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Promislow, D. E L. and P. H. Harvey. Living fast and dying young: a comparative analysis of life-history variation among mammals. Journal of Zoology (London)
Abstract
Recent comparative studies point to the importance of mortality schedules as determinants in the evolution of life-history characteristics. In this paper, we compare patterns of mortality from natural populations of mammals with a variety of life histories. We find that, after removing the effects of body weight, mortality is the best predictor of variation in life-history traits. Mammals with high levels of natural mortality tend to mature early and give birth to small offspring in large litters after a short gestation, before and after body size effects are factored out. We examine the way in which life-history traits relate to juvenile mortality versus adult mortality and find that juvenile mortality is more highly correlated with life-history traits than is adult mortality. We discuss the necessity of distinguishing between extrinsic sources of mortality (e.g. predation) and mortality caused by intrinsic sources (e.g. costs of reproduction), and the role that ecology might play in the evolution of patterns of mortality and fecundity. We conclude that these results must be explained not simply in the light of the demographic necessity of balancing mortality and fecundity, but as a result of age-specific costs and benefits of reproduction and parental investment. Detailed comparative studies of mortality patterns in natural populations of mammals offer a promising avenue towards understanding the evolution of life-history strategies.
... More generally, biologists recognize that, within broad taxa such as the class of mammals, the life histories of species vary along a fast-slow dimension, indexed not only by lifespan, but also by several related features. Relative to "slow" mammalian species, "fast" species have a shorter gestation period, grow more quickly post-gestation, reach sexual maturity earlier, produce larger litter sizes, and have shorter inter-birth intervals (Promislow & Harvey, 1990; for similar variation in birds, see Sibly et al., 2012). ...
... One primary dimension on which species vary is the fast-slow dimension, with "fast" species beginning reproduction earlier, putting more effort into reproduction upon its onset, and dying younger, relative to "slow" species (e.g., Promislow & Harvey, 1990). Uncontrolled mortality appears to be one driving factor, as greater uncontrolled mortality favors earlier reproduction, which results in foregoing allocations to bodily maintenance (see André & Rousset, 2020, for important qualifications). ...
... Chisholm (1993Chisholm ( , 1996 more explicitly grounded his model of alternative reproductive strategies within evolutionary biology. Promislow and Harvey (1990) focuses on variations in time preference-the extent to which future consequences are discounted, whereby a steeper discount rate favors smaller, immediate rewards, whereas a more gradual discount rate favors larger, delayed rewards. This is a psychological parallel to the current reproduction vs. future reproduction trade-off in life history theory; when the future is uncertain, immediate payoffs should be generally preferable. ...
... Under this strategy, females would have to take the risk of no offspring within a breeding season, and neonatal survival relies on maternal care to a great extent, with adaption to lactation, protection, and others. 4,[24][25][26] As weaning indicates the end of lactation and the independence of nutrition for an infant, it is closely related to tooth eruption and body growth. Generally, it occurs with considerable body growth and the eruption of the first molar. ...
... The reproduction of mammals has long been discussed by many studies, and its relationship with body size and phylogeny is among the most interesting topics. 2,[4][5][6]27 This study on Plesiaceratherium from the Early Miocene of revealed a reproduction strategy of singleton pregnancy iScience Article similar to that of living rhinoceroses, including traits of small litter size, long lactation period, delayed age of maturity, and small lifetime offspring number. The number of offspring per pregnancy depends mainly on genetic factors. ...
... 51,53 The maximum offspring number is the center of reproduction trade-off, and its relationship with body size has long been discussed. 4,57 According to the equation of body weight against litter size, mammals with a body weight greater than 1 kg have decreased litter size. 46 To date, all unquestionable stem fossil perissodactyls have a body weight greater than 10 kg, and living perissodactyl weigh 150-3000 kg (Table S9). ...
Reproductive strategy is among the most important characteristics of organism. Here, we report reproductive strategy of singleton pregnancy of a fossil rhinoceros, Plesiaceratherium gracile, from 18 mya of the Shanwang Basin, China. Dental and body development data revealed that after birth, the calf of P. gracile is breastfed for 2–3 years; at approximately 5 years of age, when the M2 tooth is slightly worn, the female has already reached sexual maturity and attained a size close to that of an adult and could give birth to the first calf. Furthermore, given litter size is phylogenetically conservative and closely correlates with body size, we conclude that the litter size of perissodactyls is determined by the singleton pregnancy since the Eocene. By contrast, other reproductive traits are highly variable and have a different pace of evolution, and traits observed in living rhinoceroses have been evolving at least since 18 mya.
... Studies of the class Mammalia have been particularly important in identifying patterns and causes of variation in life history strategies, generating ideas and concepts that now constitute life-history theory [6][7][8][9][10]. The fast-slow continuum first appeared in the pioneering paper of Stearns [11], and was identified as the main axis of life history variation; the altricial-precocial spectrum was the secondary axis of variation, after accounting for body mass and phylogeny. ...
... The diversity of life-history strategies has been the focus of ecological studies for many decades, with researchers seeking to describe and interpret the repertoire of life histories in different animal and plant groups [1,2,6,11]. Despite great effort in collecting data on demography and life history, several groups are often misrepresented in both general and taxon specific analyses, forming a major gap in the understanding of life histories. ...
... Juvenile survival and age at last reproduction, which can also be interpreted as an adult lifespan parameter, determined the position of species along this continuum, similar to eutherians [22]. Promislow & Harvey [6] suggested that stage-specific mortality schedules drive species position on the fast-slow continuum; therefore, juvenile survival should be a crucial variable, as we observed in marsupials (this study), but not in eutherians [9,22]. The pre-reproductive phase is in fact a critical period in the life of fast marsupials, in which juveniles are subjected to high extrinsic mortality due to predation and other environmental hazards [33]. ...
Previous studies have suggested that mammal life history varies along the fast-slow continuum and that, in eutherians, this continuum is linked to variation in the potential contribution of survival and reproduction to population growth rate (λ). Fast eutherians mature early, have large litters and short lifespans, and exhibit high potential contribution of age at first reproduction and fertility to λ, while slow eutherians show high potential contribution of survival to λ. However, marsupials have typically been overlooked in comparative tests of mammalian life-history evolution. Here, we tested whether the eutherian life-history pattern extends to marsupials, and show that marsupial life-history trade-offs are organized along two major axes: (i) the reproductive output and dispersion axis, and (ii) the fast-slow continuum, with an additional association between adult survival and body mass. Life-history traits that potentially drive changes in λ are similar in eutherians and marsupials with slow life histories, but differ in fast marsupials; age at first reproduction is the most important trait contributing to λ and fertility contributes little. Marsupials have slower life histories than eutherians, and differences between these clades may derive from their contrasting reproductive modes; marsupials have slower development, growth and metabolism than eutherians of equivalent size.
... Several theories have been proposed to explain the linkages between ecological conditions and demographic traits such as body size growth rates, age of first reproduction, reproductive rates, and adult lifespan. Extrinsic mortality risk (e.g., unavoidable mortality caused by environmental influences such as predation, low food availability, or infectious disease) may limit the benefits of investment for future reproduction (Promislow & Harvey, 1990). Species in environments with high mortality risk may attain reproductive maturity earlier, invest more heavily in reproduction earlier in life, and experience low offspring survival (Table 1). ...
... Extrinsic mortality risk (Promislow & Harvey, 1990) High extrinsic mortality Genetic adaptations Earlier Shorter Higher ...
... According to the extrinsic mortality risk hypothesis (Table 1), individuals with a higher extrinsic mortality risk are expected to have earlier maturation and faster reproductive rates than those with lower extrinsic mortality risk (Charnov & Berrigan, 1993;Kuzawa & Bragg, 2012;Promislow & Harvey, 1990). From that perspective, our results would suggest that the extrinsic mortality risk has been highest in the Virungas, followed by Bwindi, and then Mbeli. ...
Objectives:
Several theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population (Gorilla gorilla gorilla) and two mountain gorilla populations (Gorilla beringei beringei).
Materials and methods:
We compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long-term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas).
Results:
The Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns.
Discussion:
These patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolutionary mechanisms responsible for these differences, whether a consequence of genetic adaptation to fluctuating food supplies ("ecological risk aversion hypothesis") or phenotypic plasticity in response to the abundance of food ("energy balance hypothesis"). Our results do not seem consistent with the extrinsic mortality risks at each site, but current conditions for mountain gorillas are unlikely to match their evolutionary history. Not all traits fell along the expected fast-slow continuum, which illustrates that they can vary independently from each other ("modularity model"). Thus, the life history traits of each gorilla population may reflect a complex interplay of multiple ecological influences that are operating through both genetic adaptations and phenotypic plasticity.
... The small-bodied rodents show a similar set of life history traits, such as high metabolic rate, short gestation length, weaning, and sexual maturity attained at early age, large litters produced at short intervals with brief parental care, fast growth, short life span, and high mortality (Promislow and Harvey 1990). Although some traits are fairly conserved, others vary widely. ...
... There is body literature relating the r-K continuum with adult body mass among mammals. However, when the influence of body size is removed (statistically speaking), life history traits continuum is termed as fast-slow continuum (Promislow and Harvey 1990). This continuum reflects mainly the fertility related to age at maturity, but also high reproductive rate, early maturity, and low survival. ...
... Though Promislow and Harvey's (1990) analysis pertained to species-level evolutionary processes, Chisholm (1993) proposed that similar selective forces operate on life history variations within a species. Environmental mortality risks, he proposed, similarly lead to selection of withinspecies differences in life history trajectories, at least with respect to humans. ...
... For three decades, the prevailing explanation has been differences in the extrinsic mortality ratethe rate of mortality that is unaffected by the organism's allocation decisions (Promislow & Harvey, 1990;Charnov, 1991). (Intrinsic mortality, by contrast, is a result of allocation decisions, such as investment in reproduction rather than in mortality reduction and somatic maintenance.) ...
... Somatic growth is dependent on energy intake. A fundamental prediction from life history theory is that greater energy intake will accelerate growth and, therefore, pubertal timing (Kuzawa & Bragg, 2012;Promislow & Harvey, 1990). Age at menarche in girls has been decreasing worldwide, with declining rates of poverty and greater access to food being proposed as primary contributing factors (Parent et al., 2003). ...
... Rights reserved. (Braendle et al., 2011) that are often situated conceptually on a slow-fast continuum (Promislow & Harvey, 1990;cf. Richardson et al., 2017a, b). ...
Life-history-derived models of female sexual development propose menarche timing as a key regulatory mechanism driving subsequent sexual behavior. The current research utilized a twin subsample of the National Longitudinal Study of Adolescent to Adult Health (Add Health; n = 514) to evaluate environmental effects on timings of menarche and sexual debut, as well as address potential confounding of these effects within a genetically informative design. Results show mixed support for each life history model and provide little evidence rearing environment is important in the etiology of individual differences in age at menarche. This research calls into question the underlying assumptions of life-history-derived models of sexual development and highlights the need for more behavior genetic research in this area.
... These observed differences in both neural development and mental health outcomes could potentially vary as a function of instability that reflects environmental adaptation. Such inference is consistent with the life history strategy theory (Belsky et al., 2011;Promislow and Harvey, 1990), which posits that early experiences shape one's strategy for survival, leading to certain phenotypic traits that increase the organism's chances of survival and reproduction. These patterns were established in animal models such as squirrels (Dantzer et al., 2013), birds (Martin, 1995), nonhuman primates (Pereira and Fairbanks, 2002), and rodents (Careau et al., 2009), whereby variations in the environment are associated with reproductive behaviors and offspring growth. ...
... It is possible that this increased efficiency in structural network reflects an adaptive response to household instability, though with potential long-term implications for mental health. Such inference is consistent with theoretical models such as life history theories (Belsky et al., 2011;Promislow and Harvey, 1990) and the stress acceleration hypothesis (Callaghan and Tottenham, 2016), which posit that less predictable early environments or increased exposure to early life stress accelerates biological maturation to increase organism survival, though potentially at later costs. Relatedly, evidence on the "weathering . ...
Unstable and unpredictable environments are linked to risk for psychopathology, but the underlying neural mechanisms that explain how instability relate to subsequent mental health concerns remain unclear. In particular, few studies have focused on the association between instability and white matter structures despite white matter playing a crucial role for neural development. In a longitudinal sample recruited from a population-based study (N = 237), household instability (residential moves, changes in household composition, caregiver transitions in the first 5 years) was examined in association with adolescent structural network organization (network integration, segregation, and robustness of white matter connectomes; Mage = 15.87) and young adulthood anxiety and depression (six years later). Results indicate that greater instability related to greater global network efficiency, and this association remained after accounting for other types of adversity (e.g., harsh parenting, neglect, food insecurity). Moreover, instability predicted increased depressive symptoms via increased network efficiency even after controlling for previous levels of symptoms. Exploratory analyses showed that structural connectivity involving the left fronto-lateral and temporal regions were most strongly related to instability. Findings suggest that structural network efficiency relating to household instability may be a neural mechanism of risk for later depression and highlight the ways in which instability modulates neural development.
... An increase in adult mortality from an active and conspicuous movement lifestyle, as well as from other extrinsic sources of mortality, may place a priority on food acquisition for several reasons. First, greater adult mortality is widely associated with higher fecundity and reproductive effort (e.g., more offspring per reproductive attempt, higher offspring growth rates, higher levels of parental care), which depend on higher food delivery (Promislow and Harvey 1990;Martin 1995Martin , 2015Ghalambor and Martin 2001; fig. 4). ...
