Peter Kappeler

• Prof. Dr.
• Head of Department at German Primate Center

Many nocturnal mammals spend the day in nests or other shelters, but this aspect of their social organization remains obscure, despite interesting variation among species, seasons and individuals in whether they also sleep alone or in association with conspecifics. To contribute new comparative data on this neglected aspect of sociality, we monitor...

The ‘social complexity hypothesis for communicative complexity’ (SCHCC) suggests that greater social complexity promotes greater communicative complexity. This is because there is increased uncertainty in larger social groups with differentiated social interactions, providing an advantage for more diverse and more flexible signals to transfer diver...

In humans, frailty, risk-taking behaviors, and unhealthy lifestyles have been linked to shifts in adult sex ratios (ASR), which are heavily female-biased at older ages. Conversely, Madagascar’s group-living primates frequently exhibit male-biased ASRs, defying patterns commonly observed among polygynous mammals. To explore these unusual sex ratio d...

Advances in computer vision and increasingly widespread video-based behavioral monitoring are currently transforming how we study animal behavior. However, there is still a gap between the prospects and practical application, especially in videos from the wild. In this Perspective, we aim to present the capabilities of current methods for behaviora...

Mammalian species with slow life histories invest heavily in offspring care to meet offspring nutritional and developmental requirements, typically at significant costs to mothers. While maternal care has been extensively studied, understanding the mechanisms driving variation in mother‒offspring relationships during key offspring developmental per...

Most mammals, including humans, exhibit even or slightly male-biased birth sex ratios (BSRs) and female-biased adult sex ratios (ASRs) much later in life due to higher male mortality rates. The group-living primates of Madagascar are unusual in this respect because they lack female-biased ASRs, but it is unknown whether this is the result of skewed...

In many animal species, cognitive abilities are under strong natural selection because decisions about foraging, habitat choice and predator avoidance affect fecundity and survival. But how has sexual selection, which is usually stronger on males than females, shaped the evolution of cognitive abilities that influence success when competing for mat...

The measurement of biomarkers in blood and excreta can enable immune status assessment and provide prognostic information on individual health outcomes. In this respect, the fecal measurement of secretory immunoglobulin A (sIgA), the primary mammalian antibody for mucosal defense, has recently received increased interest in a few anthropoid primate...

Gray mouse lemur, Microcebus murinus , mothers either cooperatively breed plurally with kin or breed solitarily. We describe the first observations of cooperative and solitary mobbing to defend offspring by wild cooperative breeding gray mouse lemur mothers in Kirindy Forest, Western Madagascar. We observed four groups of cooperatively breeding mot...

Global biodiversity is under accelerating threats, and species are succumbing to extinction before being described. Madagascar’s biota represents an extreme example of this scenario, with the added complication that much of its endemic biodiversity is cryptic. Here we illustrate best practices for clarifying cryptic diversification processes by pre...

Wildlife tagging provides critical insights into animal movement ecology, physiology, and behavior amid global ecosystem changes. However, the stress induced by capture, handling, and tagging can impact post-release locomotion and activity and, consequently, the interpretation of study results. Here, we analyze post-tagging effects on 1585 individu...

Detection and tracking of animals is an important first step for automated behavioral studies in videos. Nowadays, animal tracking is mostly done using deep learning frameworks based on keypoints, which show remarkable results in lab settings with fixed cameras, backgrounds, and lighting. In contrast, multi-animal tracking in the wild is currently...

The costs and benefits of group living are also reflected in intraspecific variation in group size. Yet, little is known about general patterns of fitness consequences of this variation. We use demographic records collected over 25 years to determine how survival and reproductive success vary with group size in a Malagasy primate. We show that fema...

Automated acoustic analysis is increasingly used in animal communication studies, and determining caller identity is a key element for many investigations. However, variability in feature extraction and classification methods limits the comparability of results across species and studies, constraining conclusions we can draw about the ecology and e...

Intersexual dominance relationships in virtually all lemur species have been reported to be female-biased. Although a claim of male dominance in greater bamboo lemurs (Prolemur simus) which was not supported by data is unusual against this background, it is in line with recent studies on other lemur species that suggest the existence of a continuum...

