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Complexity, defined as the number of parts and their degree of differentiation, is a poorly explored aspect of macroevolutionary dynamics. The maximum anatomical complexity of organisms has undoubtedly increased through evolutionary time. However, it is unclear whether this increase is a purely diffusive process or whether it is at least partly driven, occurring in parallel in most or many lineages and with increases in the minima as well as the means. Highly differentiated and serially repeated structures, such as vertebrae, are useful systems with which to investigate these patterns. We focus on the serial differentiation of the vertebral column in 1,136 extant mammal species, using two indices that quantify complexity as the numerical richness and proportional distribution of vertebrae across presacral regions and a third expressing the ratio between thoracic and lumbar vertebrae. We address three questions. First, we ask whether the distribution of complexity values in major mammal groups is similar or whether clades have specific signatures associated with their ecology. Second, we ask whether changes in complexity throughout the phylogeny are biased towards increases and whether there is evidence of driven trends. Third, we ask whether evolutionary shifts in complexity depart from a uniform Brownian motion model. Vertebral counts, but not complexity indices, differ significantly between major groups and exhibit greater within-group variation than recognized hitherto. We find strong evidence of a trend towards increasing complexity, where higher values propagate further increases in descendant lineages. Several increases are inferred to have coincided with major ecological or environmental shifts. We find support for multiple-rate models of evolution for all complexity metrics, suggesting that increases in complexity occurred in stepwise shifts, with evidence for widespread episodes of recent rapid divergence. Different subclades evolve more complex vertebral columns in different configurations and probably under different selective pressures and constraints, with widespread convergence on the same formulae. Further work should therefore focus on the ecological relevance of differences in complexity and a more detailed understanding of historical patterns.

Intensive hunting activities such as commercial fishing and trophy hunting can have profound influences on natural populations. However, less intensive recreational hunting can also have subtle effects on animal behaviour, habitat use and movement, with implications for population persistence. Lekking species such as the black grouse (Lyrurus tetrix) may be especially prone to hunting as leks are temporally and spatially predictable, making them easy targets. Furthermore, inbreeding in black grouse is mainly avoided through female-biased dispersal, so any disruptions to dispersal caused by hunting could lead to changes in gene flow, increasing the risk of inbreeding. We therefore investigated the impact of hunting on genetic diversity, inbreeding and dispersal on a metapopulation of black grouse in Central Finland. We genotyped 1065 adult males and 813 adult females from twelve lekking sites (six hunted, six unhunted) and 200 unrelated chicks from seven sites (two hunted, five unhunted) at up to thirteen microsatellite loci. Our initial confirmatory analysis of sex-specific fine-scale population structure revealed little genetic structure in the metapopulation. Levels of inbreeding did not differ significantly between hunted and unhunted sites in neither adults nor chicks. However, immigration rates into hunted sites were significantly higher among adults compared to immigration into unhunted sites. We conclude that the influx of migrants into hunted sites may compensate for the loss of harvested individuals, thereby increasing gene flow and mitigating inbreeding. Given the absence of any obvious barriers to gene flow in Central Finland, a spatially heterogeneous matrix of hunted and unhunted regions may be crucial to ensure sustainable harvests into the future.

Accelerating rates of biodiversity loss underscore the need to understand how species achieve resilience—the ability to resist and recover from a/biotic disturbances. Yet, the factors determining the resilience of species remain poorly understood, due to disagreements on its definition and the lack of large-scale analyses. Here, we investigate how the life history of 910 natural populations of animals and plants predicts their intrinsic ability to be resilient. We show that demographic resilience can be achieved through different combinations of compensation, resistance and recovery after a disturbance. We demonstrate that these resilience components are highly correlated with life history traits related to the species’ pace of life and reproductive strategy. Species with longer generation times require longer recovery times post-disturbance, whilst those with greater reproductive capacity have greater resistance and compensation. Our findings highlight the key role of life history traits to understand species resilience, improving our ability to predict how natural populations cope with disturbance regimes.

