Sexual Dimorphism In Coloration Research Articles

Transcriptome analysis of sexual dimorphism in dorsal down coloration in goslings

BackgroundIn day-old Hungarian white goose goslings, there is a noticeable difference in dorsal down coloration between males and females, with females having darker dorsal plumage and males having lighter plumage. The ability to autosex day-old goslings based on their dorsal down coloration is important for managing them efficiently and planning their nutrition in the poultry industry. The aim of this study was to determine the biological and genetic factors underlying this difference in dorsal down colorationthrough histological analysis, biochemical assays, transcriptomic profiling, and q‒PCR analysis.ResultsTissue analysis and biochemical assays revealed that compared with males, 17-day-old embryos and day-old goslings of female geese exhibited a greater density of melanin-containing feather follicles and a greater melanin concentration in these follicles during development. Both female and male goslings had lower melanin concentrations in their dorsal skin compared to 17-day-old embryos. Transcriptome analysis identified a set of differentially expressed genes (DEGs) (MC1R, TYR, TYRP1, DCT and MITF) associated with melanogenesis pathways that were downregulated or silenced specifically in the dorsal skin of day-old goslings compared to 17-day-old embryos, affecting melanin synthesis in feather follicles. Additionally, two key genes (MC1R and MITF) associated with feather coloration showed differences between males and females, with females having higher expression levels correlated with increased melanin synthesis and darker plumage.ConclusionThe expression of multiple melanogenesis genes determines melanin synthesis in goose feather follicles. The dorsal down coloration of day-old Hungarian white goose goslings shows sexual dimorphism, likely due to differences in the expression of the MC1R and MITF genes between males and females. These results could help us better understand why male and female goslings exhibit different plumage patterns.

Possible Batesian mimicry to sexually different models in the tussock moth Numenes albofascia with a great sexual color dimorphism

AbstractMimicry with warning colors includes Batesian and Müllerian mimicries. If we divide mimicry by sex, there are theoretically four types of mimicry: unimodal, female‐limited, male‐limited and dual mimicry. The latter three cases cause sexual dimorphism in body color and marking pattern but are rarely reported. In this study, we show that the tussock moth Numenes albofascia is possibly a dual mimic. The wing color and marking pattern of male and female N. albofascia are completely different, with the male's pattern resembling that of the smoky moth Pidorus atratus, while the female pattern resembles that of the tiger moth Arctia caja. Body size also differs greatly between the sexes of N. albofascia, matching the mimicry model species of each sex. These moths are distributed sympatrically in Japan, and their adult seasons overlap with each other. According to lizard feeding experiments, N. albofascia is palatable, while both male and female model species are unpalatable. Actograms in the laboratory and the light trapping in the field suggest that females of N. albofascia fly actively from sunset to midnight, while males fly during the twilight period around dawn. Therefore, male and female N. albofascia might be Batesian mimics of diurnally active P. atratus and nocturnally active A. caja, respectively, and the great sexual dimorphism of this moth could be caused by dual mimicry.

Does cryptic dichromatism exist in the Saffron Finch (Sicalis flaveola)? Colorimetric variables and the avian visual model

Sexual dichromatism, a particular type of sexual dimorphism, occurs in several species and has been associated with sexual selection. In some cases, the differences are so small that they are imperceptible to humans, but possibly detected by birds. The objective measurement of color with spectrophotometers and detailed analyses according to the perception ability of the avian eye have revealed that some species that were once considered to be monochromatic, are in fact dichromatic and able to perceive these differences. In the tropics, the Saffron Finch (Sicalis flaveola) does not present marked sexual dimorphism in coloration, which makes studies in behavioral ecology, natural history and population dynamics difficult. To assess whether there is dichromatism in the species, the reflectance (between 300 and 700 ​nm) of ten body regions was measured in 196 wild adults in Cali-Colombia. Sex was determined using the CHD1 gene on the sex chromosomes. Reflectance spectra were analyzed using: colorimetric variables and the avian visual model. We found that reflectance shows a bimodal curve in all body regions, except the crown. Males presented higher reflectance at long wavelengths, while for females this occurred in ultraviolet wavelengths. For the visual model, we found that there are significant intrasexual differences; however only in crown coloration is there a possible perceived difference between sexes. We conclude that in the Saffron Finch there are color differences between the sexes in all regions considering the physical phenomenon (reflectance), but in general, when evaluating color perception (avian visual model), there are no differences between the sexes in most of the body regions. The intrasexual differences are significant, indicating the possibility of these being signals that influence social interactions in the species.

