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Fitness costs of reproduction are expected when resources are limited. Costs drive the evolution of life‐history strategies and can affect population dynamics if females change their allocation of resources to reproduction. We studied fitness costs of reproduction in mountain ungulates in Alberta, Canada. We monitored two populations of bighorn sheep (Ovis canadensis) for 44 and 30 years, and one of mountain goats (Oreamnos americanus) for 30 years. Both species are highly iteroparous. Heterogeneity in individual reproductive potential makes fitness costs of reproduction difficult to detect and quantify without manipulations. In capital breeders, individual differences can be partly accounted for by considering body mass and other correlates of reproductive potential. Long‐term monitoring can reveal costs that only manifest under stressful conditions such as disease or resource scarcity. Despite individual differences in reproductive potential, we detected fitness costs of reproduction in females. Costs, in terms of mass gain and survival, are almost entirely born by subsequent offspring, as mothers prioritize their own maintenance and survival. Costs are greater for primiparous females, decrease with increasing body mass and increase as resource availability declines, and sons are costlier than daughters. Costs may increase for senescent females that appear to reduce allocation to reproduction. In bighorn sheep, costs mostly involve reduced mass gain and lower survival of subsequent offspring. In mountain goats, costs include reductions in mass gain, subsequent fecundity and juvenile survival. In males, fitness costs derive mostly from attempts to reproduce rather than from siring success and likely depend upon individual competitiveness. In the absence of selective harvests, dominant males may enjoy high fitness and possibly lower costs compared to subordinates. The conservative reproductive tactic of mountain ungulate females likely explains why density dependence mostly involves later primiparity and lower recruitment, but rarely affects adult survival. Future research will seek to better account for heterogeneity in reproductive potential, assess cumulative reproductive costs and investigate the potential effects of fathers on maternal allocation tactics. Fitness costs of reproduction affect the evolution of life histories, morphology and population dynamics of wild species. They are key to the consequences of different forms of exploitation. The authors combine 104 population‐years of monitoring two species of mountain ungulates to show that fitness costs are mostly transferred to subsequent offspring. Résumé Les coûts de la reproduction émergent lorsque les ressources sont limitées et influencent l’évolution des stratégies d’histoire de vie. Si les femelles modifient l’allocation des ressources dans la reproduction pour mitiger ces coûts, ils peuvent aussi affecter la dynamique de population. Nous avons étudié les coûts de la reproduction chez des ongulés en Alberta, Canada. Nous avons suivi deux populations de mouflons d’Amérique (Ovis canadensis) pour 44 et 30 ans, et une de chèvre de montagne (Oreamnos americanus) pour 30 ans. Ces deux espèces sont itéropares. L’hétérogénéité dans le potentiel reproducteur des individus peut masquer les coûts en fitness liés à la reproduction. Ils sont donc plus souvent détectables à l’aide de manipulation expérimentale. Chez les espèces avec reproduction « sur capital », il est possible de contrôler pour les différences individuelles en incluant des variables liées au potentiel reproducteur telles que la masse corporelle. Les suivis à long terme permettent de détecter des coûts qui se manifestent seulement lors de conditions environnementales défavorables. Malgré les différences en potentiel reproducteur, nous avons détecté des coûts chez les femelles. Ces coûts, tels qu’une réduction en croissance ou en survie, sont presque toujours subis par les jeunes nés lors d’épisodes de reproduction subséquents. En effet, les mères priorisent leur propre maintien et leur survie. Les coûts sont supérieurs pour les femelles primipares et dans les conditions défavorables. Ils sont plus faibles pour les femelles plus lourdes et il semble que les fils soient plus coûteux que les filles. Les coûts augmentent aussi chez les femelles sénescentes qui semblent réduire leur allocation dans la reproduction. Chez les mouflons, les coûts impliquent une réduction du gain en masse et une survie plus faible des jeunes nés lors de reproductions subséquentes. Chez les chèvres de montagne, ces coûts sont accompagnés d’une réduction de la fécondité future. Chez les mâles, les coûts sont surtout influencés par l’investissement en temps et en énergie dans le rut plutôt que par le succès d’accouplement. Ces coûts devraient donc surtout dépendre de l’habileté compétitive individuelle. En absence de chasse sélective, les mâles dominants devraient avoir un fort succès reproducteur avec des coûts potentiellement plus faibles comparativement aux subordonnées. La tactique conservative adoptée par les ongulés de montagne femelles peut expliquer pourquoi les effets densité‐dépendant mènent à un retard dans l’âge à la primiparité et à un recrutement plus faible, mais affectent rarement la survie adulte. Nos recherches futures tenteront de mieux quantifier l’hétérogénéité individuelle, évalueront les coûts cumulatifs à la reproduction et investigueront l’effet potentiel des pères sur les tactiques d’allocation maternelles.

