Badge Of Status Research Articles

Color as an Interspecific Badge of Status: A Comparative Test.

AbstractAnimals as diverse as cephalopods, insects, fish, and mammals signal social dominance to conspecifics to avoid costly fights. Even though between-species fights may be equally costly, the extent to which dominance signals are used between species is unknown. Here, we test the hypothesis that differences in color are associated with dominance between closely related species that aggressively interact over resources, examining between-species variation in colors that are used in within-species badges of status (black, white, and carotenoid coloration) in a comparative analysis of diverse species of birds. We found that dominant species have more black, on average, than subordinate species, particularly in regions important for aggressive signaling (face, throat, and bill). Furthermore, dominant species were more likely to have more black in comparisons in which the dominant species was similar in size or smaller than the subordinate, suggesting that black may be a more important signal when other signals of dominance (size) are missing. Carotenoid colors (i.e., red, pink, orange, and yellow) were not generally associated with dominance but may signal dominance in some taxonomic groups. White may have opposing functions: white was associated with dominance in species in which black was also associated with dominance but was associated with subordinance in species in which carotenoid-based dominance signals may be used. Overall, these results provide new evidence that colors may function broadly as signals of dominance among competing species. Such signals could help to mediate aggressive interactions among species, thereby reducing some costs of co-occurrence and facilitating coexistence in nature.

Integrative approach on the diversity of nesting behaviour in fishes

AbstractNests are the key elements of the reproductive repertoire of several fish species. Understanding the physiological aspects behind their nesting behaviour is imperative to improve our knowledge about behavioural mechanisms focusing on species conservation. Nevertheless, current knowledge on fish nesting is still underexplored. Here, we show a synthesis based on an integrative approach for understanding the diversity of nesting behaviour in fish. Because a nest sometimes does not involve new buildings (as in birds), we suggest a more comprehensive definition based on the behaviour instead of the structure per se. Forty fish families were recorded as they made nests, which were sorted into six main types: bowls, burrows, foam nests, nests made of plant matter and animal parts, besides nests made on clean rock surfaces. Besides spawning and parental care, these nests also serve as a refuge against predators and male competitors, as targets for sexual selection, including bowers with no parental care function, and badges of social status. We showed that, although it is advantageous to what the Darwinian fitness of the species is concerned, nesting also requires time and energy. We propose an evolution of nest types and functions, from the ancestral bowl used as refuge to derived foam nests with sexual selection functions. Physiologically, nesting is controlled by the HPG axis and particular brain circuits, this probably being the less explored subject. Finally, we highlighted that, in the changing world of the Anthropocene, nesting behaviour emerges as a framework to indicate the quality of the aquatic environments.

Plumage colour saturation predicts long-term, cross-seasonal social dominance in a mutually ornamented bird

Dominance hierarchies are known to reduce agonistic interactions between individuals and may be influenced by differences in phenotypes such as body size, personality or cognition. Colour ornamentation, especially with melanin-based colours, can also be a badge of status signalling social dominance, but status signalling with carotenoid-based colours is little understood. Here we studied whether different phenotypes, including individual differences in carotenoid-based colour ornamentation, body size, personality-, cognition- and stress-related traits, predict social dominance in the highly social and mutually ornamented common waxbill, Estrilda astrild . We monitored aggressive interactions of waxbills living in seminatural conditions, in a large mesocosm, using data from a radiofrequency identification system in the nonbreeding and breeding seasons over 2 consecutive years. We found the position of individual waxbills in the dominance hierarchy repeatable across seasons and years. Furthermore, the steepness of the dominance hierarchy was greater in the breeding seasons, perhaps because of increased competition over mates or breeding resources. Contrary to previous work with waxbills in birdcages, here body size did not predict social dominance, perhaps because in our more natural setting aggressive encounters were mostly airborne, where large body size may not confer a fighting advantage and may even reduce manoeuvrability. Sex, reactive-to-proactive personality differences and traits related to cognition or stress did not predict social dominance either. Finally, red colour saturation, but not the size of the red patch, strongly predicted social dominance and may thus act as a badge of status. This is one of the few studies testing whether size or saturation of carotenoid-based plumage coloration indicates social dominance and suggests that saturation may more often signal dominance. • Waxbills have mildly steep but stable social hierarchies across years and seasons. • Saturation of carotenoid-based red plumage colour indicates social dominance. • Size of red plumage areas does not correlate with social dominance. • Sex, personality, cognition and size were not related to social dominance.

