Overview:
Space use and territoriality
Space use and territoriality influence population structure and dynamics and is therefore an important aspect in understanding the ecology of animals. Mean male home ranges is 669 km2, which is significantly larger than female homes ranges (mean 170 km2). Male wolverines exhibit intrasexual territoriality, with male home ranges totally exclusive of other males but completely encompassing or including a portion of up to five different females' territories. Female territories are either exclusive or with very little overlap. Both males and females regularly patrol their territories, year-round. Territory sizes can expand or contract as dispersing wolverines immigrate into new areas, or other adults die. Female wolverines have been documented defending overly large territories, and later bequeathing all or a portion of those territories to their daughters.
Snow Requirements
Until very recently, it was believed that successful wolverine populations required persistent spring snow-cover, which most wolverine females use to construct natal dens. However, in recent years the Swedish wolverine population has expanded southwards for a variety of potential factors, and has begun establishing successfully-reproducing populations in non-alpine forest areas with little-to-no snow cover during the spring denning period. Research is ongoing, but this phenomenon could potentially have significant implications for management and conservation planning worldwide.
Space use and territoriality
Space use and territoriality influence population structure and dynamics and is therefore an important aspect in understanding the ecology of animals. Mean male home ranges is 669 km2, which is significantly larger than female homes ranges (mean 170 km2). Male wolverines exhibit intrasexual territoriality, with male home ranges totally exclusive of other males but completely encompassing or including a portion of up to five different females' territories. Female territories are either exclusive or with very little overlap. Both males and females regularly patrol their territories, year-round. Territory sizes can expand or contract as dispersing wolverines immigrate into new areas, or other adults die. Female wolverines have been documented defending overly large territories, and later bequeathing all or a portion of those territories to their daughters.
Snow Requirements
Until very recently, it was believed that successful wolverine populations required persistent spring snow-cover, which most wolverine females use to construct natal dens. However, in recent years the Swedish wolverine population has expanded southwards for a variety of potential factors, and has begun establishing successfully-reproducing populations in non-alpine forest areas with little-to-no snow cover during the spring denning period. Research is ongoing, but this phenomenon could potentially have significant implications for management and conservation planning worldwide.
Mating system
Wolverines exhibit a polygamous mating system as some males produce offspring with more than one female in a single year. Females often reproduced with the same male in subsequent breeding years, but sometimes change their partner, potentially as a consequence of a change in the territory-holding male in the area. In the majority of litters, siblings were unambiguously assigned the same father, indicating that multiple paternity is rare. In one study, of 23 breeding pairs for which telemetry data were available, 20 had overlapping home ranges, suggesting that pair formation generally is consistent with the territories held by wolverine males and females.
Wolverines exhibit a polygamous mating system as some males produce offspring with more than one female in a single year. Females often reproduced with the same male in subsequent breeding years, but sometimes change their partner, potentially as a consequence of a change in the territory-holding male in the area. In the majority of litters, siblings were unambiguously assigned the same father, indicating that multiple paternity is rare. In one study, of 23 breeding pairs for which telemetry data were available, 20 had overlapping home ranges, suggesting that pair formation generally is consistent with the territories held by wolverine males and females.
Dispersal
Mean dispersal age for wolverines is 13 months for both males and females. Females display more variation in dispersal age (7–26 months) than males (7–18 months). Of the animals used in the dispersal analyses, all males and 69% of females dispersed. All sedentary females occupied their mother’s territory when she died or shifted territory, and no females dispersed from a territory vacated by their mother. For further and more recent information on territorial dynamics of wolverine females, see Aronsson 2009 (Student theses).