The evolution of sex similarities in social signals: Climatic seasonality is associated with lower sexual dimorphism and greater elaboration of female and male signals in antbirds (Thamnophilidae).

Selection on signals that mediate social competition varies with resource availability. Climate regulates resource availability, which may affect the strength of competition and selection on signals. Traditionally, this meant that more seasonal, colder, or dryer-overall harsher-environments should favor the elaboration of male signals under stronger male-male competition, increasing sexual dimorphism. However, females also use signals to compete; thus, harsher environments could strengthen competition and favor elaboration of signals in both sexes, decreasing sexual dimorphism. Alternatively, harsher environments could decrease sexual dimorphism due to scarcer resources to invest in signal elaboration in both sexes. We evaluated these contrasting hypotheses in antbirds, a family of Neotropical passerines that varies in female and male signals and occurs across diverse climatic regimes. We tested the association of sexual dimorphism of plumage coloration and songs with temperature, precipitation, and their seasonality. We found that greater seasonality is associated with lower sexual dimorphism in plumage coloration and greater elaboration of visual signals in both sexes, but not acoustic signals. Our results suggest that greater seasonality may be associated with convergent elaboration of female and male visual signals, highlighting the role of signals of both sexes in the evolution of sexual dimorphism.

Why Are Snowy Owls White and Why Have They Evolved Distinct Sexual Color Dimorphism? A Review of Questions and Hypotheses

Abstract Many Arctic animals are white throughout their life, or turn white seasonally, with no distinct sexual color dimorphism. Common knowledge assumes these animals are white for camouflage in snow-covered landscapes. Presumably, this camouflage adaptation provides concealment from predators, and conversely, concealment for predation. This adaptation appears to be independent of sex. These theories seem logical; however, natural selection could also favor white coloration for other reasons. The Snowy Owl (Bubo scandiacus) is unusual because in addition to being white, it also shows sexual color dimorphism. Both sexes exhibit delayed plumage maturation. As yearlings, males and females are heavily marked with brown bars and spots on a white-based plumage. Males and females are believed to become whiter as they age. Males become almost pure white, while females retain brown bars and spots. As adults, males and females are distinctly sexually dimorphic in coloration and plumage patterning. These traits are not consistent with most other species of white Arctic animals, or most other species of owls. Snowy Owls are thought to share a common ancestor with the genus Bubo, especially Great Horned Owls (Bubo virginianus) from North America. This separation took place approximately four million years ago. If true, the evolution of white-based plumage in Snowy Owls was probably the result of natural selection favoring camouflage color in snow-covered environments, as Snowy Owls evolved and expanded into Arctic habitat. However, natural selection in concert or compromise with sexual selection, likely drove the evolution of sexual color dimorphism, and delayed plumage maturation, as a result of a snow-free tundra, and 24 hr of daylight during the breeding season. Natural selection appears to have independently favored different male and female plumage coloration and patterning. I propose that adult females evolved white plumage, interrupted with brown bars and spots, predominately for camouflage. Likewise, I propose that adult males evolved white plumage for at least two social signaling strategies: (1) to advertise their relative age, social status, and genotypic quality to females, and (2) to advertise relative age and social status to other males.

Color Variation, Tail Banding, and Sexual Dichromatism in Washington Populations of Northern Pacific Rattlesnakes, Crotalus oreganus

Northern Pacific Rattlesnakes (Crotalus oreganus) are ambush-hunting predators that rely on crypsis to forage and to avoid encounters with predators, yet little is known about color variation in this ubiquitous rattlesnake species. This study addressed how coloration and contrast in tail banding in C. oreganus vary among habitat types in Washington State. We also explored whether C. oreganus exhibit sexual dimorphism in coloration or tail band contrast (sexual dichromatism). We sampled 127 rattlesnakes from seven different populations across northern and central Washington state during spring emergence from overwintering hibernacula in 2017 and 2018. We characterized snake coloration as red/blue color ratios from standardized photographs, and used GIS supervised classification schemes of satellite imagery to characterize habitat. We used generalized linear models to assess relationships among snake color and tail bands, habitat, and sex. We found that coloration (red/blue color ratios) in C. oreganus varied greatly across the landscape, both within and among populations, likely a reflection of their variable and heterogenous shrub-steppe and forest ecotone habitats. In 20% of 21 pairwise comparisons, populations differed in body color. Rattlesnake coloration was not associated with habitat (amount of forested land within 0.5 km of the snake den), but male and female rattlesnakes showed different associations between color and percent forested habitat. Male rattlesnakes did not differ in body coloration from females, but males showed greater contrast than females in the black and white banding present on the tail. We discuss several, nonmutually exclusive, hypotheses for sexual dichromatism in tail band contrast, including the possibility that tail banding constitutes warning coloration in rattlesnakes. Our results suggest that sexual dichromatism, and the role of tail banding in rattlesnake ecology, are topics worthy of further investigation.

