Researcher Database

Masayo Soma
Faculty of Science Biological Sciences Behavioral Neuroethology
Associate Professor

Researcher Profile and Settings


  • Faculty of Science Biological Sciences Behavioral Neuroethology

Job Title

  • Associate Professor


J-Global ID

Research Interests

  • 鳴禽類   性淘汰   コミュニケーション   求愛   進化   社会性   ディスプレイ   発達   歌鳥   比較認知   

Research Areas

  • Life sciences / Evolutionary biology
  • Humanities & social sciences / Cognitive sciences
  • Life sciences / Basic brain sciences

Academic & Professional Experience

  • 2010 - Today 北海道大学 理学(系)研究科(研究院) 理学(系)研究科(研究院) 准教授

Research Activities

Published Papers

  • Ayumi Mizuno, Masayo Soma
    Ethology Ecology & Evolution 1 - 13 0394-9370 2020/08 [Refereed]
  • Masayo Soma, Henrik Brumm
    Biology Letters 16 (8) 20200399 - 20200399 1744-9561 2020/08 [Refereed]
    The duets of birds have intrigued biologists for a long time, yet much remains unknown about the evolution of these striking collective displays. This is partly because previous studies on duet evolution have been biased to songbirds and neglected other bird groups. In songbirds, the absence of migration has been found to predict the occurrence of duetting, indirectlysupporting the idea that duet communication is linked with pair bonding. Here, we used phylogenetic comparative analyses in a sedentary clade of non-songbirds, the barbets (Capitonidae), to reveal new correlates of duet evolution. We found (i) that duets evolved several times independently in different barbet lineages and (ii) that duetting evolved in association with group living (i.e. the presence of helpers or non-breeding adults during the breeding period), but not with sexual monochromatism or habitat type. Our findings are consistent with a duet function in mate guarding and dominance against subordinate group members as well as joint territory defence. Altogether, the results highlight the importance of the social environment for the evolution of collective signalling.
  • Same-sex pair bonding in male Java sparrows
    Hiroko Adachi, Masayo Soma
    日本性科学会誌 37 (1) 45 - 54 2019/07 [Refereed][Invited]
  • Soma M, Iwama M, Nakajima R, Endo R
    Royal Society Open Science 6 190563  2019/06 [Refereed][Not invited]
  • Ayumi MIZUNO, Yutaka MARUYAMA, Masayo SOMA
    Japanese Journal of Ornithology 68 (1) 67 - 71 0913-400X 2019/04/23 [Refereed]
  • Vocalization can mediate male-male sexual interactions in Java sparrows
    Hiroko Adachi, Masayo Soma
    Animal Biology 2018/12 [Refereed][Invited]
  • Ota N, Gahr M, Soma M
    Science Advances 4 (10) eaat4779  2018/10 [Refereed][Not invited]
  • 歌鳥の雌雄の音声コミュニケーション
    Masayo SOma
    Journal of INCE/J 42 (4) 161 - 164 2018/08 [Refereed][Invited]
  • Masayo Soma, László Zsolt Garamszegi
    Behavioral Ecology 29 (3) 676 - 685 1465-7279 2018/05/09 [Refereed][Not invited]
    Color patterns, such as bars or dots that cover the body surface of animals are generally thought to play roles in signaling and camouflage. In birds, however, the macroscopic aspects of plumage coloration are less well understood, as past studies typically described plumage colorations by using spectrophotometric analyses. To provide insight into the evolution of plumage patterns as sexual signals, we characterized interspecific and intersexual variations in the plumage patterns of estrildid finches and tested their associations with other courtship signals and life-history traits using a comparative phylogenetic approach. Our results support the idea that plumage patterns in estrildids are favored by sexual selection because large-sized conspicuous plumage patterns are possessed by species with an elaborate courtship dance. These plumage patterns may also play roles in social signaling because patterns are more conspicuous in species with intraspecific brood parasitism. We predict that pattern traits can be favored by mate choice or intrasexual competition when they can serve as honest indicators of individual condition. As our results are consistent between the sexes, we suggest that the same selective force is acting on the evolution of plumage patterns in males and females in parallel. Finally, we also found a trade-off between large size and vivid color patterns, suggesting that too conspicuous patterns are costly, presumably because of the risk of catching the eyes of potential predators. Therefore, plumage patterns are also shaped by natural selection.
  • A. C. R. Gomes, C. Funghi, M. Soma, M. D. Sorenson, G. C. Cardoso
    JOURNAL OF EVOLUTIONARY BIOLOGY 30 (7) 1336 - 1346 1010-061X 2017/07 [Refereed][Not invited]
    Sexual traits (e.g. visual ornaments, acoustic signals, courtship behaviour) are often displayed together as multimodal signals. Some hypotheses predict joint evolution of different sexual signals (e.g. to increase the efficiency of communication) or that different signals trade off with each other (e.g. due to limited resources). Alternatively, multiple signals may evolve independently for different functions, or to communicate different information (multiple message hypothesis). We evaluated these hypotheses with a comparative study in the family Estrildidae, one of the largest songbird radiations, and one that includes many model species for research in sexual selection and communication. We found little evidence for either joint evolution or trade-offs between song and colour ornamentation. Some negative correlations between dance repertoire and song traits may suggest a functional compromise, but generally courtship dance also evolved independently from other signals. Instead of correlated evolution, we found that song, dance and colour are each related to different socio-ecological traits. Song complexity evolved together with ecological generalism, song performance with investment in reproduction, dance with commonness and habitat type, whereas colour ornamentation was shown previously to correlate mostly with gregariousness. We conclude that multimodal signals evolve in response to various socio-ecological traits, suggesting the accumulation of distinct signalling functions.
