Michael Taborsky

• University of Bern

Norway rats are known to liberate trapped conspecifics, which implies an empathic response to the deplorable situation of the captive. If this is an altruistic behavior reflecting an evolved decision rule, the requisite fitness enhancement to the actor may result either from close relatedness or the expectation of future returns. Neither potential...

In cooperative societies, group members typically exchange different commodities among each other, which involves an incessant negotiation process. How is the conflict of fitness interests resolved in this continual bargaining process between unequal partners, so that maintaining the cooperative interaction is the best option for all parties involv...

Delayed dispersal of sexually mature offspring is a fundamental component of cooperative breeding in fungus farming ambrosia beetles. These beetles dwell in logs of recently deceased trees, where female offspring postpone reproduction and invest in alloparental care before dispersing to found a new nest. The wood quality affects investment of adult...

Reciprocal altruism has been proposed to generate evolutionarily stable levels of cooperation, but empirical evidence in non‐human animals is contentious. A series of experimental studies on Norway rats revealed that these animals reciprocate received help by using decision rules characterising direct and generalized reciprocity. The direct recipro...

Wild-type Norway rats reciprocate help received in a well-replicated experimental food-giving task, but the criteria to appraise the received help's value are unclear. We tested whether quality or quantity of received help is more important when deciding to return help, and whether partner familiarity and own current need affect this evaluation. We...

Direct reciprocity requires the ability to recognize and memorize social partners, and to remember their previous actions. ‘Insufficient cognitive abilities’ have been assumed to potentially impair the ability to cooperate by direct reciprocity. Here we compare the propensity of rats to use direct reciprocity with their ability to memorize and reco...

Social evolution is tightly linked to dispersal decisions, but the ecological and social factors selecting for philopatry or dispersal often remain obscure. Elucidating selection mechanisms underlying alternative life histories requires measurement of fitness effects in the wild. We report on a long-term field study of 496 individually marked coope...

Members of social groups may negotiate among each other about the exchange of goods and services. If this involves asymmetries between interacting partners, for instance in condition, power, or expected payoffs, coercion may be involved in the bargain. Cooperative breeders are excellent models to study such interactions, because asymmetries are inh...

Sexually antagonistic selection, which favours different optimums in males and females, is predicted to play an important role in the evolution of sex chromosomes. Body size is a sexually antagonistic trait in the shell-brooding cichlid fish Lamprologous callipterus as ‘bourgeois’ males must be large enough to carry empty snail shells to build nest...

Mechanisms selecting for the evolution of cooperative breeding are hotly debated. While kin selection theory has been the central paradigm to explain the seemingly altruistic behaviour of non-reproducing helpers, it is increasingly recognized that direct fitness benefits may be highly relevant. The group augmentation hypothesis proposes that allopa...

Begging signals are widespread in animals and have been extensively studied in the context of brood care. In contrast, the functionality of begging signals expressed among adults has not yet been scrutinised experimentally. Norway rats (Rattus norvegicus) have been shown to express 50‐kHz calls towards a social partner when in need of help to obtai...

The decision rule of direct reciprocity states that an individual helps someone who previously helped them. An alternative explanation to observations of reciprocal exchanges of help is copying by imitation. Norway rats, Rattus norvegicus, are known to exchange food and allogrooming reciprocally among social partners. We asked whether this behaviou...

The evolution of cooperative breeding has been traditionally attributed to the effect of kin selection. While there is increasing empirical evidence that direct fitness benefits are relevant, the relative importance of alternative selection mechanisms is largely obscure. Here, we model the coevolution of the cornerstones of cooperative breeding, de...

Dopamine is part of the reward system triggering the social decision-making network in the brain. It has hence great potential importance in the regulation of social behaviour, but its significance in the control of behaviour in highly social animals is currently limited. We studied the role of the dopaminergic system in social decision-making in t...

How can individuals obtain a breeding position and what are the benefits associated with philopatry compared to dispersal? These questions are particularly intriguing in polygamous cooperative breeders, where dispersal strategies reflect major life history decisions, and routes to independent breeding may utterly differ between the sexes. We scruti...

The complex social behaviour of cichlids has fascinated scientists and hobbyists alike for almost 100 years. In this chapter, we review the breadth and complexity of cichlid behaviour, particularly with respect to social interactions. We present the case that cichlids are one of the best model systems for understanding both the mechanisms and evolu...

