Bears are simply voles writ large: social structure determines the mechanisms of intrinsic population regulation in mammals

Odden, Morten; Ims, Rolf A.; Støen, Ole‐Gunnar; Swenson, Jon E.; Andreassen, Harry P.

doi:10.1007/s00442-014-2892-z

Cited by 15 publications

(17 citation statements)

References 90 publications

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“…Reproduction is first enhanced because the benefits of sharing space (e.g., protection against infanticide) outpace the costs (e.g., competition for food). In the latter phase, intensified crowding slows down reproduction, and the crash is caused by predation of dominant males, which disrupts social groups and further decreases survival (Andreassen & Gundersen, ; Ims & Andreassen, ; Odden, Ims, Støen, Swenson, & Andreassen, ). Similar sets of intrinsic factors might be responsible for population regulation across a variety of territorial mammals (Odden et al., ).…”

Section: Discussionmentioning

confidence: 99%

Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Bogdziewicz

Zwolak

Redosh

et al. 2016

Ecology and Evolution

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Home range size generally decreases with increasing population density, but testing how this relationship is influenced by other factors (e.g., food availability, kin structure) is a difficult task. We used spatially explicit capture–recapture models to examine how home range size varies with population density in the yellow‐necked mouse (Apodemus flavicollis). The relationship between population density and home range size was studied at two distinct phases of population fluctuations induced by beech (Fagus sylvatica) masting: post‐mast peak in abundance (first summer after mast, n = 2) and subsequent crash (second summer after mast, n = 2). We live‐trapped mice from June to September to avoid the confounding effects of autumn seedfall on home range size. In accordance with general predictions, we found that home range size was negatively associated with population density. However, after controlling for the effect of density, home ranges of mice were larger in post‐mast years than during the crash phase. This indicates a higher spatial overlap among neighbors in post‐mast years. We suggest that the increased spatial overlap is caused by negative density‐dependent dispersal that leads to high relatedness of individuals within population in the peak phase of the cycle.

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Section: Discussionmentioning

confidence: 99%

Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Bogdziewicz

Zwolak

Redosh

et al. 2016

Ecology and Evolution

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“…Species with strong social structures are often more prone to experience some kind of intrinsic population regulation (Odden et al . ). In such social systems, extrinsic factors (e.g.…”

Section: Introductionmentioning

confidence: 97%

“…Population regulation is often described through intrinsic or extrinsic population processes. Species with strong social structures are often more prone to experience some kind of intrinsic population regulation (Odden et al 2014). In such social systems, extrinsic factors (e.g.…”

Section: Introductionmentioning

confidence: 99%

Let's stay together? Intrinsic and extrinsic factors involved in pair bond dissolution in a recolonizing wolf population

Milleret¹,

Wabakken²,

Liberg

et al. 2016

Journal of Animal Ecology

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Summary For socially monogamous species, breeder bond dissolution has important consequences for population dynamics, but the extent to which extrinsic or intrinsic population factors causes pair dissolution remain poorly understood, especially among carnivores.Using an extensive life‐history data set, a survival analysis and competing risks framework, we examined the fate of 153 different wolf (Canis lupus) pairs in the recolonizing Scandinavian wolf population, during 14 winters of snow tracking and DNA monitoring.Wolf pair dissolution was generally linked to a mortality event and was strongly affected by extrinsic (i.e. anthropogenic) causes. No divorce was observed, and among the pair dissolution where causes have been identified, death of one or both wolves was always involved. Median time from pair formation to pair dissolution was three consecutive winters (i.e. approximately 2 years). Pair dissolution was mostly human‐related, primarily caused by legal control actions (36·7%), verified poaching (9·2%) and traffic‐related causes (2·1%). Intrinsic factors, such as disease and age, accounted for only 7·7% of pair dissolutions. The remaining 44·3% of dissolution events were from unknown causes, but we argue that a large portion could be explained by an additional source of human‐caused mortality, cryptic poaching.Extrinsic population factors, such as variables describing the geographical location of the pair, had a stronger effect on risk of pair dissolution compared to anthropogenic landscape characteristics. Population intrinsic factors, such as the inbreeding coefficient of the male pair member, had a negative effect on pair bond duration. The mechanism behind this result remains unknown, but might be explained by lower survival of inbred males or more complex inbreeding effects mediated by behaviour.Our study provides quantitative estimates of breeder bond duration in a social carnivore and highlights the effect of extrinsic (i.e. anthropogenic) and intrinsic factors (i.e. inbreeding) involved in wolf pair bond duration. Unlike the effects of intrinsic and extrinsic factors that are commonly reported on individual survival or population growth, here we provide quantitative estimates of their potential effect on the social unit of the population, the wolf pair.

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“…This is most pronounced in female kin aggregations, where females may exclude unrelated females through “social fences,” i.e. increasing density results in increasing aggression between members of different female aggregations during dispersal (Hestbeck, ; Odden, Ims, Stoen, Swenson, & Andreassen, ; Støen et al., ). Our results did not provide evidence for social fences in modulating spatial responses, as bear density was not retained in the best model for the female–female dyad and relatedness did not explain changes in the magnitude of a female survivor's use of a female casualty's HR over time.…”

Section: Discussionmentioning

confidence: 99%

Sociodemographic factors modulate the spatial response of brown bears to vacancies created by hunting

Frank

Leclerc

Pelletier

et al. 2017

Journal of Animal Ecology

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Abstract1. There is a growing recognition of the importance of indirect effects from hunting on wildlife populations, e.g. social and behavioural changes due to harvest, which occur after the initial offtake. Nonetheless, little is known about how the removal of members of a population influences the spatial configuration of the survivors.2. We studied how surviving brown bears (Ursus arctos) used former home ranges that had belonged to casualties of the annual bear hunting season in southcentral Sweden (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015). We used resource selection functions to explore the effects of the casualty's and survivor's sex, age and their pairwise genetic relatedness, population density and hunting intensity on survivors' spatial responses to vacated home ranges.3. We tested the competitive release hypothesis, whereby survivors that increase their use of a killed bear's home range are presumed to have been released from intraspecific competition. We found strong support for this hypothesis, as survivors of the same sex as the casualty consistently increased their use of its vacant home range. Patterns were less pronounced or absent when the survivor and casualty were of opposite sex.4. Genetic relatedness between the survivor and the casualty emerged as the most important factor explaining increased use of vacated male home ranges by males, with a stronger response from survivors of lower relatedness. Relatedness was also important for females, but it did not influence use following removal; female survivors used home ranges of higher related female casualties more, both before and after death. Spatial responses by survivors were further influenced by bear age, population density and hunting intensity.5. We have shown that survivors exhibit a spatial response to vacated home ranges caused by hunting casualties, even in nonterritorial species such as the brown bear.This spatial reorganization can have unintended consequences for population dynamics and interfere with management goals. Altogether, our results underscore the need to better understand the short-and long-term indirect effects of hunting on animal social structure and their resulting distribution in space.

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Bears are simply voles writ large: social structure determines the mechanisms of intrinsic population regulation in mammals

Cited by 15 publications

References 90 publications

Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Let's stay together? Intrinsic and extrinsic factors involved in pair bond dissolution in a recolonizing wolf population

Sociodemographic factors modulate the spatial response of brown bears to vacancies created by hunting

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