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The function of cooperative traits can change over time. For example, helping behaviors that originally evolved by kin selection can later yield direct fitness benefits and be stabilized by partner choice. In such cases, there may be multiple interacting factors that drive cooperation. Here, I review evidence that food sharing in vampire bats evolved as form of extended maternal care that was co‐opted to yield reciprocal benefits, and that such reciprocal relationships may have led to investment strategies that balance the trade‐offs between greater quality and quantity of cooperative relationships. [ABSTRACT FROM AUTHOR]

Evolutionary medicine is a concept that arose mainly in the 1990s, and which applies evolutionary biological principles to human medical fields. For instance, evolutionary medicine proposed that there is an evolutionary mismatch between the human anatomy and physiology and novel, man‐made environments, leading to the so‐called diseases of civilization. Constraints exist on the process of natural selection, and evolutionary trade‐offs can prevent traits from being optimal, leaving humans with traits that at first sight seem maladaptive, such as the very narrow birth canal of humans. More generally, certain traits can increase reproduction at the cost of health and longevity. Other traits, such as pain and fever, are related to protective physiological defences, and not diseases. Some medical topics have biological roots in the field of ethology, particularly human ethology, such as the behavioural aspects of psychiatry and addiction. Compulsive overeating and binge eating show similarities to substance‐linked addictions and behavioural addictions. Interactions between behaviour, stress and diseases have ancient evolutionary roots, which may lead to a mismatch to the modern human environment. A subject of high, topical interest is the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic, as the behavioural aspects of population compliance are crucial for the success in fighting the pandemic. Ethology, and evolutionary biology in general, can substantially contribute to improving the biological understanding of medical phenomena, and therefore of medical and public health interventions. This applies not only to research but also to education. [ABSTRACT FROM AUTHOR]

Behavioural reactions towards a mirror image are frequently used to measure individual aggression in a standardized way, especially in fishes. However, this approach was criticized recently on several grounds. One point of concern is that mirror tests are often conducted under highly artificial laboratory settings, while there exists a lack of knowledge of how individuals will react towards their reflection in the wild. We measured the responses of eight sympatric lamprologine cichlid species towards their mirror images in their natural environment in Lake Tanganyika. All species reacted by showing aggression towards their mirror image. The occurrence of overt and restrained aggression varied between species, reflecting species‐specific aggressive behaviours. The finding that larger species showed a higher amount of overt attacks further supports this interpretation. A commonality across all species was that aggression escalated over time, resembling behavioural patterns during prolonged aggressive encounters between life opponents with similar resource holding potential. These results shed light on the behaviour of closely related fish species towards their mirror image under natural conditions and contribute knowledge to the ongoing discussion on the suitability of mirror tests when measuring aggression. [ABSTRACT FROM AUTHOR]

Conflicts between stable social groups ("intergroup conflicts") can be damaging and exert a strong influence on within‐group social behaviour. The success of groups during intergroup conflict may depend on the ability of individual group members to converge upon collective defence behaviour, such as approaching or attacking. In principle, collective defence can be achieved via a united front, in which each individual responds in the same way to an intergroup threat. We tested the impact of simulated intergroup conflicts on collective defence and individual behaviour in banded mongooses (Mungos mungo), a cooperatively breeding mammal in which intergroup conflict is particularly common and costly. We presented focal groups with scent markings, call playbacks and caged live animals from rival groups and compared their responses to these stimuli with their responses to own‐group control stimuli. A greater proportion of group members approached the stimulus and acted defensively in response to rival stimuli as compared to controls, consistent with a unified collective defence response. However, counter to our expectation, groups exhibited lower behavioural homogeneity when presented with rival stimuli as compared to controls. A closer examination of the behaviours competitors used revealed that lower homogeneity was driven by a greater use, and diversity, of defensive behaviours relevant to repelling simulated rivals. Finally, group size affected responses: as group size increased, the proportion of members approaching the stimulus and behavioural homogeneity decreased. Our results lend support to the hypothesis that intergroup conflict leads to coordinated collective defence behaviour during the immediate threat of an intergroup conflict. However, collective defence need not mean that all group members execute the same behaviours. [ABSTRACT FROM AUTHOR]

