Designing and testing under-road tunnels for Asian amphibians
Written By Dr. Yun Wang
China Academy of Transportation Sciences
8th February, 2021
The Asiatic toad is subject to severe rates of road mortality in Northeast China and many populations have declined in recent years.
China is home to numerous species of amphibians and many are endemic. Unfortunately, many populations have been declining in recent years due to the loss, degradation and fragmentation of habitat. While China has the longest expressway network in the world and one of the longest highway networks in the world, there is still a lack of understanding of the impacts of roads on amphibian populations. Nevertheless, major roads are likely to have significant impacts on amphibians and urgent action is required to protect them from highway construction. The latest version of the national industry standard called “Highway Engineering Technical Standards” clearly states that highways should allow wildlife to move and migrate to access food and shelter and that appropriate crossing structures should be installed at optimal location on all new road projects. As there are no relevant specifications for the design and placement of amphibian tunnels in China, we conducted a series of experimental trials to inform the Ministry of Transport of China.
We tested a range of culverts with two representative amphibian species, the Chinese brown frog, Rana chensinensis, and the Asiatic toad, Bufo gargarizans, both of which suffer severe rates of road mortality in Northeast China. We used experimental arrays of 10m-long culverts of various size (circular culverts with a diameter of 0.5, 1.0 or 1.5 m and box culverts with heights and widths of 0.5, 1.0 or 1.5 m) and substrate type (soil, concrete, and metal) to identify the preferences of both species. In each trial, the size and type of culvert varied, but the substrate type (soil, concrete or metal) of all six culverts remained the same. We conducted our experiments during the May to September migratory season in 2016 and 2017.
In each trial, we placed 30 individuals of either the Chinese brown frog or Asiatic toad in the central arena of six culverts and counted the number of individuals that passed through or remained inside each culvert after 40 minutes. Each trial was repeated three times. Altogether, we ran the experiment 21 times for Chinese brown frogs and six times for the Asiatic toad.
Design of the experimental arenas to determine the preferences of amphibians for different culverts
To assess their ability to climb slopes of different angles, we placed 10 amphibians into concrete ditches with slopes of either 45°, 60° or 75° and counted the number that escaped within 15 min. We repeated these trials with the Chinese brown frog eight times with slopes at 45°, 12 times at 60° and eight times at 75°. For the Asiatic toad, we repeated the trial three times with slopes at 45°, six times at 60°, and three times at 75°.
We were also very interested to determine the minimum height for fencing to keep these species off the road and direct them towards underpasses. However, we only investigated fence height for Chinese brown frogs because they can jump much higher than the Asiatic toad. We placed 10 frogs in the center of a fenced arena constructed and counted the number that jumped out within 15 min. We ran 10 trials with fences at a height of 40 or 37 cm, and nine trials with fences at a height of 34 or 31 cm.
Asiatic toads being released in the central arena of an experimental array of six different culverts
The results revealed that the Chinese brown frog preferred mid- and large-sized culverts as well as culverts with a soil substrate, while size appeared to have no effect on Asiatic toad. Results were less conclusive for the Asiatic toad, but encouraging signs gave us enough information to design culverts for further testing in actual road projects, which are currently underway. We concluded that square culverts with soil substrates and a height and width of at least 1 m, and accompanied by a ≥ 0.4 m high guide drift fence and ≤ 45°gradient on the roadside ditch wall would best facilitate road crossings for both species and likely for other amphibian species in Northeast China.
Author information:
Dr. Yun Wang, China Academy of Transportation Sciences
Email: wangyun80314@163.com
Source:
Yun Wang, Jiayu Lan, Hongping Zhou, Lei Guan, Yudi Wang, Yongshun Han, Jiapeng Qu, Syed Asifullah Shah, and Yaping Kong (2019). Investigating the effectiveness of road-related mitigation measures under semi-controlled conditions: a case study on Asian amphibians. Asian Herpetological Research, 2019,10(1), Pages 62-68
Article: http://www.ahr-journal.com/en/oa/DArticle.aspx?type=view&id=20190108
Editor:
Rodney van der Ree
Cite this summary:
Wang, Y. 2021. Designing and testing under-road tunnels for Asian amphibians. Edited by van der Ree, R. TransportEcology.info, Accessed at: https://transportecology.info/research/designing-testing-tunnels-asian-amphibians [Date accessed].