Samuli Heikkinen

DISPERSAL IN AN EXPANDING WOLF POPULATION IN FINLAND

Abstract Dispersal influences distribution and genetic structure of animal populations. Dispersal in expanding wolf (Canis lupus) populations is not well documented, especially in Europe, where no studies of dispersal based on marked wolves are available. We studied the dispersal of wolves in Finland, where a peripheral wolf population (160–180 animals) increased and expanded during 1998–2004. We equipped 60 wolves from 8 neighboring wolf pack territories with radio or GPS transmitters in east-central Finland during 1998–2004, and at least 30 wolves (50%) dispersed from the home territory. Additional information was collected by detecting the natal pack of captured wolves with multilocus microsatellite genotyping and paternity analysis. In the study area, the directions formed a sun-ray pattern. Wolves usually departed their home territory as pups and yearlings, and in unimodal seasonal fashion. The dispersal distance (median 98.5, range 35–445 km) did not differ by sex (P = 0.342). Long-distance travelers (>200 km) were found only among wolves that departed at the age of 10–12 months. Survival was linked to the direction of dispersal. All marked wolves that dispersed to reindeer management areas in the north were shot before being able to reproduce, whereas elsewhere, the majority of dispersers (10 of 16) reproduced.

Predation on European wild forest reindeer (Rangifer tarandus) by wolves (Canis lupus) in Finland

It is generally accepted that predation by wolves Canis lupus is one of the major factors limiting densities of woodland caribou Rangifer tarandus caribou in North America. Conversely, little is known about the role of European wild forest reindeer R. t. fennicus as wolf prey, or about the influence of wolf predation on populations of this rare subspecies. This relationship was examined in east-central Finland, where wild forest reindeer coexist with moose Alces alces at a numerical ratio of c. 1 reindeer to 1.5 moose. During the study, moose were clearly the primary prey of wolves. Reindeer were, however, an important part of wolf diet in summer, autumn and early winter, when their remains comprised roughly 20–50% of all food items identified in wolf scats. Wolves exhibited a slight preference for reindeer over moose as prey during early winter (November–December) when the reindeer were moving towards their wintering ranges. Virtually no reindeer were killed by wolves during midwinter (January–March). This held also for a pack whose territory was located in the middle of the wintering range of reindeer, where reindeer outnumbered moose during the winter months. After the approximate ratio of wolves to reindeer increased from 0.004 (1998) to 0.02 (2000), wolf predation became the most common source of mortality (50%) for reindeer. The annual net increase in the reindeer population decreased from 13% to 7% because of increased wolf predation. The results indicate that wolf predation was an important factor limiting reindeer population growth. Wolves were, however, unable to prevent entirely the number of reindeer from increasing, partly owing to behavioural traits used by reindeer during winter and calving times.

Habitat selection of adult moose Alces alces at two spatial scales in central Finland

The habitat selection criteria of moose Alces alces at several scales are the basic sets of information needed in moose management planning. We studied moose habitat use in central Finland during 1993–1996 using data from radio collared moose, satellite image based forest and land cover data, and applied the principles of compositional analysis. The habitat compositions of 54 home ranges (10 males during summer, six males during winter, 23 females during summer and 15 females during winter) were first compared with the overall landscape. The habitat compositions around moose locations within their home ranges were then compared with the habitat composition of the home range. Seasons and sexes were compared at both scales. In summer, there was only a slight difference between moose home ranges and the overall landscape. Based on tree species composition, home ranges are located in slightly more fertile areas than the overall landscape. Within their home ranges, moose favoured non-pine dominated habitats and mature forests, and avoided human settlements. In winter, the moose home ranges included significantly more pine-dominated plantations and other young successional stages than the overall landscape. The role of pine-dominated peatland forests/ shrub land was especially pronounced in winter. Winter home ranges included less agricultural land and human settlements than the overall landscape, probably due to the more distant location of important winter habitats from man-made landscapes. Within the home ranges, both sexes used non-pine dominated habitats more, and mature forests and human settlements less than expected. At the home range scale, there were no statistical differences between the sexes with respect to habitat use in either season. Within their home ranges, males and females used slightly different habitats during both seasons, suggesting spatially segregated habitat use by the individual sexes. The difference is more clear in winter when males tend to use more pine-dominated, young successional habitats than females. Compared to the situation in the summer, winter ranges are located in slightly more pine-dominated habitats with fewer settlements and agricultural fields. The shift in habitat use between the two seasons is more pronounced with respect to habitat use within the home range. Our results indicate that moose habitat selection criteria vary among different hierarchical levels of selection. We stress the importance of multi-scale assessment of the habitat and other resource selection of animals.

Interactions between Wolves Canis lupus and Dogs C. familiaris in Finland

We examined wolf Canis lupus attacks on domestic dogs C. familiaris in six Finnish wolf territories occupied by mated pairs and packs. Most incidents (76%, N = 21 confirmed cases) took place inside one territory. The wolves mostly (70%) attacked dogs in house yards. It appeared that wolves in the territory were actively seeking for dogs rather than killing them as a result of random encounters. A strong tendency to attack dogs seemed to be adopted by pups born to the wolf pack. We did not find evidence that the density of primary prey or resident dogs were associated with the risk of wolf attacks.

