Secondary Sexual Ornaments Research Articles

Habitat complexity and complex signal function – exploring the role of ornamentation

AbstractAnimals often communicate in complex, heterogeneous environments, leading to hypothesized selection for increased detectability or discriminability in signaling traits. The extent to which secondary sexual ornaments have evolved to overcome the challenges of signaling in complex environments, however, remains understudied, especially in comparison to their role as indicator traits. This study tested the hypothesis that the condition-dependent secondary sexual ornamentation in the wolf spider Rabidosa rabida functions to increase detectability/discriminability in visually complex environments. We predicted that male ornamentation would interact with the complexity of the signaling environment to affect male mating success. In particular, we expected ornaments to confer a greater mating advantage when males courted in visually complex environments. To test this, we artificially manipulated male foreleg ornamentation (present/absent) and ran repeated-measures mating trials across laboratory microcosms that represented simple versus complex visual signaling environments. Microcosm visual complexity differed in their background pattern, grass stem color, and grass stem placement. We found that ornamented males mated more often and more quickly than unornamented males across both environments, but we found no support for an ornament-by-environment interaction. Male courtship rate, however, did interact with the signaling environment. Despite achieving the same level of mating success across signaling environments, ornamented males courted less rapidly in complex versus simple environments, although environmental complexity had no influence on unornamented male courtship rates. Our results suggest that the visual complexity of the signaling environment influences the interactive influence of ornamentation and dynamic visual courtship on female mate choice.

Multiple signals predict male mating success in the lek-mating lesser prairie-chicken (Tympanuchus pallidicinctus)

Sexual selection theory maintains that traits under selection honestly advertise qualities of signaling individuals and that only individuals in the best condition can survive while displaying maximally elaborated secondary sexual ornaments. Recent trends in mate choice studies have favored the consideration of the effects of multiple traits on mating success, including suites of traits transmitted in different sensory modalities. Sexual selection is expected to be especially strong in lek-mating species. The lesser prairie-chicken (Tympanuchus pallidicinctus) is a grouse species which breeds on leks. Males of this species perform audio and locomotor displays and exhibit two pairs of brightly colored ornaments. We performed an observational study of mate choice in spring 2016–2018 and noted 40 copulations on seven leks. We quantified behavioral, territorial, and morphological characteristics of males along with ornament color properties. We found that variables from all categories considered predicted female choice. Age had the strongest effect, with adult males experiencing higher female choice relative to yearlings. Allocation of aggressive behavior and comb color properties were also strongly correlated with female choice. Our results show that modulating behavior depending on whether females are present contributes to male mating success and highlight the importance of the size and color properties of secondary ornaments. Further research is required to determine how the variables most strongly associated with mate choice relate to one another and which aspects of individual quality, if any, are signaled by color ornaments. Future studies could also incorporate variables related to females to determine if selection on females occurs. The choice of a mate can help determine the survival and reproductive success of offspring. In species where males do not care for offspring, mate choice can be highly consistent among females, and mate choice decisions are often based on the evaluation of multiple traits such as vocalizations, behavior, and morphological trait size. Based on measurements of captured males and observations of breeding behavior, we demonstrate that mate choice in lesser prairie-chickens (Tympanuchus pallidicinctus) correlates with male behavior, morphology, skin patch color, and territorial characteristics. Our findings represent a rare demonstration of mating success being influenced by how male behavior (including aggression) changes when females are present or absent. Our results show how multiple traits can transmit information about individual quality and support theoretical links between mate choice and increased male age or male-male competition.