Simple and complex, sexually dimorphic retinal mosaic of fritillary butterflies.

Butterflies have variable sets of spectral photoreceptors that underlie colour vision. The photoreceptor organization may be optimized for the detection of body coloration. Fritillaries (Argynnini) are nymphalid butterflies exhibiting varying degrees of sexual dimorphism in wing coloration. In two sister species, the females have orange (Argynnis paphia) and dark wings (Argynnis sagana), respectively, while the males of both species have orange wings with large patches of pheromone-producing androconia. In spite of the differences in female coloration, the eyes of both species exhibit an identical sexual dimorphism. The female eyeshine is uniform yellow, while the males have a complex retinal mosaic with yellow and red-reflecting ommatidia. We found the basic set of ultraviolet-, blue- and green-peaking photoreceptors in both sexes. Males additionally have three more photoreceptor classes, peaking in green, yellow and red, respectively. The latter is the basal R9, indirectly measured through hyperpolarizations in the green-peaking R1-2. In many nymphalid tribes, including the closely related Heliconiini, the retinal mosaic is complex in both sexes. We hypothesize that the simple mosaic of female Argynnini is a secondary reduction, possibly driven by the use of olfaction for intraspecific recognition, whereas vision remains the primary sense for the task in the males. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.

A review of Fukomys ochraceocinereus, an enigmatic mole-rat from Central Africa (Rodentia: Bathyergidae)

Although the biology of common mole-rats of the genus Fukomys has been intensively studied over the last three decades, some lineages of this speciose group of subterranean rodents remain virtually unknown to science. One of these poorly studied species is the Central African mole-rat, Fukomys ochraceocinereus (von Heuglin, 1864), which occurs in the tropical savannahs and woodlands of the northern Democratic Republic of the Congo, South Sudan, Uganda, and the Central African Republic. Here I summarize the taxonomic history and available data on the distribution and morphology of this enigmatic mole-rat, adding selected observations from museum collections. F. ochraceocinereus is a comparatively large representative of its genus that appears to express little sexual dimorphism and notable variation in pelage color. Its genetics and karyology remain severely understudied. The review highlights both apparent peculiarities of the species as well as research gaps which should be addressed by future studies on F. ochraeocinereus and its relatives, including taxonomic revisions.

Two sexes respond equally to food restriction in a sexually dimorphic but not body mass dimorphic jumping spider.

Natural selection favors animals that evolve developmental and behavioral responses that buffer the negative effects of food restrictions. These buffering responses vary both between species and within species. Many studies have shown sex‐specific responses to environmental changes, usually in species with sexual size dimorphism (SSD), less found in species with weak or no SSD, which suggests that sizes of different sexes are experiencing different selections. However, previous studies usually investigated development and behavior separately, and the balanced situation where males and females of sexually dimorphic species respond in the same way to food restriction remains little known. Here, we investigated this in Phintelloides versicolor (Salticidae) that presents sexual dimorphism in color and shape but weak SSD. We examined whether food restriction induced the same responses in males and females in development duration, adult body size and weight, daily time allocated to foraging, and hunting. We found food restriction induced similar responses in both sexes: both exhibited longer development duration, smaller adult body size and weight, higher probability of staying outside nests and noticing prey immediately, and higher hunting success. However, there were sexual differences regardless of food condition: females showed faster development, smaller adult body size, higher probability of staying outside of nests, and higher hunting success. These indicated the differential selection on male and female sizes of P. versicolor could be under a balanced situation, where males and females show equal developmental and behavioral plasticity to environmental constraints.

