Loren Donald Hayes

University of Tennessee at Chattanooga | Chatt · Department of Biological and Environmental Sciences

Studies that concurrently investigate the functional benefits of group living in multiple populations of the same species are rare. Over a 3‐year period (2014–2016), we examined two ecologically contrasting populations to test multiple hypotheses for the adaptive significance of group living in the communally breeding rodent Octodon degus . We quan...

Recent evidence indicates that individual behavioural variation in animals, defined as consistent individual differences in behaviour across contexts and time, influence ecological and evolutionary processes, and a growing number of studies demonstrate that individual behavioural variation can play a large role in shaping grouping dynamics among so...

Testosterone is known as a "male" hormone; however, females also synthetize testosterone, which influences female sexual and aggressive behavior. In female vertebrates, as in males, testosterone levels can vary seasonally. However, female testosterone levels may also be related with female anogenital distance (AGD) length phenotype (a proxy of pren...

While direct influences of the environment on population growth and resilience are well studied, indirect routes linking environmental changes to population consequences are less explored. We suggest that social behavior is key for understanding how anthropogenic environmental changes affect the resilience of animal populations. Social structures o...

Explaining the evolution of primate social organization has been fundamental to understand human sociality and social evolution more broadly. It has often been suggested that the ancestor of all primates was solitary and that other forms of social organization evolved later. However, previous research included the assumption that many understudied...

Elephant‐shrews (Macroscelidea) have long been considered the only mammalian order to be completely monogamous, based on observations of their pair‐living social organization. We reviewed primary studies on the four components of social systems (social organization, mating system, social structure, and care system) in elephant‐shrews to evaluate wh...

Homophily by morphological and behavioral traits has been described in several species of vertebrates, but its functional consequences remain poorly studied. Homophily by plurally breeding females may improve direct fitness by enhancing reproductive success. Female mammals may exhibit phenotypical masculinization due to exposure to androgens during...

In response to the COVID-19 crisis, numerous academic conferences and seminars were moved online. Some remote (online) seminars have the aim to be maintained permanently after the pandemic, offering weekly opportunities for scientists, postdocs, and students to learn about research and to improve global networking. Remote seminars are a good option...

Because residents and immigrants from group living species may experience fitness costs associated with permanent changes in group membership, we examined the hypothesis that females experiencing socially unstable or socially stable conditions during development compensate these costs by shaping the phenotype of their own offspring differently. Gro...

Permanent changes in group membership may result in detrimental fitness effects on both group residents and immigrants. Factors associated with this form of social instability are rarely documented. We used a 15-year dataset on degus, a social and short-lived species, to test the hypothesis that physical condition and socioecological factors experi...

Previous studies to understand the evolution of interspecific variation in mammalian social organization (SO; composition of social units) produced inconsistent results, possibly by ignoring intraspecific variation. Here we present systematic data on SO in artiodactyl populations, coding SO as solitary, pair-living, group-living, sex-specific or va...

The 2012 President's Council on Science and Technology report emphasized teaching STEM fields in undergraduate colleges, particularly in the first 2 years to recruit and retain students in STEM fields. That report recommended implementing experiential learning techniques, encouraging community involvement and nonacademic partnerships to diversify c...

Understanding inter-specific variation in social systems is a major goal of behavioural ecology. Previous comparative studies of mammalian social organisation produced inconsistent results, possibly because they ignored intra-specific variation in social organisation (IVSO). The Artiodactyla have been the focus of many comparative studies as they o...

Individuals in social species may mate with multiple opposite-sex individuals, including members of the same or different social groups. This variation may be linked to genetic benefits, where multiple mating decreases risk of inbreeding. Multiple mating may also be constrained by the sociospatial setting through its effect on availability of mates...

We report the results of a 6-year study of social (number of adult males/females, relatedness of females, communal litter size) and ecological (mean/CV of food abundance, soil hardness, burrow openings) factors influencing the direct fitness of plurally breeding degu (Octodon degus) females. The best fit models for per capita offspring weaned and s...

Alternative morphotypes have been reported in males of different taxa. In some mammals, highly masculinized and slightly masculin-ized males represent 2 opposite ends along a gradient of phenotypic variation in males. This phenotypical gradient originates during prenatal development. Laboratory studies have documented how highly and slightly mascul...

This review covers long-term ecological studies in Central America, South America, and Antarctica that include at least 10 years of data on both terrestrial and marine mammals as well as birds. Specifically, we compiled long-term research on social systems, population ecology, and community ecology. Long-term research is necessary to understand dec...

Many species show intraspecific variation in their social organization (IVSO), which means the composition of their social groups can change between solitary living, pair living, or living in groups. Understanding IVSO is important because it demonstrates species resilience to environmental change and can help us to study ultimate and proximate rea...

Strepsirrhines, that is, lemurs, galagos, and lorises, are considered basal primates, making them important to understand the evolution of primate sociality. Apart from some lemurs, they are nocturnal and solitary living, though the view of their sociality nature has changed with field studies being completed. We conducted a review of the primary l...