Conservation funding is currently limited; cost-effective conservation solutions are essential. We suggest that the thousands of field stations worldwide can play key roles at the frontline of biodiversity conservation and have high intrinsic value. We assessed field stations’ conservation return on investment and explored the impact of COVID-19. W...

Birth is a fundamental event in the life of animals, including our own species. More reports of wild non-human primate births and stillbirths are thus needed to better understand the evolutionary pressures shaping parturition behaviors in our lineage. In diurnal non-human primates, births generally occur at night, when individuals are resting. Cons...

Gums produced by trees after injuries are valuable food resources for several primate species. Yet, information on the chemical characteristics of gum is scant and inconsistent. We use gums consumed by lemurs (strepsirrhine primates of Madagascar) as an example to illustrate their possible nutritive and pharmaceutical properties. Exudates from 45 t...

Objectives: The investigation of morphological variation in animals is widely used in taxonomy, ecology, and evolution. Using large datasets for meta-analyses has dramatically increased, raising concerns about dataset compatibilities and biases introduced by contributions of multiple researchers. Materials and methods: We compiled morphological...

Cognitive performance varies widely across animal species, but the processes underlying cognitive evolution remain poorly known. For cognitive abilities to evolve, performance must be linked to individual fitness benefits, but these links have been rarely studied in primates even though they exceed most other mammals in these traits. We subjected 1...

Even after the 150th anniversary of sexual selection theory, the drivers and mechanisms of female sexual selection remain poorly studied. To understand demographic circumstances favoring female-female competition, trade-offs with kin selection and interactions with male reproductive strategies, we investigated female evictions in redfronted lemurs...

Lemurs are a well-known example of adaptive radiation. Since colonizing Madagascar, more than 100 extant lemur species have evolved to fill the variety of ecological niches on the island. However, recent work suggests that lemurs do not exhibit one of the hallmarks of adaptive radiations: explosive speciation rates that decline over time. We test t...

Seasonal tropical environments are among those regions that are the most affected by shifts in temperature and rainfall regimes under climate change, with potentially severe consequences for wildlife population persistence. This persistence is ultimately determined by complex demographic responses to multiple climatic drivers, yet these complexitie...

Animal groups regularly lose group members as a result of death and dispersal, but the consequences ofsuch a loss on the social relationships among the remaining group members remain generally under-studied. Moreover, some of the few studies on this topic reported destabilizing effects of group memberloss in some species, whereas in other species i...

Animals moving through landscapes need to strike a balance between finding sufficient resources to grow and reproduce while minimizing encounters with predators. Because encounter rates are determined by the average distance over which directed motion persists, this trade-off should be apparent in individuals’ movement. Using GPS data from 1,396 in...

Biomedical and social scientists are increasingly calling the biological sex into question, arguing that sex is a graded spectrum rather than a binary trait. Leading science journals have been adopting this relativist view, thereby opposing fundamental biological facts. While we fully endorse efforts to create a more inclusive environment for gende...

Conservation status of Microcebus berthae

Behavioral discrimination of kin is a key process structuring social relationships in animals. In this study, we provide evidence for discrimination towards non-kin by third-parties through a mechanism of phenotype matching. In mandrills, we recently demonstrated increased facial resemblance among paternally related juvenile and adult females indic...

Inhibitory control requires an individual to suppress impulsive actions in favour of more appropriate behaviours to gain a delayed reward. It plays an important role in activities such as foraging and initiating mating, but high within-species variation suggests that some individuals have greater inhibitory control than others. A standard index of...

Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competi...

In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question...

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestrial-ity is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs...

Hibernation, a hypometabolic state associated with low body temperature and reduced metabolic and activity rates, represents one adaptation to harsh seasonal environmental conditions. As a consequence of hypometabolism, energetically costly neuronal processes also ought to be reduced. Since active neuronal pathways are prerequisites for learning an...

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs,...

Objectives Sleeping ecology plays a key integrative role in the primates' lives. Selecting an adequate sleeping site is therefore critical, but both extrinsic (e.g., predation, thermoregulation) and intrinsic factors (e.g., body size, circadian activity) need to be considered simultaneously. There is, however, a notable lack of comprehensive compar...

