Play face in Japanese macaques reflects the sender's play motivation

Animals often initiate social interactions by exchanging signals. Especially when initiating amicable interactions, signaling one’s friendly stance toward others in advance may be important to avoid being misunderstood as having hostile intentions. We used data on dyadic play fighting in a group of Japanese macaques, Macaca fuscata, to examine the function of “play face” at the opening of a play session. We found no support for the previously proposed hypothesis that play face expression is likelier before entering risky situations (e.g., before gaining an undue advantage over the partner) to avoid being misunderstood. The results showed that play face expression was likelier in male juveniles before initiating play with other males than in females before initiating play with males or other females and that juveniles were likelier to express play face before initiating play with others closer in age. As male Japanese macaques play more frequently than females, and juveniles prefer to play with individuals closer in age, play face expression before play initiation may reflect the individual’s motivation for subsequent play interactions. This interpretation is supported by our observation that play bouts lasted longer when initiated with bidirectional play face by both participants than when initiated without play face. We also argued that since there was no tendency that play face was likelier to be expressed toward individuals with low play propensity (e.g., females) or infrequent partners to play with (e.g., individuals more distant in age), Japanese macaques may not tactically deploy this signal to recruit reluctant partners

Head Rubbing and Licking Reinforce Social Bonds in a Group of Captive African Lions, Panthera leo

AbstractMany social animals have a species-specific repertoire of affiliative behaviours that characterise individualised relationshipswithin a group. To date, however, quantitative studies on intragroup affiliative behaviours in social carnivores have beenlimited. Here, we investigated the social functions of the two most commonly observed affiliative behaviours in captiveAfrican lions (Panthera leo): head rubbing and licking. We conducted behavioural observations on a captive group of lionscomposed of 7 males and 14 females, and tested hypotheses regarding three social functions: tension reduction, socialbonding, and social status expression. Disproportionately frequent male–male and female-to-male head rubbing wasobserved, while more than 95% of all licking interactions occurred in female–female dyads. In accordance with the socialbond hypothesis, and in disagreement with the social status expression hypothesis, both head rubbing and lickinginteractions were reciprocal. After controlling for spatial association, the dyadic frequency of head rubbing was negativelycorrelated with age difference while licking was positively correlated with relatedness. Group reunion after daily separationdid not affect the frequencies of the affiliative behaviours, which was in disagreement with the predictions from the tensionreduction hypothesis. These results support the social bond hypothesis for the functions of head rubbing and licking.Different patterns of affiliative behaviour between the sexes may reflect differences in the relationship quality in each sex orthe differential predisposition to licking due to its original function in offspring care

タンチョウの求愛ダンス：計算統計学による構造理解と内分泌同調仮説の検証

2016～2018研究成果の概要（和文）：タンチョウはさまざまな個体間コミュニケーションを行う。本研究では、野外調査によって、これらの信号の役割を解明した。最も重要な発見が、つがいが踊るダンスの適応的意義を解明したことである。まず、ダンスという双方向コミュニケーションを分析する統計的枠組みを整理した。この枠組みを14の行動要素からなるタンチョウのダンス時系列データに当てはめた。情報理論に基づく指標を算出し、つがいのこれまでの繁殖成功のデータとの関連を調べた。その結果、これまでに繁殖に成功していないつがいほど、複雑なダンスを踊ることが判明した。この知見は、約７０年前に提唱され、未検証であったpair bond仮説と合致しない。研究成果の学術的意義や社会的意義タンチョウはさまざまな個体間コミュニケーションを行う。本研究では、北海道釧路地域における野外調査によって、これらの信号の役割を解明した。研究の最も重要な成果は、つがいが踊るダンスの適応的意義を解明したことである。個体識別されたつがいの観察により、これまでに繁殖していないペアのダンスは複雑であり、逆に、繁殖を積み重ねてきたペアは単純なダンスを踊っていたことが判明した。このことから、ペアダンスが繁殖に何らかの役割を果たしていることが示唆された。本成果は、約７０年前に提唱され、未検証であったpairbond仮説の見直しが必要であることを示している。研究成果の概要（英文）：This project aimed to clarify multimodal signals in monogamous red-crownedcranes (Grus japonensis). Particularly, we investigated a structure and function of pair dance. Ourobservation in Kushiro region, Hokkaido, suggested that red-crowned cranes use various signals insocial and reproductive contexts. We found that characteristics of the pair dances were related toreproductive success, but the results were not always consistent with the predictions. Danceduration increased as the breeding season approached. However, the past reproductive success of anindividual was negatively related to dance coordination (i.e., mutual information) of a pair. Theseresults partially support the pair bond hypothesis, but more importantly, also suggest the need todefine the vague concept of a “pair bond” in a biologically reasonable, measurable way