Long-term studies on rodents have been conducted for longer periods (up to 70 years) and more generations (up to 88 generations) than for most other mammalian taxa. These studies have been instrumental in furthering our understanding of ecophysiology, social systems, and population and community processes. Studies on African striped mice (Rhabdomys...

Recent research in behavioural ecology has revealed the structure of animal personality and connections to ecologically and evolutionarily important traits. Personality is hypothesized to influence social interactions through individual behavioural differences or personality-based dyadic interactions. We describe the structure of personality traits...

Darwin famously described special difficulties in explaining social evolution in insects. More than a century later, the evolution of sociality - defined broadly as cooperative group living - remains one of the most intriguing problems in biology. Providing a unique perspective on the study of social evolution, this volume synthesizes the features...

Game theory is used in biology to understand why otherwise rational individuals make nonintuitive decisions regarding cooperation and competition. Recently, biology teachers engaged their students in game theory curricula by presenting them with a real-world game theory challenge: the opportunity to cheat on a game theory exam. Here we present a gu...

Contrasting scenarios have been proposed to explain how resource heterogeneity influences group living or sociality. First, sociality may result from individuals in larger groups attaining net fitness benefits by monopolizing access to resources (“resource-defense” hypothesis). Second, sociality may be the fitness-neutral outcome of multiple indivi...

Group size may influence fitness benefits and costs that emerge from cooperative and competitive interactions in social species. However, evidence from plural breeding mammals indicates that group size is insufficient to explain variation in direct fitness, implying other attributes of social groups were overlooked. We studied the natural populatio...

Maternal stress and care significantly affect offspring's future behavior and physiology. Studies in laboratory rats have shown that maternal stress decreases maternal care and that low rates of certain maternal behaviors cause offspring to develop hyperreactive stress responses. Plurally breeding rodents that practice communal care, such as degus...

In this chapter, we integrate the major themes from the preceding chapters and provide a conceptual framework for future studies of social behavior. We first address integration in the context of sociality and highlight generalizations, pertinent to rodents and other mammals, emerging from studies on different aspects of social behavior. Then, we p...

Despite advances in our understanding of the ecological and evolutionary factors that drive sociality, relatively little is known about the genetic and neurobiological mechanisms underlying group living. Decades of laboratory investigations into the neural substrates supporting parental behavior and social bond formation between mates have yielded...

Understanding the fitness consequences of group-living and breeding strategies is critical to advancing a theory for the evolutionary significance of animal social systems. To date, our understanding of the fitness consequences in caviomorphs is limited to six species. The available evidence suggests that sociality positively affects fitness in fem...

Sociality, or group-living, results when conspecifics establish long-term (relative to lifespan) and spatially cohesive social units. Sociality theory states that group-living evolves whenever individuals attain net fitness benefits, or when individuals are forced to remain in groups. Among rodents, this theory comes from the study of a relatively...

Social monogamy is a mating strategy rarely employed by mammalian species. Laboratory studies in socially monogamous prairie voles Microtus ochrogaster demonstrate that oxytocin and vasopressin act within the mesolimbic dopamine pathway to facilitate pair-bond formation. Species differences in oxytocin receptor (OTR) and vasopressin 1a receptor (V1...

Maternal stress and care significantly affect offspring’s future behavior and physiology. Studies in laboratory rats have shown that maternal stress decreases maternal care and that low rates of certain maternal behaviors cause offspring to develop hyperreactive stress responses. Plurally breeding rodents that practice communal care, such as degus...

Shrews and their close relatives (order Eulipotyphla) are typically consideredto be solitary. This impacts our understanding of mammalian social evolution:(i) the ancestor of mammals is believed to have been shrew-like, and eventhough Eulipotyphla are not more basal than other mammalian orders, thismight have been one reason why the first mammals h...

A growing body of evidence showing that individuals of some social species live in non-kin groups suggests kin selection is not required in all species for sociality to evolve. Here, we investigate 2 populations of Octodon degus , a widespread South American rodent that has been shown to form kin and non-kin groups. We quantified genetic relatednes...

Natural selection is a mechanism of evolution that leads to adaptations in species or populations. Phenotypes confer habitat-specific fitness consequences, which could lead to the evolution of similar strategies (convergence) or different strategies (divergence) within and across species. The evolution of communication is an example of convergent e...

Maternal stress can significantly affect offspring fitness. In laboratory rodents, chronically stressed mothers provide poor maternal care, resulting in pups with hyperactive stress responses. These hyperactive stress responses are characterized by high glucocorticoid levels in response to stressors plus poor negative feedback, which can ultimately...

The neural and molecular mechanisms underlying social behavior – including their functional significance and evolution – can only be fully understood using data obtained under multiple social, environmental, and physiological conditions. Understanding the complexity of social behavior requires integration across levels of analysis in both laborator...

Social interactions are central to most animals and have a fundamental impact upon the phenotype of an individual. Social behavior (social interactions among conspecifics) represents a central challenge to the integration of the functional and mechanistic bases of complex behavior. Traditionally, studies of proximate and ultimate elements of social...

Sociality and cooperative rearing may have evolved to increase direct fitness when conditions are challenging to reproduction and/or to reduce environmentally induced variance in fecundity. Examination of these hypotheses comes mostly from studies on singularly breeding birds where reproduction is monopolized by a male-female adult pair. Instead, l...