Frogs exhibit complex anatomical features of the pelvis, limbs and spine, long assumed to represent specialisations for jumping. Yet frogs employ a wide range of locomotor modes, with several taxa featuring primary locomotor modes other than jumping. Using a combination of techniques (CT imaging and 3D visualization, morphometrics, phylogenetic mapping), this study aims to determine the link between skeletal anatomy and locomotor style, habitat type and phylogenetic history, shedding new light on how functional demands impact morphology. Body and limb measurements for 164 taxa from all the recognised anuran families are extracted from digitally segmented CT scans of whole frog skeletons and analysed using various statistical techniques. We find that the expansion of the sacral diapophyses is the most important variable for predicting locomotor mode, which was more closely correlated with frog morphology than either habitat type or phylogenetic relationships. Predictive analyses suggest that skeletal morphology is a useful indicator of jumping but less so for other locomotor modes, suggesting that there is a wide range of anatomical solutions to performing locomotor styles such as swimming, burrowing or walking.

I present a Bayesian phylogenetic predictive modelling (PPM) framework that allows the prediction of muscle parameters (physiological cross-sectional area, APhys) in extinct archosaurs from skull width (WSk) and phylogeny. This approach is robust to phylogenetic uncertainty and highly versatile given its ability to base predictions on simple, readily available predictor variables. The PPM presented here has high prediction accuracy (up to 95%), with downstream biomechanical modelling yielding bite force estimates that are in line with previous estimates based on muscle parameters from reconstructed muscles. This approach does not replace muscle reconstructions but one that provides a powerful means to predict APhys from skull geometry and phylogeny to the same level of accuracy as that measured from reconstructed muscles in species for which soft tissue data are unavailable or difficult to obtain.

Aim: Body size explains most variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures which often promote its evolution in sex-specific directions, leading to sexual size dimorphism (SSD). Multiple hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasise (i) the mate competition benefits to larger male size (sexual selection), (ii) the benefits of larger female size for fecundity (fecundity selection), (iii) the simultaneous benefits of niche divergence for males and females to reduce inter-sexual competition for ecological resources (natural selection), and (iv) the underlying impact of geographic variation in climatic pressures expected to shape large-scale patterns of SSD in synergy with the above selection pressures (e.g., intensification of fecundity selection as breeding seasons shorten). Based on a novel, global-scale amphibian dataset, we address the shortage of large-scale, integrative tests of these four hypotheses. Location: Global. Time period: Extant. Major taxa studied: Class Amphibia. Methods: Using a >3,500 species dataset spanning body size, ecological, life history, geographic and climatic data, we performed phylogenetic linear models to address the sexual, fecundity, ecological and climatic hypotheses of SSD. Results: SSD evolution is discordant between anurans and salamanders. Anuran SSD is shaped by climate – male-biased SSD increases with temperature seasonality – and by nesting site. In salamanders, SSD converges across species that occupy the same microhabitat types (‘ecodimorphs’), while reproductive or climatic pressures have no effects on their SSD. These contrasts are associated with latitudinal gradients of SSD in anurans, but not in salamanders. Main conclusions: Amphibian SSD is driven by ecological and climatic pressures, while no roles for sexual or fecundity selection were detected. We show that macroevolutionary processes determined by different forms of selection lead to latitudinal patterns of trait diversity, and the lack of them.

As primatologists we take photographs and videos of our study animals, both in the wild and in captivity (zoos and rescue/rehabilitation centres). We use these images across social media (personal and public accounts), on websites, and give them to TV and film crews. We use these images to promote our work and share our findings with colleagues and the general public. We also participate in films where we are often close to primates and some of us work in countries where primates are routinely kept and traded as pets. In January 2021, after extensive feedback and review from all IUCN SSC Primate Specialist Group members, we as members of the IUCN Primate Specialist Group Section for Human-Primate Interactions published the Best Practice Guidelines for Responsible Images of Non-Human Primates online https://human-primate-interactions.org/resources/. Here, we remind readers of the purpose of the guidelines, and reiterate our call to primatologists to play a key role in delivering suitable messages about primates.