  • Masayo Soma, Midori Iwama
    PLOS ONE 12 (3) e0172655  1932-6203 2017/03 [Refereed][Not invited]
    Mutual interactions between sexes have multiple signalling functions. Duet singing in songbirds is related to mutual mate guarding, joint resource defence, and signalling commitment. Coordinated visual displays of mating pairs are thought to perform similar functions, but are less well understood. The current study evaluated mutual interactions in an Estrildid species to explore the relative importance of duet dancing and male singing in mating success of pairs in a first encounter. When Java sparrows (Lonchura oryzivora) court prospective mates, only males sing. However, both males and females perform courtship dances, often in a duet-like manner. These dances are typically terminated by female copulation solicitation displays (CSDs). In the current study, we observed higher mating success when courtship dances were mutually exchanged, and when males sang. However, the sex initiating the courtship did not affect mating success. Most females produced CSDs after duet dancing but before hearing the entire song, indicating that duet dancing played a crucial role in mating. This finding highlights an unexplored aspect of duetting behaviour in the process of mutual mate choice. These results conflict with the majority of past songbird research, which has interpreted songs as primary behavioural sexual signals.
  • Nao Ota, Manfred Gahr, Masayo Soma
    BIOACOUSTICS-THE INTERNATIONAL JOURNAL OF ANIMAL SOUND AND ITS RECORDING 26 (2) 161 - 168 0952-4622 2017 [Refereed][Not invited]
    Vocalizations have been elucidated in previous songbird studies, whereas less attention has been paid to non-vocal sounds.In the bluecapped cordon-bleu (Uraeginthus cyanocephalus), both sexes perform courtship displays that are accompanied by singing and distinct body movements ( previous study revealed that their courtship bobbing includes multiple rapid steps.This behaviour is quite similar to human tap dancing, because it can function as both visual and acoustic signals.To examine the acoustic signal value of such steps, we tested if their high-speed step movements produce non-vocal sounds that have amplitudes similar to vocal sounds. We found that step behaviour affected step sound amplitude. Additionally, the dancing step sounds were substantially louder than feet movement sounds in a non-courtship context, and the amplitude range overlapped with that of song notes.These results support the idea that in addition to song cordon-bleus produce acoustic signals with their feet.
  • Kentaro Yamada, Masayo Soma
    JOURNAL OF AVIAN BIOLOGY 47 (6) 865 - 870 0908-8857 2016/12 [Refereed][Not invited]
    Song is a notable sexual signal of birds, and serves as an honest indicator of male quality. Condition dependence of birdsong has been well examined from the viewpoint of the developmental stress hypothesis, which posits that complex songs assure fitness because learned acoustic features of songs are especially susceptible to early-life stress that young birds experience in song learning periods. The effect of early stress on song phenotypes should be crucial, especially in age-limited song learners which sing stereotyped songs throughout life. However, little attention has been paid to non-learned song features that can change plastically even in adulthood of age-limited song-learners. Although it has been shown that food availability affects song rate in wild songbirds, there is limited evidence of the link between favorable nutritional conditions and song phenotypes other than song rate. Under the prediction that singing behavior reflects an individual's recent life history, we kept adult Bengalese finch males under high-nutrition or normal diet for a short term, and examined changes in body mass and songs. We found that birds on a high-nutrition diet showed higher song output (e.g. song rate and length) compared with those of the control group, while changes in body mass were moderate. In addition, note repertoire became more consistent and temporal structures got faster in both nutrition and control groups, which indicates that songs were subject to other factors than nutrition. Considering that female estrildid finches, including Bengalese and zebra finches, show a preference toward complex songs as well as longer songs and higher song rate, it is plausible that different aspects of singing behavior signal different male qualities, and provide multifaceted clues to females that choose mates.
  • Nao Ota, Manfred Gahr, Masayo Soma
    SCIENTIFIC REPORTS 5 2045-2322 2015/11 [Refereed][Not invited]
    According to classical sexual selection theory, complex multimodal courtship displays have evolved in males through female choice. While it is well-known that socially monogamous songbird males sing to attract females, we report here the first example of a multimodal dance display that is not a uniquely male trait in these birds. In the blue-capped cordon-bleu (Uraeginthus cyanocephalus), a socially monogamous songbird, both sexes perform courtship displays that are characterised by singing and simultaneous visual displays. By recording these displays with a high-speed video camera, we discovered that in addition to bobbing, their visual courtship display includes quite rapid step-dancing, which is assumed to produce vibrations and/or presumably non-vocal sounds. Dance performances did not differ between sexes but varied among individuals. Both male and female cordon-bleus intensified their dance performances when their mate was on the same perch. The multimodal (acoustic, visual, tactile) and multicomponent (vocal and non-vocal sounds) courtship display observed was a combination of several motor behaviours (singing, bobbing, stepping). The fact that both sexes of this socially monogamous songbird perform such a complex courtship display is a novel finding and suggests that the evolution of multimodal courtship display as an intersexual communication should be considered.
