Individual study: Provision of inlets and ramps fail to prevent mammal losses by drowning along the Mittellandkanal near Woltorf, Niedersachen, Germany
Wietfeld J. (1984) The effectiveness of protection measures to prevent animal losses in blocked waters. Zeitschrift für Jagdwissenschaft, 30, 176-184
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Provide mammals with escape routes from canals
A before-and-after, site comparison study in 1978–1982 of a steep-sided canal in Germany (Wietfeld 1984) found that installing shallow-water inlets and ramps did not reduce mammal drownings. There was no evidence of large mammals leaving the canal by inlets or of a reduction in the number drowned after inlet establishment (after: 15 individuals drowned in one year; before: 11 drowned in two years). There was no evidence of small mammals using ramps as exits. There was no significant difference in the density of drowned small mammals on canal sections with and without ramps where the length of canal surveyed without ramps was twice the length surveyed with ramps: hamster Cricetus cricetus (with: 50; without: 80), common vole Microtus arvalis (with: 14; without: 25), water vole Arviola terrestris (with: four; without: seven). Inlets were shallow shelving exit points (250–500 m apart) established in spring 1979. Sand at eight inlet entrances was checked daily in September 1979, and April–May of 1980 and 1981 for mammal footprints. The canal was searched every 2–3 days for drowned animals before and after inlet establishment (1978–1980). Ramps (≤50 m apart) were installed in May 1982. Sand at ramp exits was checked daily over 20 days in August for small mammal footprints. Live-trapping was conducted over 13 days.
(Summarised by Nick Littlewood)