zoologisk serie 2007-3 Raccoon dogs in N orway – potential expansion rate , distribution area and management implications

Melis, C. , Nordgård, H. , Herfindal, I. , Kauhala, K. , Åhlen, P-A. , Strann, K.B. & Andersen, R. 2007. Raccoon dogs in Norway Potential expansion rate, distribution area and management implications. NTNU Vitenskapsmuseet Rapp. Zool. Ser. 2007, 3: 1-49. The raccoon dog Nyctereutes procyonoides is an alien carnivore species in Scandinavia. Native to eastern Asia, it was introduced in 1929 in the former Soviet Union and since then has spread and established itself in several European countries. In Norway, there have been few reliable observations of this species, all in the northernmost part of country. However, the species is well established in Finland and reproduction has been recorded in Sweden. The proposed climate change is likely to make Norway more suitable to raccoon dogs invasion, for this reason Norway should develop a management strategy for this species that is adequate to accomplish the threesteps system of the European Strategy on Invasive Alien Species: prevent-control-eradicate, in cooperation with Swedish and Finnish management authorities. Factors affecting body condition of juveniles have a great potential to influence recruitment and are thus vital in predicting the future distribution of this alien species. Therefore, we examined how climatic and plant phenology variables perform in explaining body condition of raccoon dogs by using Finnish data on fat deposition of juveniles. Climatic variables describing spring and late summer conditions explained a large amount of the variation in fat deposition. Conversely, plant phenology variables were not good predictors of body condition in juveniles. These variables, effective in explaining life-history traits in herbivores, might not reflect variation in food abundance and quality for omnivore species. We therefore propose that in Europe raccoon dogs will benefit from climate warming, because of a longer growing season. However, increased spring precipitation in form of snow at higher latitudes might compensate for the effect of greater primary productivity and set the border of their expansion towards harsher environments. By means of GIS modelling it is possible to produce a suitability map for raccoon dogs in Norway according to published data on habitat preference of the species in its introduced range. We modelled the spatial distribution of suitable habitat for raccoon dogs on the Scandinavian Peninsula based on the following ecological characteristics of the environment: habitat type, elevation and length of the growing season. This helped us identifying potential dispersal corridors for this species from Sweden to Norway. We also illustrate how expansion rate and distribution area might be affected by the proposed climate change according to two possible scenarios (10 and 35 day longer growing season). The different scenarios predicted that the population front will reach Norway in a time period ranging between 10 and 40 years. The invasion is expected to cover all potential areas in a range of 35 to 145 years. Our analyses indicate that a possible control program of the invasion should focus on the valleys connecting central Norway and Sweden in order to prevent both primary and secondary invasions effectively with the lowest management cost. We point out that it is crucial for both Norway and Sweden to develop a management strategy that focuses on these most likely dispersal corridors. Finland should concentrate their effort on the areas most likely to be source populations for dispersing animals. In these areas populations should be kept as low as possible in order to reduce number of dispersers.