A migratory sparrow has personality in winter that is independent of other traits

Small birds in winter face trade-offs between predation risk and foraging, and alternate life-history strategies may arise from these trade-offs. Animal personality shows similarities with alternative life-history strategies, and using a life-history context to understand personality can provide valuable insights. Golden-crowned sparrows, Zonotrichia atricapilla , a small migratory bird, have a complex winter social system with high site-fidelity, long-term social associations between individuals and competition mediated by badges of status. We asked whether golden-crowned sparrows show personalities during winter, whether these personalities were consistent over 3 years and whether they correlated with social and morphological traits. We found that golden-crowned sparrows had highly repeatable behaviours, as measured in captive behavioural assessments, constituting personalities consistent within one season and over time for up to 3 years, a time span that covers the average life span of the sparrows. While long-term repeatability was present, it varied considerably among different behaviours and time spans, and length of time between measures did not predict the magnitude of repeatability. Two movement-based aspects of sparrow personality were independent of the traits we measured (dominance, badges of status, size and age). However, nonsong vocalizations (a repeatable aspect of personality) correlated with wing length and gold badge size in some years. Because personality did not strongly link to the social traits we measured, sparrow personality could represent a separate axis of variation that might connect with other winter life-history parameters such as foraging, predation response or survival. • We studied whether wintering golden-crowned sparrows show personalities. • Personality was stable both within and across years. • Across-year repeatability showed considerable variability, indicating plasticity. • Personality was independent of dominance, badges of status, size, sex and age. • Personality may represent a separate axis of variation (e.g. survival, foraging).

Carotenoids-based reddish pelvic spines in nonreproducing female and male sticklebacks (Gasterosteus aculeatus) - Signalling social dominance?

Conspicuous ornaments are often considered a result of evolution by sexual selection. According to the social selection hypothesis, such conspicuous traits may also evolve as badges of status associated with increased boldness or aggression toward conspecifics in conflicts about ecological resources. This study tested predictions from the social selection hypothesis to explain evolution of conspicuous red color of the pelvic spines of the three‐spine stickleback (Gasterosteus aculeatus). Wild nonreproducing sticklebacks were presented to pairs of dummies which differed at their pelvic spines, having either (i) normal‐sized gray or red pelvic spines or (ii) normal‐sized gray or large red pelvic spines. The experimental tank was illuminated by white or green light, since green light impedes the sticklebacks’ ability to detect red color. The dummies moved slowly around in circles at each end of the experimental tank. We quantified the parameters (i) which of the two dummies was visited first, (ii) time taken before the first visit to a dummy, (iii) distribution of the focal sticklebacks in the two zones close to each of the two dummies and in the neutral zone of the tank, (iv) close to which of the two dummies did the focal fish eat its first food‐piece, and (v) time spent until the first piece of food was eaten. This was carried out for 22 females and 29 males sticklebacks. The results suggested no effect of the color or size of the dummies’ pelvic spines, on none of the five behavioral parameters. Moreover, neither the color of the pelvic spines of the focal sticklebacks themselves (as opposed to redness of the dummies’ spines) nor their body length was associated with behavior toward the dummies. Thus, this study did not support predictions from the social selection hypothesis to explain evolution of red pelvic spines in sticklebacks.