  • Masayo Soma, Chihiro Mori
    PLOS ONE 10 (5) 1932-6203 2015/05 [Refereed][Not invited]
    Music and dance are two remarkable human characteristics that are closely related. Communication through integrated vocal and motional signals is also common in the courtship displays of birds. The contribution of songbird studies to our understanding of vocal learning has already shed some light on the cognitive underpinnings of musical ability. Moreover, recent pioneering research has begun to show how animals can synchronize their behaviors with external stimuli, like metronome beats. However, few studies have applied such perspectives to unraveling how animals can integrate multimodal communicative signals that have natural functions. Additionally, studies have rarely asked how well these behaviors are learned. With this in mind, here we cast a spotlight on an unusual animal behavior: nonvocal sound production associated with singing in the Java sparrow (Lonchura oryzivora), a songbird. We show that male Java sparrows coordinate their bill-click sounds with the syntax of their song-note sequences, similar to percussionists. Analysis showed that they produced clicks frequently toward the beginning of songs and before/after specific song notes. We also show that bill-clicking patterns are similar between social fathers and their sons, suggesting that these behaviors might be learned from models or linked to learning-based vocalizations. Individuals untutored by conspecifics also exhibited stereotypical bill-clicking patterns in relation to song-note sequence, indicating that while the production of bill clicking itself is intrinsic, its syncopation appears to develop with songs. This paints an intriguing picture in which non-vocal sounds are integrated with vocal courtship signals in a songbird, a model that we expect will contribute to the further understanding of multimodal communication.
  • Soma M, Garamszegi LZ
    Frontiers in Ecology and Evolution 3 4  2015/02 [Refereed][Not invited]
  • Nao Ota, Masayo Soma
    JOURNAL OF AVIAN BIOLOGY 45 (6) 566 - 573 0908-8857 2014/11 [Refereed][Not invited]
    Birdsong is a sexual signal that serves as an indicator of male quality. There is already abundant evidence that song elaboration reflects early life-history because early developmental stress affects neural development of song control systems, and leaves irreversible adverse effects on song phenotypes. Especially in closed-ended vocal learners, song features crystallized early in life are less subject to changes in adulthood. This is why less attention has been paid to lifelong song changes in closed-ended learners. However, in the eyes of female birds that gain benefits from choosing mates based on male songs, not only past but also current conditions encoded in songs would be meaningful, given that even crystallized songs in closed-ended learners would not be identical in the long term. In this study, we examine within-individual song changes in the Java sparrow Lonchura oryzivora, with the aim of shedding light on the relationship between song and long-term life history. Specifically, we compared song length, tempo, and song complexity measures between the point just after song crystallization and around 1 yr later, and also compared those traits between fathers and sons to clarify the effect of vocal learning. While it is not surprising that song complexity did not differ depending on age or between fathers and sons, we found that song length and tempo increased with age. Follow-up analyses have revealed that frequency bandwidth and peak frequency of song notes also elevated with age. Our results show that song performance related to motor skills can be improved even after song crystallization. We also suggest that song performance in closed-ended vocal learners gives a reliable clue for mate choice by reflecting male quality with aging.
  • Hiroko Kagawa, Masayo Soma
    BEHAVIOURAL PROCESSES 99 138 - 144 0376-6357 2013/10 [Not refereed][Not invited]
    Bird songs have evolved under sexual selection pressure. Songs include multiple features that are subject to female preference, but recent comparative research has indicated evolutionary tradeoffs between song performance and complexity in some species. Trill, a repetition of the same sound, is a performance-related song trait; higher trill performance can be achieved at the cost of song complexity at the among-species or population level. The aim of this study was to examine whether such tradeoffs also account for within-species variation in Java sparrow songs, which include both multiple trill types and non-trill parts. We found a great individual variation in trill proportion, trill performance, and song complexity. A positive association between trill performance and body size suggested that trills can serve as an indicator of male quality. However, contrary to the tradeoffs predicted by previous studies based on other passerine species, trill performance and song complexity, i.e., note repertoire, were positively correlated: males in better condition can sing songs with larger note repertoires and higher trill performance, which may explain how trills and non-trill notes are both maintained and have co-evolved by sexual selection in Java sparrow songs. (C) 2013 Elsevier B.V. All rights reserved.