... Conversely, the slower life history strategies of longlived species may have lower food acquisition requirements that allow for slower and less conspicuous movement lifestyles. Low reproductive effort, including fewer offspring per reproductive attempt and slower offspring growth, is typical of long-lived species (Promislow and Harvey 1990;Martin 1995Martin , 2015. Lower food acquisition rates among long-lived species that rely on slower foraging speeds and microsites that allow inconspicuous foraging behaviors appear to be sufficient to support their lower reproductive effort. ...
Why do species differ in their movement lifestyles? Animals that spend more time sitting motionless and acquire food using less conspicuous movements can be more vigilant and less obvious to predators. More active animals that use food types and sites that require more conspicuous behaviors increase vulnerability to predators. Life history theory predicts that aversiveness to mortality risk evolves inversely to adult survival probability. Consequently, we postulated that long-lived species evolved inconspicuous movement lifestyles whereas shorter- lived species use more conspicuous movement lifestyles. We tested this hypothesis by quantifying the movement lifestyles of nine tropical songbird species. Use of conspicuous movement and foraging behaviors, such as flying and hovering, was greatest in shorter-lived species and decreased with increasing adult survival probability across species. Similarly, foraging speed decreased with increasing adult survival based on a meta-analysis of 64 songbird species. Faster and conspicuous movement lifestyles of shorter-lived species likely increase food acquisition rates which fits with faster life history strategies that include more feeding trips for young and faster growth. Similarly, slow movement lifestyles of long-lived species fit with the reduced food needs of slower life history strategies. Movement lifestyles may have evolved as an integrated component of the slow-fast life history continuum.
... Ecological conditions may initially drive the evolution of life history traits, and as a result, closely related species may differ in physiology, behaviour, or morphology as a result of evolving in environments that favours a specific life history strategy (Oli 2004, Réale et al. 2010). This pace of life syndrome hypothesis incorporates aspects of the R-selected vs. K-selected concept (Pianka 1970) as well as the fast-slow continuum (Promislow andHarvey 1990, Oli 2004) by including behaviour and physiology to account for individual variation (Réale et al. 2010). "Fast" species are those previously considered R-selected, characterized by early maturity, short lifespan, low survival rates, high fertility, low parental care, lack of philopatry, and high metabolic rates (Réale et al. 2010). ...
... Many of these traits show a close correlation. For example, gestation length, age of maturity, and offspring body mass are closely linked to survival rates (Promislow and Harvey 1990). For "fast" species, fecundity and age of maturity have a greater influence on population growth, while juvenile and adult survival rates have a greater influence for "slow" species (Heppell et al. 2000, Gaillard and Yoccoz 2003, Lima et al. 2003, Oli and Dobson 2003, Oli 2004. ...
The Natal mole-rat (Cryptomys hottentotus natalensis) is a social subspecies of African mole-rat related to the common mole-rat (Cryptomys hottentotus hottentotus). They inhabit mesic grassland in eastern South Africa from coastal regions to well over 2000m elevation. There have been a few studies on their physiology and reproductive suppression, but their ecology and life history has not been reported in detail. This study used capture-mark recapture methods to investigate life history, population demographics, behaviour, and gene flow in wild Natal mole-rats living at a high elevation site in the southern Drakensberg Mountains. I captured a total of 403 individuals across 52 family groups. Individuals were weighed, measured, sexed, and assigned a reproductive status on capture. Tissue samples were collected for genetic analysis and then they were implanted with a passive integrated transponder for identification at recapture. Groups were captured every six months over the course of 2 years.
Both environmental factors and population demographics can have far reaching effects on individual life history, including altering spatial arrangement, behaviour, body condition, and fecundity rates. I found that Natal mole-rats have reduced group sizes (mean 6) compared to the more arid dwelling African mole-rat species. Population wide sex ratios were evenly split between males and females. However, within-group adult sex ratios were skewed towards males, and this skew became more pronounced in larger groups. Sex ratios, group size, and group biomass did not show any seasonal differences. Small litter sizes (1.3), slow population growth rates (0.17), long maturation time (1.2 years) of females indicate a “slow” life history. I found strong sexual dimorphism, with males being larger than females. Male exhibited a faster growth rate compared to females, but growth rates were not affected by group size. This indicates that within-group competition is reduced or absent, likely due to the smaller mean group size or increased availability of food resources. Individual body condition varied between seasons and was affected by group size. During summer body condition increased with increasing group size, highlighting the benefits of collective foraging. But during winter body condition decreased with increasing group size, likely due to low quality of food and a necessity to continue foraging through winter. Interestingly, the body condition in reproductive females increased with group size during winter, when all others decreased. However, their fecundity did not appear to be affected by group size. The expected benefits of helping effects from larger groups may be reduced in Natal mole-rats.
Observations on subterranean mammals suggest that they exhibit diel rhythms despite the lack of visual cues in their underground burrows, but it is unknown how ambient temperature, photoperiod, or individual characteristics affects their activity. I used RFID technology to monitor daily activity patterns of wild mole-rats during the summer and winter seasons. I combined the activity data with satellite climate data to investigate how their activity patterns vary between seasons and whether their activity depends on individual characteristics such as body mass, sex and reproductive status. Individual characteristics, including reproductive status, did not affect general activity. This result suggests that reproductive and non-reproductive individuals contribute equally to cooperative behaviours unlike other mole-rats where reproductive individuals exhibit reduced contributions. I found that in winter, individuals were more active during mid-day to coincide with higher soil temperatures, whereas in summer, they showed a bimodal activity pattern during early morning and late afternoon coinciding with cooler soil temperatures. Activity patterns are therefore a behavioural adaptation to avoid extreme burrow temperatures and a mechanism to maintain a stable core body temperature. Thermoregulatory behavioural adaptations appear to be more important than differences in cooperative contributions to Natal mole-rats.
vi
I extracted DNA from tissue samples and then used custom designed microsatellite markers to assess spatial grouping and gene flow in the population. Population-level analyses, such as FST, focus on genetic relatedness among social groupings, while relatedness coefficients determine relatedness between individuals in the population. I found that pairwise-relatedness coefficients were surprisingly similar to the arid dwelling Damaraland mole-rat (Fukomys damarensis) in the southern Kalahari, despite assumptions that higher rainfall would provide more dispersal opportunities and higher immigration rates. Population level FST values indicated the presence of male-biased dispersal. Relatedly, females were more related to females in neighbouring family groups than males. The study site had three landscape features which may act as dispersal barriers, such as a road, a river, and a steep rocky hillside. A non-spatial Bayesian clustering analysis determined that these features did not pose major dispersal barriers to mole-rats. I estimated dispersal distances to be between 350 – 400m, with males having slightly higher dispersal distances compared to females. There was no evidence of isolation by distance, and gene flow is well maintained within the study site.
In conclusion this study found that Natal mole-rats continue to exhibit delayed dispersal and high levels of within-group relatedness despite increased annual rainfall. Their life history and physiological adaptations allow them to cope with living in an environment with extreme seasonal fluctuations. With the projected increased ambient temperatures due to climate change, mole-rats living at higher altitude may not cope well with very minor deviations from the conditions they have adapted to. I found that body mass appeared reduced compared to 20 years ago, and this decrease may be due to climate change or habitat alteration. The evolution of various physiological traits unique to Natal mole-rats means they may be more susceptible to the effects of climate change than other subterranean rodents. Previous labelling of Natal mole-rats as “less social” should be avoided and there is evidence to support the claim that they are singular cooperative breeders.
... Comparative methods and phylogenetic ecology (e.g. Promilsow and Harvey 1990;Harvey and Pagel 1991;Sibly and Brown 2007;Dobson 2012;Brown et al. 2018;Burger et al. 2019) are often using a somewhat similar variance decomposition as applied in the current paper. Yet, these methods have no explicit focus on the underlying natural selection causality, as they have no bottom-up selection that shows how the independent traits evolve by a deeper more fundamental natural selection component. ...
The inter-specific life history and ecological variation of mammals is often explained as allometric consequences of physiological adaptations to unexplained body mass variation. But these hypotheses are unnecessary because the allometric scaling is explained already by the natural selection that explains the variation in mass. I decompose the population ecological life histories of 4,936 species of mammals to show how the selection of mass accounts for the life history and population ecological variation in mammals. This shows that 55% of the within order variance, and 91% of the between order differences, in the body mass, demography , and population ecological traits are reconciled by the response of population dynamic feedback selection to variation in net energy, mortality, and intra-specific interactive competition.
... Being based on the bottom-up unfolding of natural selection, my study is not comparable with comparative analyses that use life history correlations with body mass, mortality, lifestyles, energy use, and phylogeny to generate hypotheses of life history evolution (e.g. Promilsow and Harvey 1990;Blackburn 1991;Saether and Bakke 2000;Bielby et al. 2007;Dobson and Oli 2007;Brown et al. 2018;Burger et al. 2019). While these studies identify inter-specific trait correlations that follow from evolution, they do not necessarily identify the underlying natural selection causes. ...
Contingent life history theory explains evolution backwards by analysing the fitness consequences of trade-offs and constraints in the evolved species of today, bypassing the essential challenge of predicting evolution forwardly by the cause and effect of natural selection. I do the latter to decompose the population ecological life histories of 11,187 species of birds. This shows how the selection of mass accounts for inter-specific variation, with 76% of the within order variance, and 72% of the between order differences , in the body mass, demography, and population ecological traits being reconciled by the response of population dynamic feedback selection to variation in net energy, mortality, and intra-specific interactive competition.
... Dispersal is an inherently costly process for individuals, as it may increase exposure to predation and disease, and settlement in suboptimal habitat may also result in starvation and increased time/opportunity costs and energy expenditure (Bonte et al., 2012;Estes-Zumpf & Rachlow, 2009;Ferreras et al., 2004). Survival of dispersing subadults is typically lower than in adults across multiple taxa including birds (Beauchamp, 2023;Oppel et al., 2015), mammals (Caughley, 1966;Promislow & Harvey, 1990;Rödel et al., 2015;Sibly et al., 1997), and to a lesser degree reptiles (Pike et al., 2008). In relatively long-lived mammals, such as ungulates, adult survival is relatively constant compared with annual subadult survival which may fluctuate widely (Gaillard et al., 2000). ...
Natal dispersal and survival are the primary means of population expansion in reintroduction projects, but few projects intensively monitor the offspring of released individuals. Subadults may differ from adults in their susceptibility to threats or their habitat requirements which may require alternate management strategies. We investigated survival rates, habitat use and shelter site choice during natal dispersal in reintroduced western quolls ( Dasyurus geoffroii ). We compared data previously collected on the first cohort of subadults born to founders ( n = 17) with subadults from an established cohort 6 years after release ( n = 22). Subadult quolls were radiotracked after weaning to monitor survival and habitat use and the effects of sex and size on mortality, dispersal distance, habitat selection and shelter choice were investigated in the established cohort. We confirmed high survival with no confirmed deaths among the established cohort and only two confirmed deaths among F1 founders (12%) during the 26 weeks of monitoring. All individuals remained within the area where introduced predators, a key threat to quolls, were intensively managed through aerial baiting. Males dispersed significantly further than females, with consistent outward expansion of up to 13‐km and increased movement between shelter sites occurring between mid‐December and early‐February. During dispersal, both sexes displayed a similar preference for woodland habitats and avoidance of open areas to adult quolls. The founding cohort primarily used rabbit warrens as shelter sites, whereas the established cohort after release used more hollow logs and tree hollows. This change may indicate gradual selection towards these safer shelter sites and filial transfer of this preference to offspring. Monitoring subadult movement, mortality and habitat use is integral to determining population viability and the effectiveness of management actions in reintroduction programs.
... A key assumption in life history theory is the 'allocation rule', which states that energy is limited and individuals must make trade-offs between life functions [36]. As a result, there are two main strategies for maximizing reproductive success [36][37][38]-a fast pace of life (short life-span, short development, short inter-birth intervals and little/no parental investment) and a slow pace of life (long life-span, long development, long inter-birth intervals and substantial parental investment) [39,40]. There are different energetic costs to the development, initiation and deployment of different elements of the immune system [35,41,42] (see Table 1 for summary). ...
Life history theory indicates that individuals/species with a slow pace of life invest more in acquired than innate immunity. Factors that decrease the pace of life and predict greater investment in acquired immunity include increased nutritional resources, increased pathogen exposure and decreased risk of extrinsic mortality. Common care behaviors given to sick individuals produce exactly these effects: provisioning increases nutritional resources; hygiene assistance increases disease exposure of carers; and protection can reduce the risk of extrinsic mortality to sick individuals. This study, therefore, investigated under what conditions care giving behaviors might impact immune strategy and pace of life. The study employed an agent-based model approach that simulated populations with varying levels of care giving, disease mortality, disease transmissibility, and extrinsic mortality, enabling measurements of how the immune strategy and age structure of the populations changed over evolutionary time. We used multiple regressions to examine the effects of these variables on immune strategy and the age structure of the population. The findings supported our predictions that care was selected for an acquired immunity. However, the pace of life did not slow as expected. Instead, the population shifted to a faster, but also more cost-intensive reproductive strategy in which care improved child survival by subsidizing the development of acquired immune responses.
... The study conducted by Schraft et al. revealed that childhood trauma was a significant predictor of psychopathy facet scores. The study also found that such exposure also had a predictive effect on the behavioural components of psychopathy, even after accounting for exposure to violence in the community [99][100][101][102]. ...