The relationship between male social status, ejaculate and circulating testosterone concentration and female yolk androgen transfer in red junglefowl (Gallus gallus)

Several studies show that avian females prefer males based on their secondary sexual ornaments and dominance status. We tested in red junglefowl (Gallus gallus) how comb size affected the result of fighting and how the dominance status related to testosterone concentrations in their circulation and ejaculates. We subsequently tested how social status was related to female reproductive investment, including yolk hormone transfer. We found that after a fight 1) winners increased plasma T and decreased ejaculates T whereas losers' T remained unchanged, and 2) plasma T of winners was higher but ejaculates T was lower than those of losers. We argued those are consistent with the different reproductive strategies of dominant and subordinate males. Furthermore, in line with offspring sex-dependent growth patterns females transferred significantly more androstenedione to female than male embryos when mated with winners, while doing the opposite when mated with losers. We concluded therefore that female reproductive investment was affected by both partner quality and embryo sex. The results indicate that male quality influences sex-specific maternal investment, which could be mediated by ejaculate testosterone concentration.

Pigeon odor varies with experimental exposure to trace metal pollution.

Trace metals are chemical pollutants that have well-known noxious effects on wildlife and that are current major environmental issues in urban habitats. Previous studies have demonstrated their negative (e.g. lead) or positive (e.g. zinc) effects on body condition, immunity and reproductive success. Because of their effects on condition, trace metals are likely to influence the production of condition-dependent ornaments. The last decade has revealed that bird odors, like mammal odors, can convey information on individual quality and might be used as secondary sexual ornaments. Here, we used solid-phase microextraction headspace sampling with gas chromatography-mass spectrometry to investigate whether plumage scent varied with experimental supplementation in lead and/or zinc in feral pigeons. Zinc supplementation (alone or in combination with lead) changed the proportion of several volatiles, including an increase in the proportion of hydroxy-esters. The production of these esters, that most likely originate from preen gland secretions, may be costly and might thus be reduced by stress induced by zinc deficiency. Although lead is known to negatively impact pigeon condition, it did not statistically affect feather scent, despite most of the volatiles that increased with zinc exposure tended to be decreased in lead-supplemented pigeons. Further studies should evaluate the functions of plumage volatiles to predict how trace metals can impact bird fitness.

Asymmetries, heterosis, and phenotypic profiles of red junglefowl, White Plymouth Rocks, and F1 and F2 reciprocal crosses.

During the domestication of farm animals, humans have manipulated genetic variation for growth and reproduction through artificial selection. Here, data are presented for growth, reproductive, and behavior traits for the red junglefowl, a line of White Plymouth Rock chickens, and their F1 and F2 reciprocal crosses. Intra- and intergenerational comparisons for growth related traits reflected considerable additive genetic variation. In contrast, those traits associated with reproduction exhibited heterosis. The role of sexual selection was seen in the evolution of prominent secondary sexual ornaments that lend to female choice and male-male competition. The large differences between parental lines in fearfulness to humans were only mitigated slightly in the intercross generations. Whereas, overall F1 generation heterosis was not transferred to the F2, there was developmental stability in the F2, as measured by relative asymmetry of bilateral traits. Through multigenerational analyses between the red junglefowl and the domestic White Plymouth Rocks, we observed plasticity and considerable residual genetic variation. These factors likely facilitated the adaptability of the chicken to a broad range of husbandry practices throughout the world.

Do ornaments, arrival date, and sperm size influence mating and paternity success in the collared flycatcher?

