A news report from the International Union for the Conservation of Nature (IUCN): The survival of tigers in the wild depends largely upon the willingness of the tiger range countries to ensure adequate protection of succinctly large areas from inappropriate development and activities such as roads and poaching.
Research on Amur tigers in Russia suggests that direct mortality due to vehicle collisions can reduce survivorship and reproductive success of the species. The death of individual tigers also results in social instability. The death of a territorial male can lead to infighting of transient males trying to establish territories, infanticide by the new territorial male, and it also affects tigresses due to unstable male ranges possibly leading to depressed birth-rates. Chital and sambar, principal prey species for tigers in the tropical forests of south Asia are one of the commonly killed species in vehicular collisions, resulting in reduced food source for tigers.
Furthermore, roads are used for illegal activities including hunting of tiger and their prey. In the Russian Far East, six Amur tigers were poached over a 10-year period along one road. In 2010, poachers apprehended in southern India confessed to be illegally hunting chital and other deer species in Bandipur, Bhadra, and Biligirirangaswamy Tiger Reserves by driving on roads at night.
Highways and vehicular tracks act as barriers for movement of tigers affecting their dispersal and movement patterns thereby splitting populations into subpopulations; that cause several direct and indirect effects.
Although roads and other infrastructure are important for economic development, poor planning, disregard of ecological aspects and excessive road expansion into tiger habitats will further fragment and destroy populations and their habitats in the long-term.
Further reading: Gubbi, S. et al, Impact of vehicular traffic on the use of highway edges by large mammals in a South Indian wildlife reserve, Current Science, 2012.
Gubbi S. et al, Finding the Middle Road: Grounded approaches to mitigate highway impacts in tiger reserves, Handbook of Road Ecology, 2015.
Meet Sanjay Gubbi – IUCN Tiger Programme ITHCP