This critical review examines research on childhood trauma, personality traits, sexual fantasy, and sexually coercive behaviour. While each of these areas has been extensively studied in isolation, there is a notable lack of comprehensive research that investigates these variables collectively. This review aims to bridge this gap by synthesizing existing knowledge and emphasizing the need for a more integrated approach. Studies have uncovered intriguing links between childhood trauma, the influence of personality traits on sexual fantasies, and the potential connection between sexual fantasies and sexually coercive behaviour. However, the intricate interplay among these variables remains largely investigated in empirical research. By consolidating the research on these various relationships, this review underscores the importance of gaining a more holistic and nuanced understanding of existing complex dynamics. This work serves as a foundational step towards encouraging future research exploring these variables, assisting in elucidating their collective influence on human behaviour.
... risky behaviors can help an animal gather resources to fuel current reproduction but in doing so expose itself to greater mortality risk), but it may be that an individual's behavior is more tightly linked to its acquisition strategies rather than its allocation strategies (Laskowski et al., 2021). This is especially relevant because, while there is good evidence for tradeoffs among life-history strategies at the species level (Healy et al., 2019;Promislow & Harvey, 1990), it seems unlikely that a single species would harbor the same level of variation in the key behavioral or physiological traits that moderate allocation trade-offs as is present across a large number of species (Stearns & Rodrigues, 2020;White & Seymour, 2004). Together with results from multiple previous meta-analyses testing for the predictions of the pace-of-life syndrome hypothesis (Haave-Audet et al., 2022;Moiron et al., 2020;Royauté et al., 2018), empirical evidence on individual differences in resource allocation strategy driving individual differences in behavior appears to be weak, at best. ...
Understanding the evolutionary mechanisms underlying the maintenance of individual differences in behavior and physiology is a fundamental goal in ecology and evolution. The pace‐of‐life syndrome hypothesis is often invoked to explain the maintenance of such within‐population variation. This hypothesis predicts that behavioral traits are part of a suite of correlated traits that collectively determine an individual's propensity to prioritize reproduction or survival. A key assumption of this hypothesis is that these traits are underpinned by genetic trade‐offs among life‐history traits: genetic variants that increase fertility, reproduction and growth might also reduce lifespan. We performed a systematic literature review and meta‐analysis to summarize the evidence for the existence of genetic trade‐offs between five key life‐history traits: survival, growth rate, body size, maturation rate, and fertility. Counter to our predictions, we found an overall positive genetic correlation between survival and other life‐history traits and no evidence for any genetic correlations between the non‐survival life‐history traits. This finding was generally consistent across pairs of life‐history traits, sexes, life stages, lab vs. field studies, and narrow‐ vs. broad‐sense correlation estimates. Our study highlights that genetic trade‐offs may not be as common, or at least not as easily quantifiable, in animals as often assumed.
... The other is to allocate resources to reproductive effort, such as engaging in early and frequent mating activities, delivering more children, yet investing less in existing children's quality Geary, 2002). The two LH strategies have been understood as varying on a fast-slow continuum (Promislow & Harvey, 1990), with the former characterizing slow paces of life since it results in delayed reproduction, and the latter relatively fast paces of life since it promotes instant reproductive payoffs. ...
The species-general life history (LH) principle posits that extrinsic morbidity-mortality risks accelerate organisms’ pace of life and promotes fast LH-related traits (e.g., earlier sexual maturation and reproduction). Humans, however, have experienced uniformly decelerated LH due to their evolved abilities and efforts in controlling environmental contingencies. The present study proposes that the reason for the existence of such human-specific deceleration of LH may be rooted in human parenting, hence aims to explore the roles of parenting within the relationships between environmental adversities and children’ LH calibration. The present study used data from the NIMH Data Archive (NDA) reported by 2014 children and their caregivers, and examined the effects of parental investment in calibrating children’s LH behavioral manifestations, as well as in moderating the impacts of environmental harshness and unpredictability on children’ development of LH. The findings showed that parental investment negatively predicts the development of fast LH behavioral profiles in children and moderates the impacts of environmental adversities directly imposed on children. We conclude that human parental investment serves as an important pivot in down-regulating environmental effects on children’s LH calibration, providing an alternative insight into the species-specific deceleration of LH.
... We emphasize that biologists applying them to vertebrate populations must be explicit about the equivalence and interpretation of the parameters depending on the source of data, whether the specific model that was applied included assumptions of continuous or discrete time, and how the model corresponds to the life history of the species. Often, the estimated parameters are used in a comparative sense (Promislow and Harvey 1990) to understand relationships among reproduction and mortality among species exhibiting so-called fast and slow life histories (Oli and Dobson 2003). However, specific estimates of r or λ and MLS are fundamental to conservation and management. ...
... The concept of competition for resources between somatic and generative functions is one of the cornerstones in modern evolutionary biology (Kirkwood, 1977;Stearns, 1992). In particular, for mammals, there is a clear evolutionary trend toward earlier breeding dates and increased fecundity in species with a high mortality rate (Promislow and Harvey, 1990). In the eight studied species of cricetids, we found a negative relationship between both considered life expectancy indicators and the current costs of reproduction, as was previously shown for bats (Wilkinson and South, 2002). ...
Diverging in the initial assumptions, both mechanistic and evolutionary theories of aging suggest a positive correlation of indicators of life expectancy of animal species with body size and a negative correlation with fertility and metabolic rate. Such dependence is obviously traced within large taxa; however, when analyzing on a smaller scale (at the level of orders and families), ecological specialization of species can make a significant contribution to the variability of the corresponding indexes. In given work, correlative relationships between median and maximum life expectancy, on one hand, and the average values of body weight, fertility, muscle strength, the values of standard and maximum metabolic rates, locomotor activity, and emo-tionality in the open field test, on the other hand, are analyzed in eight species of Cricetidae family. The correlations with life expectancy were significant for all indicators except body weight. For locomotor activity, the correlation with life expectancy was positive; for other indicators, it was negative. The paper discusses possible reasons for differences in the strength of correlative relationships of the analyzed indexes with the maximum and median life expectancy from the point of view of mechanistic and evolutionary approaches to the analysis of the causes and mechanisms of aging.
... Furthermore, the body-mass scaling exponents for various biological processes/durations (e.g., gestation time, life span, age at first reproduction, individual/population growth rates, etc.) often do not match the scaling exponents for metabolic rate [30,32,34,35,86,212,213], contrary to that predicted by the MTE. Given that variation in diverse life-history traits has been linked to variation in mortality rate (e.g., [84,119,125,207,209,[267][268][269][270][271][272], as reviewed in [35]), I recommend future research that examines how the body-size scaling of various life-history traits relate to mortality rate and its scaling with body size. After all, mortality rate scales strongly with body size in a variety of organisms ( [26,35,205]), and thus, size-related mortality-based time limits should impact the rates and durations of various biological processes and how they scale with body size. ...
Various phenotypic traits relate to the size of a living system in regular but often disproportionate (allometric) ways. These “biological scaling” relationships have been studied by biologists for over a century, but their causes remain hotly debated. Here, I focus on the patterns and possible causes of the body-mass scaling of the rates/durations of various biological processes and life-history events, i.e., the “pace of life”. Many biologists have regarded the rate of metabolism or energy use as the master driver of the “pace of life” and its scaling with body size. Although this “energy perspective” has provided valuable insight, here I argue that a “time perspective” may be equally or even more important. I evaluate various major ways that time may be relevant in biological scaling, including as (1) an independent “fourth dimension” in biological dimensional analyses, (2) a universal “biological clock” that synchronizes various biological rates/durations, (3) a scaling method that uses various biological time periods (allochrony) as scaling metrics, rather than various measures of physical size (allometry), as traditionally performed, (4) an ultimate body-size-related constraint on the rates/timing of biological processes/events that is set by the inevitability of death, and (5) a geological “deep time” approach for viewing the evolution of biological scaling patterns. Although previously proposed universal four-dimensional space-time and “biological clock” views of biological scaling are problematic, novel approaches using allochronic analyses and time perspectives based on size-related rates of individual mortality and species origination/extinction may provide new valuable insights.
... Animals use different strategies to cope with seasonal differences in resource availability, predation, and climatic conditions (Kie, 1999;Roff, 1993). Animals are constrained in how they allocate energy resources to survival and reproduction, and maximizing individual fitness requires individuals to respond to seasonal changes to optimize energy acquisition and allocation (Promislow & Harvey, 1990). ...
Animal movement is the mechanism connecting landscapes to fitness, and understanding variation in seasonal animal movements has benefited from the analysis and categorization of animal displacement. However, seasonal movement patterns can defy classification when movements are highly variable. Hidden Markov movement models (HMMs) are a class of latent-state models well-suited to modeling movement data. Here, we used HMMs to assess seasonal patterns of variation in the movement of pronghorn (Antilocapra americana), a species known for variable seasonal movements that challenge analytical approaches, while using a population of mule deer (Odocoileus hemionus), for whom seasonal movements are well-documented, as a comparison. We used population-level HMMs in a Bayesian framework to estimate a seasonal trend in the daily probability of transitioning between a short-distance local movement state and a long-distance movement state. The estimated seasonal patterns of movements in mule deer closely aligned with prior work based on indices of animal displacement: a short period of long-distance movements in the fall season and again in the spring, consistent with migrations to and from seasonal ranges. We found seasonal movement patterns for pronghorn were more variable, as a period of long-distance movements in the fall was followed by a winter period in which pronghorn were much more likely to further initiate and remain in a long-distance movement pattern compared with the movement patterns of mule deer. Overall, pronghorn were simply more likely to be in a long-distance movement pattern throughout the year. Hidden Markov movement models provide inference on seasonal movements similar to other methods, while providing a robust framework to understand movement patterns on shorter timescales and for more challenging movement patterns. Hidden Markov movement models can allow a rigorous assessment of the drivers of changes in movement patterns such as extreme weather events and land development, important for management and conservation.
... Life-history strategies vary widely among species, shaped by key factors influencing fecundity and survival (e.g., environmental, ecological, physiological and socio-behavioural factors; Ricklefs & Wikelski 2002). The 'Pace-of-Life Syndrome' (PoLS) theory outlines a slow-fast continuum, with low reproductive rates, delayed maturity, repeated opportunities for reproduction over longer lifespans and high per capita investment in offspring at one end ('slow life-history') and the opposite traits defining 'fast life-history' (Promislow & Harvey 1990;Saether & Bakke 2000). High mountain species may be expected to exhibit a slower life-history to cope with the stochastic weather conditions and to allow for bet-hedging in suboptimal years that shifts investment from individual reproduction attempts to self-maintenance to minimize breeding failure costs and improve life-time reproductive success by producing fewer offspring annually and exhibiting greater longevity compared to low elevation populations (Sandercock et al. 2005;Londoño et al. 2015Londoño et al. , 2017Boyle et al. 2016). ...
Alpine birds face many challenges to live and breed at high elevations, including temperature extremes, strong winds, hypoxia, and limited opportunities to reproduce. To cope with these challenges, alpine birds have developed physiological, morphological, and behavioural adaptations, as well as potentially adopting a slower lifestyle where reduced annual reproduction is balanced by greater longevity. Alpine birds may benefit from reduced ecological constraints, such as lower interspecific competition, parasitism, and habitat loss compared to lower elevations. Here, we outline the abiotic stressors that limit avian life at high elevations, and examine the structural, physiological, genetic, and behavioural adaptations that enable birds to live and breed in alpine ecosystems. We discuss the ecological dynamics acting on birds at high elevations and highlight significant knowledge gaps in high mountain ecology globally. We contextualize high elevation adaptations within a life-history framework, and discuss how these adaptations may make alpine birds particularly vulnerable to climate change.
... For example, there is usually a strong relationship between the size of organisms and their lifespan. It is thought that this stems from the coupling between the size of organisms and their metabolism and risk of extrinsic mortality (Austad, 2010;Gaillard et al., 1994;Promislow and Harvey, 1990). However, the relationship between size and lifespan can be modified when social life induces unusual association between size and extrinsic mortality. ...
How, when, and why organisms age are fascinating issues that can only be fully addressed by adopting an evolutionary perspective. Consistently, the main evolutionary theories of ageing, namely the Mutation Accumulation theory, the Antagonistic Pleiotropy theory, and the Disposable Soma theory, have formulated stimulating hypotheses that structure current debates on both the proximal and ultimate causes of organismal ageing. However, all these theories leave a common area of biology relatively under-explored. The Mutation Accumulation theory and the Antagonistic Pleiotropy theory were developed under the traditional framework of population genetics, and therefore are logically centred on the ageing of individuals within a population. The Disposable Soma theory, based on principles of optimising physiology, mainly explains ageing within a species. Consequently, current leading evolutionary theories of ageing do not explicitly model the countless interspecific and ecological interactions, such as symbioses and host-microbiomes associations, increasingly recognized to shape organismal evolution across the Web of Life. Moreover, the development of network modelling supporting a deeper understanding on the molecular interactions associated with ageing within and between organisms is also bringing forward new questions regarding how and why molecular pathways associated with ageing evolved. Here, we take an evolutionary perspective to examine the effects of organismal interactions on ageing across different levels of biological organisation, and consider the impact of surrounding and nested systems on organismal ageing. We also apply this perspective to suggest open issues with potential to expand the standard evolutionary theories of ageing.
... Life history is a description of the development, mortality and reproduction of an organism, and how the properties of these processes change throughout its lifespan. Some of the most obvious and consistent differences between specieswhat we often think of as defining characteristics of different speciesfall under life history; for example their expected lifespan, time to reach maturity, fecundity and growth rate [1][2][3][26][27][28][29][30][31][32] . This makes life history a natural axis along which to break the extreme symmetry of neutral ecology and introduce realistic species differences. ...