Dispersal Behavior and the Connectivity Between Wolf Populations in Northern Europe

Abstract The isolated gray wolf (Canis lupus) population of the Scandinavian Peninsular is suffering from inbreeding depression. We studied dispersal of 35 wolves fitted with very high frequency (20) or Global Positioning System–global system for mobile (15) radiocollars in the neighboring Finnish wolf population. The growing wolf population in Finland has high numbers of dispersing individuals that could potentially disperse into the Scandinavian population. About half (53%) of the dispersing wolves moved total distances that could have reached the Scandinavian population if they had been straight-line moves, but because of the irregular pattern of movements, we detected no wolves successfully dispersing to the Scandinavian population. Dispersal to the Scandinavian population was also limited by high mortality of wolves in reindeer (Rangifer tarandus) management areas and by dispersal to Bothnian Bay at times of the year when ice was not present. We suggest that when a small wolf population is separated from source populations by distance, barriers, and human exploitation, wildlife managers could promote the populations viability by limiting harvest in the peripheral areas or by introducing wolves from the source population.

Tracks in snow and population size estimation: the wolf Canis lupus in Finland

The estimation of large carnivore populations presents major logistical challenges. We examined trends in the wolf Canis lupus population in Finland using two independent methods. We compared track indices from an annual wildlife winter census based on a constant, nationwide network of transect lines (wildlife triangles) with the number of reproductions confirmed to occur in the same year during 1996 to 2009. Nationwide, and in the eastern management zone, which is the core area of Finnish wolves, the frequency of wolf tracks in wildlife triangles (% of all triangles counted in a given year having wolf tracks) predicted quite well the log transformed number of reproductions taken place in these areas (adjusted R2-values for linear regression models 0.59 and 0.68, respectively), while not for the western management zone (R2 = 0.38). However, although mean wolf densities were low (< 1 wolf/1000 km2 nationwide and <3 wolves/1000 km2 in the eastern zone), track indices could detect the major trends in Finlands wolf population. A clear reason for this was the substantial changes in population size during the study period.

Problem brown bears Ursus arctos in Finland in relation to bear feeding for tourism purposes and the density of bears and humans

The practice of feeding brown bears Ursus arctos for recreational purposes is common in the easternmost areas of Finland, but this may, however, result in human-habituated bears. From 1995 to 2008, 3% of all bears killed by humans (N = 1,108 bears) in Finland represented incidents where bears were either killed for reasons of human safety under a license issued by the police or as a result of actual emergency situations where bears were shot in self defence. We constructed binary logistic regression models for comparing bears shot under police license and in self defence with bears killed in regular sport hunting by using the sex of the bear, human density, bear observation density and the distance from the nearest feeding site as independent variables. High human density was the most important factor differentiating bears shot under a license issued by police from bears killed in sport hunting. The difference in human density was largest for places located far from feeding sites. Increasing distance from feeding sites differentiated bears shot under police license and in self defence from sport hunted bears. The sex of the bears and the density of bear observation were more weakly associated with the category of shooting. Our study did not provide evidence that bear feeding for recreational purposes is associated with the nuisance-bear problem in Finland. Nevertheless, some risks for human safety might be associated with artificial bear feeding for tourism purposes. If the practice of feeding bears continues to be accepted by Finnish legislation, game management should include an action plan for occasions when bears visiting feeding sites will lose their wariness of humans.

European Wild Forest Reindeer and Wolves: Endangered Prey and Predators

Managers are sometimes faced with a situation where one endangered species increases the vulnerability of another one. According to our late-winter helicopter survey of Finlands two small populations of wild-forest reindeer (Rangifer tarandus fennicus), the eastern one decreased by half during the last 7 years. This is probably due to the return of the wolf (Canis lupus) to the area. Our data show that the annual recruitment rate of reindeer is strongly correlated with wolf density. Calf mortality was high and stable during the first months after birth. The wolf is classified as an endangered species in Finland. Thereby, our study area provides an example of a triggered situation in which a locally abundant, endangered predator increases the vulnerability of a threatened prey. There are basically two policy options for avoiding extinction: (1) to directly control the predation risk or (2) to reach further out into the ecosystem to control those factors that have led to high abundance of predators. One potential direct management action is increased wolf control in the primary summer home ranges of female reindeer. In the long term, wolf predation on wild-forest reindeer would decline if the abundance of moose (Alces alces) could be lowered, because high moose density supports high abundance of wolves. Another noteworthy option is the reintroduction of reindeer into regions where the wolf still exists at low densities.

Correction to: Balancing costs and confidence: volunteer-provided point observations, GPS telemetry and the genetic monitoring of Finland’s wolves

The original version of this article contained errors and corrected in this article.