Faunapassage at grade may connect habitats for wildlife otherwise separated by road barriers. Passage at grade is obviously much easier to construct requiring less resources compared to faunapassages underneath or on a bridge over the infrastructure barrier. This offers the possibility of establishing several faunapassage at grade instead of a few ecoducts or other resource-demanding passages at different grade. However, we expect faunapassage at grade to have somewhat reduced function, since wildlife is forced to co-use this type of multiuse passage with road traffic.
The type of species was most different in their use of two fauna passages of the same type but in different counties of Sweden (A and B). If only analyzing one object of a certain type of fauna passage, this could have generated contradicting conclusions regarding species specific requirements or limitations in relation to use of one particular type of fauna passage.
Both areas show a high abundance of fallow deer and red deer among their wildlife presence. In area A was fallow deer a frequent user of a passage at grade, but red deer was almost absent from even visiting the passage site. In contrast, in area B was red deer a frequent user of a passage at grade whereas fallow deer was almost absent.
Both grade passages are in forested areas, interspersed with crop fields in the surrounding areas. The design of the two passages is similar, and number of vehicles passing through are fairly the same between the two areas. However, there is of course several differences between the two areas. The answer behind why the results contrast in use by red deer and fallow deer between the two passages at grade, are certainly found within these differences.
In area A, there is a positive correlation in red deer crossings at the passage at grade and concurrent crossings from red deer under a nearby bridge of the same road, when comparing animal movements monthly. Red deer seem to cross at the passage at grade and under the nearby bridge mostly during the fall, overlapping with peak period of the rut. But more than four times more red deer crossings occur under the nearby bridge than through the passage at grade.
In area B, the reason behind very few visits by fallow deer at the passage is not well understood. One suggestion is that fallow deer has other well-established routs in the landscape that simply not encompass the passage site. If only considering the passage at grade in area A would suggest this type of passage is not suitable for red deer, whereas the same type of passage may be deemed unsuitable for fallow deer if only considering crossings in area B.
This highlights that to interpret the functionality of fauna passages, it is crucial to compare several different objects and to consider the surroundings at each passage site regarding alternative possibilities for wildlife crossings of infrastructure network within a home range scale in the landscape.