Males advertise their intrinsic parental and/or genetic qualities by the size of secondary sexual ornaments. Moreover, they compete with one another for the best territory and males who arrive first at the breeding ground usually have an advantage in this competition. Females may consider multiple male qualities simultaneously and prefer the one most important for their fitness in the current context. They can further improve their fitness by selecting the best care-giver as their social mate and engaging in an extra-pair copulation with a genetically superior male. In such cases, sperm competition arises in the female reproductive tract and its outcome may be affected by the sperm morphology of both the social and extra-pair male. Here, we tested these ideas in the collared flycatcher (Ficedula albicollis), a species with context-dependent choice of social partners and frequent extra-pair paternity. We recorded male arrival to breeding sites, manipulated their forehead patches, and measured sperm size. In contrast to a previous study in a Swedish population, males with enlarged patches were non-significantly less successful late in the season while no such difference was found early in the season. Besides this tendential seasonal interaction, arrival date did not affect mating and paternity success or male fitness, and the same was true for sperm size. These results suggest different benefits of male ornamentation and female mate choice between populations and call for more replicated research within and between species. The fitness of a male of a migratory species might be affected by several pathways. First, early arrival should confer benefits in the form of best territory choice. Second, in a dichromatic and sexually promiscuous species, secondary sexual ornaments are considered by females both in the choice of social and extra-pair mates. Third, by modifying sperm traits, males may outmatch their rivals in sperm competition. These ideas have usually been tested in isolation. In this experimental study, we tested the joint effect of all of these factors on the genetic fitness of males. We found little evidence for the dependence of male reproductive success on either sperm morphology or plumage ornamentation which is in contrast to other populations of the species. Our study calls for replicated research both in well-established fields like mate choice and emerging ones like sperm competition.

Testing for links between face color and age, dominance status, parity, weight, and intestinal nematode infection in a sample of female Japanese macaques.

Studies of the role of secondary sexual ornaments in mate choice tend to focus on colorful traits in males, but females of many animal species express colorful ornamentation too. Among non-human primates, investigations into the role of female secondary sexual traits as indicators of life history characteristics, reproductive success, and health status have mostly focused on sexual swellings, whereas only few studies have been conducted on the role of facial color. Recent studies on rhesus macaques and mandrills suggested that female ornamentation might provide information about female life history characteristics, but not on disease resistance factors and parasite infection, which have been shown to affect male ornamentation in some non-primate species. In Japanese macaques (Macaca fuscata), females have brightly colored faces that are indicative of their reproductive status. Here, we aimed to determine whether female facial color might also convey information about age, dominance rank, parity, weight, and intestinal nematode infection in free-ranging individuals. We analyzed whether female facial parameters (luminance and redness) were linked to these individual characteristics, using digital photography and data on intestinal parasite infection collected systematically during 1 month for each of seven free-ranging females. We found no evidence to suggest that female facial color is an indicator of any of these measures in Japanese macaques. Considering our small data set, it is still preliminary to draft any clear conclusions. Future studies combining digital, hormonal, parasitological and behavioral data are needed to assess the possible role of female face color on male preferences and mating choice in Japanese macaques.

Badge Size Reflects Sperm Oxidative Status within Social Groups in the House Sparrow Passer domesticus

The phenotype-linked fertility hypothesis proposes that male ornaments reflect male fertility. Male ornaments could honestly signal sperm quality due to the high susceptibility of sperm to free radicals on the one hand and the negative impact of oxidative stress on ornament elaboration on the other hand. Thus, only males with superior antioxidant defences could bear the cost of more elaborated sexual ornaments without suffering adverse fitness costs. Yet, in species where males experience differential access to fertile females, a trade-off emerges between investing into traits favouring mating opportunities (e.g. secondary sexual ornaments, social dominance, mate-guarding behaviours, etc.) or into traits favouring sperm competitive ability (e.g. sperm numbers and quality). When male sexual ornaments promote greater access to fertile females, a negative relationship can then be predicted between ornamentation and sperm quality. We tested the latter hypothesis and the phenotype-linked fertility hypothesis in wild House Sparrows Passer domesticus by exploring the relationships between sperm quality, melanin-based ornamentation, and redox status in blood and sperm. We found no correlation between badge size and sperm swimming performance. However, we found that within a social group, large-badged males better protect their ejaculates from oxidative stress, and thus produce less oxidized ejaculates. Additionally, we found that badge size did not reflect social dominance, and thus the protection of the ejaculate is independent of males’ ability to monopolize resources. Our results suggest that badge size might reflect male investment into the antioxidant protection of their sperm relative to a given social environment, and thus females may accrue both direct and indirect benefits by mating with large-badged males producing less oxidized ejaculates.

