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Ageing and sexual selection are intimately linked. There is by now compelling evidence from studies performed across diverse organisms that males allocating resources to mating competition incur substantial physiological costs, ultimately increasing ageing. However, although insightful, we argue here that to date these studies cover only part of the relationship linking sexual selection and ageing. Crucially, allocation to traits important in post‐copulatory sexual selection, that is sperm competition, has been largely ignored. As we demonstrate, such allocation could potentially explain much diversity in male and female ageing patterns observed both within and among species. We first review how allocation to sperm competition traits such as sperm and seminal fluid production depends on the quality of resources available to males and can be associated with a wide range of deleterious effects affecting both somatic tissues and the germline, and thus modulate ageing in both survival and reproductive terms. We further hypothesise that common biological features such as plasticity, prudent sperm allocation and seasonality of ejaculate traits might have evolved as counter‐adaptations to limit the ageing costs of sperm competition. Finally, we discuss the implications of these emerging ageing costs of sperm competition for current research on the evolutionary ecology of ageing. [ABSTRACT FROM AUTHOR]

Hopkins' Bioclimatic Law predicts geographical patterns in phenological timing by establishing a correspondence between latitudinal and altitudinal gradients. First proposed for key phenological events of plants, such as leaf sprouting or flowering dates, this law has rarely been used to assess the geographical equivalence of key life‐history traits of mammals.We hypothesize that (H1) parturition dates of European roe deer Capreolus capreolus are delayed and more synchronized at higher latitudes and altitudes, (H2) parturition timing varies along latitudinal and altitudinal gradients in a way that matches the Hopkins' Bioclimatic Law and (H3) females adjust parturition timing to match the period of high energy demand with peak resource availability.We used parturition dates of 7,444 European roe deer from Switzerland to assess altitudinal variation in birth timing and synchrony from 288 to 2,366 m a.s.l. We then performed a literature survey to compare altitudinal results with those from different populations along the species' latitudinal range of distribution. Finally, we performed spatial analysis combining our highly resolved altitudinal data on parturition dates with plant phenology data.As expected, parturition dates were delayed with increasing latitude and altitude. This delay matched the Bioclimatic Law, as the effect of 1º increase in latitude was similar to 120 m increase in altitude. However, while parturitions were more synchronized with increasing altitude, we did not detect any trend along the latitudinal gradient. Finally, plant phenology explained altitudinal variation in parturition timing better than a linear effect of altitude.Our findings clearly demonstrate the ability of a large herbivore to match parturition timing with phenological conditions across the altitudinal gradient, even at the smallest spatial scales. [ABSTRACT FROM AUTHOR]

Allometric relationships describe the proportional covariation between morphological, physiological, or life‐history traits and the size of the organisms. Evolutionary allometries estimated among species are expected to result from species differences in ontogenetic allometry, but it remains uncertain whether ontogenetic allometric parameters and particularly the ontogenetic slope can evolve. In bovids, the nonlinear evolutionary allometry between horn length and body mass in males suggests systematic changes in ontogenetic allometry with increasing species body mass. To test this hypothesis, we estimated ontogenetic allometry between horn length and body mass in males and females of 19 bovid species ranging from ca. 5 to 700 kg. Ontogenetic allometry changed systematically with species body mass from steep ontogenetic allometries over a short period of horn growth in small species to shallow allometry with the growth period of horns matching the period of body mass increase in the largest species. Intermediate species displayed steep allometry over long period of horn growth. Females tended to display shallower ontogenetic allometry with longer horn growth compared to males, but these differences were weak and highly variable. These findings show that ontogenetic allometric slope evolved across species possibly as a response to size‐related changes in the selection pressures acting on horn length and body mass. [ABSTRACT FROM AUTHOR]

The article discusses the importance of ecological concepts in supporting theory-driven research in animal ecology. Concepts are essential for developing theories and understanding complex ecological systems. The Journal of Animal Ecology has added a new article type, 'Concepts', to encourage the submission of innovative ideas that challenge existing paradigms. The article also highlights key conceptual contributions in areas such as population ecology, niche theory, trophic interactions, life history strategies, metapopulation dynamics, ecosystem services, and molecular ecology. The journal provides tips for writing strong concept articles and identifies emerging areas for future conceptual development in ecology, such as Artificial Intelligence, methodological pipelines, and applied contexts like wildlife management and conservation efforts. [Extracted from the article]

Commonly used two‐sex discrete‐time population projection models rely on mating functions developed for continuous‐time frameworks that overestimate the number of unions between reproductive individuals. This has important consequences for our understanding of the evolution and demography of two‐sex populations and consequently for management and conservation. Here, we propose a novel mating function that is robust by obeying all properties necessary to be ecologically valid and flexible by accommodating all mating systems and efficiency in mating encounters. We illustrate the usefulness of this novel function with an application to the sexually size‐dimorphic and polygynous wild boar (Sus scrofa). We show that the population growth rate depends on the harem size, the operational sex ratio, and the mating efficiency. This novel function can be applied to all mating systems and tactics and is highly relevant in the context of global changes under which mating systems and mating efficiency are expected to change. [ABSTRACT FROM AUTHOR]

Senescence—the decline in age‐specific contribution to fitness with increasing age—has been widely investigated in evolutionary ecology. A tremendous amount of detailed empirical analyses have now revealed the widespread occurrence of demographic senescence (i.e. both actuarial and reproductive senescence) and have started to identify factors (e.g. environmental conditions) that modulate its timing and intensity, both within and across species. In this special feature, we have built on this flourishing work to highlight several axes of research that would benefit from more integrative and multidisciplinary approaches.Several contributions compiled in this special feature emphasize that our understanding of senescence remains taxonomically limited, mostly focused on birds and mammals, and is therefore not representative of the biological diversity displayed across the tree of life. In line with this observation, the influence of some peculiar lifestyles (e.g. involving sociality or modularity) on the evolution of senescence is yet to be deciphered.Understanding of the diversity of senescence patterns across and within species and among traits will necessitate the establishment of new metrics as a golden standard to fully account for age‐specific changes recorded in individuals' performance. This is illustrated with the specific case of actuarial senescence.This special feature also highlights that the diversity of biological samples collected from wild plants and animals, along with accurate demographic data, is expanding. The fast development of new molecular tools now offers a unique opportunity to launch research programmes at the interface of physiology, health and ageing in non‐model organisms.We argue that while these different research axes constitute key avenues of investigations for the coming years, they are only the tip of the iceberg. To appreciate the full complexity of the senescence process in nature, from its evolutionary causes to its demographic consequences, we also need a better understanding of the role played by both environmental conditions and gene–environment interactions, of constraints, and of senescence, an improved assessment of the influence of individual heterogeneity, and the consideration of transgenerational effects when quantifying the fitness consequences of senescence. [ABSTRACT FROM AUTHOR]