The potential for selective harvests to induce rapid evolutionary change is an important question for conservation and evolutionary biology, with numerous biological, social and economic implications. We analyze 39 years of phenotypic data on horn size in bighorn sheep (Ovis canadensis) subject to intense trophy hunting for 23 years, after which harvests nearly ceased. Our analyses revealed a significant decline in genetic value for horn length of rams, consistent with an evolutionary response to artificial selection on this trait. The probability that the observed change in male horn length was due solely to drift is 9.9%. Female horn length and male horn base, traits genetically correlated to the trait under selection, showed weak declining trends. There was no temporal trend in genetic value for female horn base circumference, a trait not directly targeted by selective hunting and not genetically correlated with male horn length. The decline in genetic value for male horn length stopped, but was not reversed, when hunting pressure was drastically reduced. Our analysis provides support for the contention that selective hunting led to a reduction in horn length through evolutionary change. It also confirms that after artificial selection stops, recovery through natural selection is slow.

We know little about the determinants and demographic consequences of the marked seasonal mass changes exhibited by many northern and alpine mammals. We analysed 43 years of data on individual winter mass loss (the difference between mass in early June and mass in mid-September the previous year) and summer mass gain (the difference between mass in mid-September and in early June of the same year) in adult bighorn sheep (Ovis canadensis). We calculated relative seasonal mass change as a proportion of individual body mass at the start of each season. We first examined the effects of weather and population density on relative changes in body mass. We then assessed the consequences of relative seasonal mass changes on reproduction. Mean April–May temperature was the main driver of relative seasonal mass changes: warm springs reduced both relative winter mass loss and summer mass gain of both sexes, likely partially due to a trade-off between growth rate of plants and duration of access to high-quality forage. Because these effects cancelled each other, spring temperature did not influence mass in mid-September. Mothers that lost relatively more mass during the winter had lambs that gained less mass during summer, likely because these females allocated fewer resources to lactation. Winter survival of lambs increased with their summer mass gain. In males, relative mass loss during winter, which includes the rut, did not influence the probability of siring at least one lamb, possibly indicating that greater mating effort did not necessarily translate into greater reproductive success. Our findings improve our understanding of how weather influences recruitment and underline the importance of cryptic mechanisms behind the effects of climate change on demographic traits.

In some species where male mating success largely depends on intrasexual competition, males can adopt migratory or resident strategies to seek breeding opportunities. The resulting mixture of resident and migrant tactics within a population can have important ecological, genetic, and evolutionary consequences for metapopulations. Bighorn sheep Ovis canadensis males establish a linear dominance hierarchy that influences their mating tactics. Some males perform breeding migrations during the pre‐rut and rut to seek mating opportunities, but little is known about these seasonal movements. We analyzed presence/absence data for 62 marked bighorn males during six mating seasons (20–32 males/year) in the Sheep River Provincial Park, Alberta, Canada, where hunting was not allowed. On average, about half of males left their natal population to rut elsewhere. The proportion of males leaving (yearly range 15%–69%) increased as the number of resident mature males increased and the populational sex ratio decreased, with fewer females during the pre‐rut. Among those leaving the park, 24% did so in October, while the trophy sheep hunting season was open. Detailed monitoring of breeding migrations in protected populations could inform management strategies to limit evolutionary impacts of hunting, which can alter size‐dependent mortality and create artificial pressures driving changes on heritable traits. In bighorn sheep, Ovis canadensis, some males undertake breeding migrations during the pre‐rut and rut periods to seek mating opportunities. We explored the individual and populational determinants of male migratory rutting tactics and the timing of these movements in the fall. As male undertaking breeding migrations are more at risk of getting harvested, especially when they move out of protected areas, our results have implications for wild sheep management as gene flow may be reduced and insufficient to limit hunting‐induced artificial selection on horn size.