Female Attraction to Higher Pitched Male Enticement Calls in Barn Swallows

AbstractCurrent sexual selection studies demonstrate that female mate preference almost always favors exaggerated male traits, such as colorful plumage and elongated tails. However, such studies focused mainly on secondary sexual characteristics, i.e., traits that are fully developed at maturation, while ignoring others, which precludes generalization of the findings. We studied the expression of the male enticement call, a nestling‐like courtship trait, in relation to female attraction and to the expression of secondary sexual ornaments in the Japanese barn swallowHirundo rustica gutturalis. First, we showed that the peak amplitude frequency of male enticement calls was, on average, lower than that of nestling food‐begging calls, indicating that higher pitched calls are more similar to nestling food‐begging calls than are lower pitched calls. Second, we conducted an experimental playback of male enticement calls during the courtship period with the female's mate removed, and found that females were more attracted to heightened‐pitch calls than to control calls. Lastly, the peak amplitude frequency of male enticement calls was negatively related to the ornamentation, as measured by throat coloration. Taken together, these findings suggest the following: (1) females are attracted to a more nestling‐like trait, and (2) similarity to nestling food‐begging calls increases with decreasing secondary sexual ornaments. Nestling‐like male traits that are not secondary sexual characteristics should be considered when studying the general pattern of female attraction to male traits.

Male Investments in High Quality Sperm Improve Fertilization Success, but May Have Negative Impact on Offspring Fitness in Whitefish.

Many ejaculate traits show remarkable variation in relation to male social status. Males in disfavoured (subordinate) mating positions often invest heavily on sperm motility but may have less available resources on traits (e.g., secondary sexual ornaments) that improve the probability of gaining matings. Although higher investments in sperm motility can increase the relative fertilization success of subordinate males, it is unclear whether status-dependent differences in sperm traits could have any consequences for offspring fitness. We tested this possibility in whitefish (Coregonus lavaretus L.) by experimentally fertilizing the eggs of 24 females with the sperm of either highly-ornamented (large breeding tubercles, dominant) or less-ornamented (small tubercles, subordinate) males (split-clutch breeding design). In comparison to highly-ornamented individuals, less-ornamented males had higher sperm motility, which fertilized the eggs more efficiently, but produced embryos with impaired hatching success. Also offspring size and body condition were lower among less-ornamented males. Furthermore, sperm motility was positively associated with the fertilization success and offspring size, but only in highly-ornamented males. Together our results indicate that male investments on highly motile (fertile) sperm is not necessarily advantageous during later offspring ontogeny and that male status-dependent differences in sperm phenotype may have important effects on offspring fitness in different life-history stages.

Investment in sensory structures, testis size, and wing coloration in males of a diurnal moth species: trade-offs or correlated growth?

For dioecious animals, reproductive success typically involves an exchange between the sexes of signals that provide information about mate location and quality. Typically, the elaborate, secondary sexual ornaments of males signal their quality, while females may signal their location and receptivity. In theory, the receptor structures that receive the latter signals may also become elaborate or enlarged in a way that ultimately functions to enhance mating success through improved mate location. The large, elaborate antennae of many male moths are one such sensory structure, and eye size may also be important in diurnal moths. Investment in these traits may be costly, resulting in trade-offs among different traits associated with mate location. For polyandrous species, such trade-offs may also include traits associated with paternity success, such as larger testes. Conversely, we would not expect this to be the case for monandrous species, where sperm competition is unlikely. We investigated these ideas by evaluating the relationship between investment in sensory structures (antennae, eye), testis, and a putative warning signal (orange hindwing patch) in field-caught males of the monandrous diurnal painted apple moth Teia anartoides (Lepidoptera: Lymantriidae) in southeastern Australia. As predicted for a monandrous species, we found no evidence that male moths with larger sensory structures had reduced investment in testis size. However, contrary to expectation, investment in sensory structures was correlated: males with relatively larger antennae also had relatively larger eyes. Intriguingly, also, the size of male orange hindwing patches was positively correlated with testis size.