Kin selection plays a major role in the evolution of cooperative systems. However, many social species exhibit complex within-group relatedness structures, where kin selection alone cannot explain the occurrence of cooperative behaviour. Understanding such social structures is crucial to elucidate the evolution and maintenance of multi-layered coop...

Begging is widespread in juvenile animals. It typically induces helpful behaviours in parents and brood care helpers. However, begging is sometimes also shown by adults towards unrelated social partners. Adult Norway rats (Rattus norvegicus) display a sequence of different behaviours in a reciprocal food provisioning task that have been interpreted...

Animals may respond to ecological heterogeneity by genetic differentiation or phenotypic plasticity. Responses of organisms to their ecology can include adaptation at various levels of organization, including morphology, behaviour and social structure. Adaptations at one level might constrain or enhance adaptations on other levels, which highlights...

Delayed dispersal of sexually mature offspring is a fundamental component of cooperative breeding. In ambrosia beetles, female offspring temporarily remain in their natal nest and refrain from reproduction, instead investing in alloparental care. Previous work has demonstrated a link between helping behaviour and the increased need for pathogen def...

Direct reciprocity, where individuals apply the decision rule ‘help someone who has helped you’, is believed to be rare in non-human animals due to its high cognitive demands. Especially if previous encounters with several partners need to be correctly remembered, animals might either stop reciprocating favours previously received from an individua...

Reciprocity can explain cooperative behaviour among non-kin, where individuals help others depending on their experience in previous interactions. Norway rats (Rattus norvegicus) cooperate reciprocally according to direct and generalized reciprocity. In a sequence of four consecutive experiments, we show that odour cues from a cooperating conspecif...

In cooperatively breeding species, nonbreeding individuals provide alloparental care and help in territory maintenance and defense. Antipredator behaviors of subordinates can enhance offspring survival, which may provide direct and indirect fitness benefits to all group members. Helping abilities and involved costs and benefits, risks, and outside...

Helping behaviour in some cooperative breeders is apparently maintained by a combination of coercion and reciprocity. In such pay-to-stay systems, alloparental brood care of subordinate group members functions as a service to dominants, which tolerate subordinates based on how much help they provide. Cooperative territory defence is a key task of c...

When individuals exchange helpful acts reciprocally, increasing the benefit of the receiver can enhance its propensity to return a favour, as pay-offs are typically correlated in iterated interactions. Therefore, reciprocally cooperating animals should consider the relative benefit for the receiver when deciding to help a conspecific. Norway rats (...

Coercion is an important but underrated component in the evolution of cooperative behaviour. According to the pay-to-stay hypothesis of cooperative breeding, subordinates trade alloparental care for the concession to stay in the group. Punishment of idle subordinates is a key prediction of this hypothesis, which has received some experimental scrut...

We generally assume that animals should maximize information acquisition about their environment to make prudent decisions. But this is a naïve assumption, as gaining information typically involves costs. This is especially so in the social context, where interests between interacting partners usually diverge. The arms race involved in mutual asses...

In cooperatively breeding societies dominant breeders are assisted by other individuals in raising their young. In many of these species helping behaviours and their benefits for breeders have been studied by investigating the helpers' contribution to direct offspring care, even though a significant proportion of help is not targeted specifically t...

Members of social groups often temporally coordinate their behaviors, for instance in defense or foraging. In the context of cooperation, simultaneous or sequential coordination of behavior may allow social partners to adjust their cooperative effort quickly among each other. By manipulating individual behaviors, here we tested experimentally wheth...

Theoretical models of cooperation typically assume that agents use simple rules based on last encounters, such as 'tit-for-tat', to reciprocate help. By contrast, empiricists generally suppose that animals integrate multiple experiences over longer timespans. Here, we compared these two alternative hypotheses by exposing Norway rats to partners tha...

Social immunity—the collective behavioural defences against pathogens—is considered a crucial evolutionary force for the maintenance of insect societies. It has been described and investigated primarily in eusocial insects, but its role in the evolutionary trajectory from parental care to eusociality is little understood. Here, we report on the exi...

Reciprocal cooperation may evolve if the costs of help are reliably compensated for by delayed returns provided in future interactions. The associated probabilities and cost–benefit ratios may vary systematically between the sexes, which often display different dispersal strategies and interaction patterns. Whereas female Norway rats, Rattus norveg...