Life history, the schedule of when and how fast organisms grow, die and reproduce, is a critical axis along which species differ from each other1–4. In parallel, competition is a fundamental mechanism that determines the potential for species coexistence5–8. Previous models of stochastic competition have demonstrated that large numbers of species can persist over long timescales, even when competing for a single common resource9–12, but how life history differences between species increase or decrease the possibility of coexistence and, conversely, whether competition constrains what combinations of life history strategies complement each other remain open questions. Here we show that specific combinations of life history strategy optimize the persistence times of species competing for a single resource before one species overtakes its competitors. This suggests that co-occurring species would tend to have such complementary life history strategies, which we demonstrate using empirical data for perennial plants.
... The fundamental LH trade-off is the trade-off between prioritizing immediate reproductive success and investing in development to increase future reproductive success. The adaptive resolutions of this fundamental trade-off involve the application of LH strategies that vary along a fast-slow continuum (Promislow & Harvey, 1990). Fast LH strategists emphasize present rewards that can contribute to their competitive status for immediate reproduction, whereas slow LH strategists value long-term rewards and forgo immediate benefits Chen & Chang, 2016). ...
Unlabelled:
Visual search is an integral part of animal life. Two search strategies, intuitive vs. deliberate search, are adopted by almost all animals including humans to adapt to different extent of environmental uncertainty. In two eye-tracking experiments involving simple visual search (Study 1) and complex information search (Study 2), we used the evolutionary life history (LH) approach to investigate the interaction between childhood environmental unpredictability and primed concurrent uncertainty in enabling these two search strategies. The results indicate that when individuals with greater childhood unpredictability were exposed to uncertainty cues, they exhibited intuitive rather than deliberate visual search (i.e., fewer fixations, reduced dwell time, a larger saccade size, and fewer repetitive inspections relative to individuals with lower childhood unpredictability). We conclude that childhood environment is crucial in calibrating LH including visual and cognitive strategies to adaptively respond to current environmental conditions.
Supplementary information:
The online version contains supplementary material available at 10.1007/s12144-023-04667-1.
... The only trait assessed that affected urban exploitation across all species was litter size (both mean of and variation within), a demographic trait that had a moderately significant, positive community urbanization response (Table 2, Figure 3). This result supports other species-level mean trait analyses (Pacifici et al., 2020;Santini et al., 2019;Suraci et al., 2021) that suggest urban-exploiting mammals may exhibit faster life-history strategies or pace of life syndromes (Dammhahn et al., 2018;Promislow & Harvey, 1990). It is possible that flexibility in litter sizes allows a species to more efficiently respond to the heterogeneous availability of resources in cities (i.e., producing greater or fewer offspring when resources are more or less abundant, respectively) (e.g., Gamelon et al., 2014). ...
Identifying drivers of urban association in wildlife is a central challenge in conservation biology. Traits facilitating access to novel resources and avoiding humans often correspond with urban exploitation in mammal species, but these relationships differ by taxa and trophic guild. Variation among or within traits may be a yet untested explanation for the non-generality of species-trait relationships in cities. Using camera trap data from 1,492 sites throughout the contiguous USA in 2019, we investigated if mammal species with greater intraspecific trait variation have higher degrees of urban occupancy. We hypothesized that intraspecific trait variation would correspond with urban occupancy, but that the strength of these relationships would vary by taxonomic order due to expected phylogenetic constraints. Mean trait values (average home range size, body mass, group size, weaning age, litter size, and diet composition) varied widely across orders. The only traits that affected urban association across all species corresponded with demography (litter size), while responses across orders were more variable and informative. Mean trait values associated with home range and body size had informative relationships with urbanization for Cetartiodactyla, Rodentia, and Carnivora, while intraspecific variation in traits corresponding with diet (Carnivora), demography (Cetartiodactyla, Carnivora, Rodentia), and temporal responses to humans (Carnivora) had informative relationships to urbanization. This is the first study investigating mammalian species-level trait variation and its relationship to urban exploitation across many traits and taxa. Since natural selection requires trait variation, the variation of demographic traits, like litter size, can have significant implications for wildlife management and conservation. Our results also provide further evidence for omnivory as a form of dietary plasticity supporting urban accessibility in higher trophic guilds (e.g., Carnivora). Using this information, we can better manage and understand which species occupy and adapt to cities, thereby promoting human-wildlife coexistence.
... Most small mammals have evolved a reproductive strategylive fast and die young-characterized by rapid reproduction in the face of high mortality (Promislow and Harvey 1990). Life history evolution in the Chiroptera has taken a markedly different course, resulting in reproductive strategies for "life in the slow lane" (Barclay and Harder 2003), perhaps as a consequence of their nocturnal and volant habits (Racey and Entwistle 2000). ...
Natural selection should favor individuals that synchronize energy-demanding aspects of reproductive activity with periods of high resource abundance and predictability, leading to seasonal patterns of reproduction at the population level. Nonetheless, few studies—especially those on bats in the Neotropics—have used rigorous quantitative criteria to distinguish among phenological patterns for different populations from the same habitat or for the same species in different habitats. To explore such issues, we quantified annual patterns of reproduction in male and in female bats from lowland Amazonia (environs of Iquitos, Peru), and did so at the level of populations and ensembles. Five species exhibited unimodal patterns including Artibeus obscurus, A. planirostris, Carollia benkeithi, Phyllostomus hastatus, and Rhinophylla pumilio. Two species (A. lituratus and Glossophaga soricina) evinced bimodal patterns with reproductive peaks separated by patterns of inactivity, whereas four species (C. brevicauda, C. perspicillata, Sturnira lilium, and S. tildae) evinced a bimodal pattern in which peaks in activity occur in tandem, with the first peak generally markedly higher than the second peak. Frugivore, gleaning animalivore, and nectarivore ensembles exhibited bimodal, unimodal, and bimodal reproductive phenologies, respectively. Nonetheless, interannual variation in phenology (i.e., the monthly timing of peaks within a season rather than the number of peaks per year) characterized four (A. obscurus, C. brevicauda, C. perspicillata, and S. lilium) of the eight species and each of the three ensembles (frugivores, gleaning animalivores, and nectarivores) with adequate sampling. Regardless of interspecific variation in strategies, the phenology of reproduction enhances the likelihood that parturition and recruitment of young into the population occurs during the wet season, the period of likely highest resource abundance. Based on a comparison of our results with those from other well-studied bat populations, four species did not exhibit geographic variation in reproductive phenologies (A. obscurus, G. soricina, C. brevicauda, and R. pumilio), whereas three species evinced such geographic variation (A. lituratus, A. planirostris, and C. perspicillata). Climate change will likely alter the seasons and extents of propitious times for reproductive activities, as well as the reliability of proximate cues for initiating reproduction, compromising current reproductive strategies and leading to altered phenological patterns of reproduction or reproductive success, possibly resulting in local extinction of some species.
... This exercise shows the choice of regulation can flip systems from the 'null' pattern to either 'Williams' or 'anti-Williams'. In other words, 'fast' lives (in the sense of fast and slow life histories, DE Promislow and Harvey, 1990;Stearns, 1989), may evolve as a response to high extrinsic mortality, but this outcome does not happen under every form of population regulation. ...
Do environments or species traits that lower the mortality of individuals create selection for delaying senescence? Reading the literature creates an impression that mathematically oriented biologists cannot agree on the validity of George Williams' prediction (who claimed 'yes'). The abundance of models and opinions may bewilder those that are new to the field. Here we provide heuristics as well as simple models that outline when the Williams prediction holds, why there is a ‘null model’ where extrinsic mortality does not change the evolution of senescence at all, and why it is also possible to expect the opposite of William’s prediction, where increased extrinsic mortality favours slower senescence. We hope to offer intuition by quantifying how much delaying the ‘placement’ of an offspring into the population reduces its expected contribution to the gene pool of the future. Our first example shows why sometimes increased extrinsic mortality has no effect (the null result), and why density dependence can change that. Thereafter, a model with ten different choices for population regulation shows that high extrinsic mortality favours fast life histories (Williams) if increasing density harms the production of juveniles or their chances to recruit into the population. If instead increasing density harms the survival of older individuals in a population, then high extrinsic mortality favours slow life histories (anti-Williams). We discuss the possibility that empirically found Williams-like patterns provide indirect evidence for population regulation operating via harming the production or fitness prospects of juveniles, as opposed to the survival of established breeders.
... En esta línea, cabe destacar que, en concreto, el patrón que el Homo sapiens sigue para distribuir la energía finita de la que dispone entre los diferentes rasgos que conforman su historia biológica, es único (Kuzawa & Bragg, 2012), y se propone que, las fases que conforman el ciclo vital tal y como se conocen actualmente, no aparecerían hasta muy recientemente y, exclusivamente, con la especie Homo sapiens (Hublin et al., 2015;Nelson, Krovitz, & Thompson, 2003). Normalmente, dependiendo del contexto ecológico en el que se habita, con alto o bajo riesgo de mortalidad, se encuentran organismos con historias biológicas aceleradas (life fast, die young: Promislow & Harvey, 1990) o ralentizadas (Charnov, 1993), respectivamente. Los individuos se adaptan al contexto en el que viven y tienen una mayor o menor esperanza de vida, reducen o amplían los períodos de desarrollo y crecimiento hasta alcanzar la madurez sexual, y obtienen más o menos descendencia, con mayores o menores probabilidades de sobrevivir (Charnov, 1993;Figueredo et al., 2006;Harvey, Read, & Promislov, 1989;Kirkwood & Rose, 1991;Stearns, 1989). ...
The life of any organism is completely dependent on energy. Energy resources procurement, consumption and allocation through biological processes are essential aspects to understand an organism’s ecology. Thus, the energetic dynamics between organisms and their environment have important adaptive implications for survival and reproduction, i.e., for fitness. Under this perspective it is possible to evaluate the consequences of some anatomical and physiological human characteristics, or the assessment of certain behaviors.
Humans allocate a relevant part of their daily energy budget to locomotion and burden transport activities. Thus, around these activities, humans develop a whole range of behaviors that can be evaluated within the Human Behavioral Ecology theoretical framework. The energy distributed to these activities is not available to other biological functions, thus it is expected that humans adopt strategies that ensure their energy balance. Among these strategies it is proposed that division of labors is essential, as well as the activation of physiological and behavioral changes that ensure both mobility and reproduction.
Thus, this Ph. D. dissertation, will evaluate, from an energetic point of view, distinct physiological states and locomotion physical activities in a sample of current adult females and males. For this purpose, the data from two experimental studies were used. Both experimental studies have been designed at Bioenergy and Motion Analysis Laboratory from National Research Center of Human Evolution (CENIEH). Anthropometry, body composition and energy expenditure data have been obtained from a total of 125 subjects.
The first objective of this study was fixed to evaluate if sexual division of load transport activities, common in recent hunter-gatherer societies, is influenced by energetic differences among sexes. The data from 21 females and 27 males were used to elaborate several indices to compare, among sexes, the increment in the cost of locomotion when several burdens are transported. The results demonstrate that both females and males, carrying the same relative loads, experience the same increment over the cost of their unloaded locomotion. Therefore, apart from obvious differences in body mass, there is no evidence of an energetic advantage favoring one sex over the other that would explain the differences in load-carriage activities observed among current foraging populations.
The second research objective was planned to evaluate if body mass affects in the same way the resting energy expenditure and the locomotion costs of pregnant and nonpregnant females. Data from 77 females (42 nonpregnant and 35 pregnant females during their last gestation trimester) were obtained. All the data and the linear regression models about the relationship between body mass and energy expenditure were compared considering the physiological state. The results show that pregnant females expend less energy, both resting and during locomotion, than nonpregnant females with a similar body mass. It is proposed that this difference is caused by pregnant females having lesser percentages of metabolically active body tissues (Fat Free Mass) and larger percentages of metabolically passive body tissues (Fat Mass).
Two main conclusions were established from the outcomes obtained. On the one hand, the division of labor, frequently reported in hunter-gatherer activities, could be explained as a behavioral adaptation that increases individual fitness and, finally, the fitness of the entire group. In this line, it is proposed that the females of these populations perform preferably certain activities, because they benefit the group while the women themselves would be improving their own survival opportunities. Meanwhile, other group members could be focused on carrying out other complementary activities that would enhance the collective foraging efficacy. Consequently, it may be possible that the ability to develop different types of cooperation (phenotypic plasticity), has a great adaptive value, and it would have been selected throughout human evolution.
On the other hand, apart from behavioral adaptations, gestation related physiological changes could cause that pregnancy may not be as energetically constraining as usually assumed, agreeing with other studies that have detected a great variability in human pregnancy costs. This evidence would provide another reason for successful human pregnancies in differing ecological conditions, even when physical activity conducts do not vary during gestation. Similarly, as other researchers have found, the evolutionary relevance of Fat Mass accretion for both human survival and reproduction is highlighted.
To finally conclude, the capability to cooperate organizing the foraging tasks, as well as the changes in body composition related to pregnancy that influence gestation energy requirements, would be essential traits to understanding human populations development from a comparative perspective.
... The fitness of small mammals living in isolation is increased by maturing later and at a larger size than their mainland forerunners, so selection pushes a change in the life history strategy. Insular small-sized animals are generally characterized by an extended age at maturity and longevity, and an enlarged adult body size, as well as an increased fecundity (likely in the size of offspring, as they reproduce at larger sizes) and population density (Promislow and Harvey, 1990;Stearns, 1992;Palkovacs, 2003;Mappes et al., 2008;Rotger et al., 2023). In other words, they shift towards the slow-end of the life history continuum (Orlandi-Oliveras et al., 2016;Angelone et al., 2017;Miszkiewicz et al., 2020). ...