Large herbivores typically have consistently high prime-aged adult survival and lower, more variable, juvenile, and senescent survival. Many kangaroo populations undergo greater fluctuations in density compared with other large herbivores, but age- and sex-specific survival of kangaroos and their response to environmental variation remain poorly estimated. We used long-term capture–mark–recapture data on 920 individuals to investigate the survival component of eastern grey kangaroo (Macropus giganteus) population dynamics. Forage availability and population density were monitored quarterly and included as predictors of survival in Bayesian Cormack–Jolly–Seber models. Annual survival probabilities were estimated for five age classes: 0 years (juveniles), 1–2 years (subadults), 3–6 years (prime-aged adults), 7–9 years (presenescent adults), and ≥10 years (senescent adults). Survival of juveniles varied widely during our 12-year study, ranging from 0.07 to 0.90 for females and 0.05–0.92 for males. Subadult survival was 0.80–0.93 for females and 0.75–0.85 for males, while that of prime-aged adults was ≥0.94 for females and ≥0.83 for males, despite large fluctuations in forage and density. The survival of presenescent adults spanned 0.86–0.93 for females and 0.60–0.86 for males. Senescent survival was variable, at 0.49–0.90 for females and 0.49–0.80 for males. Male survival was significantly lower than female survival in prime-aged and presenescent adults, but not in other age classes. Although most of the models supported by Watanabe–Akaike Information Criterion selection included at least one environmental covariate, none of these covariates individually had a discernible effect on survival. Temporal variability in overall survival appeared mostly due to changes in the survival of juvenile and senescent kangaroos. Kangaroo survival patterns are similar to those of ungulates, suggesting a strong role of sex–age structure on population dynamics.

With increasing habitat fragmentation and population isolation, inbreeding becomes a pressing concern for the persistence of wildlife populations. Detailed inbreeding monitoring is crucial for assessing extinction risk and evaluating the effectiveness of conservation management strategies. Traditionally, pedigree‐based inbreeding estimates have been used. Genomic approaches now provide more powerful alternatives. Here, we compare pedigree and genomic inbreeding estimates in a long‐term study of wild bighorn sheep (Ovis canadensis) from Ram Mountain, Alberta, Canada, monitored from 1972 to the present. This population experienced a severe population bottleneck followed by genetic rescue through the translocation of 35 individuals over 13 years. We found that genomic inbreeding coefficients (FROH) dropped by 24% after genetic rescue efforts began. In contrast, pedigree inbreeding coefficients (FPED) increased, likely because greater pedigree depth improved our ability to detect inbreeding in later cohorts, highlighting a methodological bias and the need for genomic monitoring. Our findings show that genomic approaches are more effective in detecting changes in inbreeding over time in wild animals and emphasize the utility of FROH for monitoring the genetic outcomes of conservation interventions, particularly where pedigree completeness increases through time.