Competition for resources seemed to determine the female dispersal pattern, while competition for mates seemed to explain the male dispersal pattern. Dispersal distances averaged 51 km for males and 60 km for females. However, this is likely to be an underestimation, and indirect estimates of dispersal distances inferred from mother-offspring relationships suggested that wolverine males have the ability to disperse up to 500 km, and dispersal distances of more than 100 km were detected for females. Dispersal movement on average is immediately preceded by exploratory movements. The size of juvenile home ranges of males (85 km2) and females (81 km2) corresponds to the home-range area of denning females during the summer period. Wolverines have the capacity to recolonize gaps in the present distribution of the species in Scandinavia. Other factors, therefore, most likely explain the large proportion of vacant wolverine habitats.
Mean dispersal age for wolverines is 13 months for both males and females. Females display more variation in dispersal age (7–26 months) than males (7–18 months). Of the animals used in the dispersal analyses, all males and 69% of females dispersed. All sedentary females occupied their mother’s territory when she died or shifted territory, and no females dispersed from a territory vacated by their mother. For further and more recent information on territorial dynamics of wolverine females, see Aronsson 2009 (Student theses).
Competition for resources seemed to determine the female dispersal pattern, while competition for mates seemed to explain the male dispersal pattern. Dispersal distances averaged 51 km for males and 60 km for females. However, this is likely to be an underestimation, and indirect estimates of dispersal distances inferred from mother-offspring relationships suggested that wolverine males have the ability to disperse up to 500 km, and dispersal distances of more than 100 km were detected for females. Dispersal movement on average is immediately preceded by exploratory movements. The size of juvenile home ranges of males (85 km2) and females (81 km2) corresponds to the home-range area of denning females during the summer period. Wolverines have the capacity to recolonize gaps in the present distribution of the species in Scandinavia. Other factors, therefore, most likely explain the large proportion of vacant wolverine habitats.
Territory Fidelity (2018):
We examined between-year territorial fidelity in wolverines, using location data from 47 individuals collected during 1993–2013 in northern Sweden, to assess the stability of the spatial organization of this solitary carnivore. For females, the study also determined residency status from one year to the next. Both males and females showed higher fidelity at the total territory level compared to more intensively used core areas. In 86% of the yearly residency status estimates, the female remained stationary. In the remaining 14% of the cases, females either vacated their territory (8% of residency statuses) or expanded into a neighbouring territory (6% of residency statuses). The study also documented six cases of breeding dispersal, representing one of the few known cases of breeding dispersal in long-lived large mammals.
Aronsson, M. & Persson, J. 2018. Female breeding dispersal in wolverines, a solitary carnivore with high territorial fidelity. European Journal of Wildlife Research. https://doi.org/10.1007/s10344-018-1164-3. PDF
Population Growth In Areas Without Persistent Spring Snow-Cover (2017):
Official wolverine management and monitoring in Sweden focuses on alpine reindeer husbandry areas, where associated depredation conflicts have been the highest. However, this focus ignores a potential southwards population expansion because current monitoring relies on snow-based tracking methods that are not applicable outside of northern alpine areas. This study uses available data from 1996 to 2014 in Sweden to assess wolverine distribution trends in relation to national management goals and evaluates current monitoring methods against non-snow-reliant techniques in their efficiency in detecting wolverine presence at the southern periphery of the species’ distribution. The study finds that national management decisions are being made based on incomplete information, as approximately one-third of wolverines’ range in Sweden is not included in official estimates and exists south of reindeer husbandry areas. The study also suggests that the relationship between wolverine distribution and snow cover may be less strict than previously hypothesized, as the southern territories do not include persistent spring snow cover.
Aronsson, M. & Persson, J. 2017. Mismatch between goals and the scale of actions constrain adaptive carnivore management: the case of the wolverine in Sweden. Animal Conservation 20: 261-269. PDF
Habitat Selection (2013):
In a mountainous area in Sweden, we explored hierarchical habitat selection in GPS-collared individuals of two sympatric large carnivore species: the Eurasian lynx, and the wolverine. Both lynx and wolverines selected for steep and rugged terrain in mountainous birch forest and in heaths independent of scale and available habitats. However, the selection of lynx for their preferred habitats was stronger when they were forming home ranges and they selected the same habitats within their home ranges independent of home range composition. Wolverines displayed a greater variability when selecting home ranges and habitat selection also varied with home range composition. Both species selected for habitats that promote survival through limited encounters with humans, but which also are rich in prey, and selection for these habitats was accordingly stronger in winter. We suggest that the observed differences between the species result primarily from different foraging strategies but may also depend on differences in ranging and resting behavior, home range size, and relative density of each species.