Bees provide a good model to investigate the evolution of lateralization. So far, most studies focused on olfactory learning and memories in tethered bees. This study investigated possible behavioural biases in free-flying buff-tailed bumblebees (Bombus terrestris) by analysing their turning decisions in a T-maze. Bees of various size were trained to associate a syrup reward with a blue target placed at the centre of the T-maze. The bees were then tested over 16 trials by presenting them with blue targets at the end of the maze’s arms. The maze was rotated 180° after the first 8 trials to control for environmental factors. The number of turnings to the left and right arms were analysed. The bees sampled exhibited a population-level rightward turning bias. As bumblebees vary significantly in size with large bees being better learners than smaller ones, we measured the thorax width to identify a possible relationship between size and bias. No significant correlation was identified. This study shows that bees present lateralization in a visuo-motor task that mimics their foraging behaviour, indicating a possible specialization of the right side of the nervous system in routine tasks.

1. Wild animals are used in scientific research in a wide variety of contexts both in situ and ex situ. Guidelines for best practice, where they exist, are not always clearly linked to animal welfare and may instead have their origins in practicality. This is complicated by a lack of clarity about indicators of welfare for wild animals, and to what extent a researcher should intervene in cases of compromised welfare. 2. This Primer highlights and discusses the broad topic of wild animal welfare and the ethics of using wild animals in scientific research, both in the wild and in controlled conditions. Throughout, we discuss issues associated with the capture, handling, housing and experimental approaches for species occupying varied habitats, in both vertebrates and invertebrates (principally insects, crustaceans and molluscs). 3. We highlight where data on the impacts of wild animal research are lacking and provide suggestive guidance to help direct, prepare and mitigate potential welfare issues, including the consideration of end-points and the ethical framework around euthanasia. 4. We conclude with a series of recommendations for researchers to implement from the design stage of any study that uses animals, right through to publication, and discuss the role of journals in promoting better reporting of wild animal studies, ultimately to the benefit of wild animal welfare.

Carotenoid-based traits commonly act as condition-dependent signals of quality to both males and females. Such colors are typically quantified using summary metrics (e.g., redness) derived by partitioning measured reflectance spectra into blocks. However, perceived coloration is a product of the whole spectrum. Recently, new methods have quantified a range of environmental factors and their impact on reflection data at narrow wavebands across the whole spectrum. Using this approach, we modeled the reflectance of red integumentary eye combs displayed by male black grouse (Lyrurus tetrix) as a function of ornament size and variables related to male quality. We investigated the strength and direction of effect sizes of variables at each waveband. The strongest effect on the spectra came from eye comb size, with a negative effect in the red part of the spectrum and a positive effect in ultraviolet reflectance. Plasma carotenoid concentration and body mass were also related to reflectance variance in differing directions across the entire spectra. Comparisons of yearlings and adults showed that the effects were similar but stronger on adult reflectance spectra. These findings suggest that reflectance in different parts of the spectrum is indicative of differing components of quality. This method also allows a more accurate understanding of how biologically relevant variables may interact to produce perceived coloration and multicomponent signals and where the strongest biological effects are found.