The handicap process favors exaggerated, rather than reduced, sexual ornaments.

Why are traits that function as secondary sexual ornaments generally exaggerated in size compared to the naturally selected optimum, and not reduced? Because they deviate from the naturally selected optimum, traits that are reduced in size will handicap their bearer, and could thus provide an honest signal of quality to a potential mate. Thus if secondary sexual ornaments evolve via the handicap process, current theory suggests that reduced ornamentation should be as frequent as exaggerated ornamentation, but this is not the case. To try to explain this discrepancy, we analyze a simple model of the handicap process. Our analysis shows that asymmetries in costs of preference or ornament with regard to exaggeration and reduction cannot fully explain the imbalance. Rather, the bias toward exaggeration can be best explained if either the signaling efficacy or the condition dependence of a trait increases with size. Under these circumstances, evolution always leads to more extreme exaggeration than reduction: although the two should occur just as frequently, exaggerated secondary sexual ornaments are likely to be further removed from the naturally selected optimum than reduced ornaments.

Signaling efficacy drives the evolution of larger sexual ornaments by sexual selection.

Why are there so few small secondary sexual characters? Theoretical models predict that sexual selection should lead to reduction as often as exaggeration, and yet we mainly associate secondary sexual ornaments with exaggerated features such as the peacock's tail. We review the literature on mate choice experiments for evidence of reduced sexual traits. This shows that reduced ornamentation is effectively impossible in certain types of ornamental traits (behavioral, pheromonal, or color-based traits, and morphological ornaments for which the natural selection optimum is no trait), but that there are many examples of morphological traits that would permit reduction. Yet small sexual traits are very rarely seen. We analyze a simple mathematical model of Fisher's runaway process (the null model for sexual selection). Our analysis shows that the imbalance cannot be wholly explained by larger ornaments being less costly than smaller ornaments, nor by preferences for larger ornaments being less costly than preferences for smaller ornaments. Instead, we suggest that asymmetry in signaling efficacy limits runaway to trait exaggeration.

Heterospecific exposure affects the development of secondary sexual traits in male zebra finches (Taeniopygia guttata)

In many animal species, social signals can affect the reproductive physiology and behaviour of conspecifics. In a few species that exhibit vocal learning, exposure to conspecific and sometimes heterospecific sounds can also influence their vocal development. Here we show that heterospecific exposure can affect the development of secondary sexual traits of male zebra finches (Taeniopygia guttata). In a first experiment, we trained young males with a passive playback of domesticated canary (Serinus canaria) song. Song playback enhanced the sexual development of the birds: they started to sing during the presentation of a video clip of a female earlier during development and exhibited secondary sexual plumage ornaments faster than males of the control group kept in silence. Two out of five birds exhibited clear evidence of imitation of canary song. In a second experiment, we raised young male finches with young male canaries in pairs until adulthood. Again, the live contact with a heterospecific companion affected the development of plumage ornaments in finches. We also observed some evidences of vocal convergence, both for calls and song. Moreover, young males of both species could recognize the call of their heterospecific companion when adults. These results suggest that heterospecific exposure can affect both the sexual and the vocal development of the zebra finch and can have long lasting effects.This article is part of a Special Issue entitled: insert SI title.

