Dense road networks negatively affect wildlife in a number of ways: apart from direct effects such as traffic accidents, wildlife are also threatened indirectly through loss and/or fragmentation of their habitat. Passages (underpasses and overpasses) which allow animals to cross roads can help reduce these problems, but only if they fulfill certain criteria. In Germany, many of the passages built in the early 1990s were shown to be ineffective. This study (provides an overview of existing knowledge on effective game passages and) investigates the preference of fallow deer Dama dama for differently coloured underpass walls using a two-choice experiment.
The experiment was carried out in a 0.7 ha enclosure containing 20 fallow deer of varying sex and age.
A double tunnel was erected in the enclosure, each tunnel being 2 m high, 2 m wide and 8 m long. In order to encourage frequent use of the tunnels, a small area in front of one tunnel entrance was fenced off and fodder was provided in this area only. Deer could access the feeding area through the tunnel and a one-way gate but leave only through the tunnel. Movement of deer in the tunnels was registered by a photo-electric sensor which was read twice daily.
The preference of deer for six different tunnel colour schemes/designs was tested and the statistical significance of the results was assessed (Wilcoxon Test based on 10 readings per scheme). The six paired tunnels tested (including a control) were:
1) control- left and right tunnel without paint;
2) left tunnel 'agate grey', right tunnel pure white;
3) left tunnel 'deep black', right pure white;
4) left tunnel 'papyrus white' (off-white), right deep black base (80cm), above papyrus white;
5) left tunnel papyrus white, right papyrus white, with indirect light sources on ceiling;
6) left tunnel papyrus white, right papyrus white, with tree stumps distributed in tunnel.
In the trial, the deer showed a statistically significant preference for one tunnel over the other in four of the paired schemes: “grey vs. white” (scheme 2), white was preferred over grey; white was also preferred over black (scheme 3); the tunnel with the black base was preferentially used over the one without a black base (scheme 4); the illuminated tunnel (scheme 5) was strongly avoided. There was no significant difference in the usage of the tunnels under scheme 6.
The frequency of deer passing through the respective tunnels was as follows:
scheme 1: left 237, right 243
scheme 2: left 425, right 732
scheme 3: left 153, right 294
scheme 4: left 584, right 747
scheme 5: left 581, right 242
scheme 6: left 563, right 394
The results overall suggest a preference by fallow deer for underpasses with pale coloured walls and no illumination.
Note: If using or referring to this published study, please quote the original paper. This German language paper, translated and summarised for Conservation Evidence, has a basic English and French abstract, and is available at: http://www.springerlink.com/