Rauset, G.R., Mattisson, J., Andrén, H., Chapron, G., and Persson, J. 2013. When species’ ranges meet: assessing differences in habitat selection between sympatric large carnivores. Oecologia 172: 701-711. PDF
We examined between-year territorial fidelity in wolverines, using location data from 47 individuals collected during 1993–2013 in northern Sweden, to assess the stability of the spatial organization of this solitary carnivore. For females, the study also determined residency status from one year to the next. Both males and females showed higher fidelity at the total territory level compared to more intensively used core areas. In 86% of the yearly residency status estimates, the female remained stationary. In the remaining 14% of the cases, females either vacated their territory (8% of residency statuses) or expanded into a neighbouring territory (6% of residency statuses). The study also documented six cases of breeding dispersal, representing one of the few known cases of breeding dispersal in long-lived large mammals.
Aronsson, M. & Persson, J. 2018. Female breeding dispersal in wolverines, a solitary carnivore with high territorial fidelity. European Journal of Wildlife Research. https://doi.org/10.1007/s10344-018-1164-3. PDF
Population Growth In Areas Without Persistent Spring Snow-Cover (2017):
Official wolverine management and monitoring in Sweden focuses on alpine reindeer husbandry areas, where associated depredation conflicts have been the highest. However, this focus ignores a potential southwards population expansion because current monitoring relies on snow-based tracking methods that are not applicable outside of northern alpine areas. This study uses available data from 1996 to 2014 in Sweden to assess wolverine distribution trends in relation to national management goals and evaluates current monitoring methods against non-snow-reliant techniques in their efficiency in detecting wolverine presence at the southern periphery of the species’ distribution. The study finds that national management decisions are being made based on incomplete information, as approximately one-third of wolverines’ range in Sweden is not included in official estimates and exists south of reindeer husbandry areas. The study also suggests that the relationship between wolverine distribution and snow cover may be less strict than previously hypothesized, as the southern territories do not include persistent spring snow cover.
Aronsson, M. & Persson, J. 2017. Mismatch between goals and the scale of actions constrain adaptive carnivore management: the case of the wolverine in Sweden. Animal Conservation 20: 261-269. PDF
Habitat Selection (2013):
In a mountainous area in Sweden, we explored hierarchical habitat selection in GPS-collared individuals of two sympatric large carnivore species: the Eurasian lynx, and the wolverine. Both lynx and wolverines selected for steep and rugged terrain in mountainous birch forest and in heaths independent of scale and available habitats. However, the selection of lynx for their preferred habitats was stronger when they were forming home ranges and they selected the same habitats within their home ranges independent of home range composition. Wolverines displayed a greater variability when selecting home ranges and habitat selection also varied with home range composition. Both species selected for habitats that promote survival through limited encounters with humans, but which also are rich in prey, and selection for these habitats was accordingly stronger in winter. We suggest that the observed differences between the species result primarily from different foraging strategies but may also depend on differences in ranging and resting behavior, home range size, and relative density of each species.
Rauset, G.R., Mattisson, J., Andrén, H., Chapron, G., and Persson, J. 2013. When species’ ranges meet: assessing differences in habitat selection between sympatric large carnivores. Oecologia 172: 701-711. PDF
Spatial & Temporal Space Use in Northern Scandinavia (2010):
We investigated spatial and temporal space use of wolverines in northern Scandinavia. We estimated home ranges of 24 radio-marked individuals (17 females and seven males). Male home ranges (mean 669 km2) were significantly larger than female home ranges (mean 170 km2) and encompassed or included parts of up to five different females. Home range sizes of reproducing (170 km2) and barren (171 km2) adult females did not differ. Wolverines in Scandinavia exhibit intrasexual territoriality, with male home ranges totally exclusive and female home ranges either exclusive or with little home range overlap. Overlap between wolverine territories is most likely explained by intrasexual tolerance and kinship.