Sustainable exploitation must minimize its impact on the ecology and evolution of exploited wildlife. Intense phenotype‐based selective harvests can induce evolutionary change. Refuges could mitigate those evolutionary effects if individuals not subject to selective hunting in harvest refuges migrated and reproduced in hunted areas. The role of harvest refuges on phenotypic rescue of trophy‐hunted species, however, has rarely been tested. We investigated spatial and temporal variation in the effect of refuges on horn size and age at harvest in bighorn sheep Ovis canadensis. We analysed data on 5,826 males harvested over 39 years in Alberta, Canada. Horn length, a trait targeted by hunters, and age at harvest increased with the amount of protected areas 5–40 km around each kill. Horn base circumference, however, was independent of proximity to refuges. The number of males harvested increased during the last 10 days of the hunting season in late October, corresponding to the timing of bighorn male breeding migrations. Males shot during those 10 days were on average 17% closer to a refuge than males shot earlier in the season. Apparently, some large males exit refuges late in the hunting season, are shot, and cannot contribute to rescue. Uncertainty remains about the proportion of males exiting refuges after the hunting season and how many survive to reproduce. Synthesis and applications. Harvest refuges are unlikely to rescue hunted populations of bighorn sheep in Alberta, because some males exiting refuges are at risk of harvest before they mate. For phenotypic rescue to be effective, unselected males must reproduce before they are shot. Closing the hunting season 10 days earlier would increase survival of unselected rams exiting refuges. Résumé L’exploitation durable doit minimiser ses impacts sur l’écologie et l’évolution des espèces exploitées. Une récolte sélective intense peut induire des conséquences évolutives. Les refuges peuvent atténuer ces effets évolutifs si des individus non sujets à cette récolte, provenant de ces refuges, migrent et se reproduisent dans les zones chassées. Cependant, le rôle des refuges sur la rescousse phénotypique des espèces chassées pour le trophée a rarement été évalué. Nous avons étudié les variations spatiales et temporelles dans l’effet des refuges sur la taille des cornes et l’âge à la récolte chez le mouflon d’Amérique (Ovis canadensis). Nous avons analysé les données sur 5 826 béliers récoltés sur 39 ans en Alberta, Canada. La longueur des cornes, un trait ciblé par les chasseurs, et l’âge à la récolte augmentaient avec la proportion d’aires protégées dans des zones de 5–40 km autour de chaque localisation de bélier tué. Toutefois, la circonférence à la base des cornes était indépendante de la proximité aux refuges. Le nombre de béliers récoltés augmentait pendant les 10 derniers jours de la saison de chasse à la fin octobre, correspondant avec la période de migration des béliers pour le rut. Les mâles tués pendant ces 10 jours étaient en moyenne 17% plus près d’un refuge que ceux récoltés plus tôt pendant la saison de chasse. Nos résultats suggèrent que certains mâles pourvus de grandes cornes sortaent des refuges vers la fin de la saison de chasse sont récoltés et ne peuvent donc pas contribuer à la rescousse. Cependant, de l’incertitude demeure quant à la proportion de mâles qui sortent des refuges après la saison de chasse et qui survivent pour se reproduire. Synthèse et applications. Il est peu probable que les refuges assurent une rescousse aux populations chassées de mouflon d’Amérique en Alberta puisque certains mâles qui sortent des refuges sont à risque d’être récoltés avant de s’être reproduits. Pour qu’une rescousse phénotypique soit efficace, les mâles doivent se reproduire avant d’être récoltés. Une fermeture de la saison de chasse 10 jours plus tôt permettrait une meilleure survie des mâles provenant des zones protégées. Harvest refuges are unlikely to rescue hunted populations of bighorn sheep in Alberta, because some males exiting refuges are at risk of harvest before they mate. For phenotypic rescue to be effective, unselected males must reproduce before they are shot. Closing the hunting season 10 days earlier would increase survival of unselected rams exiting refuges.

Heterogeneity among individuals influences the life‐history trajectories we observe at the population level because viability selection, selective immigration and emigration processes, and ontogeny change the proportion of individuals with specific trait values with increasing age. Here, we review the two main approaches that have been proposed to account for these processes in life‐history trajectories, contrasting how they quantify ontogeny and selection, and proposing ways to overcome some of their limitations. Nearly all existing approaches to model individual heterogeneity assume either a single normal distribution or a priori known groups of individuals. Ontogenetic processes, however, can vary across individuals through variation in life‐history tactics. We show the usefulness of describing ontogenetic processes by modelling trajectories with a mixture model that focuses on heterogeneity in life‐history tactics. Additionally, most methods examine individual heterogeneity in a single trait, ignoring potential correlations among multiple traits caused by latent common sources of individual heterogeneity. We illustrate the value of using a joint modelling approach to assess the presence of a shared latent correlation and its influence on life‐history trajectories. We contrast the strengths and limitations of different methods for different research questions, and we exemplify the differences among methods using empirical data from long‐term studies of ungulates.

Wildlife management attempts to balance consumptive and non‐consumptive values to manage hunting opportunities, considering population resilience. Mountain goats Oreamnos americanus are particularly sensitive to harvest. Using data from 33 792 mountain goats harvested in British Columbia (BC), Canada, between 1977 and 2019, we performed Bayesian regressions to examine the effect of regulations (limited entry hunting (LEH) or general open season (GOS)) on yearly harvest and harvest sex ratios. We also investigated temporal trends and the effect of licensed hunter residency (resident in British Columbia, or not) on harvest sex ratios. We then examined how horn length of harvested mountain goats was influenced by sex, year of harvest, age and mountain range. The more restrictive LEH regulations generally reduced harvest of mountain goats. The annual proportion of males harvested appeared independent of regulation and increased over time. Non‐resident hunters harvested a greater proportion of males compared to resident hunters. The combined length of the first and second horn growth increments decreased slightly with age at harvest for males but increased for females, suggesting a possible very weak hunter selection for males with rapid early horn growth and possibly against lactating females. Our study supports LEH regulations and hunter education to distinguish sex and age as key tools for mountain goat harvest management. Similar tools could be considered to manage other ungulates that are sensitive to harvest.