  • M. Soma, K. Okanoya
    BEHAVIOUR 150 (13) 1491 - 1508 0005-7959 2013 [Refereed][Not invited]
    Postmating sexual selection plays an important part in the evolution of secondary sexual characters. Based on differential allocation theory that predicts biased reproductive investment of females depending on the attractiveness of mates, a number of previous studies have shown that egg production is related in various ways to ornamental sexual traits of males, but evidence for behavioural sexual traits is less abundant. In this study we examine such maternal effects in relation to birdsong. Because the Bengalese finch is a monomorphic songbird, courtship song serves a key role in mate choice. To take into account individual female differences in egg production performance, we sequentially paired naive, captive, female Bengalese finches to two different males, and investigated if their reproductive investment (clutch size, egg mass and hatchling sex ratio) was related to the song traits of their mates. We found that clutch size and egg mass were highly repeatable within individual females while sex ratio was not. Despite the inflexibility of egg mass within each female, egg mass increased when females were mated to males with longer songs. In addition, we found a non-significant weak tendency toward male-biased sex ratio in relation to longer song duration of mates. Our findings suggest that females mated to better mates adjusted their reproductive investment by producing heavier eggs and possibly offspring of the more costly sex.
  • Masayo F. Soma
    ORNITHOLOGICAL SCIENCE 10 (2) 89 - 100 1347-0558 2011/12 [Not refereed][Not invited]
    Birdsong is an important sexually selected trait, and its acoustic features are socially transmitted in the process of song learning. Though a great deal of research has been conducted to shed light on the mechanisms and functions of song learning, we still do not have clear answers as to why for some species, including Estrildid finches and humans, the ability of "social" vocal learning has evolved. Therefore, this paper addresses social factors responsible for song learning, especially focusing on tutor choice in Estrildid finches, with the aim of elucidating what is already clear about how the social environment shapes songs and what is needed in future studies.
  • Ai Hasegawa, Masayo Soma, Toshikazu Hasegawa
    ORNITHOLOGICAL SCIENCE 10 (1) 73 - 80 1347-0558 2011/06 [Refereed][Not invited]
    Estrildine finches are important model species in experimental studies on female mating preferences, but research has focused on only two species from this family, namely, the Zebra Finch Taeniopygia guttata and the Bengalese Finch Lonchura striata var. domestica, and we know comparatively little about other closely related species. Therefore, we investigated sexual dimorphism and female choice in the Java Sparrow Padda oryzivora, which also belongs to the family Estrildidae, to open up the potential for comparative research and to better understand sexual selection in this family. First, we took measurements of eight morphological traits of six male and six female Java Sparrows: natural wing length, maximum wing length, tarsus length, tail length, exposed culmen length, bill width, bill depth and body mass. We quantitatively confirmed that Java Sparrows show sexual dimorphism in bill depth, with males having deeper bills than females. Second, we examined individual variation in male courtship songs by analyzing their acoustic and syntactical structure. After collecting data on male morphological and song-related traits, we conducted two-way choice tests to ask which kinds of male traits predicted which males were preferred by female Java Sparrows. In the choice tests, we put a cage with a female in between two cages each containing one male and recorded the position of the female every 30 seconds by point sampling. We performed a stepwise regression analysis to assess the relationship between the time females spent in front of each male and male morphological and song-related traits. The results indicated that females base their preference upon large body size, which is likely to act as a good indicator of male quality. However, no preference was observed for song-related traits or sexually dimorphic bill depth. Perhaps the sexual dimorphism in bill size is instead the evolutionary outcome of male-male competition.
  • Masayo Soma, Laszlo Zsolt Garamszegi
    BEHAVIORAL ECOLOGY 22 (2) 363 - 371 1045-2249 2011/03 [Not refereed][Not invited]
    The theory of sexual selection predicts a relationship between male sexual traits and reproductive success. This prediction has been tested extensively using the complexity of birdsong as a model for trait elaboration. However, contradictory results have emerged. Some studies have demonstrated that males with large repertoires enjoy a reproductive advantage, whereas other studies have failed to support this prediction. To make general inferences from this mixed evidence, we quantitatively reviewed the relevant literature using a meta-analytic approach. The mean effect size for the song/mating success association was significant, but the effects were generally weak, affected by publication bias, confounded by uncontrolled variables, and differing across the traits examined. Effect sizes were heterogeneous across studies due to species-specific effects, differences in mating systems, and song phenotypes. The degree of association between song complexity and reproductive success was independent of the strength of sexual selection, as assessed by the degree of polygyny and extrapair paternity. Our results highlight the importance of considering various biological factors to understand the role of repertoires in mediating mating success in different species.
