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1. In wild vertebrates, some individuals survive and reproduce better than othersand this has led to the concept of individual quality. Despite its importance whenstudying ecological processes and life‐history trade‐offs, measuring individualquality is complex because individuals must be followed during a large part oftheir life.2. Recently, telomere biology has been successfully brought into ecology and telomerelength has been suggested to be a promising molecular tool to evaluate individualquality in wild vertebrates (“the telomere–individual quality hypothesis”).3. In this study, we tested this hypothesis in a long‐lived species, the black‐browedalbatross (Thalassarche melanophrys) by simultaneously measuring telomere lengthand several potential complementary phenotypic proxies of individual quality in asingle year. In addition, we followed the return rate and the reproductive performanceof these same albatrosses for a decade.4. We found that long telomeres were associated with several markers of high individualquality (foraging behaviour, body size and stress hormone levels).Furthermore, we found that a single measure of telomere length could predictfuture offspring productivity, for at least several years following telomere measurement(better productivity being associated with longer telomeres).5. Altogether, these results support the “telomere–individual quality hypothesis”and suggest that telomere length can be useful to estimate individual quality inlong‐lived seabirds.

The aim of this paper is to explore the usage and impact of the Internet-of-Things-based Smart Home Technology (IoT-SHT) in Malaysia. Face-to-face interviews were conducted with a total of eleven IoT-SHT users who had a minimum of 2-year usage experience. The semi-structured interview consisted of six questions which were compartmentalised into two sections. Common themes were identified through constant comparison of the inductive data in the coding process. The in-depth interview uncovered six uses of IoT-SHT. Mainly, it was used for real-time remote control, surveillance, sensing, home automation, entertainment, and family communication. It seems clear that the IoT-SHT helped people to save time, changed their lives, improved security, safety, environment condition, fun, convenience, and comfort within the home ground. It also facilitated better health tracking, family care, and energy conservation. Psychologically, the IoT-SHT also enhanced one’s image, offered better companionship, and improved the sense of belongingness, and closeness within the family. This study fills the research gap by providing insights into how the IoT-SHT was used, thereby benefiting users in Malaysia. With the arrival of industrial revolution 4.0, a comprehensive knowledge on the usage of IoT is pertinent. The findings of this study may also serve as a foundation for future research in IoT-SHT adoption. Practically, this study accelerates IoT-SHT diffusion by providing insights to vendors in designing better IoT products and services, based on the popular usages and impactful benefits.

This article discusses three steps involved in moving us toward a theory of individual quality of life: developing a conceptual model, integrating theory components, and applying and evaluating the theory. Each of the proposed steps is guided by established standards regarding theory development and use. The article concludes with a discussion of criteria that can be used to evaluate the theory and the contribution that a theory of individual quality of life would make to the field of disability.

Population dynamics models have long assumed that populations are composed of a restricted number of groups, where individuals in each group have identical demographic rates and where all groups are similarly affected by density-dependent and -independent effects. However, individuals usually vary tremendously in performance and in their sensitivity to environmental conditions or resource limitation, such that individual contributions to population growth will be highly variable. Recent efforts to integrate individual processes in population models open up new opportunities for the study of eco-evolutionary processes, such as the density-dependent influence of environmental conditions on the evolution of morphological, behavioral, and life-history traits. We review recent advances that demonstrate how including individual mechanisms in models of population dynamics contributes to a better understanding of the drivers of population dynamics within the framework of integrated population models (IPMs). IPMs allow for the integration in a single inferential framework of different data types as well as variable population structure including sex, social group, or territory, all of which can be formulated to include individual-level processes. Through a series of examples, we first show how IPMs can be beneficial for getting more accurate estimates of demographic traits than classic matrix population models by including basic population structure and their influence on population dynamics. Second, the integration of individual- and population-level data allows estimating density-dependent effects along with their inherent uncertainty by directly using the population structure and size to feedback on demography. Third, we show how IPMs can be used to study the influence of the dynamics of continuous individual traits and individual quality on population dynamics. We conclude by discussing the benefits and limitations of IPMs for integrating data at different spatial, temporal, and organismal levels to build more mechanistic models of population dynamics.