It has been proposed that naked mole‐rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non‐breeding individuals. Earlier studies suggested that non‐breeders belong to distinct castes that specialise permanently or temporarily in specific cooperative tasks. In contrast, recent research on naked mole‐rats has shown that behavioural phenotypes are continuously distributed across non‐breeders and that mole‐rats exhibit considerable behavioural plasticity suggesting that individuals may not specialise permanently in work tasks. However, it is currently unclear whether individuals specialise temporarily and whether there is a sex bias in cooperative behaviour among non‐breeders. Here, we show that non‐breeding individuals vary in overall cooperative investment, but do not specialise in specific work tasks. Within individuals, investment into specific cooperative tasks such as nest building, food carrying and burrowing is positively correlated, and there is no evidence that individuals show trade‐offs between these cooperative behaviours. Non‐breeding males and females do not differ in their investment in cooperative behaviours and show broadly similar age and body mass related differences in cooperative behaviours. Our results suggest that non‐breeding naked mole‐rats vary in their overall contribution to cooperative behaviours and that some of this variation may be explained by differences in age and body mass. Our data provide no evidence for temporary specialisation, as found among some eusocial insects and suggest that the behavioural organisation of naked mole‐rats resembles that of other cooperatively breeding vertebrates more than that of eusocial insect species. [ABSTRACT FROM AUTHOR]

Cooperative behaviour often co‐occurs with the defence of key resources, typically in the form of a breeding site or territory communally exploited by a group of cooperating individuals. Nevertheless, not all animals that defend resources evolve advanced forms of cooperation and sociality—many non‐cooperative species occupy resources that do not differ in obvious ways from those inhabited by cooperative species. A key question is thus whether cooperation confers more subtle benefits, for example by allowing access to higher quality resources through competitive exclusion of less social rivals. In other words, it is not clear whether defendable resources are a necessary precondition for sociality or whether they also contribute to the maintenance and enhancement of cooperative societies. Here, we highlight how advances in imaging technology, machine‐learning, and environmental reconstruction enable the collection of behavioural and ecological data in unparalleled quantity and quality to address this question. These new techniques are especially suited to compare small‐scale differences in resource use between cooperative and non‐cooperative species that share a general habitat and have similar ecologies. The lamprologine cichlids of Lake Tanganyika are a prominent example of such a system and Michael Taborsky's pioneering work on this group has done much to promote these fishes as models of social evolution. We show that habitat features indicative of increased resource quality, namely increased stone cover, are indeed associated with the distribution of cooperative cichlids—at least where these resources are relatively scarce. We thus support a point Michael Taborsky made in 1981: the evolution of cooperative behaviour among cichlids is tied to their close association with a crucial resource, the substrate in which they hide and breed. In the future, the techniques we introduce here will allow to also investigate whether this substrate is indeed more than just the necessary precondition for cooperation among fishes; in addition, they will likely find application in a wide range of research fields interested in the interplay between biotic and abiotic environmental factors. [ABSTRACT FROM AUTHOR]

ABSTRACT The affective state of animals, that is, their mood and emotions, is altered by stressful (negative) or enriching (positive) experiences. In turn, the affective state influences decision making, thereby helping animals when coping with environmental challenges and opportunities. However, it is largely unknown how social experiences modulate the affective state. Here, we performed a judgement bias test to study the effects of rearing group‐size and experimentally assigned current rank on the affective state of the cooperatively‐breeding cichlid fish Neolamprologus pulcher. To assess affective state, we developed and validated a judgement bias test for this species. Fish learned to discriminate between a positive and a negative stimulus as shown by different latencies to approach the stimulus. Furthermore, the response curves to the stimuli conformed to the ones expected in judgement bias tests: fish showed an intermediate latency to approach an ambiguous stimulus, which significantly differed from the latencies to approach the positive and the negative stimulus. Unexpectedly, there were no significant effects of rearing group size and current social rank on the affective state of N. pulcher, despite known effects of these two social parameters on behaviours and physiology of this species. This may mean that observed behavioural and physiological differences in the treatment environments do not allow valid predictions about the affective state elicited by these environments. Alternatively, it may need more socioecologically relevant testing paradigms when evaluating the valence of social environments. [ABSTRACT FROM AUTHOR]