An increasing number of studies have investigated the diversity of actuarial senescence (i.e. the increase of mortality with age) and mortality patterns in the wild. Most of these studies used maximum longevity as a metric, and only some of them were based on the analysis of mortality or survival curves. However, maximum longevity is not a reliable metric to assess mortality patterns. Two types of metrics can be distinguished: the metrics of pace that include biological times and describe how long individuals live and the metrics of shape that are dimensionless and describe the form of mortality patterns for a given pace.We review the use of pace metrics in comparative analyses of mortality curves and actuarial senescence performed so far, with a special focus on longevity metrics. We demonstrate that multiple statistical issues are associated with the use of maximum longevity, although this metric is the most commonly used to analyse actuarial senescence patterns in research fields such as genomics of ageing. We thus argue for using alternative metrics of longevity.We then propose different metrics of shape and point out the relevance of using several metrics in future comparative analyses of mortality. In particular, two shape metrics can be easily computed from observed distributions of ages at death. We illustrate our approach based on both pace and shape metrics by performing a comparative analysis of actuarial senescence and mortality across 30 species of mammals. The results strongly support the relevance of using shape metrics based on the distribution of the ages at death to assess reliably patterns of mortality. In particular, we found that the pace and the shape of ageing, although statistically independent, could be associated in mammals.We conclude that the metrics defined from the distribution of ages at death provide a complementary approach to mortality or survival curve analyses and, by offering straightforward standardization, provide a promising tool for future comparative analyses of actuarial senescence and mortality across the tree of life. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Little is known about whether female mating tactics vary with age based on their preference for mates. To fill this knowledge gap, we examined how maternal age is related to the age of their mates using detailed individual long-term monitoring of a genotyped and pedigreed European roe deer (Capreolus capreolus Linnaeus, 1758) population. We found that mating between old females and prime-aged males was more frequent than mating between prime-aged females and prime-aged males. This suggests that old females avoid old mates. Old females might be more selective in their mate choice than prime-aged females owing to increased mate-sampling effort. Our finding is in line with the terminal investment/allocation hypothesis. The study of age-related variation in female mating behaviour is particularly important because this behaviour can influence the intensity and direction of sexual selection and the maintenance of variation in male sexually selected traits. Further studies are needed to quantify the exact fitness benefits of age-specific mating tactics in females. [ABSTRACT FROM AUTHOR]

For social species, the environment has two components: physical and social. The social environment modifies the individual's interaction with the physical environment, and the physical environment may in turn impact individuals' social relationships. This interplay can generate considerable variation among individuals in survival and reproduction. Here, I synthesize more than four decades of research on the baboons of the Amboseli basin in southern Kenya to illustrate how social and physical environments interact to affect reproduction and survival.For immature baboons, social behaviour can both mitigate and exacerbate the challenge of survival. Only c. 50% of live‐born females and c. 44% of live‐born males reach the median age of first reproduction. Variation in pre‐adult survival, growth and development is associated with multiple aspects of the social environment. For instance, conspecifics provide direct care and are a major source of social knowledge about food and the environment, but conspecifics can also represent a direct threat to survival through infanticide.In adulthood, both competition (within and between social groups) and cooperative affiliation (i.e. collective action and/or the exchange of social resources such as grooming) are prominent features of baboon social life and have important consequences for reproduction and survival. For instance, adult females with higher social dominance ranks have accelerated reproduction, and adult females that engage in more frequent affiliative social interactions have higher survival throughout adulthood.The early life environment also has important consequences for adult reproduction and survival, as in a number of other bird and mammal species. In seasonal breeders, early life effects often apply to entire cohorts; in contrast, in nonseasonal and highly social species such as baboons, early life effects are more individual‐specific, stemming from considerable variation not only in the early physical environment (even if they are born in the same year) but also in the particulars of their social environment. An animal's survival and reproduction are determined by how it interacts with its environment; for social species, this includes both the physical and the social environment. The variation in resource distribution that results from social behavior can generate considerable variation in survival and reproduction. This study synthesizes more than four decades of long‐term research on the ecology and social behavior of baboons of the Amboseli basin to describe the challenges and opportunities presented by the physical and social environments, how they unfold over the course of an animal's life, and how animals meet them. Photo credit A.C. Markham [ABSTRACT FROM AUTHOR]

An introduction to articles published within the issue is presented on topics including the role of individual heterogeneity in ecology and evolution, impact of individual heterogeneity on life histories and population dynamics, and consequences of heterogeneity over multiple generations.

An introduction to articles published within the issue is presented on topics including the influence of individual heterogeneity on life history trajectories as well as its impact on population dynamics and eco-evolutionary interactions, and individual heterogeneity in ecology and evolution.

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. [ABSTRACT FROM AUTHOR]

ABSTRACT: Early survival is highly variable and strongly influences observed population growth rates in most vertebrate populations. One of the major potential drivers of survival variation among juveniles is body mass. Heavy juveniles are better fed and have greater body reserves, and are thus assumed to survive better than light individuals. In spite of this, some studies have failed to detect an influence of body mass on offspring survival, questioning whether offspring body mass does indeed consistently influence juvenile survival, or whether this occurs in particular species/environments. Furthermore, the causes for variation in offspring mass are poorly understood, although maternal mass has often been reported to play a crucial role. To understand why offspring differ in body mass, and how this influences juvenile survival, we performed phylogenetically corrected meta‐analyses of both the relationship between offspring body mass and offspring survival in birds and mammals and the relationship between maternal mass and offspring mass in mammals. We found strong support for an overall positive effect of offspring body mass on survival, with a more pronounced influence in mammals than in birds. An increase of one standard deviation of body mass increased the odds of offspring survival by 71% in mammals and by 44% in birds. A cost of being too fat in birds in terms of flight performance might explain why body mass is a less reliable predictor of offspring survival in birds. We then looked for moderators explaining the among‐study differences reported in the intensity of this relationship. Surprisingly, sex did not influence the intensity of the offspring mass–survival relationship and phylogeny only accounted for a small proportion of observed variation in the intensity of that relationship. Among the potential factors that might affect the relationship between mass and survival in juveniles, only environmental conditions was influential in mammals. Offspring survival was most strongly influenced by body mass in captive populations and wild populations in the absence of predation. We also found support for the expected positive effect of maternal mass on offspring mass in mammals (rpearson = 0.387). As body mass is a strong predictor of early survival, we expected heavier mothers to allocate more to their offspring, leading them to be heavier and so to have a higher survival. However, none of the potential factors we tested for variation in the maternal mass–offspring mass relationship had a detectable influence. Further studies should focus on linking these two relationships to determine whether a strong effect of offspring size on early survival is associated with a high correlation coefficient between maternal mass and offspring mass. [ABSTRACT FROM AUTHOR]

