Abstract
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.
Highlights
Population regulation is often described through intrinsic or extrinsic population processes
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 causes
Summary
Population regulation is often described through intrinsic or extrinsic population processes. Many threatened large carnivore populations are exposed to human-caused mortality events If these species have strong social bonding between members of a social unit, or experience sexually selected infanticide, such humancaused mortality can result in the social disruption of the group and/or the loss of dependent offspring (Brainerd et al 2008; Rutledge et al 2010; Gosselin et al 2015). Many species have evolved complex social systems, with a few dominant individuals monopolizing reproduction within the social unit (Macdonald 1983; Jennions & Macdonald 1994; Hatchwell 2009) This is the case for some threatened large carnivore species, from which several have developed a monogamous mating system. The duration of pair bonds has been suggested to have positive effects on reproductive performance of socially monogamous species by increasing pair familiarity (Sanchez-Macouzet, Rodriguez & Drummond 2014)
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