A transcriptomic investigation of handicap models in sexual selection

Handicap models link the evolution of secondary sexual ornaments to physiological costs and thus provide a mechanistic explanation for signal honesty in sexual selection. Two commonly invoked models, the immunocompetence handicap hypothesis (ICHH) and the oxidative stress handicap hypothesis (OSHH), propose suppression of immunocompetence or increase of oxidative stress by testosterone, but empirical evidence for both models is controversial and based on morphological and physiological assays. Here, we investigated these two models on the gene transcription level using microarrays to quantify the transcriptomic response of red grouse (Lagopus lagopus scoticus) caecal, spleen and liver tissues to experimental manipulation of testosterone levels. We used a geneontology framework to identify genes related to immune function and response to reactive oxygen species and examined how transcription levels changed under experimentally increased testosterone levels in birds with parasites present or absent. Contrary to our expectations, testosterone had virtually no effect on gene transcription in spleen and liver. A small number of genes were significantly differentially regulated in caecum, and while their functions and transcription changes are consistent with the ICHH, we found little support for the OSHH. More genes responded to testosterone in the presence rather than absence of parasites, suggesting that handicap mechanisms may be context dependent and more pronounced in the presence of adverse environmental conditions. These findings illustrate the utility of transcriptomics to investigating handicap models, suggest that classic models may not underlie the handicap mechanism, and indicate that novel emerging models involving different mediators and physiological systems should be examined.

The condition dependence of a secondary sexual trait is stronger under high parasite infection level

Indicator models of sexual selection predict that the expression of sexual ornaments should be condition dependent. This is only partly supported by data, as many studies do not find positive associations between ornaments and condition. The reason for this inconsistency remains poorly understood. It has been hypothesized that environmental context may explain variation in the condition dependence of sexual traits, with stronger relationships between ornaments and condition expected in harsher environments. However, field tests of this idea are scarce. We studied 9 populations of wild red grouse Lagopus lagopus scoticus over 11 years, and compared the relationship between ornamentation and body mass (an index of body condition) in relation to environmental variability. We used the abundance of a key parasite in this system, Trichostrongylus tenuis, as an index of environmental conditions. We found that both ornament expression and body mass negatively correlated with parasite infection at both population and individual levels. More interestingly, we found that the relationship between ornamentation and body mass was stronger in populations with high parasite infection levels. Our findings support the idea that the condition dependence of secondary sexual ornaments varies in relation to environmental context. In sites and years when parasites are abundant, sexual ornaments provide better signals of condition.

Female Barn Swallows Gain Indirect but not Direct Benefits through Social Mate Choice

AbstractFemale mate choice is responsible for the evolution of male secondary sexual ornaments. If male ornamental traits reflect indirect, genetic benefits and/or direct, material benefits to females, choosy females may benefit from their choice, indirectly and/or directly. We examined a breeding population of Japanese barn swallowsHirundo rustica gutturalisto determine whether male tail streamer length reflected indirect and/or direct benefits to females. There was no significant positive relationship between male streamer length and the number of extra‐pair young (EPY) sired, suggesting that male tail streamers are not a signal of indirect benefits (i.e. good genes theory). In addition, we found no evidence that males with longer streamers fed their offspring more frequently or sired more within‐pair young (WPY). The result indicates that male streamer length probably does not act as a signal of direct benefits. Our finding that the length of tail streamers in Japanese barn swallows plays no role in sexual selection is not consistent with studies on European subspecies, but is consistent with studies on North American subspecies where sexual selection on tail streamer is weak. The present study supports the recent suggestion that the pattern of sexual selection on tail streamer length in barn swallows varies geographically. Instead of tail length, males in better condition sired more EPY and WPY. Males in better condition, however, did not feed their nestling more frequently. These results indicate that females gain indirect benefits but not direct benefits, in terms of feeding of young, on choosing social mates.

Plumage brightness and age predict extrapair fertilization success of male tree swallows, Tachycineta bicolor