Sex Differences in Anti-Predatory Behaviour in Lined Seedeaters Sporophila lineola

Altricial birds face the challenge of defending their offspring against potential threats in a fixed location: their nest. In species with biparental care, both parents have an equal interest in defending their nest, although the sexes may differ in their investment in anti-predatory behaviours. We conducted a field experiment to investigate sex-asymmetry in anti-predatory behaviours in a breeding population of Lined Seedeaters Sporophila lineola, a small passerine that exhibits sexual dimorphism in adult plumage colour, in south-eastern Brazil. In Lined Seedeaters females are known to be solely responsible for nest building and incubation. Males help to feed the nestlings and are expected to assume the main role in performing anti-predatory behaviours. We presented stuffed models of nest predators (toucans Ramphastidae) and non-predators (pigeons Columbidae) at active nests and measured the number of alarm calls per minute, number of visits during the trial and latency to resume nest visits after the trial. Our results show that birds emitted alarm calls at higher rates when facing a predator than a control stimulus. Moreover, males generally emitted more alarm calls than females, irrespective of the treatment. Both parents did not visit the nest during the predator trials and they took longer to return to the nest after the model had been concealed than during the control trials. Although males seem to take the main role when it comes to responding to intruders (predator and non-predator), further studies, testing a bigger array of predatory stimuli, are needed to better test and understand sex asymmetry in risk-taking behaviours.

Redescription of the Rio skate Rioraja agassizii (Rajiformes: Arhynchobatidae) with notes on internal anatomy and intraspecific variation

Abstract Rioraja agassizii belongs to the monotypic genus Rioraja and differs from the other Riorajini species of the genus Atlantoraja by the shape of anterior nasal flap, squamation, clasper skeleton, body measurements and color pattern. Although R. agassizii is a well-known species, commonly captured in inshore waters of the southwestern Atlantic, its external morphology and internal anatomy have never been fully described and little is known on intraspecific variation within the species. Juvenile and adult, male and female specimens were examined, measured and dissected. Herein, we redescribe the species and present detailed descriptions and illustrations of external morphology, neurocranium, jaws, hyoid and gill arches, and pelvic fin and girdle. Additionally, notes on sexual dimorphism and ontogenetic differences in coloration, body and cranial measurements, and dermal denticles are provided.

Reproduction in Sceloporus licki (Reptilia: Phrynosomatidae) in the Cape Region, Baja California Sur

AbstractSceloporus licki, an endemic lizard of the Cape Region from Baja California Sur, Mexico, shows evident sexual dimorphism in coloration and in snout‐vent length between males and females. The gonadal analysis showed that both sexes have a synchronous spring–summer reproductive cycle. The males show maximum gonadal activity from March to July; in August, they show a rapid regression, and in September, quiescence is evident only in some males while in others recrudescence has already begun. Finally, in October and November, the process of recrudescence is obvious. The females showed some asynchrony, but for most, vitellogenesis occurred from April to June and eggs in the oviduct were evident in May, June and August. Oviposition occurs in July and August and by September or October there is no more gonadal activity in the ovaries. The clutch size was 5 ± 0.2 eggs, and hatchlings appeared in May–June and September suggesting that possibly two clutches are produced per breeding season. Reproductive activity in both sexes was like that of other lizards from temperate environments. However, the long period of gonadal recrudescence in both sexes (6 months) and rapid regression and quiescence in males of the studied population suggest plasticity in gonadal activity.

Subtle sexual plumage color dimorphism and size dimorphism in a South American colonial breeder, the Monk Parakeet (Myiopsitta monachus)

BackgroundParrots (Psittacidae Family) are one of the most colorful groups of birds in the world, their colors produced both structurally and via unusual pigments (psittacofulvins). Most species are considered to be monogamous, and many have been viewed historically as sexually monomorphic and monochromatic. However, studies using morphometric analysis and spectrophotometric techniques have revealed sexual size dimorphism and also sexual plumage color dimorphism among some species. The Monk Parakeet (Myiopsitta monachus), a native parrot of South America, is an interesting species for the study of plumage coloration and size since it is considered sexually monochromatic and monomorphic. Furthermore, recent studies show that the Monk Parakeet has extra-bond paternity behavior and even breeding trios, which suggests that sexual selection may play an important role in this species, and that it might have sexually dimorphic plumage (albeit imperceptible by humans) and be dimorphic in size.MethodsFor the determination of plumage color we used spectrophotometry in the range of avian vision (300‒700 nm) and performed a morphological analysis.ResultsOur spectrophotometric results indicate that the Monk Parakeet shows subtle sexual plumage color dimorphism in three (crown, nape and wing) out of twelve body regions. Similarly, our morphometric analysis showed that there are subtle sex differences in body size (bill and weight).ConclusionsAlthough the Monk Parakeet shows extra-bond paternity and breeding trio behaviors which could increase sexual dimorphism, these behaviors occur among highly related individuals; perhaps the high rate of inbreeding is responsible for the attenuation of sexual plumage color dimorphism and sex differences in body size observed.