Quantifying animal movements is necessary for answering a wide array of research questions in ecology and conservation biology. Consequently, ecologists have made considerable efforts to identify the best way to estimate an animal’s home range, and many methods of estimating home ranges have arisen over the past half century. Most of these methods...

How social and ecological factors are associated with variation in dominance style across species of animals has been studied frequently, but the underlying processes are often not addressed. Theoretical research indicates that stronger spatial cohesion among individuals in a group causes a higher frequency of fighting and, thus, through the self-r...

The endemic lemurs of Madagascar (Lemuriformes: Primates) exhibit great social and communicative diversity. Given their independent evolutionary history, lemurs provide an excellent opportunity to identify fundamental principles in the coevolution of social and communicative traits. We conducted comparative phylogenetic analyses to examine patterns...

Animal vocalizations may provide information about a sender’s condition or motivational state and, hence, mediate social interactions. In this study, we examined whether vocalizations of gray mouse lemurs ( Microcebus murinus ) emitted in aggressive contexts (grunts, tsaks) co-vary with physical condition, which would underly and indicate honest si...

The causes and consequences of being in a particular dominance position have been illuminated in various animal species, and new methods to assess dominance relationships and to describe the structure of dominance hierarchies have been developed in recent years. Most research has focused on same-sex relationships, however, so that intersexual domin...

We highlight current problems, challenges and dilemmas of conservation action in Madagascar, which is one of the poorest countries, but also the hottest global biodiversity hotspot. Consequences of climate change and the COVID‐19 pandemic exacerbate an already dramatic situation for many protected areas that are under pressure from illegal logging...

The relationship between age and reproductive performance is highly variable across species. Humans and some cetaceans exhibit an extreme form of reproductive senescence in that female reproduction ceases years or even decades before average life expectancy is reached. However, neither the existence of reproductive senescence in some taxa nor its a...

Sex-specific reproductive strategies are shaped by the distribution of potential mates in space and time. Labord’s chameleon (Furcifer labordi) from southwestern Madagascar is the shortest-lived tetrapod whose life-time mating opportunities are restricted to a few weeks. Given that these chameleons grow to sexual maturity within about three months...

In animal societies, control over resources and reproduction is often biased towards one sex. Yet, the ecological and evolutionary underpinnings of male–female power asymmetries remain poorly understood. We outline a comprehensive framework to quantify and predict the dynamics of male–female power relationships within and across mammalian species....

Behavioral discrimination of kin is a key process structuring social relationships in animals. In this study, we provide a first example of discrimination towards non-kin by third-parties through a mechanism of phenotype matching. In mandrills, we recently demonstrated increased facial resemblance among paternally-related juvenile and adult females...

Aim Macroecological studies that require habitat suitability data for many species often derive this information from expert opinion. However, expert‐based information is inherently subjective and thus prone to errors. The increasing availability of GPS tracking data offers opportunities to evaluate and supplement expert‐based information with deta...

The extant primates of Madagascar (Lemuriformes) represent the endpoints of an adaptive radiation following a single colonization event more than 50 million years ago. They have since evolved a diversity of life history traits, ecological adaptations and social systems that rivals that of all other living primates combined. Their social systems are...

Intergroup conflict is a major evolutionary force shaping animal and human societies. Males and females should, on average, experience different costs and benefits for participating in collective action. Specifically, among mammals, male fitness is generally limited by access to mates whereas females are limited by access to food and safety. Here w...

It has long been recognized that the patterning of social interactions within a group can give rise to a social structure that holds very different places for different individuals. Such within-group variation in sociality correlates with fitness proxies in fish, birds, and mammals. Broader integration of this research has been hampered by the lack...

How the presence of conspecifics affects scent mark deposition remains an understudied aspect of olfactory communication, even though scent marking occurs in different social contexts. Sex differences in scent-marking behaviour are common, and sex-specific effects of the audience could therefore be expected. We investigated sex differences in intra...

Kin discrimination is a key process structuring social relationships in animals. We show how it may be generalized to entail discrimination towards non-kin, and provide a first example of this process in a primate. In mandrills, we recently demonstrated increased facial resemblance among paternally-related females indicating adaptive opportunities...