A Distinct Role of the Queen in Coordinated Workload and Soil Distribution in Eusocial Naked Mole-Rats

We investigated how group members achieve collective decision-making, by considering individual intrinsic behavioural rules and behavioural mechanisms for maintaining social integration. Using a simulated burrow environment, we investigated the behavioural rules of coordinated workload for soil distribution in a eusocial mammal, the naked mole-rat (Heterocephalus glaber). We tested two predictions regarding a distinct role of the queen, a socially dominant individual in the caste system: the presence of a queen would increase the workload of other caste individuals, and the cues by a queen would affect the soil distribution. In experiment 1, we placed four individuals of various castes from the same colony into an experimental burrow. Workers exhibited the highest frequency of workload compared to other castes. The presence of a queen activated the workload by other individuals. Individuals showed a consistent workload in a particular direction so as to bias the soil distribution. These results suggest that individuals have a consensus on soil distribution and that the queen plays a distinct role. In experiment 2, we placed the odour of a queen in one of four cells and observed its effect on other individuals’ workload and soil distribution. Relative to other cells, individuals frequently dug in the queen cell so the amount of soil in the queen cell decreased. These results suggest that queen odour is an important cue in coordinated workload and soil distribution in this species

The naked truth:a comprehensive clarification and classification of current 'myths' in naked mole-rat biology

The naked mole-rat (Heterocephalus glaber) has fascinated zoologists for at least half a century. It has also generated considerable biomedical interest not only because of its extraordinary longevity, but also because of unusual protective features (e.g. its tolerance of variable oxygen availability), which may be pertinent to several human disease states, including ischemia/reperfusion injury and neurodegeneration. A recent article entitled 'Surprisingly long survival of premature conclusions about naked mole-rat biology' described 28 'myths' which, those authors claimed, are a 'perpetuation of beautiful, but falsified, hypotheses' and impede our understanding of this enigmatic mammal. Here, we re-examine each of these 'myths' based on evidence published in the scientific literature. Following Braude et al., we argue that these 'myths' fall into four main categories: (i) 'myths' that would be better described as oversimplifications, some of which persist solely in the popular press; (ii) 'myths' that are based on incomplete understanding, where more evidence is clearly needed; (iii) 'myths' where the accumulation of evidence over the years has led to a revision in interpretation, but where there is no significant disagreement among scientists currently working in the field; (iv) 'myths' where there is a genuine difference in opinion among active researchers, based on alternative interpretations of the available evidence. The term 'myth' is particularly inappropriate when applied to competing, evidence-based hypotheses, which form part of the normal evolution of scientific knowledge. Here, we provide a comprehensive critical review of naked mole-rat biology and attempt to clarify some of these misconceptions

Data from Harano & Kutsukake 2018 J Evol Biol

Posterior observations for each parameter (θ0, the trait value for the most recent common ancestor; μ0, the baseline evolutionary rate; and drsl, the effect of consistent directional selection in a specific branch) of five independent MCMC chains

Data from: Directional selection in the evolution of elongated upper canines in clouded leopards and sabre-toothed cats

Extremely developed or specialised traits such as the elongated upper canines of extinct sabre-toothed cats are often not analogous to those of any extant species, which limits our understanding of their evolutionary cause. However, an extant species may have undergone directional selection for a similar extreme phenotype. Among living felids, the clouded leopard, Neofelis nebulosa, has exceptionally long upper canines for its body size. We hypothesised that directional selection generated the elongated upper canines of clouded leopards in a manner similar to the process in extinct sabre-toothed cats. To test this, we developed an approach that compared the effect of directional selection among lineages in a phylogeny using a simulation of trait evolution and approximate Bayesian computation. This approach was applied to analyse the evolution of upper canine length in the Felidae phylogeny. Our analyses consistently showed directional selection favouring longer upper canines in the clouded leopard lineage and a lineage leading to the sabre-toothed cat with the longest upper canines, Smilodon. Most of our analyses detected an effect of directional selection for longer upper canines in the lineage leading to another sabre-toothed cat, Homotherium, although this selection may have occurred exclusively in the primitive species. In all the analyses, the clouded leopard and Smilodon lineages showed comparable directional selection. This implies that clouded leopards share a selection advantage with sabre-toothed cats in having elongated upper canines