Williams' evolutionary theory of senescence based on antagonistic pleiotropy has become a landmark in evolutionary biology, and more recently in biogerontology and evolutionary medicine. In his original article, Williams launched a set of nine ' testable deductions' from his theory. Although some of these predictions have been repeatedly discussed, most have been overlooked and no systematic evaluation of the whole set of Williams' original predictions has been performed. For the sixtieth anniversary of the publication of the Williams' article, we provide an updated evaluation of all these predictions. We present the pros and cons of each prediction based on recent accumulation of both theoretical and empirical studies performed in the laboratory and in the wild. From our viewpoint, six predictions are mostly supported by our current knowledge at least under some conditions (although Williams' theory cannot thoroughly explain why for some of them). Three predictions, all involving the timing of senescence, are not supported. Our critical review of Williams' predictions highlights the importance of William's contribution and clearly demonstrates that, 60 years after its publication, his article does not show any sign of senescence. [ABSTRACT FROM AUTHOR]

ABSTRACT According to recent empirical studies, reproductive senescence, the decline in reproductive success with increasing age, seems to be nearly ubiquitous in the wild. However, a clear understanding of the evolutionary causes and consequences of reproductive senescence is still lacking and requires new and integrative approaches. After identifying the sequential and complex nature of female reproductive senescence, we show that the relative contributions of physiological decline and alterations in the efficiency of parental care to reproductive senescence remain unknown and need to be assessed in the light of current evolutionary theories of ageing. We demonstrate that, although reproductive senescence is generally studied only from the female viewpoint, age-specific female reproductive success strongly depends on male-female interactions. Thus, a reduction in male fertilization efficiency with increasing age has detrimental consequences for female fitness. Lastly, we call for investigations of the role of environmental conditions on reproductive senescence, which could provide salient insights into the underlying sex-specific mechanisms of reproductive success. We suggest that embracing such directions should allow building new bridges between reproductive senescence and the study of sperm competition, parental care, mate choice and environmental conditions. [ABSTRACT FROM AUTHOR]

Individual body mass often positively correlates with survival and reproductive success, whereas fitness costs of growing large are rarely detected in vertebrates in the wild. Evidence that adult body mass progressively declines with increasing age is accumulating across mammalian populations. Growing fast to a large body can increase the cellular damage accumulated throughout life, leading body growth in early life to be negatively associated with the rate of body mass senescence. Moreover, the onset of mass senescence may strongly depend on both sex-specific reproductive tactics and environmental conditions. Assessing the timing and the rate of body mass decline with increasing age thus offers an opportunity to look for costs of having grown fast, especially after a poor start during early life, in both sexes and in different environments. Using a unique dataset including 30 years of longitudinal data on age-specific body mass collected in two roe deer Capreolus capreolus populations subjected to contrasted environmental conditions, we looked for potential costs of high post-weaning growth rate in terms of steeper rate of body mass senescence. Our analyses of body mass senescence accounted for the potential variation in the onset of senescence and allowed explicit comparisons of this variable between sexes and populations. Higher growth rates late in the growing period (after weaning) were associated with a steeper rate of body mass senescence, regardless of early mass (gained before weaning), but at different extents depending on sex and environmental conditions. Body mass senescence occurred earlier in males than in females, especially in the population facing limiting resources. In the wild, although heavy individuals generally survive better than small ones, the costs of growing large late in the growing period only became apparent late in life through mass senescence. [ABSTRACT FROM AUTHOR]

The canalization hypothesis postulates that the rate at which trait variation generates variation in the average individual fitness in a population determines how buffered traits are against environmental and genetic factors. The ranking of a species on the slow-fast continuum - the covariation among life-history traits describing species-specific life cycles along a gradient going from a long life, slow maturity, and low annual reproductive output, to a short life, fast maturity, and high annual reproductive output - strongly correlates with the relative fitness impact of a given amount of variation in adult survival. Under the canalization hypothesis, long-lived species are thus expected to display less individual heterogeneity in survival at the onset of adulthood, when reproductive values peak, than short-lived species. We tested this life-history prediction by analysing long-term time series of individual-based data in nine species of birds and mammals using capture-recapture models. We found that individual heterogeneity in survival was higher in species with short-generation time (< 3 years) than in species with long generation time (> 4 years). Our findings provide the first piece of empirical evidence for the canalization hypothesis at the individual level from the wild. [ABSTRACT FROM AUTHOR]

Why and how we age are 2 intertwined questions that have fascinated scientists for many decades. However, attempts to answer these questions remain compartmentalized, preventing a comprehensive understanding of the aging process. We argue that the current lack of knowledge about the evolution of aging mechanisms is due to a lack of clarity regarding evolutionary theories of aging that explicitly involve physiological processes: the disposable soma theory (DST) and the developmental theory of aging (DTA). In this Essay, we propose a new hierarchical model linking genes to vital rates, enabling us to critically reevaluate the DST and DTA in terms of their relationship to evolutionary genetic theories of aging (mutation accumulation (MA) and antagonistic pleiotropy (AP)). We also demonstrate how these 2 theories can be incorporated in a unified hierarchical framework. The new framework will help to generate testable hypotheses of how the hallmarks of aging are shaped by natural selection. Why and how we age are two intertwined questions that have fascinated scientists for many decades. This Essay proposes a new hierarchical model that links genes to vital rates, enabling a critical re-evaluation of the disposable soma theory and the developmental theory of aging in terms of their relationship to evolutionary genetic theories of aging. [ABSTRACT FROM AUTHOR]