Background Various aspects of sociality can benefit individuals’ health. The host social environment and its relative contributions to the host-microbiome relationship have emerged as key topics in microbial research. Yet, understanding the mechanisms that lead to structural variation in the social microbiome, the collective microbial metacommunity...

Investigating factors influencing infant physical and social development is important to elucidate primate adaptations and life history evolution. Infant sifakas exhibit a puzzling mismatch between dental precocity and relatively slow postnatal growth, but only anecdotal reports of infant development are available for a comparative appraisal of the...

Cognitive abilities covary with both social and ecological factors across animal taxa. Ecological generalists have been attributed with enhanced cognitive abilities, but which specific ecological factors may have shaped the evolution of which specific cognitive abilities remains poorly known. To explore these links, we applied a cognitive test batt...

Maternal effects mediated by nutrients or specific endocrine states of the mother can affect infant development. Specifically, pre- and postnatal maternal stress associated with elevated glucocorticoid (GC) output is known to influence the phenotype of the offspring, including their physical and behavioral development. These developmental processes...

Audience effects, i.e. changes in behaviour caused by the presence of conspecifics, have rarely been studied in the context of olfactory communication, even though they may provide important insights into the functions of olfactory signals. Functional sex differences in scent-marking behaviours are common and influenced by the social system. To dat...

Understanding species' responses to climate change is crucial for the mitigation of its effects. Few studies, however, have examined how climate change impacts timing in reptile life cycles, or how it may interact with other life history traits. Here, we explore associations between climatic variation, reptile phenology, and juvenile growth. We use...

Social influence is distributed unequally between males and females in many mammalian societies. In human societies, gender inequality is particularly evident in access to leadership positions. Understanding why women historically and cross-culturally have tended to be under-represented as leaders within human groups and organizations represents a...

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, w...

Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We test the ‘invariant rate of ageing’ hypothesis, which posits that the rate of ageing is relatively fixed within species, with a collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the hi...

Ecological communities are structured by interactions between coexisting species that mutually influence their distribution and abundance. Ecologically similar species are expected to exclude one another from suitable habitat, so the coexistence of two mouse lemur species in an assemblage of several closely related cheirogaleid primates in the cent...

A framework for studying social systems

Forest edges change micro-environmental conditions, thereby affecting the ecology of many forest-dwelling species. Understanding such edge effects is particularly important for Malagasy primates because many of them live in highly fragmented forests today. The aim of our study was to assess the influence of forest edge effects on activity budgets,...

Social learning is widespread in the animal kingdom, but individuals can differ in how they acquire and use social information. Personality traits, such as neophobia, may, for example, promote individual learning strategies. Here, we contribute comparative data on social learning strategies in carnivorans by examining whether narrow-striped mongoos...

Schon die ersten Naturforscher, die Madagaskar besuchten, erkannten die Besonderheit dieser „Schatzinsel der Natur“. Auf Schritt und Tritt begegneten sie unbekannten Tieren, die so exotisch waren, dass sie sie mit Worten aus ihrer Welt nicht zu benennen wussten. Die Madagassen hatten sie wohl aus demselben Grund oft einfach nach den Lauten benannt,...

Behavioural biology is a discipline of biology that uses scientific methods to study the behaviour of animals and humans. But what exactly is “behaviour“? Everyone probably has a spontaneous, concrete, and very personal idea about it. A barking dog, a singing bird, a fluttering butterfly - many people most likely have these vivid examples in mind w...

The members of a species are distributed in a characteristic manner in space and time; they mate with different numbers of members of the opposite sex, differ in parental care behaviour, and their social interactions are not randomly distributed among conspecifics. Analyses of social systems deal with the causes, patterns, mechanisms and consequenc...

Although modern sex roles acknowledge the fact that males and females both compete for and chose mates, there are sound theoretical reasons for expecting massive sex differences in these behavioural domains. Because of the resulting sex bias in the empirical evidence, this overview of the mechanisms and consequences of intrasexual selection focuses...