Habitat light sets the boundaries for the rapid evolution of cichlid fish vision, while sexual selection can tune it within those limits.

Cichlid fishes' famous diversity in body coloration is accompanied by a highly diverse and complex visual system. Although cichlids possess an unusually high number of seven cone opsin genes, they express only a subset of these during their ontogeny, accounting for their astonishing interspecific variation in visual sensitivities. Much of this diversity is thought to have been shaped by natural selection as cichlids inhabit a variety of habitats with distinct light environments. Also, sexual selection might have contributed to the observed visual diversity, and sexual dimorphism in coloration potentially co-evolved with sexual dimorphism in opsin expression. We investigated sex-specific opsin expression of several cichlids from Africa and the Neotropics and collected and integrated data sets on sex-specific body coloration, species-specific visual sensitivities, lens transmission and habitat light properties for some of them. We comparatively analysed this wide range of molecular and ecological data, illustrating how integrative approaches can address specific questions on the factors and mechanisms driving diversification, and the evolution of cichlid vision in particular. We found that both sexes expressed opsins at the same levels-even in sexually dimorphic cichlid species-which argues against coevolution of sexual dichromatism and differences in sex-specific visual sensitivity. Rather, a combination of environmental light properties and body coloration shaped the diversity in spectral sensitivities among cichlids. We conclude that although cichlids are particularly colourful and diverse and often sexually dimorphic, it would appear that natural rather than sexual selection is a more powerful force driving visual diversity in this hyperdiverse lineage.

Colour dimorphism in labrid fishes as an adaptation to life on coral reefs.

Conspicuous coloration displayed by animals that express sexual colour dimorphism is generally explained as an adaptation to sexual selection, yet the interactions and relative effects of selective forces influencing colour dimorphism are largely unknown. Qualitatively, colour dimorphism appears more pronounced in marine fishes that live on coral reefs where traits associated with strong sexual selection are purportedly more common. Using phylogenetic comparative analysis, we show that wrasses and parrotfishes exclusive to coral reefs are the most colour dimorphic, but surprisingly, the effect of habitat is not influenced by traits associated with strong sexual selection. Rather, habitat-specific selective forces, including clear water and structural refuge, promote the evolution of pronounced colour dimorphism that manifests colours less likely to be displayed in other habitats. Our results demonstrate that environmental context ultimately determines the evolution of conspicuous coloration in colour-dimorphic labrid fishes, despite other influential selective forces.

Conjoint Analysis of SMRT- and Illumina-Based RNA-Sequencing Data of Fenneropenaeus chinensis Provides Insight Into Sex-Biased Expression Genes Involved in Sexual Dimorphism.

Fenneropenaeus chinensis (F. chinensis) is one of the most commercially important cultured shrimps in China. The adult F. chinensis exhibit sexual dimorphism in growth and body color. In this research, we profiled the whole transcriptome of F. chinensis by using single molecule real-time-based full-length transcriptome sequencing. We further performed Illumina-based short reads RNA-seq on muscle and gonad of two sexes to detect the sex-biased expression genes. In muscle, we observed significantly more female-biased transcripts. With the differentially expressed transcripts (DETs) in muscle, some pathways related to the energy metabolism were enriched, which may be responsible for the difference of growth. We also digged out a pathway named porphyrin and chlorophyll metabolism. It was speculated to relevant to the difference of body color between the two sexes of shrimp. Interestingly, almost all DETs in these pathways were female-biased expression in muscle, which could explain the phenomenon of better growth performance and darker body color in female. In gonad, several pathways involved in reproduction were enriched. For instance, some female-biased DETs participated in the arachidonic acid metabolism, which was reported crucial in female reproduction. In conclusion, our studies identified abundant sex-biased expression transcripts and important pathways involved in sexual dimorphism by using the RNA-seq method. It provided a basis for future researches on the sexual dimorphism of F. chinensis.