Despite the observed distribution of variable individual phenotypes, survival and reproductive performance in wild populations, models of population dynamics often focus on mean demographic rates. Populations are constituted by individuals with different phenotypes and thus different performances. However, many models of population dynamics provide no understanding of the influence of this phenotypic variation on population dynamics., In this paper, we investigate how the relationships between demographic rates and phenotype distribution influence the transmission and the upholding of phenotypic variation, and population dynamics. We used integral projection models to measure associations between differences of phenotypic trait (size or mass) among individuals and demographic rates, growth and inheritance, and then quantify the influence of phenotypic variation on population dynamics. We build an analytical and general model resulting from simplifications assuming small phenotypic variance. We illustrate our model with two case studies: a short- and a long-lived life history., Population growth rate r is determined by a Lotka style equation in which survival and fertility are averaged over a phenotypic distribution that changes with age. Here, we further decomposed r to show how much it is affected by shifts in phenotypic average as well as variance. We derived the elasticities of r to the first and second derivative of each demographic rate. In particular, we show that the nonlinearity of change in selective pressure with phenotype matters more to population dynamics than the strength of this selection. In other words, the variance of a given trait will be most important when the strength of selection increases (or decreases) nonlinearly with that trait., Inheritance shapes the distribution of newborn phenotypes. Even if newborns have a fixed average phenotype, the variance among newborns increases with phenotypic variance among mothers, strength of inheritance and developmental variation. We explain how the components of inheritance can influence phenotypic variance and thus the demographic rates and population dynamics. In particular, when mothers of different ages produce offspring of different mean phenotype, the inheritance function can have a large influence on both the mean and variance of the trait at different ages and thus on the population growth rate., We provide new tools to understand how phenotypic variation influences population dynamics and discuss in which life histories we expect this influence to be large. For instance, in our short-lived life history, individual variability has larger effect than in our long-lived life history. We conclude by indicating future directions of analysis. [ABSTRACT FROM AUTHOR]

In stochastic environments, a change in a demographic parameter can influence the population growth rate directly or via a resulting impact on age structure. Stochastic elasticity of the long-run stochastic growth rate λs to a demographic parameter offers a suitable way to measure the overall demographic response because it includes both the direct effect of changing the demographic parameter and its indirect effect through changes in the age structure. From 25 mammalian populations with contrasting life histories, we investigated how pace of life and population growth rate influence the demographic responses (measured as the relative contributions of the direct and indirect components of stochastic elasticity on λs). We found that in short-lived species, the change in population structure resulting from an increase in yearling survival leads to an additional increase in λs, whereas in long-lived species, the same change in population structure leads to a decrease. Short-lived species thus display a boom-bust life history strategy contrary to long-lived species, for which the long lifespan dampens the demographic consequences of changing age structure. Irrespective of the species' life history strategy, the change in population age structure resulting from an increase in adult survival leads to an additional increase in λs due to an increase of the proportion of mature individuals in the population. On the contrary, a change in population age structure resulting from an increase of reproductive performance leads to a decrease in λs that is due to the increase of the proportion of immature individuals in the population. Our comparative analysis of stochastic elasticity patterns in mammals shows the existence of different demographic responses to changes in age structure between short- and long-lived species, which improves our understanding of population dynamics in variable environments in relation to the species-specific pace of life. [ABSTRACT FROM AUTHOR]

The fitness costs of reproduction can be masked by individual differences, and may only become apparent during adverse environmental conditions. Individual differences, however, are usually assessed by reproductive success, so how fitness costs are influenced by the interplay between the environmental context and overall individual differences requires further investigation. Here, we evaluated fitness costs of reproduction based on 15 yr of monitoring of individual Alpine ibex ( Capra ibex) during a period when the population was affected by a severe disease outbreak (pneumonia). We quantified fitness costs using a novel multi-event capture-mark-recapture ( CMR) modeling approach that accounted for uncertainty in reproductive status to estimate the survival and reproductive success of female ibex while also accounting for overall individual heterogeneity using mixture models. Our results show that the ability of females to reproduce was highly heterogeneous. In particular, one group including 76% of females had a much higher probability of giving birth annually (between 0.66 and 0.77, depending on the previous reproductive status) than females of the second group (24% of females, between 0 and 0.05 probability of giving birth annually). Low reproductive costs in terms of future reproduction occurred and were independent of the pneumonia outbreak. There was no survival cost of reproduction either before or after the epizootic, but the cost was high during the epizootic. Our findings indicate that adverse environmental conditions, such as disease outbreaks, may lead to survival costs of reproduction in long-lived species and select against females that have a high reproductive effort. Thereby, the occurrence of adverse conditions increases the diversity of reproductive tactics within a population. [ABSTRACT FROM AUTHOR]

In most mammals, both sexes display different survival patterns, often involving faster senescence in males. Being under intense sexual competition to secure mating opportunities, males of polygynous species allocate resources to costly behaviors and conspicuous sexual traits, which might explain these observed differences in longevity and senescence patterns. However, comparative studies performed to date have led to conflicting results. We aimed to resolve this problem by first reviewing case studies of the relationship between the strength of sexual selection and age-specific survival metrics. Then, we performed a comprehensive comparative analysis to test whether such relationships exist among species of captive ruminants. We found that the strength of sexual selection negatively influenced the onset of actuarial senescence in males, with males senescing earlier in polygynous than in monogamous species, which led to reduced male longevity in polygynous species. Moreover, males of territorial species senesced earlier but slower, and have a shorter longevity than males of species displaying other mating tactics. We detected little influence of the strength of sexual selection on the rate of actuarial senescence. Our findings demonstrate that the onset of actuarial senescence, rather than its rate, is a side effect of physiological mechanisms linked to sexual selection, and potentially accounts for observed differences in longevity. [ABSTRACT FROM AUTHOR]

We test whether the intensity of tooth wear influences the strength of actuarial senescence across species of large herbivores. We collected from the literature data on tooth wear in the wild (measured as the slope of the regression of log-transformed M1 crown height on age), longevity (measured as the age at which 90% of individuals are dead) and two metrics of actuarial senescence in captive populations (rate of senescence between 6 and 12 years of age and Gompertz rate of senescence). Between-species differences and variation in tooth height accounted for most of the observed variation in tooth wear among large herbivores: tooth height and tooth wear were positively correlated. In contrast, tooth wear was little influenced by sex, body mass, or taxonomy. No marked between-sex differences in longevity occurred. Males senesced faster than females when tooth wear was low (for both senescence metrics), while between-sex differences in actuarial senescence when tooth wear was high depended on the metric used to measure actuarial senescence. While longevity was mostly independent of the intensity of tooth wear, we found general support for a positive relationship between both measures of actuarial senescence and tooth wear. These patterns were consistent whether hypsodonty was controlled for or not. Although varying according to sex and to the metric used for assessing actuarial senescence, our findings suggest overall that tooth wear could be positively associated with actuarial senescence among large herbivores. Further longitudinal studies focusing on changes within individuals will be required to test whether a mechanistic link between tooth wear and actuarial senescence occurs in large herbivores. [ABSTRACT FROM AUTHOR]