Male–male interactions select for conspicuous male coloration in damselflies

Male ornamentation, such as conspicuous male coloration, can evolve through female mate choice. Alternatively, in species without overt female mate preference, conspicuous male coloration can evolve as a badge of status via intrasexual selection to avoid costly fights or prevent mating attempts with other males. Here, we investigated the drivers of conspicuous male coloration in an ontogenetic colour-changing damselfly, Xanthagrion erythroneurum, where the juvenile males are yellow and change colour to red upon sexual maturity. We first showed that red males were chromatically and achromatically more conspicuous than the yellow males. We then quantified the condition of the males: red males were larger and in better condition than yellow males. We tested female preference in a choice experiment where we artificially manipulated male colour and found that females did not choose mates based on male coloration. We further tested whether the male coloration affected male–male interactions. We presented red and yellow males at the breeding site and measured behavioural responses from conspecific males and heterospecific ( Ischnura heterosticta ) males. Red males received less aggression from conspecifics and heterospecifics than yellow males. Our study experimentally showed that male conspicuousness is not a target of female mate choice in damselflies. Instead, intra- and interspecific male–male interactions appear to be the driver of its evolution. • X. erythroneurum changes colour from yellow to red during ontogeny. • Red males are more conspicuous and in better condition than yellow males. • Females do not prefer more conspicuous red males to yellow males. • Red males incur less within- and across-species aggression. • Males' conspicuous colour appears to have evolved to reduce male-male interactions.

Male characteristics as predictors of genital color and display variation in vervet monkeys

In the animal kingdom, conspicuous colors are often used for inter- and intra-sexual communication. Even though primates are the most colorful mammalian taxon, many questions, including what potential information color signals communicate to social partners, are not fully understood. Vervet monkeys (Chlorocebus pygerythrus) are ideal to examine the covariates of color signals. Males have multi-colored genitals, which they present during distinctive male-male interactions, known as the “Red-White-and-Blue” (RWB) display, but the genitals are also visible across a variety of other contexts, and it is unclear what this color display signals to recipients. We recorded genital color presentations and standardized digital photos of male genitals (N = 405 photos) over one mating season for 20 adult males in three groups at the Samara Private Game Reserve, South Africa. We combined these with data on male characteristics (dominance, age, tenure length, injuries, and fecal glucocorticoid metabolite concentrations). Using visual modeling methods, we measured single colors (red, white, blue) but also the contrasts between colors. We assessed the frequency of the RWB genital display and male variation in genital coloration and linked this to male characteristics. Our data suggest that the number of genital displays increased with male dominance. However, none of the variables investigated explained the inter- and intra-individual variation in male genital coloration. These results suggest that the frequency of the RWB genital display, but not its color value, is related to dominance, providing valuable insights on covariation in color signals and their display in primates.Significance statementConspicuous colors in animals often communicate individual quality to mates and rivals. By investigating vervet monkeys, a primate species in which males present their colorful genitals within several behavioral displays, we aim to identify the covariates of such colorful signals and their behavioral display. Using visual modeling methods for the color analysis and combining behavioral display data and color data with male characteristics, we found that high-ranking males displayed their colorful genitals more frequently than lower-ranking ones. In contrast, color variation was not influenced by male dominance, age, tenure length, or health. Our results can serve as a basis for future investigations on the function of colorful signals and behavioral displays, such as a badge of status or mate choice in primates.

Variation in plumage reflects avian habitat associations not revealed by abundance

For bird species in which plumage characteristics are associated with social dominance, the analysis of status badges may reveal habitat preferences. We analyzed the extent of male Chestnut-sided Warbler (Setophaga pensylvanica) chestnut-colored plumage in relation to age and body size to determine whether badge size was a potential indicator of resource-holding potential. We then modeled badge size in relation to habitat variables including habitat patch size, patch shape, and microhabitat characteristics in 101 different silvicultural openings in western Massachusetts during 2014 and 2015. Overall, older and larger Chestnut-sided Warblers had larger badges. Badge size showed a strong positive relationship with patch area. Notably, our findings reveal a greater sensitivity to area than was apparent from a different study's analysis of abundance at the same study site during the same time period. Badge size was positively related to patch shape complexity—an environmental variable not previously identified as important for this species by other studies. Our findings indicate that remote assessments of avian status badges may serve as reliable indicators of habitat preferences and suggest that this approach has the potential to reveal responses to gradients in habitat not reflected by abundance.