Telomere length is associated with cellular senescence, lifestyle and ageing. Short telomeres indicate poor health in humans and reduced life expectancy in several bird species, but little is known about telomeres in relation to phenotypic quality in wild animals. We investigated telomere lengths in erythrocytes of known-age common terns (Sterna hirundo), a migratory seabird, in relation to arrival date and reproductive performance. Cross-sectional data revealed that, independent of age, individuals with short telomeres performed better: they arrived and reproduced earlier in the season and had more chicks in the nest. The latter effect was stronger the older the brood and stronger in males, which do most of the chick provisioning. Longitudinal data confirmed this pattern: compared with birds that lost their brood, birds that raised chicks beyond the 10th nestling day experienced higher telomere attrition from one year to the next. However, more detailed analysis revealed that the least and most successful individuals lost the fewest base pairs compared with birds with intermediate success. Our results suggest that reproductive success is achieved at the expense of telomeres, but that individual heterogeneity in susceptibility to such detrimental effects is important, as indicated by low telomere loss in the most successful birds.

Extreme climatic conditions and their ecological impacts are currently emerging as critical features of climate change. We studied extreme sea ice condition (ESIC) and found it impacts both life-history traits and population dynamics of an Antarctic seabird well beyond ordinary variability. The Southern Fulmar ( Fulmarus glacialoides ) is an ice-dependent seabird, and individuals forage near the ice edge. During an extreme unfavorable year (when sea ice area is reduced and distance between ice edge and colony is high), observed foraging trips were greater in distance and duration. As a result, adults brought less food to their chicks, which fledged in the poorest body condition. During such unfavorable years, breeding success was extremely low and population growth rate (λ) was greatly reduced. The opposite pattern occurred during extreme favorable years. Previous breeding status had a strong influence on life-history traits and population dynamics, and their responses to extreme conditions. Successful breeders had a higher chance of breeding and raising their chick successfully during the following breeding season as compared to other breeding stages, regardless of environmental conditions. Consequently, they coped better with unfavorable ESIC. The effect of change in successful breeder vital rates on λ was greater than for other stages' vital rates, except for pre-breeder recruitment probabilities, which most affected λ. For environments characterized by ordinary sea ice conditions, interindividual differences were more likely to persist over the life of individuals and randomness in individual pathways was low, suggesting individual heterogeneity in vital rates arising from innate or acquired phenotypic traits. Additionally, unfavorable ESIC tended to exacerbate individual differences in intrinsic quality, expressed through differences in reproductive status. We discuss the strong effects of ESIC on Southern Fulmar life-history traits in an evolutionary context. ESICs strongly affect fitness components and act as potentially important agents of natural selection of life histories related to intrinsic quality and intermittent breeding. In addition, recruitment is a highly plastic trait that, if heritable, could have a critical role in evolution of life histories. Finally, we find that changes in the frequency of extreme events may strongly impact persistence of Southern Fulmar populations.

The horns and antlers borne by the males of many species of ungulate are considered to be both badges of quality, and armaments for use during intraspecific combat. Underpinning arguments concerning their dual utility is the idea that these structures should be costly to produce in order that the signal value of the structure is maintained. In agreement with such theorising is the belief that fluctuating asymmetry (FA), small deviations from symmetry around a mean of zero, measures individual quality as it represents the ability of the individual to withstand stress. We investigated whether the antlers of fallow deer indicated something of the quality of the bearer by assessing whether the degree of antler FA was associated with breakage (i.e., badge of quality) or with tactical investment in fighting (i.e., armament). We show the anticipated relationship between FA and antler damage, however, there was no relationship between FA and contest tactics. The present study, therefore, shows partial support for the idea that the magnitude of fluctuating asymmetry expressed by weaponry is related to individual quality.

