Social structure of brown bear (Ursus arctos) in Eastern and Central Finland
1University of Oulu, Faculty of Science, Biology
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Oulu : A. Olejarz,
The brown bear is the largest carnivore living in Europe, is well represented in Finland with approx. 2000 individuals and is not in danger of extinction according to the annual census size estimation which is done by Luke (Natural Resource Institute Finland). However, this has not always been the case. At the beginning of the 20th century, the bear population in Finland was drastically reduced, mainly due to illegal bear killing such as hunting or to reindeer herder protecting reindeers in the north. After legal protection of bear started in the middle of the 20th century and closer monitoring of the bear population was established, there was increase in the bear population in Finland. Many bears have immigrated from the eastern Russia (mainly Karelia). Nowadays the bear population is mainly focused on the east, near the Russian border and in the central part of Finland.
The aim of this master thesis is to evaluate the social structure of the solitary living brown bear. The social structure was studied analyzing the relatedness of the brown bears and the overlap of the individual home ranges. It is believed that the higher the degree of kinship is, the more the home ranges of brown bears overlap. We measured the relatedness in two areas: In Eastern and Central Finland in order to study if there is difference in the social structure of brown bear between these two areas: We also used GPS coordinates from radio collared brown bears in order to calculate their home range size and the percentage of overlaps. A total number of 119 samples has been analyzed for their degree of genetic relationship. Furthermore, out of 119, 53 bears were marked with GPS collars.
According to the results the female’s brown bears are in Central Finland more closely related to each other than females in Eastern Finland. Male bears did not show the same significant relatedness difference between the two regions. One possible explanation might be that in eastern Finland a higher number of migrations can be observed between the Russian Karelian brown bear population and the eastern brown bear population. This leads to a higher gene flow and a higher density of brown bears in that area and less relatedness. Subadult male brown bears tends to disperse from natal area in order to find mates and to reduce the probability of inbreeding. This fact might be the reason that there was no difference in relatedness in males in the two regions.
In average the female home range was significantly smaller than in male brown bears in both regions. Also, the female home range in Eastern Finland was significantly smaller than the home ranges of female brown bears in Central Finland. The size of the home range of brown bears is influenced by several characteristics such as habitat quality, density and for female reproductivity. High food availability and high bear density lead to the fact that brown dears decrease their home range. In order to avoid infanticide of cubs, female bears try to protect their offspring against male brown bears by reducing contact with other brown bears and reducing home ranges.
A slightly positive correlation was detected among the relatedness and the degree of home range overlaps. The more closely the brown bears are related to each other the more home range overlaps were detected. These results can be explained by the fact that brown bears tend to be more social animals than expected. In order to increase their reproductive fitness brown bear mother’s, seem the accept home range overlap with a female offspring. With this social behavior she increases the probability that her offspring will survive successfully and on the other hand her own home range is better protected from other dominant and non-related females. Dominant females are usually older brown bears, so that it seems that age structure has also some influence for this social organization. This social interaction seems to be fluid and is not constant over years. Home ranges are strongly depended on habitat quality and reproduction status of the dominant female. Good food availability increases the acceptance in bears to overlap home ranges. Females that do not have a cup seem also roam to mate as males and thus to increase the home range overlaps.
Monitoring the social behavior of brown bears is recommended as the future will challenge large carnivores with new problems such as an increasing number of human settlements’ along with more fragmented areas because of infrastructure and increasing wild animal tourism in Finland.
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