  • Masayo Soma, Mariko Hiraiwa-Hasegawa, Kazuo Okanoya
    ANIMAL BEHAVIOUR 78 (5) 1107 - 1113 0003-3472 2009/11 [Not refereed][Not invited]
    Birdsong is an important sexually selected trait, and its acoustic features are socially transmitted in the process of song learning. The preference of some female songbirds for song complexity as measured by repertoire size has driven the evolution of many song traits and song-learning programs in males. If juvenile birds adopt the attractiveness of model birds by copying their repertoires, tutor choice in the early song-learning period should be crucial for future reproductive success. Thus, we hypothesized that the song quality of tutors influences the tutor choice of chicks in the Bengalese finch, Lonchura striata var. domestica. Each subject chick was reared by a foster pair in an individual breeding cage. At around the fledging period, we introduced another unrelated adult male (subtutor) into each cage to simulate the natural social environment in which chicks have opportunities to hear the songs of nonfather males after fledging. Subject chicks learned from both tutors when the total note repertoire size of the two models was small; they tended to learn from the subtutor when the father had a smaller note repertoire size. The acquired note repertoire size was not affected by whether subjects learned songs from the foster father or not. Song learning from the subtutor contributed to a larger note repertoire. Observed patterns in tutor choice, in particular song learning from a subtutor, could be an adaptive strategy that helps chicks compensate for exposure to smaller repertoire size in models. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
  • Masayo Soma, Mariko Hiraiwa-Hasegawa, Kazuo Okanoya
    BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY 63 (3) 363 - 370 0340-5443 2009/01 [Not refereed][Not invited]
    Birdsong differs from other sexual traits in that the acquisition process involves learning. Especially in close-ended learning species like the Bengalese finch, conditions experienced during the critical song-learning period can have a profound influence on song quality. Therefore, to understand song evolution from a life-history perspective, we investigated early ontogenetic effects on song quality. In particular, we focused on maternal effects and sibling competition. In asynchronously hatching bird species, the age hierarchy among nestlings affects physical development due to competition for food; mothers may influence this competition by adjusting their investment in each egg according to its sequence in the laying order. To independently assess these effects, chicks of the Bengalese finch were cross-fostered so that the age hierarchies formed in fostered broods were independent of the laying order. Our results indicate that song quality partially reflects early ontogenetic conditions, whereas song duration and note-type repertoire were independent of either laying order or age hierarchy. The syntactical complexity of note order declined over the laying sequence. This finding suggests that the song learning ability is influenced by within-clutch variation in maternal investment toward eggs. Considering that song syntactical complexity is subject to female preference in the Bengalese finch, it is likely that maternal resource allocation strategies play a role in song evolution.
  • Masayo Soma, Toshikazu Hasegawa, Kazuo Okanoya
    JOURNAL OF AVIAN BIOLOGY 39 (1) 101 - 107 0908-8857 2008/01 [Not refereed][Not invited]
    Recent studies of the vocal mechanisms of songbirds have shown that there are physical effects on sound production. Interspecific and phylogenetic comparisons have shown that body mass and bill morphology are two major factors affecting vocalizations such as songs. We analyzed the distance calls of female Bengalese finches Lonchurastriata var. domestica, the non-vocal learning sex, to assess the potential physical effects on the acoustic structure of vocalizations. By experimentally controlling rearing condition using cross-fostering we could examine the effects of the developmental environment and genetic background. None of the tested factors affected the peak frequency of the distance calls, but we found that larger-billed birds tended to produce shorter bout calls with higher trill rates. These results suggest that the divergence of bill morphology can affect acoustic features at the within-population level. We also found that the birds reared in the same foster brood and siblings from the same genetic parents tended to produce calls with similar trill rates. This implies that the trill rate is under the influence of developmental and genetic factors.
  • Masayo Soma, Daichi S. Saito, Toshikazu Hasegawa, Kazuo Okanoya
    BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY 61 (11) 1695 - 1705 0340-5443 2007/09 [Not refereed][Not invited]
    Maternal effects, such as investment in eggs, have profound effects on offspring fitness. Mothers are expected to skew their investment depending on the laying order and sex when unequal sibling competition occurs within a brood because of sex-specific vulnerability and age hierarchy caused by asynchronous hatching. The Bengalese finch hatches asynchronously and shows a moderate reversed sexual size dimorphism. However, contrary to commonly accepted assumptions of size-dependent vulnerability, the smaller sex (male) is more vulnerable to developmental stress caused by sibling competition. We investigated whether maternal investment would be biased by the position in laying order and the sex of eggs, and also explored the possible differences in growth patterns depending on sex, laying order, and age hierarchy by observing chicks fostered to experimentally manipulated broods where brood composition was controlled and age hierarchy was more enhanced than in natural breeding conditions. We found that overall patterns of maternal investment favored the disadvantageous sectors of sibling competition, i.e., eggs of later laying order and sons over those of early laying order and daughters. We also examined the effect of laying order on adult body size and sex differences in growth patterns. When reared in the subordinate age hierarchy, females could compensate for the deficit of decreased growth rate by taking longer to mature, whereas males could not. We suggest that this sex-specific growth pattern could be the cause of sex differences in vulnerability to early developmental stress.
