Ganges River, India

摘要

Information on activity profile of the Ganges river dolphin (Platanista gangetica gangetica) and its responses to human interference were lacking. A study following focal animal sampling protocol with individual-follow method and assessment of human interference on dolphin occurrence and behavior was hence conducted. Based on logical reasoning and prior assumptions, dolphin activities were broadly categorized into four types viz., surfacing, movement, chasing/feeding and underwater. Percentage frequencies of occurrence of these activities in dolphin activity budget were 50%, 26%, 6% and 18% with corresponding time allocations of 1%, 60%, 4% and 35%, respectively; without any significant difference between male and female activity patterns (%2 = 0.832, df '= 3, P> 0.05). Five different modes of surfacing were observed with dive-times ranging from 4 to 504 sec and average prey chase-time of 38 (SD = ±29) sec. Human interference had a negative relationship with dolphin presence (beta = -0.6398, z = -3.816, P < 0.001). All recorded dolphin activities showed a positive relationship with human presence except underwater activity ((3 = -0.1115, z = -3.76, P < 0.001). Detailed behavioral study and proper check on increasing anthropogenic influence is necessary to ensure the species safe survival.