Sexual ornaments but not weapons trade off against testes size in primates.

Males must partition their limited reproductive investments between traits that promote access to females (sexual ornaments and weapons) and traits that enhance fertilization success, such as testes and ejaculates. Recent studies show that if the most weaponized males can monopolize access to females through contest competition, thereby reducing the risk of sperm competition, they tend to invest less in sperm production. However, how males invest in sexual ornaments relative to sperm production remains less clear. If male ornaments serve as badges of status, with high-ranking males attaining near-exclusive access to females, similar to monopolizing females through combat, their expression should also covary negatively with investment in post-mating traits. In a comparative study across primates, which exhibit considerable diversification in sexual ornamentation, male weaponry and testes size, we found relative testes size to decrease with sexual ornaments but increase with canine size. These contrasting evolutionary trajectories might be driven by differential selection, functional constraints or temporal patterns of metabolic investment between the different types of sexual traits. Importantly, however, our results indicate that the theory of relative investments between weapons and testes in the context of monopolizing females can extend to male ornaments.

Manipulating badges of status only fools strangers.

Conflict is risky, but mechanisms that allow animals to assess dominance status without aggression can reduce such costs. Two different mechanisms of competitor assessment are expected to evolve in different contexts: badges of status are expected in larger, anonymous groups, whereas individual recognition is feasible in small, stable groups. However, both mechanisms may be important when social interactions occur both within and across stable social groups. We manipulated plumage in golden-crowned sparrows (Zonotrichia atricapilla) and found that two known badges of status - gold and black head plumage patch sizes - independently affect dominance among strangers but manipulations had no effect on dominance among familiar flockmates. Moreover, familiar flockmates showed less aggression and increased foraging relative to strangers. Our study provides clear experimental evidence that social recognition affects badge function, and suggests that variation in social contexts maintains coexistence and context-dependent use of these two dominance resolution mechanisms.

Variation in female aggression in 2 three-spined stickleback populations with female throat and spine coloration.

Despite growing interest in female ornament evolution, we still have a rudimentary understanding of female display traits relative to similar traits in males. Under one popular adaptive scenario, female ornaments are hypothesized to function in female–female competition and serve as badges of status, such that their expression is linked with elevated aggression in some cases. In this study, we investigated the relationship between 2 female ornaments—male-like red throat color and red spine coloration—and female aggression in 2 independently derived stream-resident populations of three-spined stickleback Gasterosteus aculeatus. Using simulated intrusions, we tested whether females with redder ornaments were generally more aggressive, and for variation in aggressive and social behaviors between the 2 populations. We found that the red intensity of the throat and spine did not predict aggression levels in either population, suggesting a limited role for both female ornaments during female–female interaction. The 2 populations exhibited different levels of aggressive behaviors, unrelated to the color patches. Our results suggest that variation in selective pressures between populations may promote interpopulation variance in aggressive behavior but not the correlation between female ornamentation and aggression, and raise the possibility that red coloration may have evolved through different mechanisms or processes in the 2 populations.