In socially monogamous passerines, extrapair paternity can increase the variance in male reproductive success. If gaining extrapair fertilizations is linked to specific secondary sexual ornaments, the opportunity for sexual selection is enhanced. Therefore, to understand the evolution of male phenotypic characteristics, it is important to identify traits that predict male extrapair mating success. Tree swallows show among the highest rates of extrapair paternity known to occur in birds, yet it is unclear whether male extrapair mating success is associated with phenotypic traits that honestly advertise individual quality. We compared morphological characteristics and plumage coloration of male tree swallows that sired extrapair offspring with those that sired only within-pair offspring in the same breeding population to identify the characteristics that predict extrapair fertilization success. Males who produced extrapair offspring had brighter plumage, and were more likely to be returning breeders, than males that did not have extrapair young. In paired comparisons, however, there was no difference between extrapair males and the male they cuckolded. These results suggest that female tree swallows may prefer brighter or older individuals as extrapair mates, but also, that older males may invest more energy in pursuing extrapair copulations. Furthermore, since females had extrapair offspring in their nest regardless of their social mate's morphometric or plumage attributes, we suggest that extrapair mating may be a reproductive strategy allowing females to increase the genetic diversity, while maintaining genetic quality, of their offspring.

REGIONAL SEISMIC SONG DIFFERENCES IN SKY ISLAND POPULATIONS OF THE JUMPING SPIDER HABRONATTUS PUGILLIS GRISWOLD (ARANEAE, SALTICIDAE)

Jumping spiders have long been used as model organisms to study visual communication. However, recent studies documenting the presence of intricate multicomponent seismic songs during court- ship displays suggest an important role of seismic communication as well. Given the relatively recent focus on seismic communication, the extent to which seismic songs vary among jumping spider species or even among populations remains poorly understood. Here, we use the extensively studied Habronattus pugillis Griswold 1987 complex to explore putative seismic song diversity among males from isolated populations. H. pugillis populations have been studied extensively because of the tremendous diversifi- cation of male visual secondary sexual ornaments observed among adjacent mountain-top populations in southeastern Arizona (''sky islands''). Here, we aim to explore putative parallel patterns of diversification in seismic courtship songs between different sky island populations. Using laser vibrometry, we examined in detail the songs of three mountaintop populations (Atascosa (AT), Santa Rita (SR), and Santa Catalina (SC)) and observed an extraordinary diversity of songs and song types among these three populations. Large differences were seen in both the temporal and spectral properties of male seismic songs. In addition, we observed differences in song complexity between populations with some populations having ''simple'' songs (1 component) and others having ''complex'' songs (3 components). We also present preliminary data from four additional populations (Galiuro (GA), Huachuca (HU), Mule (MU), and Patagonia (PA)). Results from this study suggest that the diversification of male visual signals observed among populations of H. pugillis finds a counterpart in male seismic songs

Secondary sexual characters and female quality in primates

Honest advertisement models of sexual selec- tion propose that exaggerated secondary sexual ornaments are condition-dependent, and that only individuals with superior disease resistance will be able to express costly ornamentation. Studies of secondary sexual ornamentation and their maintenance by sexual selection tend to focus on males. However, females may also possess showy orna- ments. We investigated whether female ornaments, in the form of sexual swellings, reliably signal female fitness in a semifree-ranging colony of mandrills (Mandrillus sphinx) at the Centre International de Recherches Medi- cales, Franceville (CIRMF), Gabon. We measured swell- ing height and width using photographs of periovulatory females over three mating seasons and compared swelling size with parasitism (using fecal analysis over one annual cycle), immune status (ratio of lymphocytes to neutrophils in blood smears made during captures), and genetic diversity (microsatellite heterozygosity). Swelling size varied by up to 10% between cycles in individual females, giving some support to the hypothesis that size differences may indicate the quality of individual swelling cycles. However, there was no significant difference in swelling size between conceptive and nonconceptive cycles. Mea- sures of swelling size varied more between females than within females across swelling cycles, implying that swelling size was a relatively consistent characteristic of individual females. Swelling size was not significantly related to either general measures of parasitism and immune status, or to the closest available measures to each swelling cycle. Nor was swelling size significantly related to genetic diversity. The healthy, provisioned nature of the colony and problems associated with observational, correlational studies restrict interpretation of our data. However, in combination with previous findings that females of higher reproductive success do not show larger swellings, and that males do not allocate mating effort as a function of swelling size, these results imply that sexual swelling size does not indicate female quality in these semifree-ranging mandrills.