  • Masayo Soma, Miki Takahasi, Maki Ikebuchi, Hiroko Yamada, Madoka Suzuki, Toshikazu Hasegawa, Kazuo Okanoya
    ETHOLOGY 112 (11) 1071 - 1078 0179-1613 2006/11 [Not refereed][Not invited]
    Birdsong is an acoustic ornament. According to indicator models, a trait must be costly to act as an honest signal, but the potential costs of elaborate songs are still poorly understood. The developmental stress hypothesis Suggests that learned song characteristics Could be an honest indicator of early developmental conditions because the brain structures associated with learning songs are susceptible to early developmental stress, which could thus affect song development. Unlike previous studies of developmental stress that examined the effect of a stress hormone or restricted nutrition, we observed Bengalese finches under semi-natural breeding conditions in captivity to investigate the relationship between early rearing conditions (e.g., brood size and sex ratio) and the subsequent variation in body size and song among individuals. Our results suggest that the early rearing environment directly affects body size and song complexity, whereas song output is determined mainly by' body size. These results support the developmental stress hypothesis. Moreover, Our findings are the first to show that developmental condition affects not only the number of note types but also the syntactical complexity of the song.
  • Masayo Soma, Toshikazu Hasegawa, Miki Takahasi, Kazuo Okanoya, Kazuo Okanoya
    Ornithological Science 5 (1) 77 - 84 1347-0558 2006 [Refereed][Not invited]
    A birdsong involves multiple traits that may have evolved under sexual selection pressure. There are two types of song traits: performance-related and elaboration-related traits. These two aspects of songs are partially independent, reflecting neural development and physical condition, respectively, but some song traits might interact with each other because they share the same mechanism for song production. Understanding the evolution of multiple ornaments requires knowledge of correlations among ornaments in the same individual. We explored the potential relationships between the following five song measures. We measured song duration and note rate as performance-related traits and average note types, linearity index score, and entropy as elaboration-related traits for the analysis. First, we found a significant relationship between linearity and entropy, indicating that syntactical complexity was consistently measured in both different variables. However, note type repertoire was not significantly associated with the two measures of syntactical complexity. Different song nuclei are responsible for each aspect of hierarchically organized song structures. Specifically, a lower-order song nucleus (RA) codes note type, while higher-order song nuclei (HVC and Nif) program transition patterns. Considering that female Bengalese Finches prefer syntactically complex songs, sexual selection, especially female choice, has played a role in shaping brains however, the sexual selection pressure for each song nucleus may differ in its intensity. Our investigation also revealed that those birds having a larger repertoire of note types tended to sing at lower speeds and require longer song bouts to sing syntactically complex songs. Hence, these results indicate that there are trade-offs and correlations between distinct aspects of performance-related and elaboration-related traits. © 2006, The Ornithological Society of Japan. All rights reserved.
  • M Soma, T Hasegawa
    BEHAVIOUR 141 1121 - 1134 0005-7959 2004/09 [Not refereed][Not invited]
    Social foraging is a far more complex phenomenon than individual foraging because of the many social interactions and communications that affect individual behaviour. Social dominance and social learning markedly influence the foraging efficiency of individuals in an unfamiliar environment. This study investigated how these two factors affect the costs and benefits of social foraging. We presented a novel feeding environment to captive budgerigars, Melopsittacus undulatus, and then compared the latency to feeding and number of pecks at the food for social and individual conditions, and for high-, middle-, and low-ranking birds. When in the social condition, birds started foraging faster and pecked more food than in the individual condition. Presumably, this lowered neophobia and enhanced foraging efficiency in the social condition was caused by social facilitation. Low-ranking birds had less resource accessibility in the social condition, probably because they were constrained by the existence of higher-ranking birds when it came to accessing the feeder. Nevertheless, the food intake of low-ranking birds almost equaled that of high- or middle-ranking birds in the social condition. In summary, high status is definitely an advantage, while low status adds some costs to individuals. Nevertheless, low-ranking birds compensate for this through enhanced foraging. It was clear that social foraging provides a great advantage to foragers of each rank, because of social facilitation.