Under life‐history theories of ageing, increased senescence should follow relatively high reproductive effort. This expectation has rarely been tested against senescence varying between and within the two sexes, although such an approach may clarify the origins of sex‐specific ageing in the context of a given mating system. Nazca boobies (Sula granti; a seabird) practise serial monogamy and biparental care. A male‐biased population sex ratio results in earlier and more frequent breeding by females. Based on sex‐specific reproductive schedules, females were expected to show faster age‐related decline for survival and reproduction. Within each sex, high reproductive effort in early life was expected to reduce late‐life performance and accelerate senescence. Longitudinal data were used to (a) evaluate the sex specificity of reproductive and actuarial senescence and then (b) test for early‐/late‐life fitness trade‐offs within each sex. Within‐sex analyses inform an interpretation of sex differences in senescence based on costs of reproduction. Analyses incorporated individual heterogeneity in breeding performance and cohort‐level differences in early‐adult environments. Females showed marginally more intense actuarial senescence and stronger age‐related declines for fledging success. The opposite pattern (earlier and faster male senescence) was found for breeding probability. Individual reproductive effort in early life positively predicted late‐life reproductive performance in both sexes and thus did not support a causal link between early‐reproduction/late‐life fitness trade‐offs and sex differences in ageing. A high‐quality diet in early adulthood reduced late‐life survival (females) and accelerated senescence for fledging success (males). This study documents clear variation in ageing patterns—by sex, early‐adult environment and early‐adult reproductive effort—with implications for the role mating systems and early‐life environments play in determining ageing patterns. Absent evidence for a disposable soma mechanism, patterns of sex differences in senescence may result from age‐ and condition‐dependent mate choice interacting with this population's male‐biased sex ratio and mate rotation. This study reveals striking sex differences in senescent decline in a monogamous seabird with biparental care. Surprisingly, breeding often and eating a low‐quality diet in early adulthood associated positively with late‐life performance. These individual effects were different for males and females, as expected for this population's mate rotation system.

1. Individuals are heterogeneous in many ways. Some of these differences are incorporatedas individual states (e.g. age, size, breeding status) in population models.However, substantial amounts of heterogeneity may remain unaccounted for, dueto unmeasurable genetic, maternal or environmental factors.2. Such unobserved heterogeneity (UH) affects the behaviour of heterogeneous cohortsvia intra-cohort selection and contributes to inter-individual variance in demographicoutcomes such as longevity and lifetime reproduction. Variance is alsoproduced by individual stochasticity, due to random events in the life cycle of wildorganisms, yet no study thus far has attempted to decompose the variance in demographicoutcomes into contributions from UH and individual stochasticity for ananimal population in the wild.3. We developed a stage-classified matrix population model for the southern fulmarbreeding on Ile des Pétrels, Antarctica. We applied multievent, multistate mark–recapturemethods to estimate a finite mixture model accounting for UH in all vitalrates and Markov chain methods to calculate demographic outcomes. Finally, wepartitioned the variance in demographic outcomes into contributions from UH andindividual stochasticity.4. We identify three UH groups, differing substantially in longevity, lifetime reproductiveoutput, age at first reproduction and in the proportion of the life spent in eachreproductive state.– 14% of individuals at fledging have a delayed but high probability of recruitmentand extended reproductive life span.– 67% of individuals are less likely to reach adulthood, recruit late and skip breedingoften but have the highest adult survival rate.– 19% of individuals recruit early and attempt to breed often. They are likely to raisetheir offspring successfully, but experience a relatively short life span.Unobserved heterogeneity only explains a small fraction of the variances in longevity(5.9%), age at first reproduction (3.7%) and lifetime reproduction (22%).5. UH can affect the entire life cycle, including survival, development and reproductiverates, with consequences over the lifetime of individuals and impacts on cohort dynamics. The respective role of UH vs. individual stochasticity varies greatly amongdemographic outcomes. We discuss the implication of our finding for the gradient oflife-history strategies observed among species and argue that individual differencesshould be accounted for in demographic studies of wild populations.

Although population studies have long assumed that all individuals of a givensex and age are identical, ignoring among-individual differences may strongly bias our perceptionof eco-evolutionary processes. Individual heterogeneity, often referred to as individualquality, has received increasing research attention in the last decades. However, there are stillsubstantial gaps in our current knowledge. For example, there is little information on how individualheterogeneity influences various life-history traits simultaneously, and studies describingindividual heterogeneity in wild populations are generally not able to jointly identify possiblesources of this variation. Here, based on a mark–recapture data set of 9,685 known-agedWandering Albatrosses (Diomedea exulans), we investigated the existence of individual qualityover the entire life cycle of this species, from early life to senescence. Using finite mixturemodels, we investigated the expression of individual heterogeneity in various demographictraits, and examined the origin of these among-individual differences by considering the natalenvironmental conditions. We found that some individuals consistently outperformed othersduring most of their life. In old age, however, the senescence rate was stronger in males thatshowed high demographic performance at younger ages. Variation in individual quality seemedstrongly affected by extrinsic factors experienced during the ontogenetic period. We found thatindividuals born in years with high population density tended to have lower performancesduring their lifespan, suggesting delayed density dependence effects through individual quality.Our study showed that among-individual differences could be important in structuringindividual life history trajectories, with substantial consequences at higher ecological levelssuch as population dynamics.