The Trivers-Willard theory proposes that the sex ratio of offspring should vary with maternal condition when it has sex-specific influences on offspring fitness. In particular, mothers in good condition in polygynous and dimorphic species are predicted to produce an excess of sons, whereas mothers in poor condition should do the opposite. Despite the elegance of the theory, support for it has been limited. Here we extend and generalize the Trivers-Willard theory to explain the disparity between predictions and observations of offspring sex ratio. In polygynous species, males typically have higher mortality rates, different age-specific reproductive schedules and more risk-prone life history tactics than females; however, these differences are not currently incorporated into the Trivers-Willard theory. Using two-sex models parameterized with data from free-living mammal populations with contrasting levels of sex differences in demography, we demonstrate how sex differences in life history traits over the entire lifespan can lead to a wide range of sex allocation tactics, and show that correlations between maternal condition and offspring sex ratio alone are insufficient to conclude that mothers adaptively adjust offspring sex ratio. [ABSTRACT FROM AUTHOR]

Demographic rates can vary not only with measured individual characters like age, sex and mass but also with unmeasured individual variables like behaviour, genes and health., Predictions from population models that include measured individual characteristics often differ from models that exclude them. Similarly, unmeasured individual differences have the potential to impact predictions from population models. However, unmeasured individual differences are rarely included in population models., We construct stage- and age-structured models (where stage is mass) of a roe deer population, which are parameterized from statistical functions that either include, or ignore, unmeasured individual differences., We found that mass and age structures substantially impacted model parameters describing population dynamics, as did temporal environmental variation, while unmeasured individual differences impacted parameters describing population dynamics to a much smaller extent once individual heterogeneity related to mass and age has been included in the model. We discuss how our assumptions (unmeasured individual differences only in mean trait values) could have influenced our findings and under what circumstances unmeasured individual differences could have had a larger impact on population dynamics., There are two reasons explaining the relative small influence of unmeasured individual differences on population dynamics in roe deer. First, individual body mass and age both capture a large amount of individual differences in roe deer. Second, in large populations of long-lived animals, the average quality of individuals (independent of age and mass) within the population is unlikely to show substantial variation over time, unless rapid evolution is occurring. So even though a population consisting of high-quality individuals would have much higher population growth rate than a population consisting of low-quality individuals, the probability of observing a population consisting only of high-quality individuals is small. [ABSTRACT FROM AUTHOR]

Patterns of actuarial senescence vary among long-lived species. A proposed explanation of the evolution of species-specific senescence patterns is that increased levels of energy allocation to intra-male competition decrease the amount of energy available for somatic maintenance, leading to earlier or faster actuarial senescence. Previous studies did not provide support for such relationships, but did not focus on the intensity of allocation likely to shape inter-specific variation in actuarial senescence in males. Here, by analyzing data from 56 species of captive large herbivores, we tested whether actuarial senescence is more pronounced in species displaying a well-defined ‘rut’ period than in species with year-round reproduction. Using an original quantitative metric of the annual duration of reproductive activity, we demonstrated that the length of the mating season has no detectable effect on actuarial senescence. On the other hand, both diet and body mass are important factors shaping actuarial senescence patterns in male captive herbivores. [ABSTRACT FROM AUTHOR]

The evolutionary theories of senescence predict that investment in reproduction in early life should come at the cost of reduced somatic maintenance, and thus earlier or more rapid senescence. There is now growing support for such trade-offs in wild vertebrates, but these exclusively come from females. Here, we test this prediction in male red deer (Cervus elaphus) using detailed longitudinal data collected over a 40-year field study. We show that males which had larger harems and thereby allocated more resources to reproduction during early adulthood experienced higher rates of senescence in both harem size and rut duration. Males that carried antlers with more points during early life did not show more pronounced declines in reproductive traits in later life. Overall, we demonstrate that sexual competition shapes male reproductive senescence in wild red deer populations and provide rare empirical support for the disposable soma theory of ageing in males of polygynous vertebrate species. [ABSTRACT FROM AUTHOR]

In most species of vertebrates, teeth play a central role in the long-term performance of individuals. However, patterns of tooth development have been little investigated as an indicator of animal performance. We filled this gap using data collected during long-term capture-mark-recapture monitoring of 1152 roe deer fawns at Chizé, western France. This population fluctuated greatly in size during the 27 years of monitoring, offering a unique opportunity to assess how the eruption patterns of front teeth perform as indicator of animal performance. We used three indices of the eruption of permanent front teeth, the simplest being whether or not incisor I2 has erupted, and the most complex being a 12-level factor distinguishing the different stages of tooth eruption. We also assessed the relevance of these indices as compared to fawn body mass, a widely used indicator of animal performance of deer populations. Dental indices and body mass were positively correlated (all r > 0.62). Similarly to body mass, all indices based on tooth eruption patterns responded to changes of population size and can be reliably used to assess the relationship between roe deer and their environment. We found a linear decrease in body mass with increasing population size (r² = 0.54) and a simultaneous delay in tooth development (r² = 0.48-0.55 from the least to the most accurate indicator). However, tooth development would be not further delayed in years with the highest densities (>15 adult roe deer/100 ha). A path analysis supported the population density effect on tooth eruption patterns being mainly determined by the effect of population size on body mass. Our study provides managers with simple indices (e.g., presence-absence of I2) that provide a technically more easy way to standardize measurements of deer density-dependent responses over large geographical and temporal scales than would be possible with body mass. [ABSTRACT FROM AUTHOR]

: This study of a French deer population reveals the demographic costs associated with the failure of a herbivore to modify its life cycle timing to respond to a warming world. [ABSTRACT FROM AUTHOR]

In seasonal environments, parturition of most vertebrates generally occurs within a short time-window each year. This synchrony is generally interpreted as being adaptive, as early born young survive better over the critical season than late born young. Among large herbivores, the factors involved in driving among- and within-individual variation in parturition date are poorly understood. We explored this question by analyzing the relative importance of attributes linked to female quality (longevity, median adult body mass and cohort), time-dependent attributes linked to female condition (reproductive success the previous year, relative annual body mass and offspring cohort (year)), and age in shaping observed variation in parturition date of roe deer. A measure of quality combining the effects of female longevity and median adult body mass accounted for 11% of the observed among-individual variation in parturition date. Females of 2 yr old give birth 5 d later than older females. Our study demonstrates that high quality (heavy and long-lived) females give birth earlier than low quality females. Temporally variable attributes linked to female condition, such as reproductive success in the previous year and relative annual body mass, had no detectable influence on parturition date. We conclude that parturition date, a crucial determinant of reproductive success, is shaped by attributes linked to female quality rather than by time-dependent attributes linked to female condition in income breeders (individuals that rely on current resource intake rather than on accumulated body reserves to offset the increased energy requirements due to reproduction) such as roe deer. [ABSTRACT FROM AUTHOR]