Books etc

  • 動物行動学 原書11版
    J. Alcock (原著), D. R. Rubenstein (原著), 松島 俊也 (翻訳), 相馬 雅代 (翻訳), 的場 知之 (翻訳) 
    丸善出版 2021/01
  • 生物音響学会 (第5章共編共著)
    朝倉書店 2019/11 (ISBN: 9784254171679) xii, 441, 4p, 図版 [4] p
  • 上田, 恵介, 田中, 啓太, 伊澤, 栄一, 森本, 元, 相馬, 雅代, 三上, かつら, 関, 伸一, 齋藤, 武馬, 杉田, 典正, 泉, 洋江, 久井, 貴世, 江田, 真毅, 田中, 康平, 綿貫, 豊, 出口, 智広, 笠原, 里恵, 森, さやか(環境学), 森口, 紗千子, 浅井, 芝樹, 佐藤, 雪太 
    一色出版 2019/11 (ISBN: 9784910389080) 431p
  • 日本生態学会, 沓掛, 展之, 古賀, 庸憲 (第8章)
    共立出版 2012/06 (ISBN: 9784320057388) xi, 275p, 図版 [4] p
  • Eldredge, Niles, 長谷川, 真理子, 長谷川, 寿一, 相馬, 雅代 
    麗澤大学出版会 2012/06 (ISBN: 9784892056123) xv, 253p

Awards & Honors

  • 2016 資生堂女性研究者サイエンスグラント
    受賞者: 相馬雅代
  • 2015 文部科学大臣表彰 若手科学者賞
    受賞者: 相馬雅代
  • 2011 日本鳥学会 黒田賞
    受賞者: 相馬雅代
  • 2005 第30 回鳥類内分泌研究会若手奨励賞
    受賞者: 相馬雅代