When we don’t know what we know – Sex and skin color

In 3 experiments, we examine how the abstract category of gender, grounded by the lightness-darkness dimension, derived from the universal sexual dimorphism of skin color, is represented and how such representations lead to visual accentuation processes, i.e. polarization of differences between male and female faces. In the first two experiments, we show that irrespective of whether grayscale male and female faces are presented sequentially or jointly, female faces are judged to be lighter than male faces when participants are asked to indicate the level of lightness of the faces. This pattern was found for the majority of participants who explicitly stated that men and women do not differ in skin color. The third experiment was designed to examine the cognitive consequences of what people implicitly ‘know’ with a perceptual accentuation study. Participants were provided with male and female faces of equal skin color. Subsequently, in a memory recall task, they were asked to select, from a row of several faces varying in skin color, the original face. They chose, as predicted, lighter versions of faces for females compared to the male faces. This research reveals that the evolutionarily based sexual dimorphism in skin color implicitly grounds gender categories and shapes implicit visual accentuation processes.

The brightness dimension as a marker of gender across cultures and age

Universally, female skin color is lighter than male skin color, irrespective of geographical location. This difference is a distinctive and universal adaptive pattern that emerges after puberty. We address whether this sexual dimorphism is cognitively and culturally represented to ground gender. To this end, we examine a non-Western, non-industrialized population, namely the Wichí (Salta, Argentina) and a Western industrialized population (Spain). The two cultural populations included both adults and prepubescent children. Across two experiments, we utilized a novel task with children and adults who had to make a choice for a female (male) target person between two identical objects that differed only in terms of their brightness. The results in both experiments revealed that the children from the two cultural communities choose a lighter colored object for the female target and a darker version of the same object for the male target. This pattern held across cultures irrespective of the age of participants, except for the male Wichí participants. We discuss how sexual dimorphism in skin color contributes to a universal grounding of the gender category, and advance possible explanations as to why Wichi males did not consistently link gender and brightness.

Sexual Dichromatism Drives Diversification within a Major Radiation of African Amphibians.

Theory predicts that sexually dimorphic traits under strong sexual selection, particularly those involved with intersexual signaling, can accelerate speciation and produce bursts of diversification. Sexual dichromatism (sexual dimorphism in color) is widely used as a proxy for sexual selection and is associated with rapid diversification in several animal groups, yet studies using phylogenetic comparative methods to explicitly test for an association between sexual dichromatism and diversification have produced conflicting results. Sexual dichromatism is rare in frogs, but it is both striking and prevalent in African reed frogs, a major component of the diverse frog radiation termed Afrobatrachia. In contrast to most other vertebrates, reed frogs display female-biased dichromatism in which females undergo color transformation, often resulting in more ornate coloration in females than in males. We produce a robust phylogeny of Afrobatrachia to investigate the evolutionary origins of sexual dichromatism in this radiation and examine whether the presence of dichromatism is associated with increased rates of net diversification. We find that sexual dichromatism evolved once within hyperoliids and was followed by numerous independent reversals to monochromatism. We detect significant diversification rate heterogeneity in Afrobatrachia and find that sexually dichromatic lineages have double the average net diversification rate of monochromatic lineages. By conducting trait simulations on our empirical phylogeny, we demonstrate that our inference of trait-dependent diversification is robust. Although sexual dichromatism in hyperoliid frogs is linked to their rapid diversification and supports macroevolutionary predictions of speciation by sexual selection, the function of dichromatism in reed frogs remains unclear. We propose that reed frogs are a compelling system for studying the roles of natural and sexual selection on the evolution of sexual dichromatism across micro- and macroevolutionary timescales.

Diurnal colour change in a sexually dimorphic trait in the Andean lizard Anolis heterodermus (Squamata: Dactyloidae)

ABSTRACTSexual dimorphism in body size, shape and colour is widespread in lizards as well as in other taxa. In the context of sexual selection, these sex differences are commonly manifested as exaggerated male traits, which are selected by females to assess the quality of males. However, differences in sex by environment interactions can also lead to sexual dimorphism. The genus of Anolis lizards is particularly well known for sharp sexual dimorphism in dewlap colour and size; however, this is not the case in all anole species. Using digital image analyses, I assessed the existence of sexual differences in the diurnal change in colour and size of a conspicuous patch on the tail of the lizard Anolis heterodermus Duméril 1851. Results showed that the tail patch of both males and females changed in colour, but not size, from red to blue throughout the day in a similar fashion. This process took almost half a day to complete and occurred in the absence of conspecifics, suggesting that the change itself may not have an active role in social communication. However, the colour patches of males were consistently larger. The cause of the substantial variation in colour and size of the tail patch of A. heterodermus is still unknown and deserves more research. This study highlights the importance of continuous wildlife observations to identify life history traits that may be important in animal behaviour but are challenging to observe in nature.