Female incubation attendance and nest vigilance reflect social signaling capacity: a field experiment

Due to the reduced conspicuousness of female signals, their evolution has traditionally been interpreted as a by-product of sexual or natural selection in males. Recent studies have argued that they may be the result of sexual or social selection acting on females. Here, we explored the role of the white wing patch during the incubation period in female-female competition contests in a migratory cavity-nesting songbird, the pied flycatcher Ficedula hypoleuca. At this stage, female investment is crucial for offspring survival, while competition among females for nest cavities is still operating. We experimentally performed an extreme reduction of signaling capacity by covering the wing patch with dark paint in a group of females and compared their incubation attendance and social interaction patterns (vigilance and aggression at the nest as defense variables) during simulated territorial intrusion tests with female decoys, with those of an unmanipulated group of females. Tests were performed both before and after the manipulation. We hypothesized that these patches constitute signals of social dominance in female-female interactions that allow them to maintain high levels of incubation attendance by reducing the need for vigilance. We found a marked decrease in incubation attendance in experimental females after manipulation, a change that was not found in the control group. Moreover, vigilance decreased in the control group after the manipulation, a change not detected in manipulated females. No effects on aggressive nest defense were found. Female wing ornamental traits would act as a badge of status in social interactions allowing more intense incubation and reduced vigilance. Implications of social interactions on incubation patterns should be incorporated in future studies. Animals can transmit information to the others through different traits. Ornamental signals have been proposed as status indicators in social interactions in birds in many studies. Although some of them concern their function and evolution in females, only a few have been focused on their role during incubation. Our experimental study suggests that the female’s white wing patch in pied flycatchers acts as a badge of dominance status in social encounters. Thus, dominant females may enforce respect from competitors through signaling, thereby being able to reduce vigilance at the nest with positive effects on incubation efficiency. Implications of social status for incubation patterns should be considered in future studies as an additional factor modulating this crucial parental activity.

The looks matter; aggression escalation from changes on phenotypic appearance in the domestic fowl.

Domestic fowl in small groups are assumed to establish hierarchical systems based on individual recognition. Conversely, interactions in large groups are modulated by badges of status. Previous studies suggested that birds differing in phenotypic appearance (PA) became targets for aggression, possibly mistaking altered PA for badges of status. We evaluated the impact of altering PA on 0, 30, 50, 70 or 100% of the birds’ house at three experimental group sizes (GS). Tested GS were 10, 20 or 40 (8 birds/m2, 3 pens/GSxPA, 45 total). Thus, for each GS we had groups initially homogenous (100U, U = Unmarked; 100M, M = Marked), or heterogeneous M and U phenotypes coexisting in different proportions: 30M/70U, 50M/50U, and 70M/30U, remaining unchanged until 33 weeks of age. Then, homogeneous groups (100U and 100M) were sequentially altered by marking or unmarking 30, 50 and 70% of birds at 34, 38 and 44 weeks, respectively. Aggressive interactions were observed before applying changes at 27–28 weeks (T0), and after each sequential PA change on week 35–36 (T1), 39–40 (T2) and 45–46 (T3). Frequency of aggressive interactions in altered groups at T1, T2, and T3 were compared with non-altered heterogeneous controls. Results indicate no differences across initial PA and GS treatments (T0; P>0.05). However, aggression escalation was observed at T1 immediately after the first PA manipulation (Tukey P<0.05 altered vs controls). Aggression in altered groups remained high at T2 when compared to controls (Tukey, P<0.05), although by T3 interactions declined to almost initial levels (Tukey, P>0.05 altered vs controls). Aggressive interactions at T1 and T2 were predominantly directed from un-altered towards recently altered birds, irrespectively of their initial phenotype and of the GS. These results demonstrate that a sudden change in PA affects group dynamics. Altered birds were exposed to escalated aggression even in small groups, where individual recognition was presumed.

Is male rhesus macaque facial coloration under intrasexual selection?

