Guwahati: A new scientific study has found that human disturbance significantly alters the behaviour of the greater one-horned rhinoceros (Rhinoceros unicornis) in Assam’s Kaziranga National Park, with tourists and intruders triggering alertness, flight, or even aggressive chases depending on distance and conditions.
The research, carried out between 2016 and 2018 by Sangita Medhi of Suren Das College and Malabika Kakati Saikia of Gauhati University, analysed how rhinos respond to human interference by measuring what scientists call “disturbance distance.”
Using road transects and scan sampling, the study recorded rhinos’ behavioural changes when exposed to human presence in both tourist and non-tourist zones of the park.
“Indian Rhinoceros is a large herbivore and Kaziranga National Park holds its highest population with diverse habitat. The park is highly attractive to tourists from various parts of the world because of this charismatic species, which gives high revenue that can be helpful for developing various conservation strategies. Hence it is important to study the disturbance limit to guide the tourists so that the animals are less disturbed and recreation and conservation can coexist,” the authors say.
The authors say no such work has been carried out in the case of large mammal species so far or estimated what is the minimum approach distance of the Indian rhinoceros in Kaziranga National Park. “Hence, this study has been formulated to find out the disturbance distance of the Indian Rhinoceros. The study also attempts to find out the effects of habitat type, wind direction, age-sex, and tourist–non-tourist area on the disturbance distance and effects of tourism on behavioural profile,” the authors say.
Disturbance distance is the distance at which the rhino felt disturbed due to certain unusual external factors like the presence of any intruder or human beings that leads to a change in their normal behavioural activity. The findings show three distinct responses: rhinos first become alert (stopping normal activity and scanning for threats), then may flush (flee from disturbance), or in some cases chase the source of the disturbance. The average alert distance was the longest at 72 meters, followed by flushing at 67 meters and chasing at 40 meters.
Alert behaviour: It is the behaviour when the animal feels the existence of some intruder; they stop their normal activities and immediately try to identify and locate the source of disturbance by moving their head in either direction with ears erected or act as if scanning the intruder. While being unable to identify the problem or if the animal feels safe from the intruder, they were found to continue the previous activity. This type of behaviour was regarded as alert behaviour and the distance at which the animal shows such behaviour has been regarded as alert distance.
Flushing behaviour: It is the behaviour when the animal feels some disturbance due to the existence of some intruder and runs away from the point of disturbance creating the source. Such behaviour was regarded as flushing behaviour and the distance at which the animal flushed away has been regarded as flushing distance.
Chasing behaviour: It is the behaviour when the animal feels disturbance due to the existence of some intruder and chases toward the disturbance-creating source. Such behaviour was regarded as chasing behaviour and the distance at which the species started to chase has been regarded as chasing distance. In this behaviour, the animal tries to attack the source of disturbance.
Interestingly, disturbance distances were higher in non-tourist areas than in zones frequented by visitors, suggesting that rhinos in tourist-heavy areas may be partially habituated to human presence. Sub-adults were the most sensitive, showing the highest disturbance distances, while females with calves displayed defensive behaviour, often delaying flight to protect offspring. Habitat type and wind direction also played a crucial role. Rhinos in short grassland reacted at greater distances compared to those in woodlands, where visibility is lower.
Wind direction mattered too—when the wind carried human scent from the observer to the rhino, disturbance distances increased sharply, highlighting the species’ keen sense of smell.
The study warns that frequent human intrusion disrupts natural behaviours such as feeding and resting. In tourist areas, rhinos showed higher levels of vigilance and movement but rested less compared to those in undisturbed zones. For conservation management, the authors suggest using “alert distance” as a guide to set buffer zones between rhinos and tourists. They recommend maintaining a minimum approach distance of 100–200 meters, which should extend to 200–400 meters when wind direction increases the risk of detection.
Kaziranga, home to the world’s largest population of one-horned rhinos, is a major tourist draw and a vital source of conservation revenue. But as the study underlines, balancing tourism and wildlife protection remains a challenge. “Understanding the behavioural thresholds of rhinos is key to reducing human–wildlife conflict and ensuring that conservation and recreation can coexist,” the authors note.
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