Katja Holmala

Home ranges and densities of medium-sized carnivores in south-east Finland, with special reference to rabies spread.

Home ranges and densities of medium-sized carnivores were studied in south-east Finland by radio tracking. The species studied included potential vectors of rabies: the raccoon dogNyctereutes procyonoides (Gray, 1834), red foxVulpes vulpes (Linnaeus, 1758), European badgerMeles meles (Linnaeus, 1758) and domestic catFelis silvestris catus (Schreber, 1777). Home ranges of badgers were largest (mean 14.7 km2) and those of cats smallest (1.5 km2). Home ranges overlapped largely, both within and between species. Most home ranges were larger and population densities lower in south-east Finland compared with those in Western Europe. The pooled density of medium-sized carnivores with overlapping home ranges was, however, high, which may indicate a high risk of a rabies epizootic in this multi-host community. Rabies might also spread rapidly to new areas, because of the large home ranges and, consequently, long dispersal distances.

Rabies in northeastern Europe - the threat from invasive raccoon dogs.

The red fox (Vulpes vulpes) is the main terrestrial wildlife rabies vector in Europe. However, recently the raccoon dog (Nyctereutes procyonoides)—an invasive species originating from East Asia—has become increasingly important as secondary host, especially in the Baltic States. This imposes problems on neighboring rabies-free countries (such as Finland), where the density of each of the two vector species on its own might be too low to sustain a long-term rabies epizootic, but the community of vectors could be large enough to support a rabies epizootic. In this modeling study, we analyzed rabies epizootics in a community of foxes and raccoon dogs. We focused on the impact of density and behavioral differences (hibernation) between the two vector species. We found that rabies could persist in the community, even if the disease would not spread in the single vector species because its density was too low. Epizootics in the community were stronger than expected for single species, and raccoon dogs were usually the major rabies host. If raccoon dog territory density was high, invasive raccoon dogs could even outcompete native foxes because of apparent competition via the rabies virus. The enhancement in disease risk and disease intensity caused by raccoon dogs suggests that current strategies to control wildlife rabies in Europe should be reviewed, and that oral rabies vaccination also should target raccoon dogs after they emerge from hibernation.

Habitat use of Medium-Sized Carnivores in Southeast Finland — Key Habitats for Rabies Spread?

Understanding the dynamics of a disease spread requires information on various aspects of the ecology of vector species. The habitat selection and habitat use of raccoon dogs (Nyctereutes procyonoides), badgers (Meles meles), red foxes (Vulpes vulpes) and domestic cats (Felis silvestris catus) were studied in southeastern Finland between 2000 and 2004. The aim was to find out the habitats where these species are most likely to come into contact and possibly transmit diseases, such as rabies, to each other. Raccoon dogs and badgers showed preference for fields and deciduous forests in all scales studied. Raccoon dogs favoured also watersides in summer and young mixed forests in autumn. Foxes and cats showed more individual variation in their habitat selection/use. Analysis of the overlapping areas of seasonal home ranges further demonstrated the significance of deciduous forests and fields. These, and also young mixed forests and open areas, could be called the risky habitats in terms of rabies spread.

Landscape Features, Home-Range Size and Density of Northern Badgers (Meles meles)

Knowledge of badger density is important for their conservation especially in areas with low badger densities. Therefore, we aimed to build a simple model to estimate badger density in northern Europe on the basis of habitat characteristics. A radio-tracking study in southern Finland showed that habitat structure of the landscape affects home-range sizes of northern badgers. The data collected from the literature indicate that badger density and home-range size correlate negatively but the relationship was non-linear, with highest densities and smallest home ranges in England. Consequently, badger density can be estimated on the basis of habitat characteristics of the area: density is higher when the proportion of mixed forests is high and that of large spruce forests low and vice versa. Because other factors, such as hunting and predation may be involved, density values should be treated as rough estimates of the density in different landscapes in Finland.

Optimal radio-tracking strategy - The best results with the least effort?

We tested the need to radio-track nocturnal mammals, such as raccoon dogsNyctereutes procyonoides (Gray, 1834) and badgersMeles meles (Linnaeus, 1758), throughout the night for reliable estimates of home range size and habitat selection. We also tested the possibility to reduce the tracking effort by decreasing the number of tracking-nights. The results indicated that the locations collected before midnight gave good estimates of home range sizes but those collected after midnight or by reducing the number of tracking-nights resulted in smaller home ranges than those estimated using the total data. Thus, if one aims to estimate only the home range size, locations before midnight would be adequate. Locations of raccoon dogs taken only before or after midnight did not reveal all habitats, which were favoured on the basis of the total data. Although locations of badgers before midnight seemed to give correct results of habitat selection, we recommend radio-tracking also badgers at least few times through the night, because their core areas shifted during the night. In the case of badgers, but not of raccoon dogs, we obtained correct results of habitat selection by reducing the tracking effort by decreasing the number of tracking-nights.

Genetic evidence of female kin clusters in a continuous population of a solitary carnivore, the Eurasian lynx

Abstract Large terrestrial carnivores can sometimes display strong family bonds affecting the spatial distribution of related individuals. We studied the spatial genetic relatedness and family structure of female Eurasian lynx, continuously distributed in southern Finland. We hypothesized that closely related females form matrilineal assemblages, clustering together with relatives living in the neighboring areas. We evaluated this hypothesis using tissue samples of 133 legally harvested female lynx (from year 2007 to 2015), genotyped with 23 microsatellite markers, and tested for possible spatial genetic family structure using a combination of Bayesian clustering, spatial autocorrelation, and forensic genetic parentage analysis. The study population had three potential family genetic clusters, with a high degree of admixture and geographic overlap, and showed a weak but significant negative relationship between pairwise genetic and geographic distance. Moreover, parentage analysis indicated that 64% of the females had one or more close relatives (sister, mother, or daughter) within the study population. Individuals identified as close kin consistently assigned to the same putative family genetic cluster. They also were sampled closer geographically than females on average, although variation was large. Our results support the possibility that Eurasian lynx forms matrilineal assemblages, and comparisons with males are now required to further assess this hypothesis.