Persson, J., Wedholm, P. & Segerström, P. 2010. Space use and territoriality of wolverines (Gulo gulo) in northern Scandinavia. European Journal of Wildlife Research. 56 (1): 49-57. PDF
Mating System & Home Range Overlap (2007):
In this study, we use 20 microsatellite loci for paternity testing in 145 wolverine offspring with known mothers. Samples were collected over >10 years in two Scandinavian populations, mainly in connection with radio-telemetry studies and as part of long-term population monitoring. In total, 51% of the offspring were assigned a father. Our results demonstrate that the wolverine exhibits a polygamous mating system as some males were shown to produce offspring with more than one female in a single year. Females often reproduced with the same male in subsequent breeding years, but sometimes changed their partner, potentially as a consequence of a change in the territory-holding male in the area. In the majority of litters, siblings were unambiguously assigned the same father, indicating that multiple paternity is rare. 87% of had overlapping home ranges, suggesting that pair formation generally is consistent with the territories held by wolverine males and females.
Hedmark, E., Persson, J., Landa, A. & Segerström, P. 2007. Paternity and mating system in wolverines. Wildlife Biology 3 (Suppl. 2): 13-30. PDF
Immigration and Dispersal Counteracting Genetic Erosion (2004):
The southern Norwegian wolverine population was considered functionally extinct in the 1960s but has partly recovered in recent years. We report on a large-scale population monitoring project assessing these parameters through genetic tagging of individuals, with feces as the source of DNA. Sixty-eight different individuals were detected among 147 successfully genotyped samples collected in 2000 and 2001. A capture-recapture estimate based on the observed resampling rates suggested a population size of 89 wolverines, which is approximately 35% higher than an estimate of 64 obtained from the number of active natal dens. Indirect estimates of dispersal distances inferred from mother-offspring relationships suggested that wolverine males have the ability to disperse up to 500 km, and dispersal distances of more than 100 km were detected for females. Bayesian clustering analysis and subsequent assessment of individual relationships suggest that immigrants from northern Scandinavia have contributed and still contribute to the southern Norwegian gene pool, counteracting genetic erosion and reducing the risk of inbreeding depression.
Flagstad, Ö., Hedmark, E., Landa, A., Brøseth, H., Persson, J., Andersen, R., Segerström, P. & Ellegren, H. 2004. Colonization history and non-invasive monitoring of a re-established wolverine (Gulo gulo) population. Conservation Biology 18(3): 1-13. PDF
Juvenile Dispersal and Home Range Size (2011):
We studied patterns of dispersal and sizes of home ranges of juvenile wolverines. Mean dispersal age was 13 months for both male and female wolverines. Females displayed more variation in dispersal age (7–26 months) than males (7–18 months). Of the animals used in the dispersal analyses, all males and 69% of females dispersed. All sedentary females occupied their mother’s territory when she died or shifted territory, and no females dispersed from a territory vacated by their mother. Competition for resources seemed to determine the female dispersal pattern, while competition for mates seemed to explain the male dispersal pattern. Eight cases of exploratory movements were observed, and on average, these immediately preceded dispersal movements. The size of juvenile home ranges of males and females corresponded to the home-range area of denning females during the summer period.