The study of past pathologies by means of quantitative reports is an underexplored approach to deal with the biology and ecology of extinct taxa. In the present study, we assessed the prevalence rate of primary osteoarthritis in a large sample of Prolagus sardus (Mammalia, Lagomorpha) from Medusa Cave (also known as Grotta Dragonara, Sardinia, Italy; Late Pleistocene) to shed light on the evolutionary history of small mammals under isolation regimes. The hip and knee joints of 246 femora were examined grossly, microscopically, and using advanced radiology, recording essential biological features such as age or weight. We noted that 27.7% of skeletally mature sample had degenerative disorder of the joints, with higher frequency in adults (p-value < 0.05), regardless of their body mass (p-value > 0.05). Histologically, affected joints displayed changes in subchondral plate potentially reflecting adaptive modeling. Our analysis revealed ageing (the extended lifespan) as the main driver of this prevalence rate, whereas mechanical factors (caused by a particular lifestyle) were considered of significantly lesser importance. Our results provide additional empirical support to the analytical framework of life history theory from a new perspective, according to which, under low extrinsic mortality regimes, selection should favor slow-strategies (extended lifespan) in small-sized mammals.
... Las diferentes estrategias que emplean los organismos para moldear su historia biológica están influidas por factores ambientales (Griskevicius, Delton, Robertson, & Tybur, 2011;Hill & Kaplan, 1999;McDade, 2003;McDade et al., 2008;Quinlan, 2007;Roff, 2002). En los contextos más impredecibles, con mayores tasas de mortalidad, la energía se destina a una rápida reproducción (Promislow & Harvey, 1990). ...
Esta tesis doctoral responde al interés de comprender el papel de la energía en las relaciones entre el ser humano y su entorno, siendo la energía la que modela y ajusta las adaptaciones biológicas y conductuales de los organismos terrestres y, por extensión, de la especie humana.
Son varios los estudios dentro de la ecología del comportamiento humano que han utilizado la energía para comprender la adaptación y la adaptabilidad humana. Dicha adaptabilidad es fruto de la flexibilidad que muestra nuestra especie, adquirida gracias a la prolongada inmadurez de Homo sapiens. Sin embargo, son menores los estudios que se han centrado en comprender cómo actúa la energía en la conducta y la biología de los individuos subadultos. Por ello, el principal interés de esta investigación es estudiar cómo afecta la energía a la puesta en marcha de diferentes actividades de subsistencia imprescindibles en los grupos de cazadores y recolectores. Concretamente, se evaluará si el inicio de la división de labores por sexo se explica en base a diferencias en el coste y la eficiencia energética de los distintos individuos. Así mismo, se valorará el papel activo y la productividad de los individuos subadultos dentro de un grupo humano, y si ello se ve limitado por cuestiones energéticas. Finalmente, se analizará si el coste de la locomoción y la velocidad óptima alcanzada por sujetos subadultos puede limitar la movilidad y la puesta en marcha de actividades que dependen de la locomoción en grupos humanos. Con todo, se tratará de conocer si la energía actúa como un limitante a la hora de aprender y desarrollar actividades complejas propias de nuestra especie y cómo afecta esto a las dinámicas energéticas del resto de individuos de un grupo humano.
Para ello se han empleado datos de dos estudios experimentales, llevados a cabo en el Laboratorio de Bioenergía y Análisis del Movimiento del Centro Nacional de Investigación sobre la Evolución Humana (CENIEH). Estos corresponden a 118 voluntarios de entre 7 y 14 años de edad, y recogen diferentes medidas antropométricas, de composición corporal y de gasto energético. Los dos estudios experimentales incluían simulaciones de actividades comunes entre los individuos subadultos de ciertos grupos de cazadores y recolectores de la actualidad, como la recolección y la extracción de recursos y caminar a diferentes velocidades.
Los resultados obtenidos en el conjunto de las pruebas revelan que, tanto la energía gastada, como la eficiencia en una actividad productiva, no explican la diferencia de labores entre sexos, pero tampoco entre edades si se comparan con las velocidades óptimas adultas. Se propone que la división de labores en base al sexo debe responder a otras cuestiones, relacionadas con el aprendizaje temprano en habilidades complejas específicas para cada sexo. Además, debido a la relación entre el gasto energético y el tamaño corporal en actividades productivas en las que se aprenden esas habilidades, los individuos juveniles gozan de una ventaja, ya que comienzan a aprender en una fase en la que el crecimiento corporal se retiene y se consume menos energía porque se tiene un tamaño menor. Por ello, practicar durante esta etapa, supone un ahorro en forma de energía respecto a otras fases en las que se tiene un mayor tamaño corporal y sí se invierte más energía en crecimiento y desarrollo, como en la adolescencia. Por otro lado, el gasto energético de la prueba de extracción de recursos bien se cubriría con el retorno calórico facilitado por diferentes autores, pero no podríamos confirmar que se alcancen ya tasas de productividad adulta. En esta prueba también se ha demostrado que, igual que se observa en el gasto energético del resto de actividades aquí desarrolladas, tampoco existen diferencias entre sexos en la eficiencia derivada de extraer recursos del suelo. Este resultado se ha obtenido al tener en cuenta la tasa de eficiencia (energía gastada/retorno conseguido). Respecto a las actividades que dependen de la locomoción bípeda, no existen diferencias entre sexos en la velocidad óptima, ni el gasto derivado de alcanzar esta velocidad. Por lo tanto, se propone que ambas variables no condicionarían a los individuos aquí estudiados a la hora de acompañar a un grupo adulto de cazadores y recolectores, ni durante la movilidad ni mientras se captan recursos. Por otro lado, la capacidad para alcanzar velocidades óptimas semejantes a las publicadas para individuos adultos, podría suponer a los subadultos ventajas al consumir menos energía por ser más pequeños. No obstante, en determinadas sociedades estos individuos no se involucran en ciertas actividades de manera temprana, por lo que existen otras causas, más allá de la velocidad o el gasto energético, que pueden dificultar la participación de los subadultos en algunas actividades adultas.
Todas estas ventajas han podido propiciar en la especie Homo sapiens un ahorro de energía que directamente, no solo beneficia al individuo subadulto, sino también a otros individuos del grupo. Muchas de las ventajas aquí expuestas se ven acompasadas por la peculiar historia biológica humana. Por ello, otras especies de homininos que hayan requerido del aprendizaje de habilidades complejas para subsistir, se habrían beneficiado de las mismas ventajas que exponemos en esta investigación, solo si hubiesen tenido los mismos patrones de desarrollo y crecimiento encontrados en Homo sapiens.
The main interest of this Ph.D. Dissertation is to understand the key-role of the energy in the relationship between humans and the environment, since energy is the factor that models and adjusts the biological and behavioural adaptations of all living organisms and, by extension, of humans too.
Several studies within the Human Behavioural Ecology have used the energy to understand human adaptation and adaptability. This adaptability is the main result of human plasticity, acquired thanks to the prolonged immaturity of Homo sapiens. However, fewer studies have focused on understanding how energy affects subadult behaviour and biology. Therefore, the main interest of this research is to study how energy affects the implementation of different essential human behaviours in hunter-gatherer societies. Specifically, it will be evaluated if the onset of division of labour by sex is caused by differences in the efficiency and the energetic demands of different individuals. In addition, the active role and the productivity of non-adult individuals will be assessed, together with possible energetic limitations in this regard. Finally, the cost of locomotion and the optimal speed will be analysed to test if non-adult individuals limit group mobility or the participation in foraging activities involving locomotion. Consequently, it will be discussed if energy is a limitation while learning-by-doing complex activities, commonly practiced by Homo sapiens species, and how this affects the energetic dynamics of a human group.
To achieve this, data from two experimental studies carried out in the Laboratory of Bioenergy and Analysis of the Movement of the CENIEH have been used. Data were obtained from 118 volunteers between 7 and 14 years of age, and referred to different anthropometric, body composition and energy expenditure measurements. The two experimental studies consisted of three trials, simulating common activities among subadult individuals of certain groups of current hunter-gatherers. The recreated activities were a gathering test, a digging tubers trial, and a locomotion activity at different speeds.
The results obtained in all of the experimental studies reveal that the energy
expended and the efficiency in a productive activity do not explain the onset of sex division of labor. It is proposed that the division of labor is caused by other questions related to the early learning in sex-specific complex skills. In addition, due to the relationship between energy expenditure and body size in some productive activities (through which non-adults learn these skills), juvenile individuals have an energetic advantage, because they decelerate the body growth in this phase and they consume less energy due to their smaller body size. Therefore, learning-by-doing at this stage promotes energy savings compared to other phases with a larger body size and a greater somatic investment, like adolescence.
On the other hand, the energy expenditure of digging would be covered with the energetic return reported by other investigations, but we cannot confirm that our individuals have already achieved adult productivity rates. In this test, taking into account the results of the efficiency index (energy expended/items reported) it has also been shown that there are no differences among sexes based on the efficiency of extracting tubers from the ground, as we have observed for the energy expenditure of the rest of the activities carried out here.
Regarding the locomotion test, there are no differences among sexes, or ages when compared with adult values from other studies, neither comparing the optimal walking speed, nor the energy expenditure at this speed. Thus, it is proposed that both variables are not a limitation for the individuals here studied if they would be part of a hunter-gatherer group, neither during the mobility of the group, nor while foraging.
On the other hand, our volunteers reach similar optimal speeds as those reported in the literature for adult individuals. This could constitute and advantage for non-adult individuals, as they are consuming less energy because they are smaller. Nonetheless, in certain societies, non-adult individuals are not involved in some activities anyway, thus there may be other causes, beyond speed or energy costs, that can hinder the
participation of non-adults in some adult activities.
All the mentioned advantages would allow energy savings for Homo sapiens. This savings would directly benefit the non-adult individual, but also the rest of the group. However, most of the advantages highlighted here are linked to the peculiar Homo sapiens Life History. Therefore, the advantages we expose in this research would benefit other extinct species with subsistence complex skills, only if Homo sapiens-like development and growth patterns were already present.
... The best-studied life history strategies are those that shape the fast-slow axis (233,234). The fast strategy characterizes rats: They are short-lived, grow quickly, have many offspring but invest little in them, and have high pup mortality. ...
Personality disorders (PDs) are currently considered dysfunctions. However, personality differences are older than humanity and are ubiquitous in nature, from insects to higher primates. This suggests that a number of evolutionary mechanisms—other than dysfunctions—may be able to maintain stable behavioral variation in the gene pool. First of all, apparently maladaptive traits may actually improve fitness by enabling better survival or successful mating or reproduction, as exemplified by neuroticism, psychopathy, and narcissism. Furthermore, some PDs may harm important biological goals while facilitating others, or may be globally beneficial or detrimental depending on environmental circumstances or body condition. Alternatively, certain traits may form part of life history strategies: Coordinated suites of morphological, physiological and behavioral characters that
optimize fitness through alternative routes and respond to selection as a whole. Still others may be vestigial adaptations that are no longer beneficial in present times. Finally, variation may be adaptative in and by itself, as it reduces competition for finite resources. These and other evolutionary mechanisms are reviewed and illustrated through human and non-human examples. Evolutionary theory is the best-substantiated explanatory framework across the life sciences, and may shed
light on the question of why harmful personalities exist at all.
To this day, parent-child intervention has been guided by attachment theory, addressing issues of sensitivity and parenting competence from the standpoint of the mother-child relationship. The absence of a theory-driven model of fathering hindered the development of specific interventions addressing the father-child relationship. Since 2004, the activation relationship theory has propelled research and theory influencing how we intervene with fathers and their children. This chapter presents the emergence and development of the activation relationship theory, before examining an early intervention program involving father-child dyads.
To expand the human exploration footprint and reach Mars in the 2030s, we must explore how humans survive and thrive in demanding, unusual, and novel ecologies (i.e., extreme environments). In the extreme conditions encountered during human spaceflight, there is a need to understand human functioning and response in a more rigorous theoretically informed way. Current models of human performance in space‐relevant environments and human space science are often operationally focused, with emphasis on acute physiological or behavioral outcomes. However, integrating current perspectives in human biology allows for a more holistic and complete understanding of how humans function over a range of time in an extreme environment. Here, we show how the use of evolution‐informed frameworks (i.e., models of life history theory to organize the adaptive pressures of spaceflight and biocultural perspectives) coupled with the use of mixed‐methodological toolkits can shape models that better encompass the scope of biobehavioral human adjustment to long‐duration space travel and extra‐terrestrial habitation. Further, we discuss how we can marry human biology perspectives with the rigorous programmatic structures developed for spaceflight to model other unknown and nascent extremes.
The COVID‐19 pandemic has caused governments and individuals to face important but difficult trade‐offs between health and the economy. How do individuals choose between health and economic outcomes during the pandemic? Based on the behavioural immune system (BIS) theory and the life history (LH) theory, the present study examined the effects of individual differences in pathogen disgust sensitivity and life history strategy on people's health‐economic trade‐offs during the COVID‐19 pandemic. Results of an online study ( N = 300) showed that people with higher pathogen disgust sensitivity felt less sense of control during the pandemic, and therefore chose health‐related options over economic‐related options. In addition, the association between pathogen disgust sensitivity and health outcome preference only existed in people with relatively faster life history strategies. Further, people's health‐economic trade‐offs were not influenced by their current economic status. Findings have important implications for policymakers and the public to understand people's health‐economic choices during the pandemic.
Abortion policy is conventionally viewed as a political matter with religious overtones. This article offers a different view. From the perspective of evolutionary biology, abortion at a young age can represent prioritization of long-term development over immediate reproduction, a pattern established in other animal species as resulting from stable ecologies with low mortality risk. We examine whether laws and moral beliefs about abortions are linked to local mortality rates. Data from 50 U.S. states, 202 world societies, 2,596 adult individuals in 363 U.S. counties, and 147,260 respondents across the globe suggest that lower levels of mortality risk are associated with more permissive laws and attitudes toward abortion. Those associations were observed when we controlled for religiosity, political ideology, wealth, education, and industrialization. Integrating evolutionary and cultural perspectives offers an explanation as to why moral beliefs and legal norms about reproduction may be sensitive to levels of ecological adversity.