Lack proposed that the average clutch size of altricial species should be determined by the average maximum number of young the parents can raise such that all females in a given population should share a common optimal clutch size. Support for this model remains equivocal and recent studies have suggested that intra-population variation in clutch size is adaptive because each female has its own optimal clutch size associated with its intrinsic ability to raise offspring., Although Lack litter size and condition-dependent litter size are presented as two competing models, both are based on the concept of individual optimization. We propose a unified optimal litter size model (called 'adaptive litter size') and identify a set of conditions under which a common vs. a state-dependent optimal litter size should be observed., We test whether females of Eurasian lynx ( Lynx lynx) have a common optimal litter size, or whether they adjust their litter size according to their state. We used a detailed individual-based data set collected from contrasting populations of Eurasian lynx in Scandinavia., Observed reproductive patterns in female lynx provide strong support for the existence of a common optimal litter size. Litter size did not vary according to female body mass or reproductive category, or among contrasted populations and years. A litter size of 2 was associated with a higher fitness than both smaller and larger litters, and thus corresponded to the 'adaptive litter size' for female lynx., We suggest that the reproductive pattern of female lynx might correspond to a risk avoidance tactic common to all individuals, which has evolved in response to strong environmental constraints generated by a highly unpredictable food supply during lactation. [ABSTRACT FROM AUTHOR]

Large horns or antlers require a high energy allocation to produce and carry both physiological and social reproductive costs. Following the principle of energy allocation that implies trade-offs among fitness components, growing large weapons early in life should thus reduce future growth and survival. Evidence for such costs is ambiguous, however, partly because individual heterogeneity can counterbalance trade-offs. Individuals with larger horns or antlers may be of better quality and thus have a greater capacity to survive. We investigated trade-offs between male early horn growth and future horn growth, baseline mortality, onset of actuarial senescence, and rate of ageing in an Alpine ibex ( Capra ibex ibex) population. Horn growth of males in early life was positively correlated to their horn length throughout their entire life. Cohort variation and individual heterogeneity both accounted for among-individual variation in horn length, suggesting both long-lasting effects of early life conditions and individual-specific horn growth trajectories. Early horn growth did not influence annual survival until 12 years of age, indicating that males do not invest in horn growth at survival costs over most of their lifetime. However, males with fast-growing horns early in life tended to have lower survival at very old ages. Individual heterogeneity, along with the particular life-history tactic of male ibex (weak participation to the rut until an old age after which they burn out in high mating investment), are likely to explain why the expected trade-off between horn growth and survival does not show up, at least until very old ages. [ABSTRACT FROM AUTHOR]

In highly variable environments, the optimal reproductive tactics of iteroparous organisms should minimize variance in yearly reproductive success to maximize the long-term average reproductive success. To minimize among-year variation in reproductive success, individuals can either minimize the variance in the number of offspring produced at each reproductive attempt (classical bet-hedging) or maximize the phenotypic diversity of offspring produced within or among reproductive attempts (coin-flipping)., From a long-term detailed study of an intensively exploited population facing a highly unpredictable environment, we identify a continuum of reproductive tactics in wild boar females depending on their body mass., At one end, light females adjusted litter size to their body mass and produced highly similar-sized offspring within a litter. These females fitted the hypothesis of individual optimization commonly reported in warm-blooded species, which involves both an optimal mass and an optimal number of offspring for a given mother. At the other end of the continuum, heavy females produced litters of variable size including a mixture of heavy and light offspring within litters., Prolific heavy wild boar females diversify the phenotype of their offspring, providing a first evidence for coin-flipping in a warm-blooded species. [ABSTRACT FROM AUTHOR]

There is increasing evidence that environmental conditions experienced early in life can markedly affect an organism's life history, but the pathways by which early environment influences adult phenotype are poorly known. We used long-term data from two roe deer (Capreolus capreolus) populations (Chizé and Trois-Fontaines, France) to investigate the direct and indirect (operating through fawn body mass) effects of environmental conditions during early life on adult body mass. We found that environmental conditions (population size and spring temperatures) around birth influenced body mass of adult females through both direct and indirect effects in both populations. The occurrence of direct effects means that, for a given fawn body mass, adult female mass decreases with adverse conditions in early life. In contrast, we found no evidence for direct effects of early-life conditions on adult body mass of males, suggesting the existence of sex-specific long-term responses of body mass to stressful early conditions. Our results provide evidence that early environmental conditions influence the adult phenotype through persistent effects over the body development in wild mammal populations. [ABSTRACT FROM AUTHOR]

In several taxonomic groups, females mate with several males during a single reproductive cycle. Although there is evidence that polyandry provides some benefits to females, it often involves mortality costs. However, empirical evidences of mortality costs of polyandry have so far been reported only in invertebrates. Whether polyandry has mortality costs in vertebrates is currently unknown. In the present study, we aimed to fill the gap by investigating the relationships between the level of polyandry (measured either by male relative testes mass or the percentage of multiple paternities) and female patterns of mortality across mammals. While we found that the two metrics of female mortality co-varied with pace of life, we did not find any evidence that polyandry leads to either decreased median lifespan or increased aging rate in mammals. We discuss such an absence of detectable mortality costs of polyandry in female mammals in light of recent advances in the study of mammalian reproductive biology and life-history tactics. [ABSTRACT FROM AUTHOR]

Few mammalian organs vary as dramatically among species as the placenta. This variation is remarkable considering that the placenta's primary function-transfer of nutrients and waste between mother and offspring-does not differ among species. Evolutionary changes in placental morphology remain poorly understood, with suggestions that parent-offspring conflict or evolutionary changes in life history might drive placental evolution. Here we demonstrate that life history differences among eutherian mammals are associated with major transitions in maternofetal interdigitation and placental invasiveness. We show that the repeated evolution of villous interdigitation is associated with reduced offspring production early in life and an increased lifespan. Further changes in placental morphology that reestablish a larger surface area are also associated with a change back to greater offspring production. After controlling for these differences in interdigitation, we also show that the least invasive placental type is associated with a fast pace of life. We predict that selection for a faster pace of life intensifies parent-offspring conflict, and that the repeated evolution of less-invasive placental structures might have allowed mothers to wrest back control of gestation from the fetus and alter their relative allocation to offspring production across life. [ABSTRACT FROM AUTHOR]