Tracking wild animals over long periods of time is a non-trivial challenge. This has caused a bias in the availability of individual-based long-term datasets with the majority including birds and mammals. Visual Implant Elastomer (VIE) tags are now a widely used technique that may facilitate the collection of such data for fish and amphibians. Howe...

Video showing brood care of a dominant female and her helper in Neolamprologus savoryi

Video showing spawning and pseudospawning of Neolamprologus savoryi

Helping behaviour in cooperative breeders has been intensively studied in many animal taxa, including arthropods, birds and mammals. In these highly social systems, helpers typically engage in brood care and the protection of dependent young. Such helping systems also exist in cooperatively breeding cichlid species of Lake Tanganyika. However, bree...

Hormones influence the social behaviour of dogs. Castration of male dogs induces a reduction of testosterone and has been shown to affect social behaviours associated with aggression and reproduction. Changes in social behaviour could be critical in working dogs, which should be well trainable and behave reliably. It is currently unknown whether an...

Background: The evolution of complex social organization is mediated by diverse environmental constraints, including predation risk and the availability and distribution of food resources, mating partners, and breeding habitats. The cooperatively breeding cichlid Neo-lamprologus pulcher inhabits highly distinct habitats ranging from sheer rock face...

Males pursuing alternative reproductive tactics have been predicted to face a trade-off between maximizing either swimming performance or endurance of their sperm. However, empirical evidence for this trade-off is equivocal, which may be due to simplistic assumptions. In the shell-brooding cichlid fish Lamprologus callipterus, two Mendelian male mo...

Reciprocal cooperation has been observed in a wide range of taxa, but the proximate mechanisms underlying the exchange of help are yet unclear. Norway rats reciprocate help received from partners in an iterated Prisoner's Dilemma game. For donors, this involves accepting own costs to the benefit of a partner, without obtaining immediate benefits in...

Kin selection and reciprocity are two mechanisms underlying the evolution of cooperation, but the relative importance of kinship and reciprocity for decisions to cooperate are yet unclear for most cases of cooperation. Here, we experimentally tested the relative importance of relatedness and received cooperation for decisions to help a conspecific...

Direct reciprocity can establish stable cooperation among unrelated individuals. It is a common assumption of direct reciprocity models that agents exchange like with like, but this is not necessarily true for natural interactions. It is yet unclear whether animals apply direct reciprocity rules when successive altruistic help involves different ta...

The prevalence of reciprocal cooperation in non-human animals is hotly debated [1, 2]. Part of this dispute rests on the assumption that reciprocity means paying like with like [3]. However, exchanges between social partners may involve different commodities and services. Hitherto, there is no experimental evidence that animals other than primates...

Reciprocity can generate stable levels of cooperation among unrelated social partners. If individuals interact repeatedly, costs of altruistic acts can be compensated through an exchange of donor and receiver roles. Frequent interactions are conducive to attaining evolutionarily stable reciprocal exchange. High interaction frequencies are typical f...

Domestic dogs (Canis familiaris) are social animals and, therefore, social interactions with conspecifics are crucial for their welfare. However, in kennelled dogs, the ability to interact with conspecifics may be limited. Swiss military dogs, for instance, are kept individually without direct contact to conspecifics. Here we asked whether short-te...

Direct reciprocity can establish stable cooperation. Nevertheless, the significance of this mechanism is yet unclear. A frequent assumption is that both commodity and context should be the same when help is exchanged between social partners. Yet, an exchange of different favours appears more likely in a natural setting. This is assumed to be cognit...

Direct and generalised reciprocity can establish evolutionarily stable levels of cooperation among unrelated individuals, with animals reciprocating help based on whether they have been helped by a social partner before. It has been argued that the actual cooperative act by a social partner may be of minor importance for seemingly reciprocal cooper...

If individuals help more those who have previously helped them, stable cooperation may ensue through alternation of roles between donors and recipients. Allogrooming, which is costly to donors and beneficial to recipients, is often exchanged between social partners. Arguably, allogrooming and allopreening are the most frequently exchanged social se...

Social bonds reflect specific and enduring relationships among conspecifics. In some group-living animals, they have been found to generate immediate and long-term fitness benefits. It is currently unclear how important and how widespread social bonds are in animals other than primates. It has been hypothesized that social bonds may help in establi...