The differential specialization of each side of the brain facilitates the parallel processing of information and has been documented in a wide range of animals. Animals that are more lateralized as indicated by consistent preferential limb use are commonly reported to exhibit superior cognitive ability as well as other behavioural advantages. We assayed the lateralization of 135 young pheasants (Phasianus colchicus), indicated by their footedness in a spontaneous stepping task, and related this measure to individual performance in either 3 assays of visual or spatial learning and memory. We found no evidence that pronounced footedness enhances cognitive ability in any of the tasks. We also found no evidence that an intermediate footedness relates to better cognitive performance. This lack of relationship is surprising because previous work revealed that pheasants have a slight population bias towards right footedness, and when released into the wild, individuals with higher degrees of footedness were more likely to die. One explanation for why extreme lateralization is constrained was that it led to poorer cognitive performance, or that optimal cognitive performance was associated with some intermediate level of lateralization. This stabilizing selection could explain the pattern of moderate lateralization that is seen in most non-human species that have been studied. However, we found no evidence in this study to support this explanation. Electronic supplementary material The online version of this article (10.3758/s13420-019-00402-8) contains supplementary material, which is available to authorized users.

Despite the increasing importance of molecular sequence data, morphology still makes an important contribution to resolving the phylogeny of many groups, and is the only source of data for most fossils. Most systematists sample morphological characters as broadly as possible on the principle of total evidence. However, it is not uncommon for sampling to be focused on particular aspects of anatomy, either because characters therein are believed to be more informative, or because preservation biases restrict what is available. Empirically, the optimal trees from partitions of morphological data sets often represent significantly different hypotheses of relationships. Previous work on hard-part versus soft-part characters across animal phyla revealed significant differences in about a half of sampled studies. Similarly, studies of the craniodental versus postcranial characters of vertebrates revealed significantly different trees in about one-third of cases, with the highest rates observed in non-avian dinosaurs. We test whether this is a generality here with a much larger sample of 81 published data matrices across all major dinosaur groups. Using the incongruence length difference test and two variants of the incongruence relationship difference test, we found significant incongruence in about 50% of cases. Incongruence is not uniformly distributed across major dinosaur clades, being highest (63%) in Theropoda and lowest (25%) in Thyreophora. As in previous studies, our partition tests show some sensitivity to matrix dimensions and the amount and distribution of missing entries. Levels of homoplasy and retained synapomorphy are similar between partitions, such that incongruence must partly reflect differences in patterns of homoplasy between partitions, which may itself be a function of modularity and mosaic evolution. Finally, we implement new tests to determine which partition yields trees most similar to those from the entire matrix. Despite no bias across dinosaurs overall, there are striking differences between major groups. The craniodental characters of Ornithischia and the postcranial characters of Saurischia yield trees most similar to the “total evidence” trees derived from the entire matrix. Trees from these same character partitions also tend to be most stratigraphically congruent: a mutual consilience suggesting that those partitions yield more accurate trees. [Dinosauria; homoplasy; partition homogeneity.]

Blood oxygen-carrying capacity is shaped both by the ambient oxygen availability as well as species-specific oxygen demand. Erythrocytes are a critical part of oxygen transport and both their size and shape can change in relation to species-specific life-history, behavioural or ecological conditions. Here, we test whether components of the environment (altitude), life history (reproductive mode, body temperature) and behaviour (diving, foraging mode) drive erythrocyte size variation in the Lepidosauria (lizards, snakes and rhynchocephalians). We collected data on erythrocyte size (area) and shape (L/W: elongation ratio) from Lepidosauria across the globe (N = 235 species). Our analyses show the importance of oxygen requirements as a driver of erythrocyte size. Smaller erythrocytes were associated with the need for faster delivery (active foragers, high-altitude species, warmer body temperatures), whereas species with greater oxygen demands (diving species, viviparous species) had larger erythrocytes. Erythrocyte size shows considerable cross-species variation, with a range of factors linked to the oxygen delivery requirements being major drivers of these differences. A key future aspect for study would include within-individual plasticity and how changing states, for example, pregnancy, perhaps alter the size and shape of erythrocytes in Lepidosaurs.