Research Grants & Projects

  • カエデチョウ科を中心とする鳥類の目の顕著性進化に関わる種間比較および行動学的検討
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    Date (from‐to) : 2020/04 -2023/03 
    Author : 相馬 雅代
  • 雌雄に備わる複雑な性的信号の進化:鳴禽類の性淘汰再考にむけて
    日本学術振興会:科学研究費助成事業 若手研究(A)
    Date (from‐to) : 2016/04 -2020/03 
    Author : 相馬 雅代
    (1) 行動研究においては,特に求愛に用いられる視覚ディスプレイ(求愛ダンス)がなぜ雌雄に共有されるのか,について多角的に見当し,多くの成果を得た.これまでの鳴禽類鳥類の研究では,雌雄に共有される視聴覚ディスプレイがある場合,これを双方向的に同期させることで,有効なコミュニケーションシグナルとして機能していることがしばしば指摘されてきた.しかし,カエデチョウ科の一種であるブンチョウによる研究からは,実際には雌雄で求愛ダンスを同期しているというよりは,個体内でのリズムが求愛ダンスの表出に影響を与えていることが明らかになった.さらに,メスのコンディションが求愛ダンスの表出に影響を与えることも分かったことから,一見同期しているかに見える求愛ダンスは,実際にはさほど同期性が高くなく,単に高頻度な求愛が一見同期しているように見えている可能性が高い.
    (2) 種間比較研究においては,引き続き視覚シグナルに関しての検討を行っている.これまでの研究では,カエデチョウ科の求愛ダンスの複雑さは,色の派手さではなく,模様の派手さと相関進化しており,そのことは,模様の性的信号としての有効性を間接的に示唆している.実際に,いくつかの種について求愛ダンスと模様の関連に着目し調査をおこなったところ,模様のある部分の羽だけを逆立てて求愛ダンスを呈することが判明した.これに関し,カエデチョウ科ではなぜ模様が性的シグナルとして機能しうるのか,感覚便乗仮説からの説明が可能ではないかという洞察を得て,さらなる検討をすすめようとしている.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)
    Date (from‐to) : 2011/04 -2015/03 
    Author : SOMA Masayo
    Estrildid finches have multiple sexual traits, including courtship display that is composed of song and dance and ornamental plumage colors. This study shed light on song and dance, and asked why multiple sexual signals evolved and how they function. Estrildid finches showed a capacity to coordinate multimodal signals, such as singing, dancing, and bill sounds. In addition, young finches of a Estrildid species show practicing behavior of dance very early in their life, which might contribute to master fine coordination between singing and dancing. As dances are often displayed in parallel with songs, they are likely to evolve non-independently of songs. However, by using phylogenetic comparative approaches I found that dance and song evolved independently. The mechanisms and functions of the two behaviors are at least partially independent.
  • コミュニケーションにおける身体動作リズムの機能と進化:鳴禽類をモデルとした研究
    日本学術振興会:科学研究費助成事業 研究活動スタート支援
    Date (from‐to) : 2010 -2011 
    Author : 相馬 雅代
  • 動作の時系列的規則性獲得の認知メカニズム:鳥をモデルとした研究
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2007 -2009 
    Author : 相馬 雅代
    卵生の動物のメスにとって産卵量の調節は,限られた繁殖資源を配分投資し,自身とさらに子の適応度を最適化するという面で,重要な繁殖パラメータである.一般的に,卵1個に対する栄養投資量が多いほど子の生存率は高まる一方,メスには総投資量として大きな負担を強いることになる.また,一度の繁殖で産む卵は多いほうが,効率的に子の数を増やすことができ,適応度に寄与する可能性もあるが,他方で,育児・育雛のコストが大きくなり兄弟間競争が激化するぶん,メス自身や子の各個体にとって必ずしも利益となるとは限らない.そのため,産卵量の調節は,繁殖コンディションの影響を鋭敏に反映するのではないかと予測されている。このような産卵量の調節に関わるのが,繁殖コンディションやつがい相手オスの質である.ジュウシマツのような鳴禽類は,性淘汰形質として発声行動(歌)を求愛ディスプレイに用いる.そこでメスは,どのような歌をうたうオスとつがうと産卵投資を増加させるのか検討を行った. その結果,それぞれのメスがつがった相手の歌の音響特性が,初期発達期にさらされた歌とどれだけ似ているかどうかという指標が,卵重・一腹卵数・性比の増減に関連していた.メスの配偶投資に反映される選好性には,父親よりも,発達初期に社会交渉のあった非父親オスの歌の方が影響を与えていることが示唆された.このことは,初期聴覚記憶にもとづく性的刷り込み学習が繁殖投資に影響している一方で,近親交配を促進するような,すなわち父親の歌を選好するような傾向は無いことを示唆している.この結果については,学会において発表を行い,論文を準備中である.
  • 初期環境による認知機能の個体差:鳥類の音声学習をモデルとした研究
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2005 -2006 
    Author : 相馬 雅代
    昨年度までの研究によって,ジュウシマツヒナの発達コンディションの影響の受けやすさに性差があることが示唆された.この理由として,(1)母性効果の性差,(2)性特異的な成長パターンという2つの要因を考え検討した. (1)母性効果の性差:卵順と性によって卵に量的差異が生じている可能性について検討した.卵重には性と卵順の交互作用の影響がみとめられた.すなわち母親は,産卵順が遅いほど重い卵を産む傾向があった.この傾向はメス卵よりもオス卵でより顕著で,また全般に,メスよりオスで卵重が重かった.このことは,母親がヒナ間競争で不利になりやすい孵化順の遅い卵,脆弱な性であるオスの卵に多く投資し,ヒナの減少を回避しようとする戦略を反映すると考えられる.しかしこれらの結果から,オスの脆弱性を母性効果で説明することはできなかった. (2)成長パターンの性差:性および卵順がヒナ間競争中での発達におよぼす影響を検討するため,里子実験によってヒナ間に実験的に日齢差をもうけることで,ヒナ間競争に有利な年長個体と不利な年少個体との身体発達(体重増加)を比較した.発達初期にヒナの性判定を行い,実験巣が全て両性とも2羽ずつ,各性年少・年長1羽ずつになるようヒナを配置した.各ヒナの体重増加を成長曲線にあてはめ,最終体重と成長速度に影響を与えている要因を分析した.この結果,成長速度には性と日齢差の影響が,最終体重には卵順・性・日齢差の影響がみられた.実験巣で年少群に割り当てられたヒナは成長速度の低減がみられ,特にメスにおいて顕著であった.しかし,最終体重は,年長群・年少群ともメスの方が大きかった.つまり,不利なヒナ間競争下でのメスは成長速度の大幅な低減を示すが,成長期間を柔軟に長くとることで補完していたと考えられる.他方オスは,成長期間の可塑性が低いことが,発達ストレスに対する脆弱性の原因であることが示唆された.

Educational Activities

Teaching Experience

  • Inter-Graduate School Classes(General Subject):Natural and Applied Sciences
    開講年度 : 2019
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 生命システム, 生命機能, 研究方法論, 研究技術論

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