Sperm competition theory predicts that males should use cues indicating the risk and intensity of sperm competition to tailor their sperm investment accordingly. Rival males are an important source of social information regarding sperm competition risk. However, revealing such information may not be in the rival males' interest. Here we use a theor...

Sensory modalities individuals use to obtain information from the environment differ among conspecifics. The relative contributions of genetic divergence and environmental plasticity to this variance remain yet unclear. Numerous studies have shown that specific sensory enrichments or impoverishments at the postnatal stage can shape neural developme...

Cooperation by generalised reciprocity implies that individuals apply the decision rule “help anyone if helped by someone”. This mechanism has been shown to generate evolutionarily stable levels of cooperation, but as yet it is unclear how widely this cooperation mechanism is applied among animals. Dogs (Canis familiaris) are highly social animals...

Adjusting ejaculates to sperm competition can lead to sperm limitation. Particularly in polygynous species, males may face a trade-off between investing sperm in current or future mating opportunities. The optimal sperm allocation decision should depend on the relative intensity of sperm competition experienced in a mating sequence. Here we asked h...

Visual signals, including changes in coloration and color patterns, are frequently used by animals to convey information. During contests, body coloration and its changes can be used to assess an opponent's state or motivation. Communication of aggressive propensity is particularly important in group-living animals with a stable dominance hierarchy...

The communication of aggressive propensity is an important component of agonistic interactions. For this purpose, animals use different sensory modalities involving visual, acoustical and chemical cues. While visual and acoustic communication used in aggressive encounters has been studied extensively in a wide range of taxa, the role of chemical co...

Alternative reproductive tactics (ARTs), which can be plastic or fixed for life, may be characterized by distinct hormonal profiles. The relative plasticity hypothesis predicts flexible androgen regulation for adult males pursuing plastic tactics, but a less flexible regulation for males using a fixed tactic throughout life. Furthermore, androgen p...

Alternative reproductive tactics (ARTs), which can be plastic or fixed for life, may be characterized by distinct hormonal profiles. The relative plasticity hypothesis predicts flexible androgen regulation for adult males pursuing plastic tactics, but a less flexible regulation for males using a fixed tactic throughout life. Furthermore, androgen p...

The reciprocal exchange of goods and services among social partners is a conundrum in evolutionary biology because of its proneness to cheating, but also the behavioral and cognitive mechanisms involved in such mutual cooperation are hotly debated. Extreme viewpoints range from the assumption that, at the proximate level, observed cases of “direct...

Norway rats (Rattus norvegicus) cooperate according to indirect reciprocity, which implies the involvement of a reputation mechanism. Here, we test whether the rats employ such mechanism in repeated cooperative interactions. Focal subjects were first trained individually to pull food towards a social partner. During the experiment, the focal rats w...

Significance It is widely accepted that high predation risk may select for group living, but predation is not regarded as a primary driver of social complexity. This view neglects the important effect of predation on dispersal and offspring survival, which may require cooperation among group members. The significance of predation for the evolution...

Reproductive and agonistic behaviours typically diverge between individuals pursuing alternative reproductive tactics (ARTs). When tactics are fixed for life, evolutionary theory predicts that the relative frequencies of alternative male genotypes are stabilized in a population by negative frequency dependence. This implies that competition is grea...

requency-dependent selection may drive adaptive diversification within species. It is yet unclear why the occurrence of alternative reproductive tactics (ARTs) is highly divergent between major animal taxa. Here we aim to clarify the environmental and social conditions favouring the evolution of intra-population variance of male reproductive phenot...

The general belief that cooperation and altruism in social groups result primar- ily from kin selection has recently been challenged, not least because results from cooperatively breeding insects and vertebrates have shown that groups may be composed mainly of non-relatives. This allows testing predictions of reciprocity theory without the confound...

Two alternative frameworks explain the evolution of cooperation in the face of conflicting interests. Conflicts can be alleviated by kinship, the alignment of interests by virtue of shared genes, or by negotiation strategies, allowing mutually beneficial trading of services or commodities. Although negotiation often occurs in kin-structured populat...

Colonial species breed in densely aggregated territories containing no resources other than nest sites. This behaviour is usually explained by natural selection, for instance through benefits resulting from reduced predation risk. An alternative hypothesis suggests that, as in lek breeding systems, sexual selection may be responsible for the aggreg...