Studying the causes and reproductive consequences of social variation can provide insight into the evolutionary basis of sociality. Individuals are expected to behave adaptively to maximize reproductive success, but reproductive outcomes can also depend on group structure. Degus (Octodon degus) are plurally breeding rodents, in which females allonu...

The cort-adaptation hypothesis indicates that an association between glucocorticoid (cort) levels and fitness may vary with the extent to which reproduction or breeding effort is a major determinant of cort levels. Support for a context dependent association between cort and fitness comes mostly from relatively long-lived, bird species. We tested t...

Social animals are susceptible to high infection levels by contact-transmitted parasites due to increased conspecific interaction. Exotic parasites are known to have adverse consequences on native hosts. We examined the relationship between social group size and exotic ectoparasite loads, and adult infection levels with per capita fitness and offsp...

1. Understanding how variation in fitness relates to variation in group living remains critical to determine whether this major aspect of social behaviour is currently adaptive. 2. Available evidence in social mammals aimed to examine this issue remains controversial. Studies show positive (i.e. potentially adaptive), neutral or even negative fitne...

Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Int...

Background/Question/Methods Vertebrates produce various auditory, olfactory, tactile, and visual signals that function to attract mates, deter rivals, warn conspecifics of predators or alert offspring to the presence of parents with food. Alarm signals, such as vocalizations, play a critical role in the social structure of group-living mammals an...

Background/Question/Methods Variation in ecology has been linked to mating system strategies; however the underlying mechanisms controlling changes in these strategies are largely unknown. It has been proposed that ecological variation could influence the expression of neuroanatomical structures controlling for social behavior. In mammals, social...

Variation in sociality may have an important impact on population genetic structure. In highly social species, the formation of kin clusters leads to decreasing variation within but increasing genetic variation among social groups. Studies on less social species in which social groups may be more short lived have revealed a greater diversity of con...

While ecological causes of sociality (or group living) have been identified, proximate mechanisms remain less clear. Recently, close connections between sociality, glucocorticoid hormones (cort) and fitness have been hypothesized. In particular, cort levels would reflect a balance between fitness benefits and costs of group living, and therefore ba...

In social or group living species, members of groups are expected to be affected differentially by competition through the effect of group size (i.e., the “social competition hypothesis”). This hypothesis predicts an increase in the probability of dispersal with increasing size of social groups. At a more mechanistic level and based on the known ef...

Group living is thought to evolve whenever individuals attain a net fitness advantage due to reduced predation risk or enhanced foraging efficiency, but also when individuals are forced to remain in groups, which often occurs during high-density conditions due to limitations of critical resources for independent breeding. The influence of ecologica...

In the late 1990s and early 2000s it was recognized that behavioral ecologists needed to study the sociality of caviomorph rodents (New World hystricognaths) before generalizations about rodent sociality could be made. Researchers identified specific problems facing individuals interested in caviomorph sociality, including a lack of information on...

This Special Feature highlights the diversity of social systems in the South American caviomorph (New World hystricognath) rodents. It includes 3 single-species accounts, 2 reviews of broad taxomomic groups, and 2 synthetic reviews with suggestions for directions for future research. Esta selección especial de artículos ilustra la diversidad de sis...

Social interactions among conspecifics are a fundamental and adaptively significant component of the biology of numerous species. Such interactions give rise to group living as well as many of the complex forms of cooperation and conflict that occur within animal groups. Although previous conceptual models have focused on the ecological causes and...

Both breeding activity and abundance and quality of available food are expected to influence daily movements of animals. Animals are predicted to range over large areas to meet high energy demands associated with reproduction (females) or to increase mating success (males). However, animals should expand their range areas whenever food conditions d...

Trap type may influence captures of individuals in different age-sex categories in small mammal studies, resulting in biased population and demographic information. We deployed 4 live trap types at burrow systems of the rodent, Octodon degus Molina, 1782, in central Chile to determine trap efficacy in capturing individuals of 6 demographic categori...

Determination of fecal steroid metabolites is a noninvasive technique that characterizes the physiological state of organisms without the physiological and psychological stress of handling. Although this technique has many applications in the study of wildlife and/or captive animals without the necessity of capturing individuals, it requires a spec...

The fitness consequences of plural breeding vary considerably among social vertebrates. We tested three hypotheses for the direct reproductive fitness consequences of group living in the degu Octodon degus, a social rodent endemic to central Chile. To test the ‘benefits of communal care’ hypothesis, we determined the relationship between the number...

It has been hypothesized that animal groups in socially cohesive species are inherently unstable, ultimately the result of constraints to independent breeding, and proximately the product of adult fidelity and offspring philopatry. Other processes, including emigration of individuals that join pre-existing groups would be less important. We examine...

Quantifying genetic kinship and parentage is critical to understanding the adaptive consequences of sociality. To measure fitness in a species with variable group structure, we isolated 14 microsatellite loci from Octodon degus, a semi-fossorial rodent endemic to Chile. The number of alleles per locus ranged from four to 14. Thirteen loci were in H...