Female reproductive effort is defined as the proportion of total energy or resources devoted to reproduction. In reptiles, there is frequently high inter-and intra-population variation related to several factors, such as food availability, climatic conditions, age and size, all of which, in turn, also influence survival and future reproduction. The present study is the first reproductive effort analysis of a population of the high-mountain scincid lizard Plestiodon copei in central Mexico, focusing on relative litter mass (RLM), investment per capita (INV) and productivity (PROD). We also compared the reproductive efficacy of P. copei to those of other Mexican congeners. We collected 24 gravid females of P. copei over a 4-year period and recorded a total of 90 neonates born in captivity. We found significant variation in neonatal mass amongst individual females and across years. We recorded an average litter size of 3.75 and an average litter mass of 1.25 g, which were positively correlated with both the size and total mass of the reproductive females. The RLM, INV and PROD values (0.301, 0.428 g and 1.236 g × year-1 , respectively) for P. copei were greater than those for other Mexican species in the P. brevirostris group (0.290, 0.412 g and 1.135 g × year-1), revealing that females of P. copei from Tenango invest a comparatively high amount of their resources in reproduction.
Early life adversity predicts shorter adult lifespan in several animal taxa. Yet, work on long‐lived primate populations suggests the evolution of mechanisms that contribute to resiliency and long lives despite early life insults. Here, we tested associations between individual and cumulative early life adversity and lifespan on rhesus macaques at the Cayo Santiago Biological Field Station using 50 years of demographic data. We performed sex‐specific survival analyses at different life stages to contrast short‐term effects of adversity (i.e., infant survival) with long‐term effects (i.e., adult survival). Female infants showed vulnerability to multiple adversities at birth, but affected females who survived to adulthood experienced a reduced risk later in life. In contrast, male infants showed vulnerability to a lower number of adversities at birth, but those who survived to adulthood were negatively affected by both early life individual and cumulative adversity. Our study shows profound immediate effects of insults on female infant cohorts and suggests that affected female adults are more robust. In contrast, adult males who experienced harsh conditions early in life showed an increased mortality risk at older ages as expected from hypotheses within the life course perspective. Our analysis suggests sex‐specific selection pressures on life histories and highlights the need for studies addressing the effects of early life adversity across multiple life stages.
The digitization and open availability of life history traits measured directly from individuals provide a key means of linking organismal function to environmental and ecological contexts at fine resolution. These linkages play a critical role in understanding trait‐mediated response to global change, with particular need to resolve them for taxa that are secretive and hard to monitor, like most mammals. In this study, we use digitized museum specimen and census data to document how climate and body size each shape a key life history trait – litter size – in 39 small mammals across North America. We employ mixed models to test associations between litter size, climate and body size, with a focus on joint estimation of inter‐ and intraspecific trends. Among species, no single climate predictor explained a large amount of litter size variation. Instead, interactions between temperature‐related (continentality, solar irradiation) and moisture‐related (annual precipitation, relative humidity) indices, along with body size, exert a stronger influence on litter size. We observed maximal litter sizes for species inhabiting seasonal or xeric regions under conditions of increased moisture availability, or conversely, mesic or aseasonal regions under conditions of reduced moisture availability. These patterns are consistent with primary productivity as a mechanistic driver of litter size. At the intraspecific level, litter size responds to continentality and temperature‐related indices experienced by populations, but is most strongly shaped by body size of individual females. We also find evidence of phylogenetic covariation in these intraspecific trends. Our study demonstrates how life history traits assembled from individual‐level biodiversity records improve precision and granularity of ecological studies, help to parse among‐ and within‐species trends, and foster improved understanding of tradeoffs between energetic supply and demand (e.g. reproduction) in wild mammals.
Household food waste is one of the major contributors of the food waste across the supply chain raising concerns over environmental, economic and social issues. Global forums like United Nations have targeted to bring down the amount of waste generated to at least half by 2030 through the implementation of sustainable solutions. Therefore, considering the importance of the topic, the present work aims to explore how an individual's food waste behaviour takes shape during the scarcity context in a crisis‐based situation like the recent COVID‐19 pandemic. We collected the data online from 398 individuals residing in India, an emerging market context. This study presents a new avenue that during resource scarcity people can show generous behaviour as opposed to self‐interestedness and make efforts to conserve food. This, in turn, also increases their environmental and societal tendency. Thus, we argue that scarcity bridges the gap between food chain responsibility and sustainable development. We also accounted for the influence of environmental consciousness as a moderator affecting the behaviour of an individual as it further intensifies responsible food behaviour. The insights from the findings can help practitioners, public policymakers and academicians exploring the phenomenon of food waste to devise effective strategies, favourable policies and future research directions.
Primate life histories represent a general description of the pace of living and dying in this diverse group of mammals. Life histories represent evolved mechanisms for trading the energy and time costs of each life event (e.g., pregnancy) against other such events (e.g., living to old age) on at least two independent dimensions. Originally life histories were differentiated along a single axis into species with rapid rates of living and dying ( r ‐strategists), and species living at their population maxima and therefore investing in high individual quality and competitive ability (K‐strategists). Current theory suggests that there are two separate dimensions: (1) production or the balance of offspring size against offspring numbers; and (2) timing or rates of reproduction. Primate life histories are distinct from those of many mammals, specifically in their strategy of trading time against energy, resulting in slow rates of reproduction, at low costs, associated with early survival and greater longevity. Factors affecting primate life histories are complex, ranging from the stability or unpredictability of foods (energy capture) to social context and strength of social networks, and include body and brain size as correlated traits. This complexity makes their study both rewarding and difficult.
Introduction
Birth, and the period shortly thereafter, is a perilous time for any organism. Following parturition or hatching, individuals face many challenges, including environmental stressors (e.g., temperature or humidity), competition, and/or predation, all of which can impact selection (Lindstrom 1999; Metcalfe and Monaghan 2001; Gluckman and Hanson 2004). Furthermore, major anatomical, behavioral, and physiologic changes occur throughout the ontogenetic period. As such, the conditions an organism experiences throughout the ontogenetic period have implications for their survival, success, and ultimately, their fitness (Lindstrom 1999; Lee et al. 2003; Nord and Nilsson 2016; Nord and Giroud 2020). An understanding of developmental strategy, neonatal condition, and environmental challenges, as well as the physiology of newly born/hatched individuals experiencing those conditions, is critical for evaluating how adult organisms function and survive. However, these topics are often studied in isolation, both across different systems, and at a single point in time.
Two sibling symposia “Biology at birth: the role of infancy in providing the foundation for lifetime success” and “Pathways to adulthood: environmental, developmental, and evolutionary influences on the ontogeny of form and function” address these concerns from different but complementary perspectives. The first, “Biology at birth,” highlights the importance of understanding infancy from an integrated perspective, and how infancy can shape an individual’s future. The goal of this symposium is to bring together researchers across various life science disciplines for conversation, collaboration, and interaction across boundaries as a way of promoting novel and innovative research at this specific moment of development. Herein, we examine infancy through multiple physiologic and comparative perspectives, under three general topic headings: (1) how the pre- and perinatal environments shape infant phenotype (e.g., maternal effects); (2) infant physiology and development; and (3) the lifetime impacts of infant experiences on phenotype and performance, especially when development is disrupted. Authors in this symposium span multiple physiologic systems (including neurological, cardiovascular, musculoskeletal, digestive, endocrine) and multiple model species (humans, pigs, sheep, rodents).
Objectives:
Cross-population variation in age at menarche is related to many factors. The purpose of this study was to examine climate variables in relation to mean age at menarche among 87 modern human populations. We hypothesized a later age at menarche among populations living in areas with high precipitation variability, heavy seasonal rainfall, and high temperatures year-round due to water-borne diseases and periods of resource scarcity.
Methods:
Using a comparative dataset, we examined geospatial distribution and climate variables in relation to age at menarche for 87 modern human populations.
Results:
We found the strongest predictor of a later age at menarche was higher fertility followed by a later mean age at death. In addition, higher annual rainfall, higher precipitation seasonality, and lower annual mean temperature were moderate predictors of age at menarche.
Conclusions:
We propose that later ages at menarche in countries with high fertility may be a life-history strategy developed in response to climatic conditions that have resulted in higher immunological load. In these conditions, females may prioritize growth rather than reproduction. Shifts in climate and global population growth may change the future biological landscape of age at menarche.
Social behaviors vary among individuals, and social networks vary among groups. Understanding the causes of such variation is important for predicting or altering ecological processes such as infectious disease outbreaks. Here, we ask whether age contributes to variation in social behavior at multiple levels of organization: within individuals over time, among individuals of different ages, among local social environments, and among populations. We used experimental manipulations of captive populations and a longitudinal dataset to test whether social behavior is associated with age across these levels in a long-lived insect, the forked fungus beetle (Bolitotherus cornutus). In cross-sectional analyses, we found that older beetles were less connected in their social networks. Longitudinal data confirmed that this effect was due in part to changes in behavior over time; beetles became less social over 2 years, possibly because of increased social selectivity or reproductive investment. Beetles of different ages also occupied different local social neighborhoods. The effects of age on behavior scaled up: populations of older individuals had fewer interactions, fewer but more variable relationships, longer network path lengths, and lower clustering than populations of young individuals. Age therefore impacted not only individual sociality but also the network structures that mediate critical population processes.
Through artificial selection and inbreeding, strains of laboratory mice have been developed that vary in the expression of a single or suite of desired traits valuable to biomedical research. In addition to the selected trait(s), these strains also display variation in pelage color, body size, physiology, and life history. This article exploits the broad phenotypic variation across lab mouse strains to evaluate the relationships between life history and metabolism. Life history variation tends to exist along a fast-slow continuum. There has been considerable interest in understanding the ecological and evolutionary factors underlying life history variation and the physiological and metabolic processes that support them. Yet it remains unclear how these key traits scale across hierarchical levels, as ambiguous empirical support has been garnered at the intraspecific level. Within-species investigations have been thwarted by methodological constraints and environmental factors that obscure the genetic architecture underlying the hypothesized functional integration of life history and metabolic traits. In this analysis, we used the publicly available Mouse Phenome Database by the Jackson Laboratory to investigate the relationships among life history traits (e.g., body size, reproduction, and life span) and metabolic traits (e.g., daily energy expenditure and insulin-like growth factor 1 concentration). Our findings revealed significant variation in reproductive characteristics across strains of mice as well as relationships among life history and metabolic traits. We found evidence of variation along the fast-slow life history continuum, though the direction of some relationships among these traits deviated from interspecific predictions laid out in previous literature. Furthermore, our results suggest that the strength of these relationships are strongest earlier in life.
Principal component analysis and cluster analysis were applied to 2 data sets-65 mammal species (14 orders, 30 families, 10 traits) and 162 mammal species (22 orders, 64 families, 6 traits). In both data sets, most of the covariation in life-history traits could be accounted for by the first 2 factors, and in both data sets their interpretation was similar. The 1st factor, accounting for 68-75% of covariation of life-history traits, ranked the animals from early maturing, small, short-lived animals with short gestation periods, many small altricial young, and long lactation periods, to the opposite suite of traits in large animals. The 2nd factor, accounting for 12-20% of the covariation in life-history traits, ranked the animals from altricial to precocial. When order and family effects were removed, the proportion of variance accounted for by the 1st factor dropped 29-36%, and the number of high level clusters increased. Weight alone accounts for much of the tendency for mammals to be arranged on a single axis ranging from early maturing, highly fecund, and short-lived small animals to the opposite, but after the effects of weight were removed, order and family effects still had significant impact on patterns of covariation. Thus, morphological design, in addition to size, may constrain life-history evolution.-from Author
Stearns' (1984) major conclusion was that patterns of covariation in life history traits within squamate reptiles are strongly influenced by classwide correlations with female body length. This result minimizes the importance of microevolutionary processes, such as adaptation to local environmental conditions, in shaping life history variation. Microevolution would, in effect, be constrained by ancestry or lineage, which limits the magnitude and direction of covariation in life history variables. On the basis of a corrected and expanded data base, we present evidence that argues against strong phylogenetic constraint at the ordinal level on the patterns of covariation in life history traits among squamate reptiles. Rather, our finding of significant effects of family-level taxonomy on four life history variables (clutch size, mode of reproduction, brood frequency, and age at maturity), with the effects of size removed, suggests that tests of historical hypotheses within the squamates should be limited to ...
I present a model to investigate the effects of density-dependent resource availability on per capita population growth rate. By considering a continuous time model of inclusive fitness, population losses as well as growth are essential determinants of phenotypic fitness. The outcome of natural selection for various life-history characteristics is dependent upon not only the shape of the life history-specific population growth curves, but also upon the form of the seasonality function. As the magnitude and length of a resource shortage period increases, the rate of decrease becomes a more important component of fitness. Seasonality is often characterized by (1) a period of population decrease, when natural selection favors functions which minimize somatic or embryonic mortality, and (2) a period of high resource availability when high somatic and gametic productivity are favored. Assuming that mean resource availability remains constant, seasonally deterministic and/or random variation in the availability...
