Impact of Anatolian Motorway on Large Mammals: Quantifying the Permeability and Impact Zones

Abstract

Roads are one of the major structures that cause habitat fragmentation all over the world. Motorways and highways especially create a greater disturbance due to their size and extent, not only by increasing the fragmentation but also by resulting in edge effect. Large mammals, due to their need for extensive areas for resources, have large home-ranges, which are more easily fragmented by roads acting as barriers. Motorways and highways may further act as total barriers for certain species, dividing their populations.

Turkey is home, still, to a great diversity of large mammals. However, being a developing country, an extensive amount of infrastructure projects have been under way in an increasing fashion during the last two decades. Roads have been built in excessive amounts, serving as the main infrastructural elements to connect new and enlarged settlements and resource extraction sites such as mines and dams. A total of 17,000 kms of highways were built in Turkey during the last decade. Unfortunately, the effects of roads on wildlife have not been assessed. This study is the first one evaluating the road's effects on wildlife in Turkey.

In order to evaluate the effects of roads on wildlife, a 100 km. segment of the Anatolian motorway, connecting Ankara and İstanbul, is monitored for two years, using 200+ camera traps located at every underpass. The surrounding forest areas were monitored using additional 55 camera traps utilizing systematic grids at 1,5 x 1,5 kms.

A total of 2068 red fox, 1926 golden jackal, 934 wolf, 692 wild boar, 168 brown bear, 32 lynx, 10 red deer and 3 roe deer passing events recorded (filtered by hour). Out of three types of underpasses - culvert, multi-use underpass, viaduct - herbivores used only the viaducts. The heights of underpasses - but not the length or width - significantly affect the preference of all carnivores except red fox. An additional effect of the road on the use of large mammals at varying distances from the road is determined: the use of roadside areas were lower than average use in the 0-500 m. zone while it peaked in 500-1500 m. zone, and undulating around average use at 1500-5000 m. zone on both sides of the road. Such a pattern, caused by the effect of road was also determined in several other studies.