Design of engineered modifications to allow frogs to escape from irrigation channels

• Published in: Ecological engineering 2020-09, Vol.156, p.105967, Article 105967
• Main Authors: Bi, Bo, Chen, Dan, Bi, Lidong, Rutherfurd, Ian, Luo, Zhaohui, Chen, Jing, Tang, Shuhai
• Format: Article
• Language: English
• Subjects: Agricultural engineering; Amphibians; Amphibious corridor; Aquatic reptiles; Body size; Channel lining; Channels; Concrete; Crushed stone; Design modifications; Ditches; Ecological engineering; Frog ecology; Frogs; Irrigation; Irrigation efficiency; Irrigation systems; Irrigation water; Population studies; Populations; Retrofitting; Substrates; Technicians; Water conveyance; Water delivery; Water flow
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2020.105967

Amphibian populations are under threat worldwide, one such threat is frogs getting trapped in concrete-lined irrigation channels. Earlier studies have found that concrete ditches are acting as barriers to animal movement, fragmenting habitat, and trapping amphibians. China has over 3,000,000 kms of irrigation channels and they are a major threat to frog populations. In this study, we assessed the capacity of a common Chinese frog, Rana nigromaculata, to escape from a typical concrete-lined irrigation channel via ‘frog-ways’ cut into the walls of the channel. The twelve different designs varied gradients, substrates and widths of the frog-ways. The results showed that these simple and inexpensive retrofits of irrigation channels are very effective at allowing the great majority of frogs to escape. Male frogs were more likely to be trapped in concrete ditches, probably due to their smaller body size. The best design was N11 (55 degree slopes, a crushed stone surface, and 100 cm width) that can help the frogs to successfully escape in just 1 min. Taking water conveyance efficiency of irrigation water delivery systems into consideration, we recommend a longitudinal design (the frog-way is parallel to the water-flow direction) of simple concrete with slopes less than 55° and crushed stone. The findings can serve as a reference for technicians involved in future ecological engineering designs of irrigation channels throughout the world. •A simple and cost-effective frog-way design for irrigation channels•Physical characteristics of frogs and differences in behavioral ability•Capacity of a common Chinese frog to escape from a typical irrigation channel•Effects of different designs with gradients, substrates and widths