Cooperative breeders serve as a model to study the evolution of cooperation, where costs and benefits of helping are typically scrutinized at the level of group membership. However, cooperation is often observed in multi-level social organizations involving interactions among individuals at various levels. Here, we argue that a full understanding o...

It is generally assumed that there is sexual conflict over the mating system. In this view, polygyny benefits males at a cost to females, and it is hence unclear why females accept polygynous mating. However, in the facultatively polygynous fish, Neolamprologus pulcher, no costs of polygyny to females have thus far been detected. We hypothesized th...

Some animals reciprocate help, but the underlying proximate mechanisms are largely unclear. Norway rats (Rattus norvegicus) have been shown to cooperate in a variant of the iterated prisoner's dilemma paradigm, yet it is unknown which sensory modalities they use. Visual information is often implicitly assumed to play a major role in social interact...

When and where to disperse is a major life history decision with crucial fitness consequences. Before dispersing, individuals may benefit from checking the suitability of potential future habitats. In highly social species, such prospecting may be directed towards other groups rather than alternative habitats. This may increase familiarity with nei...

The expected strong directional selection for traits that increase a male's mating ability conflicts with the frequent observation that within species, males may show extreme variation in sexual traits. These male reproductive polymorphisms are usually attributed to direct male-male competition. It is currently unclear, however, how directional sel...

Life history theory predicts that the amount of resources allocated to reproduction should maximize an individual's lifetime reproductive success. So far, resource allocation in reproduction has been studied mainly in females. Intraspecific variation of endogenous energy storage and utilization patterns of males has received little attention, altho...

Direct reciprocity, according to the decision rule 'help someone who has helped you before', reflects cooperation based on the principle of postponed benefits. A predominant factor influencing Homo sapiens' motivation to reciprocate is an individ-ual's perceived benefit resulting from the value of received help. But hitherto it has been unclear whe...

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...

Many anti‐predator benefits of group living are predicted to scale with prey density. Nevertheless, evidence for a general density‐dependent increase of prey survival is scarce. A possible reason for this discrepancy is the reduction of costly anti‐predator behaviour of prey with increasing density, which may offset density‐dependent survival gains...

Behavioural variation among conspecifics is typically contingent on individual state or environmental conditions. Sex-specific genetic polymorphisms are enigmatic because they lack conditionality, and genes causing adaptive trait variation in one sex may reduce Darwinian fitness in the other. One way to avoid such genetic antagonism is to control s...

In resource defence polygyny, where males defend resources that females use for reproduction, the resource characteristics preferred by the two sexes are expected to match. We tested this expectation by comparing the shell characteristics preferred by males and females in the shell- brooding cichlid fish Lamprologus callipterus. In this species, ma...

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...

The group augmentation (GA) hypothesis states that if helpers in cooperatively breeding animals raise the reproductive success of the group, the benefits of living in a resulting larger group - improved survival or future reproductive success - favour the evolution of seemingly altruistic helping behaviour. The applicability of the GA hypothesis re...

The behaviour of animals towards their mirror image (“mirror test”) is routinely used as a proxy to measure aggression levels, especially in fish. The lack of evidence for visual self-recognition in fish supports this method. However, recent work points towards different hormonal and gene expression responses when fish are exposed either to conspec...

Tinbergen's (1963, Z. Tierpsychol. 20, 410–433) four questions have guided the conceptual thinking of behavioural biologists over five decades. This is partly based on a misunderstanding of the aims and virtue of this article. Tinbergen called attention to the fact that his classification of problems is somehow illogical. Here, an attempt is made t...

Zusammenfassung: Die Bedeutung der Blockierung des Eingangstunnels beim Kleinen Holzbohrer Xyleborinus saxesenii Ratzeburg (Coleoptera; Scolytinae) Die Evolution von Kooperation und Altruismus im Tierreich lässt sich in vielen Systemen durch Hamiltons Theorie der Verwandtenselektion (1964) erklären. Sie besagt, dass Helfer indirekt die eigene Fitne...

The theory of cooperation predicts that altruism can be established by reciprocity, yet empirical evidence from nature is contentious. Increasingly though, experimental results from social vertebrates challenge the nearly exclusive explanatory power of relatedness for the evolution of cooperation.