Every animal must feed regularly to secure the energetic basis for growth, maintenance of basic functions and reproduction. Therefore, the search, selection, defence and intake of food has an important function in daily survival. These behaviours usually take place in a particular habitat that is suitable for a given species. In addition to abiotic...

There are a number of other forms of reproduction in the animal kingdom besides the gonochoristic reproduction familiar to us. These variants can be described as life history characteristics that generate certain reproductive strategies. The theory of sexual selection provides an overarching framework for analysing these and other adaptations relat...

During their individual development, newly hatched or new-born animals begin to interact directly with their environment, but their development is not limited to the early postnatal phase. Fitness-relevant behaviours should be functionally in place as soon as possible, i.e., they are under strong genetic control. Other behaviours are species-specif...

The behaviour and physiology of an organism are tightly integrated so as to keep an animal in a regulated state of equilibrium. A regulated energy and water balance, or thermoregulation, is an important aspect of well-being and survival that can take up a qualitatively large proportion of an animal’s activity budget. However, the underlying behavio...

How can the continuous stream of movements, events and interactions that we can operationalize as behaviour be described and quantified? To do this, it is first necessary to clearly define what can be measured with which methods. To provide a better impression of the complexity, but also the fascination of behavioural research, I will discuss some...

Parental care is defined as any activity by a parent that contributes to increasing the fitness of its offspring (Clutton-Brock 1991). It can begin before birth with the building of a nest or den for the eggs or offspring. During reproduction, mothers can positively influence their developmental and survival chances by producing eggs that are as la...

Eating and being eaten are closely related. Since many animals live entirely or partially on animal matter, the feeding behaviour of these predators has drastic negative consequences for the fitness of their prey. Predation and its avoidance are therefore central aspects of all animals’ survival strategies. The evolutionary arms race resulting from...

In contrast to males, females cannot increase their reproductive success by engaging in additional matings. Instead, they can improve the quality and survival chances of their offspring through increased maternal care and the choice of an appropriate mate. When choosing a mate, members of closely related species and conspecific kin should be avoide...

The species-specific endowment of various sensory organs enables animals to perceive changes in their environment and respond accordingly. The vast majority of animals are exposed to temporal fluctuations in aspects of their environment that are relevant for survival. A large part of these fluctuations is highly predictable, such as the alteration...

The individuals of a species do not interact with their conspecifics randomly. These interactions involve the exchange of actions and/or signals. The exchange of signals is called communication and is an important contribution to the establishment and maintenance of social relationships, but also to the general exchange of information among individ...

Modern evolutionary theory provides a theoretical framework for functional analyses of animal behaviour. In order to investigate the adaptive value of individual behaviour patterns, it is necessary to operationalize fitness and to characterize the evolutionary mechanisms that influence it. In terms of the most important fitness components - surviva...

Behavioural flexibility allows animals to adapt their behaviour to changing situations in their current habitat. Flexibility is involved in behaviours comprising decision‐making in their ecological or social environment. However, the ability to behave flexibly can co‐vary with an individual's personality and its level of inhibitory control, so that...

Variation in cognitive abilities is thought to be linked to variation in brain size, which varies across species with either social factors (Social Intelligence Hypothesis) or ecological challenges (Ecological Intelligence Hypothesis). However, the nature of the ecological processes invoked by the Ecological Intelligence Hypothesis, like adaptation...

Background Life history theory predicts that during the lifespan of an organism, resources are allocated to either growth, somatic maintenance or reproduction. Resource allocation trade-offs determine the evolution and ecology of different life history strategies and define an organisms’ position along a fast–slow continuum in interspecific compari...

Is it possible to slow the rate of aging, or do biological constraints limit its plasticity? We test this ‘invariant rate of aging’ hypothesis with an unprecedented collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifesp...

[This corrects the article DOI: 10.1093/biosci/biaa082.].

Pheromones mediate a wide range of functions across the animal kingdom [ 1 • Wyatt T.D. Pheromones. Curr. Biol. 2017; 27 : R739-R743 • Abstract • Full Text • Full Text PDF • PubMed • Scopus (17) • Google Scholar ], and such chemosensory communication is especially widespread among mammals [ 2 • Brennan P.A. • Keverne E.B. Something in the air...