How populations respond to climate change depends on the interplay between life history, resource availability, and the intensity of the change. Roe deer are income breeders, with high levels of allocation to reproduction, and are hence strongly constrained by the availability of high quality resources during spring. We investigated how recent climate change has influenced demographic processes in two populations of this widespread species. Spring began increasingly earlier over the study, allowing us to identify 2 periods with contrasting onset of spring. Both populations grew more slowly when spring was early. As expected for a long-lived and iteroparous species, adult survival had the greatest potential impact on population growth. Using perturbation analyses, we measured the relative contribution of the demographic parameters to observed variation in population growth, both within and between periods and populations. Within periods, the identity of the critical parameter depended on the variance in growth rate, but variation in recruitment was the main driver of observed demographic change between periods of contrasting spring earliness. Our results indicate that roe deer in forest habitats cannot currently cope with increasingly early springs. We hypothesise that they should shift their distribution to richer, more heterogeneous landscapes to offset energetic requirements during the critical rearing stage. [ABSTRACT FROM AUTHOR]

Understanding causes of between-sex differences in survival patterns is a long-standing challenge in evolutionary biology. Interspecific differences in male allocation to sexual competition have been suggested to shape species-specific patterns of male adult survival and actuarial senescence, and thereby the extent of between-sex differences in these parameters. Sexual competition is complex and involves both competition for gaining mating (i.e., precopulatory competition) and competition for fertilization opportunities (i.e., postcopulatory competition). However, to date, studies seeking for a relationship between allocation to precopulatory competition and male absolute adult survival have led to contrasting results and the influence of postcopulatory competition on these parameters has never been yet investigated. To fill the gap, we performed a comparative study in large herbivores using median lifespan (i.e., age at which only half of the initial cohort is still alive) and actuarial intensity of senescence (i.e., number of years elapsed between the median lifespan and the age where only one-tenth of the initial cohort is still alive). As expected, we found a lower adult survival and a stronger actuarial intensity of senescence in males than in females. Conversely, we did not find any evidence that variation in male allocation to pre- and/or postcopulatory traits explain between-species differences of both absolute and relative adult survival and intensity of actuarial senescence. These results challenge the idea that allocation to specific traits associated with sexual competition is responsible for between-sex differences in survival and senescence patterns generally reported in mammals. [ABSTRACT FROM PUBLISHER]

Abstract: Although evidence that survival decreases with age in animal species is compelling, the existence of variation in aging rates across different populations of a given species is still questioned. Here, we compared aging rates of 22 pairs of ruminant species living in captive and free-ranging conditions. Based on the recent suggestion that feeding niche is a key factor influencing aging in captivity, we also investigated whether a species'' natural diet influences the aging rates of captive ruminants relative to their wild conspecifics. We found that aging rate in a given species was higher under free-ranging conditions than in captivity, which provides the first evidence of consistent aging rate variation within species. Additionally, our study clearly demonstrates that differences in aging rates between captive and free-ranging ruminants increased as species were more specialized on grass diets. [Copyright &y& Elsevier]

1. Harvest models are often built to explore the sustainability of the dynamics of exploited populations and to help evaluate hunting management scenarios. Age-structured models are commonly used for ungulate population dynamics. However, the age of hunted individuals is usually not recorded, and hunting data often only include body weight and sex limiting the usefulness of traditional models. 2. We propose a new modelling approach that fits data collected by hunters to develop management rules when age is not available. Using wild boar Sus scrofa scrofa as a case study, we built a matrix model structured according to sex and body weight whose output can be directly compared with the observed distribution of hunted individuals among sex and body weight classes. 3. In the face of the current wide scale increase in populations of wild boar, the best feasible option to stop or slow down population growth involves targeting the hunting effort to specific sex and body weight classes. The optimal harvest proportion in the target body weight classes is estimated using sensitivity analyses. 4. The number of individuals shot in each sex and body weight class predicted by our model was closely associated with those recorded in the hunting bag. Increasing the hunting pressure on medium-sized females by 14·6% was the best option to limit growth rate to a target of 0·90. 5. Synthesis and applications. We demonstrate that targeting hunting effort to specific body weight classes could reliably control population growth. Our modelling approach can be applied to any game species where group composition, phenotypic traits or coat colour allows hunters to easily identify sex and body weight classes. This offers a promising tool for applying selective hunting to the management of game species. [ABSTRACT FROM AUTHOR]

For species living in seasonal environments the understanding of demographic processes requires identifying the environmental factors during spring and summer that shape phenotypic variation. We assessed the effects of plant phenology and population abundance during spring-summer on variation in autumn body mass among cohorts (1995-2006) of juvenile alpine chamois (Rupicapra rupicapra). We computed several metrics based on the normalized difference vegetation index (NDVI) to assess interannual variation in plant phenology and productivity. Body mass of both sexes decreased similarly during years with late springs (-20%) and with increasing population abundance (-15%), with no interactive effect. Our results also suggested that forage quality more than forage quantity influenced body mass of juveniles. Variation in body mass of juveniles thus can be used as an indicator of the relationship between chamois populations and their environment. This study also demonstrates the utility of satellite-based data in increasing our understanding of the consequences of spring-summer conditions on life-history traits. [ABSTRACT FROM AUTHOR]

1. Demographic tactics within animal populations are shaped by selective pressures. Exploitation exerts additional pressures so that differing demographic tactics might be expected among populations with differences in levels of exploitation. Yet little has been done so far to assess the possible consequences of exploitation on the demographic tactics of mammals, even though such information could influence the choice of effective management strategies. 2. Compared with similar-sized ungulate species, wild boar Sus scrofa has high reproductive capabilities, which complicates population management. Using a perturbation analysis, we investigated how population growth rates (λ) and critical life-history stages differed between two wild boar populations monitored for several years, one of which was heavily harvested and the other lightly harvested. 3. Asymptotic λ was 1·242 in the lightly hunted population and 1·115 in the heavily hunted population, while the ratio between the elasticity of adult survival and juvenile survival was 2·63 and 1·27, respectively. A comparative analysis including 21 other ungulate species showed that the elasticity ratio in the heavily hunted population was the lowest ever observed. 4. Compared with expected generation times of similar-sized ungulates (more than 6 years), wild boar has a fast life-history speed, especially when facing high hunting pressure. This is well illustrated by our results, where generation times were 3·6 years in the lightly hunted population and only 2·3 years in the heavily hunted population. High human-induced mortality combined with non-limiting food resources accounted for the accelerated life history of the hunted population because of earlier reproduction. 5. Synthesis and applications. For wild boar, we show that when a population is facing a high hunting pressure, increasing the mortality in only one age-class (e.g. adults or juveniles) may not allow managers to limit population growth. We suggest that simulations of management strategies based on context-specific demographic models are useful for selecting interventions for population control. This type of approach allows the assessment of population response to exploitation by considering a range of plausible scenarios, improving the chance of selecting appropriate management actions. [ABSTRACT FROM AUTHOR]