L’étude d’une population d’hermines (Mustela erminea) dans le Val de Ruz (Jura neuchâtelois, Suisse) a permis la capture et le marquage de 95 individus d’avril 1978 à avril 1980. La structure mensuelle moyenne de la population a été établie à partir d’un calendrier de captures intégrant les 178 captures et recaptures réalisées. Un taux de mortalité (TMa ; estimé constant) de 0,68 et un taux de renouvellement (TRa ; dépendant de l’émigration) de 0,93 caractérisent la labilité de la population des adultes. TMa est en accord avec la proportion élevée de juvéniles. TRa traduit le large rayon de dispersion des adultes par rapport aux dimensions du terrain d’étude (616 ha). L’âge moyen de la population active estimée a été calculé pour chaque mois. Il oscille entre 9,8 mois en août et 18,7 mois en mai. La longévité estimée est un peu plus élevée que les valeurs trouvées dans des populations intensivement chassées, mais inférieure à la longévité potentielle de l’espèce. Les hermines du Val de Ruz paraissent donc être soumises à une pression de sélection élevée.
Extensive variation in life-history patterns is documented across primate species. Variables included are gestation length, neonatal weight, litter size, age at weaning, age at sexual maturity, age at first breeding, longevity, and length of the estrous cycle. Species within genera and genera within subfamilies tend to be very similar on most measures, and about 85% of the variation remains when the subfamily is used as the level for statistical analysis. Variation in most life-history measures is highly correlated with variation in body size, and differences in body size are associated with differences in behavior and ecology. Allometric relationships between life-history variables and adult body weight are described; subfamily deviations from best-fit lines do not reveal strong correlations with behavior or ecology. However, for their body size, some subfamilies show consistently fast development across life-history stages while others are characteristically slow. One exception to the tendency for relative values to be positively correlated is brain growth: those primates with relatively large brains at birth have relatively less postnatal brain growth. Humans are a notable exception, with large brains at birth and high postnatal brain growth.
Survival pattern of adult Lepus europaeus was analysed in c2400ha in the N part of the Great Hungarian Plain. Adult survival is independent of age, though a certain variation was traced in survival rates. Life expectancy of the first age group before the start of the breeding season was 1.1yr. Mean mortality rate per year for adults was 0.625, which corresponds with the proportions of young of the 2 consecutive study years, 0.607 and 0.623 respectively.-from Author
During the period from 1963-1973 individually marked wid boar (Sus scrofa L i n n a e u s, 1756) were frequently caught in the Kampinos National Park near Warsaw (N=376). The mortality rate of piglets was estimated as 15% of young born, and the number of wild boar from 2-5 years old leaving the area due to emigration as 12-32%. W Kampinowskim Parku Narodowym kolo Warszawy, w latach 1963-1973 lowiono wielokrotnie uprzednio znakowane dziki (Sus scrofa L i n n a e u s, 1758) (N=376) (Tabela 1), ktorych daty uodzenia i ubycia z badanej populacji byly znane. Oznakowano wielkośc śmiertelności oseskowej i liczbe osobnikow ubywających na skutek migracji. Nastepnie zestawiono tabele zyciową i oceniono maksymalny i średni czas zycia, charakter krzywej przezywania, tempo wymierania samcow i samic, dalszy oczekiwany czas zycia osobnikow z poszczegolnych klas wiekowych oraz sezonowośc śmiertelności dzikow z dwoch rozniących sie przebiegiem tego zjawiska grup wiekowych - warchlakow i dzikow starszych niz jeden rok.
Two hundred and twelve wolves (Canis lupus labradorius) shot by hunters in northern Quebec and Labrador during the winters of 1976-77 through 1983-84 were examined for various population parameters. An estimated annual adult survival rate of 55% and a recruitment rate of 49% suggest a population of moderate exploitation. The sex ratio did not differ significantly from 1:1. Fifty-five percent of yearling females were pregnant or in breeding condition. The average litter size for all females was 6.8. Internal fat deposits were greatest in young males and older females. Caribou (Rangifer tarandus caribou) was the most common food item found in stomachs. A sample of caribou killed by wolves in the winter showed a selection for older-aged caribou with fat deposits slightly below that of the general population.
Key words: wolf, caribou, northern Quebec, Labrador, predation
Populations of many species, including man, are age-structured: the individuals present in the population at any one time were born over a range of different times, and their fertility and probability of future survival depend on age. Aspects of age-structured populations discussed include demography and ecological dynamics; the theory of natural and artificial selection; and the genetic effects of finite population size. Chapters are: models of age-structured populations; genetics of populations without selection; selection - construction of a model and the properties of equilibrium populations; selection - dynamic aspects; the evolution of life-histories.- P.J.Jarvis
Fall-to-fall mortality of livetrapped adult cottontail rabbits (Sylvilagus floridanus) on a study area in east-central Illinois averaged 0.79 ± 0.06 for the years 1960-71. The average rate of annual mortality was higher (0.84) for years that the population was hunted than for years (0.75) when there was no hunting.
A total of 1625 female eastern cottontail rabbits (Sylvilagus floridanus) were collected from 28 states and from Ontario, Canada, during 1964 and 1965. Onset of breeding, first and second litter sizes, and body weights were calculated. Latitude, longitude, and elevation of each collection site were recorded. Data were analyzed using multiple regression procedures. Onset of reproduction was positively related to latitude and elevation for each year. That is, onset of reproduction occurred later at higher latitudes and elevations. There was a negative relationship with longitude in 1964, but the relationship was positive in 1965. In 1964, size of first litter was positively related to conception date, body weight, and latitude while it was negatively related to elevation. The same results were obtained for 1965, but longitude also had a positive relationship. Size of second litter was positively related to body weight in 1964, and to body weight and latitude in 1965. Body weight was positively related to latitude in each year, while it was negatively related to longitude in 1964 and to longitude and elevation in 1964 and 1965.
A maximum density of one adult Felis rufus per 11.0 km2 was estimated for the Ouachita National Forest, SE Oklahoma. Statewide population trends determined by scent-station surveys declined from 1977-81, with a finite rate of increase of 0.89/yr. Sex ratios did not differ from an expected 50:50 ratio. The age structure of the harvest was 26% juveniles, 32% yearlings, and 43% adults. Pregnancy rate of yearling females (46%) was lower than in adults (92%). Yearling pregnancy rate was further reduced following a major drought. Mean in utero litter sizes of yearlings and adults were 2.3 and 2.7 kittens/litter, respectively. Estimates of adult survival rate ranged 0.53-0.66; juvenile survival was 0.30. Harvest was the sole source of non-study-related mortality of radio-collared bobcats. Continued harvest of already low density bobcat populations may further depress the populations and result in local extirpations.-from Author
Dokonano analizy wiekowej populacji kreta, Talpa europaea Linnaeus, 1758 z terenow zielonych Krakowa i okolic (N=800), oraz Beskidu Sądeckiego i Tatr (N=76), badanych w latach 1955-1962. Oparto sie na stopniu zuzycia trzonowcow i przedtrzonowcow oraz ksztalcie kla. Wykorzystano rowniez cechy dodatkowe, jak ubarwienie futra, pigmentacje odnozy, wysokośc czaszki, wielkośc jąder, rozwoj prącia i macicy. Wyodrebniono 5 grup wiekowych.
W lasach grądowych (Tilio-Carpinetum) Puszczy Niepolomickiej w ciągu czterech kolejnych lat oceniano liczebnośc gryzoni poslugując sie metodą zanecania i intensywnego wylowu (Ryc. 1). Nornice rude (Clethrionomys glareolus) i myszy leśne (Apodemus flavicollis) stanowią 92,5% wszystkich gryzoni w tym lesie (Tabela 1).
Mean litter size in Peromyscus leucopus is 4.7 (mode = 5). We attempted to answer the question: 'Does this litter size produce the greatest number of surviving offspring?' by experimentally examining the effect of litter size and female parity on the following parameters: size of young at birth and at weaning, survivorship and growth rates of young during their first four weeks of life, and the ability of weanlings to survive exposure to acute stress. Results indicated that (1) net productivity increased with parity because of a significantly higher survivorship in larger litters of more parous females; (2) weight at birth and early growth rates did not vary with litter size (or parity); these parameters interact to create a weaning weight that probably represents an optimal balance between size and number of offspring that maximizes parental fitness; (3) artificial decreases or increases in litter size after birth significantly increased or decreased nursling growth rates, respectively, but did not affect their survival rates, suggesting that females may be capable of adjusting their rates of milk production to maximize their production of young; and (4) time until exhaustion in an ice water bath was positively correlated with weanling size, which suggests that the ability to survive a stressful situation in weanlings may be size-dependent. Taken together, these results indicate that a litter size of five is ultimately most productive of successful offspring in reproductively inexperienced females whereas a larger litter is more productive in older, more experienced females. Perhaps the main reason why modal litter size in P. leucopus is five is that populations in the laboratory and nature are dominated by young, rather than old, females. It is suggested that the latitudinal or altitudinal trends in litter size that have been documented in Peromyscus may reflect shifts in age structure towards older, more fecund females in northern or higher elevation populations.
Populations of the eastern chipmunk (Tamias striatus) were studied during the years 1962 to 1970 at locations in Pennsylvania and Vermont by means of repetitive live-trapping of gridded plots. Analysis of the resultant data provided life tables, survivorship curves, and population age classes for this species. Calculations were based on disappearance of individuals from the trapped plots rather than on known mortality. Four thousand individuals were trapped of which 1580 were first captured as juveniles. Survival tended to be constant over much of the adult life span but differed among populations at different localities and between sexes. Season of birth also affected survival rate. Yearly survival rates based on a composite series of known-age chipmunks varied from 0.34 to 0,64 with an average of 0.43. Mean life expectancy at first capture ranged from 1.0 to 2.25 years with a mean of 1.29 years. There is a shift in age distribution from year to year as a result of different numbers of juveniles entering the population in each breeding season. Fluctuations in the numbers of chipmunks handled over the period of the study indicated the possibility of a cycle of 3 to 4 years. There also appeared to be synchrony in these fluctuations between the populations in Pennsylvania and those in Vermont.
One hundred sixty-one bobcats (Lynx rufus pallescens) were collected by federal and private trappers throughout Wyoming from 1970 to 1973. The age of each was established by meristic characters of the canine teeth and cementum annuli. Maximum life span was approximately 12 years and the animals remained sexually active until death. Females reached sexual maturity within a year and were polyestrus from February to June. Litters averaged 2.8 young and most were born from 15 May to 15 June. The numbers of luteal bodies in the ovaries of older females suggested they remain as separate entities for relatively long periods, possibly throughout the life of the animal. Males were seasonally fertile, but were not sexually mature until their second year.
A population model was developed to estimate demographic parameters and abundance of a black bear (Ursus americanus) population in eastcentral Ontario, using data from a 12-year mark-recapture program. The model enables the separation of natural and hunting mortality and allows for immigration to the study area. Parameter fitting was done by a nonlinear least-squares criterion. Abundance estimates using the 0-truncated Poisson, Petersen, and Jolly-Seber procedures allowed comparison of the different methods. The population growth rate was estimated as 2.9%/year for the female segment. Age-specific reproductive value was calculated, and its significance for black bear conservation is discussed.
The characteristics of an unexploited population of gray squirrels (Sciurus carolinensis) in North Carolina were studied over the period 1956-1964. The research area totalled 400 acres and was a part of a 5,200 acre continuous woodland. Density and survival information were obtained from an intensive tagging and recapturing program utilizing live traps and nest boxes. Life table and survival data were derived from the recapture records of 1,769 marked squirrels, 1,023 of which were of known age. Survival estimates are minimal because dispersal movements are included in mortality. An average annual dispersal rate of 14.5 percent is suggested. The mean value for survival during the first year was calculated as 0.26. No significant difference (P > 0.05) was detected between the recapture rates of spring and summer litters. The high rate of mortality (0.75) in the first year is counterbalanced by a high survival rate (0.52) in the adult categories. Adult females had a slightly higher survival rate than males (0.59 vs. 0.44). Mean life expectancy at birth was approximately 1 year (0.99). In the adult age groups the mean life expectancy increased from 1.82 years in the 1-2-year cohort to a high of 2.41 years in the 2-3-year cohort and remained above 1 year until the 7-8-year cohort when the mean life expectancy fell to 0.50 years. Cohort longevity was 6.4 years on a 99.5 percent turnover basis. Ecological longevity was about 9 years.
Populations of pipistrels hibernating in two West Virginia caves were studied over a 14-year period. Methods are developed for determining the percentages of surviving bats not recaptured in the caves, the annual survival percentages, survival rates for each sex and age group and the structure of the populations by age and sex. Sex ratios observed in the caves, which fluctuate between 69.5% and 85.1% males, do not show the sex ratio of the species; analysis of survival rates indicates that the true sex ratio is 61♂: 39♀. Life tables are presented for the species and for random cohorts of adults. Annual survival rates are different for each age group. Survival is low in youngest bats, climbs to a peak at 3.5 years and then decreases, falling rapidly as maximum life span is approached.
