ORV trails often follow stream beds, disturbing animals and rare plants.
Repeated studies have shown that they disturb animals and create air and noise pollution.
They also damage soils and vegetation, disturb animals and interfere with cross-country skiing and dog-sledding.
Another problem is that running dogs through the countryside disturbs animals other than hogs: not all of the dogs can be counted on to chase hogs only.
Noise emanating from passing ships may disturb animals such as killer whales and dolphins far more than previously thought, with new research showing that the animals' communication and ability to find prey could be hampered by the underwater din.
But conservationists argue that the planned highway would cut into mountains, increasing the threat of landslides, disturb animals with the upheaval of industrial construction, and involve chopping down trees which line the Struma river, causing soil erosion and flooding.
For example, when hunters "disturb" animals such as bison in order to maneuver them toward a trap or ambush, the animals rearrange themselves spatially by age and sex in such a way that the subset of animals actually killed may not be a random sample of the living population.
Planning bosses recommended banning any setup or clearing work taking place at night, and restrictions on the amount of light and noise overnight which could disturb animals nearby.
But the possiblity that the signals could harm marine wildlife or disrupt migratory patterns delayed the project for more than a year and forced scientists to extend their tests to see whether the sounds would disturb animals.
A spokesperson says it has prohibited nighttime construction, which disturbs animals' sleep habits.
Other clusters of human bones were also present but had been disturbed by animals.