In polygynous mammals, sex-specific patterns of body growth are linked to divergent selection pressures on male and female body size, resulting in sexual dimorphism (SD). For males, reproductive success is generally linked to body size, hence, males should prioritise early growth. For females, reproductive success is linked to resource availability, so they may adopt a more conservative growth tactic. Using longitudinal monitoring of known-age animals in two contrasting populations and an allometric approach to disentangle the relative contribution of structural size and physiological condition to SD, we addressed these issues in the weakly polygynous roe deer. Despite very different environmental conditions, we found remarkably similar patterns in the two populations in the mass - size allometric relationship at each life history stage, suggesting that relative allocation to structural size and physiological condition is highly constrained. SD in structural size (indexed by hind foot length) involved sex-specific growth trajectories governed by a single mass - size allometric relationship during the juvenile stage, such that males were both bigger and heavier than females. In contrast, SD in physiological condition (indexed by the allometric relationship between body mass and hind foot length, expressed as body mass for a given body size) developed markedly during the sub-adult stage in relation to sex differences in the timing of first reproduction. Among adults, males were heavier for a given size than females, suggesting that, relative to females, males express a capital breeder tactic, accumulating fat reserves to offset reproductive costs. By the senescent stage, SD in physiological condition had disappeared, with both sexes governed by a single allometric relationship, suggesting more rapid senescence in males than females. Individuals born into poor cohorts were generally lighter for a given size, indicating growth priority for skeletal size over physiological condition in both sexes. However, sex differences in cohort effects among sub-adults resulted in lower size-specific SD in poor cohorts, indicating that body condition of sub-adult females is buffered against environmental harshness. We conclude that sex-differences in reproductive tactics impose constraints on the ontogeny of SD in roe deer, leading to sex-specific trajectories in structural size and physiological condition. [ABSTRACT FROM AUTHOR]

Background: Data on spatial genetic patterns may provide information about the ecological and behavioural mechanisms underlying population structure. Indeed, social organization and dispersal patterns of species may be reflected by the pattern of genetic structure within a population. Methodology/Principal Findings: We investigated the fine-scale spatial genetic structure of a roe deer (Capreolus capreolus) population in Trois-Fontaines (France) using 12 microsatellite loci. The roe deer is weakly polygynous and highly sedentary, and can form matrilineal clans. We show that relatedness among individuals was negatively correlated with geographic distance, indicating that spatially proximate individuals are also genetically close. More unusually for a large mammalian herbivore, the link between relatedness and distance did not differ between the sexes, which is consistent with the lack of sex-biased dispersal and the weakly polygynous mating system of roe deer. Conclusions/Significance: Our results contrast with previous reports on highly polygynous species with male-biased dispersal, such as red deer, where local genetic structure was detected in females only. This divergence between species highlights the importance of socio-spatial organization in determining local genetic structure of vertebrate populations. [ABSTRACT FROM AUTHOR]

Little is known about traits under sexual selection in territorial mammals with low sexual size dimorphism. We examined the potential for sexual selection on male body mass and antler length in the European roe deer Capreolus capreolus, a territorial ungulate in which males are less than 10% heavier than females. Independently, both body mass and antler length (irrespective of age) had a positive effect on male yearly breeding success. However, when corrected for body mass, antler length at a given mass only had a slight effect on male breeding success. This suggests that: (1) ‘bigger is better’ and (2) sexual selection is responsible for at least part of the observed variation in body mass and antler length in roe deer. High body mass and large antlers may be advantageous to males for two reasons: (1) they enhance fighting ability and dominance, so allowing males to defend better their territory and hence access mates, and (2) they attract females because they are honest signals of male phenotypic quality. This suggests that, even in weakly dimorphic ungulate species, sexual selection may lead to a marked influence of body mass on male breeding success, as long as body mass is also strongly selected in females. [ABSTRACT FROM AUTHOR]

We quantified the repeatability of .900 individual measures of hind foot length from 2 French populations of roe deer (Capreolus capreolus) monitored by capture-recapture. We found a high repeatability (i.e., high intra-class correlation, 0.76, 95% CI = 0.72- 0.83 and 0.92, 95% CI = 0.91-0.95) in both populations. We also found that inexperienced observers reached a high level of intra- (1.00, 95% CI = 0.96-1.00) and inter-observer repeatability (0.99, 95% CI = 0.98-1.00) when measuring hind foot length of harvested animals with a tool specifically designed for this task. Managers should pay particular attention to limit measurement errors because unreliable measurements require an increased sample size to assess individual variation and can mask biological patterns. [ABSTRACT FROM AUTHOR]

The field of habitat ecology has been muddled by imprecise terminology regarding what constitutes habitat, and how importance is measured through use, selection, avoidance and other bio-statistical terminology. Added to the confusion is the idea that habitat is scale-specific. Despite these conceptual difficulties, ecologists have made advances in understanding 'how habitats are important to animals', and data from animal-borne global positioning system (GPS) units have the potential to help this clarification. Here, we propose a new conceptual framework to connect habitats with measures of animal performance itself-towards assessing habitat-performance relationship (HPR). Long-term studies will be needed to estimate consequences of habitat selection for animal performance. GPS data from wildlife can provide new approaches for studying useful correlates of performance that we review. Recent examples include merging traditional resource selection studies with information about resources used at different critical life-history events (e.g. nesting, calving, migration), uncovering habitats that facilitate movement or foraging and, ultimately, comparing resources used through different life-history strategies with those resulting in death. By integrating data from GPS receivers with other animal-borne technologies and combining those data with additional life-history information, we believe understanding the drivers of HPRs will inform animal ecology and improve conservation. [ABSTRACT FROM AUTHOR]

Ecology Letters (2010) 13: 915-935 Abstract Fitness costs of reproduction play a key role in understanding the evolution of reproductive tactics. Nevertheless, the detection and the intensity of costs of reproduction vary according to which life-history traits and species are studied. We propose an evolutionary model demonstrating that the chance of detecting a cost of reproduction should be lower when the fitness component studied has a low rather than high variance. Consequently, the fitness component that is affected the most by costs of reproduction should vary with life speed. Since long-lived species have developed a strategy that avoids jeopardizing their survival and short-lived species favour current reproduction, variance in survival is smaller and variance in reproduction higher in long-lived vs. short-lived species. We review empirical studies of costs of reproduction in free-ranging mammals, comparing evidence of costs reported among species and focal traits. In support of our model, more studies reported evidence of reproductive costs of reproduction in ungulates than in rodents, whereas survival costs of reproduction were more frequent in rodents than in ungulates. The life-history model we propose is expected to apply to any species, and hence provides a better understanding of life-history variation, which should be relevant to all evolutionary ecologists. [ABSTRACT FROM AUTHOR]