The Tibetan plateau is the highest plateau in the world and home to a variety of endemic endangered species. One species of particular concern is the Tibetan antelope (Pantholops hodgsonii). Its seasonal migration results in bi-annual railway and highway crossings on the plateau. Large bridges along the railway (width>100m, including kekexili bridges) have been previously studied and found to be effective passages for antelope movement. However, numerous small bridges and culverts located along railway have not been examined. The Qinghai-Tibet expressway, planned for construction in the near future, will likely parallel the existing highway (G109) and Qinghai-Tibet railway. Consequently, knowledge gained from studying the use of existing small bridges and culverts by wildlife will contribute to improvements in the design of wildlife crossing structures for the expressway.
Twenty infra-red cameras were located inside 11 small bridges and 5 culverts along Qinghai-Tibet railway from August to December in 2014 to determine their effectiveness for wildlife passage. Factors related to usage of structures were recorded, including structural characteristics (length, width, height, openness, type), landscape features (water size, distance to highway, distance to the nearest structure) and human disturbance. Highway traffic volume data was collected from the local transportation management agency.
At least 10 mammal species were found to cross the railway by means of small bridges and culverts. Over a period of 1312 trap-days, the total number of wildlife crossings observed was 1597. The total average crossing rate for all structures combined was 1.22 per day, or 0.076 crossings per structure per day. Three species were listed Chinese National First-class Protective species (Tibetan antelope, Kiang (Equus kiang) and Wild Yak (Bos mutus Przewalski) and two species were listed Chinese National Second-class Protective species (Tibetan gazelle (Procapra picticaudata Hodgson) and Eurasian Lynx (Lynx lynx)). Crossing frequency of all species were: Tibetan gazelle: 381, Kiang: 361, Gray-tailed hare (Lepus oiostolus): 287, fox (Tibetan fox (Vulpes ferrilata) and Corsac fox (Vulpes corsac): 211, Tibetan antelope: 199, Common wolf (Canis lupus): 143, Mountain weasel (Mustela altaica): 10, Badger (Meles meles): 2, Wild Yak: 2, Eurasian lynx: 1. Common wolf, fox, Tibetan gazelle and Kiang all used more than 10 structures.
In general, most species were found to prefer to large crossing structures with a high openness ratio. The frequency of use of small bridges was significantly higher than culvert use. However, Tibetan antelope and kiang were never observed to use culverts. We found a negative relationship between hourly traffic volume and frequency of fox and kiang use of crossing structures.
The results demonstrate that crossing structures for the planned expressway should be tall, wide, and short in length, with high openness ratios. To protect Tibetan antelope, the openness ratios should exceed 4.2. Presently only 5 structures were found to be used by Tibetan antelope. More extensive and comprehensive long-term studies and monitoring are required.
Tibetan Antelope; small bridges; culverts; wildlife; Qinghai-Tibet railway; road ecology; China