Vangen, K.M., Persson, J. Landa, A. Andersen, R. & Segerström, P. 2001. Characteristics of dispersal in wolverines. Canadian Journal of Zoology 79: 1641-1649. PDF
We investigated spatial and temporal space use of wolverines in northern Scandinavia. We estimated home ranges of 24 radio-marked individuals (17 females and seven males). Male home ranges (mean 669 km2) were significantly larger than female home ranges (mean 170 km2) and encompassed or included parts of up to five different females. Home range sizes of reproducing (170 km2) and barren (171 km2) adult females did not differ. Wolverines in Scandinavia exhibit intrasexual territoriality, with male home ranges totally exclusive and female home ranges either exclusive or with little home range overlap. Overlap between wolverine territories is most likely explained by intrasexual tolerance and kinship.
Persson, J., Wedholm, P. & Segerström, P. 2010. Space use and territoriality of wolverines (Gulo gulo) in northern Scandinavia. European Journal of Wildlife Research. 56 (1): 49-57. PDF
Mating System & Home Range Overlap (2007):
In this study, we use 20 microsatellite loci for paternity testing in 145 wolverine offspring with known mothers. Samples were collected over >10 years in two Scandinavian populations, mainly in connection with radio-telemetry studies and as part of long-term population monitoring. In total, 51% of the offspring were assigned a father. Our results demonstrate that the wolverine exhibits a polygamous mating system as some males were shown to produce offspring with more than one female in a single year. Females often reproduced with the same male in subsequent breeding years, but sometimes changed their partner, potentially as a consequence of a change in the territory-holding male in the area. In the majority of litters, siblings were unambiguously assigned the same father, indicating that multiple paternity is rare. 87% of had overlapping home ranges, suggesting that pair formation generally is consistent with the territories held by wolverine males and females.
Hedmark, E., Persson, J., Landa, A. & Segerström, P. 2007. Paternity and mating system in wolverines. Wildlife Biology 3 (Suppl. 2): 13-30. PDF
Immigration and Dispersal Counteracting Genetic Erosion (2004):
The southern Norwegian wolverine population was considered functionally extinct in the 1960s but has partly recovered in recent years. We report on a large-scale population monitoring project assessing these parameters through genetic tagging of individuals, with feces as the source of DNA. Sixty-eight different individuals were detected among 147 successfully genotyped samples collected in 2000 and 2001. A capture-recapture estimate based on the observed resampling rates suggested a population size of 89 wolverines, which is approximately 35% higher than an estimate of 64 obtained from the number of active natal dens. Indirect estimates of dispersal distances inferred from mother-offspring relationships suggested that wolverine males have the ability to disperse up to 500 km, and dispersal distances of more than 100 km were detected for females. Bayesian clustering analysis and subsequent assessment of individual relationships suggest that immigrants from northern Scandinavia have contributed and still contribute to the southern Norwegian gene pool, counteracting genetic erosion and reducing the risk of inbreeding depression.
Flagstad, Ö., Hedmark, E., Landa, A., Brøseth, H., Persson, J., Andersen, R., Segerström, P. & Ellegren, H. 2004. Colonization history and non-invasive monitoring of a re-established wolverine (Gulo gulo) population. Conservation Biology 18(3): 1-13. PDF
Juvenile Dispersal and Home Range Size (2011):
We studied patterns of dispersal and sizes of home ranges of juvenile wolverines. Mean dispersal age was 13 months for both male and female wolverines. Females displayed more variation in dispersal age (7–26 months) than males (7–18 months). Of the animals used in the dispersal analyses, all males and 69% of females dispersed. All sedentary females occupied their mother’s territory when she died or shifted territory, and no females dispersed from a territory vacated by their mother. Competition for resources seemed to determine the female dispersal pattern, while competition for mates seemed to explain the male dispersal pattern. Eight cases of exploratory movements were observed, and on average, these immediately preceded dispersal movements. The size of juvenile home ranges of males and females corresponded to the home-range area of denning females during the summer period.
Vangen, K.M., Persson, J. Landa, A. Andersen, R. & Segerström, P. 2001. Characteristics of dispersal in wolverines. Canadian Journal of Zoology 79: 1641-1649. PDF