Exaggerated male traits can evolve under intra- or intersexual selection, but it remains less clear how often both mechanisms act together on trait evolution. While the males of many anthropoid primate species exhibit colorful signals that appear to be badges of status under intrasexual selection, the red facial coloration of male rhesus macaques (Macaca mulatta) appears to have evolved primarily under intersexual selection and female mate choice. Nonetheless, experiments show that red color is salient to males, raising the question of whether the signal may also be under intrasexual selection. Here, we examine whether males express this signal more strongly in competitive contexts. Facial images were collected on all 15 adult males of a free-ranging social group during the peak of the mating season, and coloration was quantified using visual models. Results show that males more similar in facial redness were more likely to interact aggressively than more dissimilar ones, suggesting that color may be involved in the assessment of rivals. Furthermore, males exhibited darker coloration on days they were observed copulating, and dominance rank predicted facial redness only on copulating days, suggesting that coloration may also advertise motivation to defend a mate. Male rhesus macaque facial coloration may thus mediate agonistic interactions with rivals during competition over reproductive opportunities, such that it is under both inter- and intrasexual selection. However, color differences were small, raising perceptibility questions. It remains possible that color variation reflects differences in male condition, which in turn alter investment towards male-male competition and mating effort.

Social function of a variable lateral stripe in Xiphophorus hellerii?

AbstractIn a single population of a livebearing fish, the green swordtail (Xiphophorus hellerii), a trait considered a static badge of status in males of other populations, the color of a stripe covering the lateral line, has been found to be dynamic relative to their social environment, potentially rendering this signal meaningless. Males change the color expression of their lateral stripe dynamically based on social environment. We investigated if males (n = 26) respond to visual and chemical information about other males with a color change and aggressive behavior. We found that visual information is indeed causing color change, whereas chemical information is less effective. Aggressive responses and frequency of response did not change significantly with the mode of communication. We also studied female preferences for color, but found no significant preference (n = 32). Our results lead to questions as to how interpopulation variation can affect preferences and how dynamic signaling—in this case signal transmission presumably dependent on sex and/or status—influences the behavioral interactions we might expect between X. hellerii in the field.

Female plumage coloration signals status to conspecifics

Intrasexual competition in female birds is a widespread phenomenon but remains scarcely explored. Females compete for limited resources and the expression of signals that indicate their social status will be favoured by natural selection, generating a dominance hierarchy among individuals. However, which signals might be involved in female–female competition is unclear. In this study, we tested the role of rump coloration as a badge of status within a context of intrasexual competition using common kestrels, Falco tinnunculus, in two populations over 3 years. We used natural decoys with two different ‘phenotypes’, since the expression of this melanin-pigmented trait within the brown–grey range has been suggested to be a reliable proxy of individual quality in female common kestrels. By showing natural decoys with grey and brown rumps to breeding females, we simulated territorial invasions of high- and low-quality females, respectively. Our results show that rump coloration generates a differential response during territorial invasions. Specifically, we found that grey-rumped decoys (high quality) elicited lower levels of aggressiveness. In addition, female agonistic response was negatively associated with clutch size. Based on our results, we suggest that female rump coloration works as a badge of status in breeding female kestrels. This trait may signal female competitive ability and can generate a dominance hierarchy among individuals in our population. We also suggest that aggressiveness can be costly to females in terms of reproductive outcome. Overall, we provide evidence that melanin-pigmented traits in females can play a key role in intrasexual competition.

Testosterone levels in relation to size and UV reflectance of achromatic plumage traits of female pied flycatchers

In a substantial number of species, females show some development of secondary sexual characters. These traits can function as signals of individual phenotypic or genetic qualities and status to conspecifics. Individuals may benefit potentially from expressing signals or badges of status if they are reliable and honest signals of individual quality. In many species, badge sizes have been shown to correlate with dominance rank, which may be mediated by testosterone (T) levels. Here, we explored geographic variation in the size and properties of the white wing patch of female pied flycatchersFicedula hypoleucaand its relation to circulating T levels in three populations (two southern populations in central Spain and a northern population in Finland). Furthermore, we aimed at detecting if the size of the white wing patch and its ultraviolet (UV) reflectance indicate individual quality. We found that females in Spain had larger, brighter and more UV reflecting wing patches than those in Finland. Females with higher UV reflectance and larger primary white patches bred earlier. Younger females and females with larger primary white wing patches showed higher T levels. In contrast, higher values of UV reflectance in feathers from these patches were associated with low T levels. Despite genetic differentiation and differences in trait expression between populations, female pied flycatchers from different populations may converge and use the size of white wing patches to signal their T levels and thereby their social dominance.