This paper describes red squirrel population dynamics on two intensive study areas (Camp and Main) in mixed-forest types near Rochester, Alberta. It also examines local and regional population fluctuations, and their relationship to cone crops and weather factors. Adult red squirrel numbers on our study areas varied little from 1967 to 1968. Yearly differences in reproductive output were caused principally by changing ovulation and pregnancy rates. Mean litter size increased significantly from 3.4 in 1967 to 4.3 in 1968; while the per cent adult females breeding increased significantly from 67 to 88. A life-table analysis of age-ratio data estimated mean annual mortality among juveniles (postweaning) at 67%; and an adult mortality rate of 34% for yearlings and 61% for older cohorts. A time-specific estimate of adult mortality on the Camp study area during the year starting summer 1967 was 21%. Red squirrel territories appeared to be of two distinct types: (1) defended winter food caches which were subsequently abandoned during the summer, and (2) @'prime@' territories in which a specific area was defended year round. During the summers of 1967 and 1968, 31% and 26% of study-area adult populations occupied prime territories. The distribution of prime territories chiefly reflected the presence of mature seed-producing conifers, and hence a potential year-round food supply. Deciduous areas were particularly important in overwintering the juvenile cohort. Fur returns were used as population indices in determining synchrony and periodicity of red squirrel fluctuations. Fluctuations tend to occur synchronously over much of the Prairie Provinces. Furthermore, mean intervals between peak years in Alberta (2.6) and Saskatchewan (2.8) were significantly shorter than in random series of comparable length, while the 2.9-year mean interval in Manitoba approached significance. A statistically significant correlation was found between white spruce cone crops and red squirrel populations in Alberta as indexed by annual fur harvests. The negative correlation between cone crops in late summer and rainfall during summer of the preceding year was almost significant. This supported the widely held view that weather factors influence bud differentiation and hence determine the size of the following year's cone crop. Our contention that cone production may in this way provide a vehicle through which weather affects squirrel populations was supported by a number of statistically significant negative correlations between Alberta and Saskatchewan fur returns and the preceding year's summer rainfall. Such a mechanism would explain the observed widespread synchrony of population fluctuations, since extensive regional weather patterns could be involved.
Rates of survival of Myotis sodalis are calculated from recaptures of bats marked in cohorts of unknown age. Such data can be misleading, so the proper types ot interpretation are identified. Survival rates are high for 10 years after marking in females and 6 years in males. Females can live as long as 14.8 years and males as long as 13.5 years. Survival of the species is good in undisturbed environments, and endangerment results from loss of habitat.
Free-ranging domestic cats on farmsteads were censused annually in August 1977-81 within a 5,182-ha area typical of the cash-grain region in central Illinois. The estimated average number of cats on the area in late summer was 326 (6.3/100 ha). Annual recruitment of immature cats into the late summer population averaged 1.5/adult female. Survival beyond 3-5 years of age was rare; <1% survived 7 or more years. Eleven adult cats were radio-monitored during a 30-day period in summer; four males ranged over larger areas (P < 0.01) than seven females (228 ± 100 ha and 112 ± 21 ha, respectively). When cats were not on farmsteads, approximately 73% of their radiolocation points (N = 1,227) were in edge or linear configurations of cover. Cats made disproportionately high (P < 0.05) use of farmsteads and perimeters, roadsides, and field interfaces and disproportionately low use (P < 0.05) of fields of corn and soybeans. Domestic cats on the area were well fed by humans but routinely deposited prey at their residences.
The Uganda defassa waterbuck was studied in the Queen Elizabeth Park, western Uganda. A description of the area is given with emphasis on its recent history showing that the large mammal populations are relative newcomers to the study areas. Counts over 4 years showed an approximate density of 5.5/square mile (2.6 km2), in the range of 0.4-28.3. Actual densities range from 0 to >100/square mile seasonally. The overall sex ratio was 1:1.6 males:females. Calf mortality is high, at least 50% dying in the first year. Factors causing mortality in calves and adults are discussed. Counts over 4 years suggest that the population is stable and provisional life tables, based on skulls collected in the Park, have been constructed. Assuming a mortality of 50% in the first year these give a mean expectation of life in the male of 4.6+-1.7 years, and in the female 4.4+-3.4 years. The life span of the male is approximately 11 years and of the female 13 years. The male curve suggests that older animals predominate with accelerated mortality in old age, whilst in the female death occurs more randomly through life. Population changes on the Mweya Peninsula, following the removal of the hippopotamus population in 1958, are discussed. The overgrazed study area which has a stable population of less density than the Peninsula, but identical vegetation, is contrasted with it. Density differences appear to be due more to topography than to food preferences but no single factor is alone responsible.
The survival curves of four species of African ungulate--impala, buffalo, zebra, and warthog--derived from skulls found in the Akagera National Park, Rwanda, are compared. Three of the species are shown to have the typical logarithmic negatively-skewed adult curve shown by undisturbed large mammal populations, but warthogs apparently have a heavy age-constant number of deaths to middle-age. Attention is drawn to the limitations of time-specific data in the study of population dynamics.
We quantitatively test theoretical predictions concerning mammalian life histories, using published data on survival, reproduction, and body mass for 29 eutherian mammals. Larger mammals have a greater age at maturity, greater generation length, greater life expectancy, lower reproductive value at maturity, and smaller litters than do smaller mammals. Residual reproductive value at maturity is not correlated with adult body mass or survival. Litter size varies inversely with generation length and adult survival. Age at maturity is positively correlated with life expectancy. Twenty-seven of 29 mammals display a generation length longer than their life expectancy at birth, and the same proportion shows a greater life expectancy at maturity than at birth. A fairly high proportion (76-82%) of the variation in these dependent variables is attributable to adult mass. Many life table characteristics of mammals are interrelated, although not necessarily in the ways predicted by theory. Design constraints may preclude significant differences in life history patterns among mammals, so that the life table characteristics of only a few species may depict the pattern of life table evolution in most eutherian mammals.
(1) Red deer population dynamics were studied on Rhum for 9 years, following the Nature Conservancy's acquisition of the island in 1957, to find a means of controlling deer numbers in relation to reserve management. (2) Numbers were determined each year in late winter or early spring by means of classified counts, the validity of which was tested ultimately by reconstructing each standing population after ageing all the deer recovered dead. (3) Totals, calculated for the first 4 years, differed from the counted by only 2.1 +- 1.6%, but errors in classification were greater; 11.3 +- 2.6% of the stags were found to have been classified as hinds, whilst the latter had been over-estimated by 17.3 +- 8.6%. Depending on previous growing conditions, calves also tended to be classified as hinds (13.0 +- 19.0%). (4) Since the difference between counted and dead adult sex ratios for the first 6 years averaged 6.0 +- 1.3% in favour of stags, and culled stags (average age 6.4 +- 0.8 years) were older than culled hinds (average age 5.2 +- 0.4 years) every year, it was assumed that the errors remained constant, and all measurements of births, deaths and sex ratios were corrected accordingly before the effects of changes in management were assessed. (5) Two life tables were constructed, one time-specific for the standing population in 1957, the other dynamic, based on the subsequent history of the 1957 yearlings up to the age of 9 years. Whilst stags had a greater further-expectation-of-life than hinds in both tables for the first 9 and 4 years respectively, survival of both sexes was reduced following changes in management after 1957. (6) Because of the errors in classification, culling, which was intended to take one-sixth of the adults of each sex each year, fell relatively more heavily on the hinds, taking almost one-fifth of their numbers (average 19.3 +- 1.29%) in contrast with stags (average 15.2 +- 1.37%). (7) In neither sex was all natural mortality ever replaced completely by culling. Natural deaths occurred most frequently among calves (9.4% p.a.) and in deer of both sexes after the age of 10 years (c. 33% p.a.), perhaps a consequence of inefficient rumination due to ineffective check teeth. (8) Factors determining hind recruitment were complex. The sex ratio at birth, calculated from 1381 calves which died later during the study, favoured females (46.6 male male: 53.4 female female), principally due to prime hinds (5-8 year-olds) producing significantly more females calves (61.6 male male :100 female female, P<0.02) in contrast with other classes (parity). But, following bad weather conditions during late summer and winter, there was a significant reduction (P<0.05) in the number of females born in the following summer; males were not affected. (9) Total recruitment was probably most influenced by the change in land usage, the innate capacity for increase (rc) being reduced from 0.04731 in 1957 to -0.01717 for the first yearling cohort which could be followed to near extinction. Records for later cohorts, when complete, are expected to show a further decline following a significant reduction in the fecundity of 2-year-olds after 1959 from 62.1 to 31.4% (P<0.01). This was thought to be largely a consequence of the cessation of muirburn, since the fecundity of 2-year-olds having access to areas burnt as fire-breaks after 1962 recovered significantly to around its former level (70%; P = 0.044) in contrast with the rest (30.5%). (10) After 1959, the combination of all these factors contributed to a slow rate of population decline, but none was thought responsible for the marked decrease in stags during the last 2 years. Since nine stags and no hinds have been found washed up on the beaches of Rhum, floating in the sea or washed up on the mainland, and all of them since 1963, there is a suggestion that the missing stags may have attempted emigration as a result of the disturbed sex ratio.
For 11 consecutive field seasons (1969-1979) we studied the demography of a free-living population of Belding's ground squirrels (Spermophilus belding) at Tioga Pass, in the central Sierra Nevada of California. Our research involved repeatedly capturing and directly observing individually marked, known-age animals within and between years. Here we present information on age-specific survival and dispersal rates for both sexes and age-specific fecundity and reproductive value for females. Our data indicate that: (1) The 7-8 mo hibernation period (October-May) is a hazardous time; 66-70% of juveniles and 36-39% of adults disappear during the winter. (2) Males apparently live about half as long as females; males that survive their first winter typically remain in the population an additional 1.1 yr vs. 1.6 yr for females; while few males live > yr, some females live >11 yr. (3) The sex of ration of the adult population is female-biased, especially in the older age-classes. (4) Throughout the active season (summer), males disappear more rapidly than females; this disappearance is due both to dispersal and to mortality. (5) During intrasexual combat for mates, males injure each other severely; such injuries lead directly and indirectly to male mortality. (6) Litter size and reproductive value change with female age; they are lowest for young (0-1 yr) and old (5-9 yr) female and highest for 2-4 olds. (7) The net reproductive rate (R"0) for 1969-1975 was 1.36 daughters per dam, while the mean generation length (@?) was 2.26 yr. Sexual asymmetries in the demographic characteristics of S. beldingi appear to result from the animals' polygynous breeding system.
Studies were carried out over the period from 1970-1981 in an area 15,000 ha in extent, for the purpose of determining some aspects of spatial organization of a field roe deer population, their survival and longevity, by means of individual marking of members of the population. It was found that the study roe deer population consisted almost entirely of resident individuals, the activity of which was limited to the area of their home ranges.
Breeding records from a laboratory colony of Peromyscus maniculatus bairdii were used to examine patterns of covariation among variables describing reproduction, size, age, parity, and survival. Litter size was strongly negatively correlated with average weights of young at birth and at weaning, but positively related to the total mass of young. Mother's weight was correlated with the number of young in a litter and the average and total weights of young at birth and weaning, though the strength of the correlation varied according to when young were weighed. Weight gained by young during the nursing period also was positively related to mother's size. Parity strongly affected litter sizes and birth weights; however, this effect was attributable to continuing growth of the mother. Similarly much, but not all, of the effect of parity on weaning weights and growth rates was attributable to mother's weight. Female age (independent of weight and parity) was important in determining the number of young born (but not their birth weight), the rate of growth of young during the nursing period, and the average weights of individual young at laboratory weaning. The size of young at birth and their number of littermates was clearly related to their probability of surviving the nursing period, and size differences among young at weaning persisted well into adult life. Parity had no effect on the survival of young. The duration of gestation also was related to the weight of a mother and to the weight of her previous litter; the size of the litter in utero had no significant effect on gestation length. These relationships are discussed from the points of view of (1) the advantage to females and their young of large size, (2) the compromises a female makes in determining the number, size, and timing of birth of her offspring, and (3) the implications of these patterns of covariation for investigations of the evolution of reproductive patterns.
Female age class and spring adult sex ratios were found to consistently affect (P < 0.05) reproductive performance of North Dakota red fox (Vulpes vulpes). Reproductive performance was found to increase through 8 age classes. Increases (P < 0.05) in ovulation rates, embryonic litter sizes, and declines in prenatal mortality were observed as a function of increasing female age. Body fat was found to increase in relation to female age class. An inverse relationship was noted between annual estimates of ovulation rates compared to March adult sex ratios and embryonic litter size compared to March adult sex ratios. A direct relationship was determined for annual estimates of prenatal mortality and March adult sex ratios. No consistent relationship was found between annual estimates of ovulation rates, embryonic litter sizes, or prenatal mortality when compared to annual spring population density.
Data on the population of grizzly bears in the environs of Yellowstone National Park suggest that the population has not recovered from the reductions following closure of garbage dumps in 1970 and 1971, and may continue to decline. A computer simulation model indicates that the risk of extirpation over the next 30 yr is small, if the present population parameters continue to prevail. A review an further analysis of the available data brings out the importance of enhancing adult female survival if the population is to recover, and assesses various research needs. In particular, a reliable index of population trend is needed to augment available data on the population. 12 references, 9 figures, 6 tables.
Annular layering of cementum was evident in hematoxylin-stained sections of canine teeth from otters (Lontra (Lutra) canadensis canadensis) collected throughout the year. A wide cementum layer was formed during the first summer and narrower layers were formed in subsequent summers. The winter deposition formed a darkly stained line which was observed in animals of known age up to 4½ years and in wild-caught animals up to 13 years. The number of annuli in known-age specimens over 1 year old showed complete agreement with age. Indistinct and extraneous lines were encountered in the cementum of a few specimens which required subjective interpretation. Ages were assigned to 99% of otters examined for cementum annuli. Males were larger (P < 0.05) than females as indicated by body weights and body and skull measurements. Juvenile otters could be distinguished by the size of the body, skull, and baculum and morphology of the skull. Extensive overlap in weights and measurements in older age classes prevented a re...
After size effects were removed, significant differences between taxonomic families were found for most of the 8 examined life history traits. At the family level, most life histories do not correlate with ecological factors; some differences do exist, however; in Canidae, dietetic differences are associated with variation in birth weight, gestation length, and weaning age; in Canidae ad Felidae, vegetational effects are observed with litter weight and, in the Mustelidae, with onset of sexual maturity. - from Author