Medium-sized carnivores as predators, competitors and transmitters of disease

In 2005, a study began on the role of medium-sized carnivores, especially the raccoon dog, in the Finnish ecosystem. The raccoon dog is an alien species in Finland, sometimes preying on game animals like waterfowl, and competing with other medium-sized mammalian carnivores, especially the European badger. It is also a significant transmitter of parasites and diseases, such as rabies. The red fox is another medium-sized carnivore that transmits rabies.

Although they have been considered a threat to waterfowl, several recent studies have found that raccoon dogs do not feed on many birds. A predator removal experiment in Häme, southern Finland, found no evidence that raccoon dogs were harmful to game animals, but the impact of the species may vary between regions.

The distribution area of the raccoon dog and the European badger extends north to Finland. Due to global warming (causing shorter winters and hibernation periods), the abundance of both species may increase in this country and they may spread further north. A study conducted in Virolahti, southeast Finland, showed that the home ranges of raccoon dogs and European badgers overlap. They prefer similar habitats and sometimes use common dens. Their diets are also fairly similar. Hence, these species may compete for food or den sites with each other, especially in southern Finland, where populations are dense. On the northernmost border of the distribution area, where population densities are lower, the competition may be less significant.

European badgers are often difficult to capture, but before the spring thaw they start to move around and are caught more easily. The badger in the photo is anesthetized for collaring. Photo: Mervi Kunnasranta

The aim of the project was to study the impact of raccoon dogs on the native animals of Finland. Predation on waterfowl and competition with the European badger are investigated. Also, the habitat use and diet of both species and their interaction in different areas and different population densities are studied. We also examine the genetic structure of the raccoon dog and fox populations and the dispersal distances of young animals. In the case of a rabies epidemic, the dispersal of juveniles has a great impact on the spread of the disease.

The most important methods utilized in the study are radio tracking, scat analyses and DNA-analyses. The dens and latrines of these carnivores are mapped with the aid of trained dogs. The study areas are in Ruissalo, near Turku and in Tuulos, the province of Häme. Radio tracking of the animals in the urban environment of Turku is also planned.

A dog points to a raccoon dog latrine. Photo: Miina Auttila

Hundreds of DNA-samples have been collected from both raccoon dogs and foxes. With the help of samples, the genetic structure, the extent of inbreeding and the proportion of individuals originating in other areas are studied. Also the average dispersal distances of young individuals will be calculated.

Fieldwork was started in Ruissalo and Tuulos in the summer of 2005 for raccoon dog and in the summer of 2006 for the European badger. In the summer of 2005, 14 raccoon dogs were fitted with radio collars and in the summer of 2006, 11 raccoon dogs and 4 badgers were collared. In the spring of 2007, 10 more raccoon dogs and 9 European badgers were collared. In the summer of 2008 badgers were monitored both in Ruissalo and Tuulos, and data for 8 badgers were collected. Dens and latrines have been mapped and plenty of fecal samples have been collected from the latrines of both species.

Several students have assisted with the project: Päivi Immonen, Riitta Kumpulainen and Liina Seikola from the University of Turku and Miina Auttila from the University of Joensuu. Julia Schregel is responsible for the analysis of DNA samples, in cooperation with the University of Oulu. The city of Turku is also assisting the study.

Scientist in charge of project

Kaarina Kauhala
Turku Game and Fisheries Research
Itäinen Pitkäkatu 3
FI-20520 Turku, Finland
Phone +358 295 327 6921

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