Multiple Ornaments—Multiple Signaling Functions? The Importance of Song and UV Plumage Coloration in Female Superb Fairy-wrens (Malurus cyaneus)

Showy ornaments are considered as outcomes of sexual selection processes. They provide a “badge of status” to impress conspecific rivals or potential mating partners. Single ornaments may signal attractiveness or individual quality, yet many species display multiple ornaments. There are several hypotheses that explain the existence of multiple ornaments, suggesting that different ornaments serve as different information sources. They may provide either additive or redundant information on the same quality traits, or are simply evolutionary leftovers with no further relevant information. Although females of many species display elaborated traits, most studies regarding multiple ornaments focus on males. However, given that in many species females also display multiple ornaments, the question about their functional significance arises. To understand the existence of female multiple ornaments we investigated ornamental features of female Superb Fairy-wrens (Malurus cyaneus), focusing on song and variation in plumage characteristics. Female Superb Fairy-wrens produce complex solo songs, for territorial defense, and have bright blue tail feathers. We examined the relationships between song and plumage coloration characteristics in relation to female quality parameters to investigate whether, and to what extent existing hypotheses on multiple ornaments in males may also apply to females. Based on song recordings and spectrometric measurements of UV-coloration of tail feathers, we derived a series of different song and plumage parameters. Our results indicate interrelationships between the song length (total number of elements in female song) and female body size, but not UV-coloration. Interestingly, song complexity (number of different elements in female song) did not correlate with morphological parameters, UV-Chroma and song length respectively. This suggests that i) song and plumage characteristics evolved independently and ii) even within one trait, namely song, multiple signalling should be considered. To our knowledge, this is the first study investigating multiple traits in female songbirds, raising the idea that multiple signalling of sexually selected traits is not restricted to males only.

A quality signaling–recognition trade-off at the level of the type of interaction not species: a response to comments on Sheehan and Bergman

benefit from, social knowledge also have the more overt badge of status, if social knowledge limits quality signal evolution? If the answer is that there is no requirement for social knowledge and quality signals to be antagonistic in this sense, why are social knowledge and signal quality presented as somehow imposing limits on each other? These questions are not intended as refutations, nor do we have the answers, but we consider them sufficiently interesting to raise and would be interested to know the authors’ views.

Sexually selected lip colour indicates male group-holding status in the mating season in a multi-level primate society.

Sexual selection typically produces ornaments in response to mate choice, and armaments in response to male–male competition. Unusually among mammals, many primates exhibit colour signals that may be related to one or both processes. Here, we document for the first time correlates of facial coloration in one of the more brightly coloured primates, the black-and-white snub-nosed monkey (Rhinopithecus bieti). Snub-nosed monkeys have a one-male unit (OMU) based social organization, but these units aggregate semi-permanently into larger bands. This form of mating system causes many males to become associated with bachelor groups. We quantified redness of the prominent lower lip in 15 males (eight bachelors, seven OMU holders) in a group at Xiangguqing, China. Using mixed models, our results show that lip redness increases with age. More interestingly, there is a significant effect of the interaction of group-holding status and mating season on redness; that is, lip colour of OMU males undergoes reddening in the mating season, whereas the lips of subadult and juvenile bachelor males become paler at that time of year. These results indicate that lip coloration is a badge of (group-holding) status during the mating season, with non-adults undergoing facial differentiation, perhaps to avoid the costs of reproductive competition. Future research should investigate whether lip coloration is a product of male–male competition, and/or female mate choice.