The disturbance caused by big projects and infrastructure creation around tiger habitats is affecting the animals' behavioural patterns, Parliament was told on Tuesday
Environment Minister Anil Madhav Dave also told the Lok Sabha that his ministry received no report on illegal mining or deforestation in the tiger reserves.
As per the ministry, over 15 lakh acres of forest land in India is under encroachment, of which Madhya Pradesh and Assam, both tiger range states, top the list.
"Tigers do disperse and become transient mostly owing to ethological (science of animal behaviou) reasons, " he told the house in a written reply.
"Disturbances of any kind viz.
large projects, big infrastructure creation as well as linear projects might cause fragmentation of habitat, thereby affecting behavioral pattern of tiger, " the minister added.
Experts from many national parks and tiger reserves have noticed some behaviour change among the tigers, believed to be human induced, especially due to breach in the animal's space from excessive tourist inflow.
Experts often give the example of T - 16 known as "Machli" and T - 24 known as "Ustad" from Ranthambore National Park.
While Machli became fond of photographers, Ustaad became aggressive due to breach in space.
Machli died in August this year at an abnormal age of 19 years and Ustaad now lives under captivity after being labelled as man - eater.
Experts believe that they were not the only tigers in Ranthambore exhibiting such changes.
There are total 50 tiger reserves spread over 18 tiger states across the country, with 1, 820 tigers, as per National Tiger Conservation Authority.