Influences on mammals frequency of use of small bridges and culverts along the Qinghai-Tibet railway, China

Understanding the use of small bridges and culverts by wildlife to cross the Qinghai-Tibet railway will aid in the design of wildlife crossing structures for similar transportation infrastructure. From 2014 to 2016, 36 infrared cameras were placed inside 14 small bridges and 11 culverts along the Qinghai-Tibet railway to determine the structures' effectiveness as wildlife passages. Thirteen species of mammals were found to use the small bridges and culverts to cross the railway. The crossing rates for all mammals were significantly higher for small bridges than for culverts. Tibetan antelope (Pantholops hodgsonii), Tibetan gazelle (Procapra picticaudata), kiang (Equus kiang), and wild yak (Bos mutus) preferred small bridges over culverts to cross the railway. In contrast, mountain weasel (Mustela altaica) and Asian badger (Meles leucurus) preferred culverts to cross the railway. The crossing rates of all mammals, particularly Tibetan gazelle and woolly hare, were positively influenced by structure width. Structure height had a positive influence on wild yak, but structure length had a negative influence on kiang. The distance to the highway had a positive influence on the crossing rates of all mammals, particularly wild yak and woolly hare. Human use of the structures had no influence on the crossings of most mammals except for common wolf. We suggest that road design schemes include large and open crossing structures to benefit most species with limitations on human activities near wildlife passages.