The size and shape of red blood cells (erythrocytes) is determined by key life history strategies in vertebrates. They have a fundamental role to deliver oxygen to tissues, and their ability to do so is shaped by the tissue's need and their shape. Despite considerable interest in how other components of blood are shaped by ecology and life history, few studies have considered erythrocytes themselves. We tested how erythrocyte size and shape varied in relation to energetically demanding activities using a dataset of 631 bird species. We found that in general, birds undergoing greater activities such as long distance migration had smaller and more elongated cells, while those with greater male-male competition had smaller and rounder cells. Smaller, more elongated erythrocytes allow more rapid oxygenation/deoxygenation and support greater aerobic activity. The rounder erythrocytes found in species with strong male–male competition may stem from younger erythrocytes deriving from androgen-induced erythropoiesis rates. Finally, diving species of bird had larger erythrocytes, indicating that erythrocytes are acting as a vital oxygen store. In summary, erythrocyte size and shape in birds are driven by the need to deliver oxygen during energetically costly activities.

Sexual selection theory has proven to be fundamental to our understanding of the male-female 15 (sperm-egg) interactions that characterise fertilisation. However, sexual selection does not operate 16 in a void and abiotic environmental factors have been shown to modulate the outcome of pre17 copularory sexual interactions. Environmental modulation of post-copulatory interactions are 18 particularly likely because the form and function of primary reproductive traits appears to be acutely 19 sensitive to temperature stress. Here we report the effects of developmental temperature on female 20 reproductive architecture and the interaction between male and female developmental 21 temperature on the outcome of sperm competition in the bruchid beetle Callosobruchus maculatus. 22 When females were reared at developmental temperatures above and below typical temperatures 23 the bursa copulatrix (site of spermatophore deposition) were smaller and, were either shorter and 24 broader (high temperatures) or longer and thinner (low temperatures) than those reared at 25 intermediate temperatures. Males and females reared at low developmental temperatures were 26 less likely to mate than those reared at higher temperatures. Where copulation occurred, females 27 reared at the highest temperature copulated for longest, whilst males reared at the lowest 28 temperature spent longer in copula. Male developmental temperature had a significant impact on 29 the outcome of sperm competition: males reared at 17oC were largely unsuccessful in sperm 30 competition against control (27oC) males, although some of the variation in the outcome of sperm 31 competition was a product of the interaction between male and female developmental 32 temperature. Our results demonstrate that male-female interactions that characterise pre- and post33 copulatory outcomes are sensitive to developmental temperature and that plasticity in cryptic 34 female preferences could lead to heterogeneous selection on the male reproductive phenotype.

There is much evidence in mammals and birds demonstrating the importance of providing sufficient space to allow captive animals to exhibit natural behaviours, however, little such evidence exists for reptiles. The aim of this study was to ascertain whether enclosure size impacted on the behaviour and welfare of captive corn snakes (Pantherophis guttatus). Snakes (N = 12) were housed in enclosures that were either 2/3 their length (small) or longer than the length of the snake (large) for c.32 days. Their welfare was assessed through observations of the animals in their enclosure and behavioural tests; after completing these tests, each animal was switched to the other housing condition (order counterbalanced across individuals) and received the same welfare assessment. Following the second set of behavioural tests, all animals received a preference test. When housed in large enclosures, snakes were found to be more active and spent time stretched out - a behaviour that was not possible in the small enclosure. The behavioural tests revealed few effects of space provision; however, when given a choice, snakes showed a clear preference for the large enclosure whilst active, although this preference was not observed while resting. These findings suggest that providing a larger enclosure is beneficial to the behaviour and welfare of captive snakes. Not providing sufficient space to allow snakes to fully elongate appears to thwart a behavioural need and thus impacts negatively on their welfare. We therefore recommend that captive snakes be kept in an enclosure longer than their body length.

The braincase anatomy of the Pennsylvanian diadectomorphLimnoscelis dynatisis described in detail, based upon high-resolution X-ray microcomputed tomography. Both supraoccipitals and most of the prootics and opisthotics are preserved. The known portions of the left prootic, opisthotic, and supraoccipital enclose complete sections of the endosseous labyrinth, including the anterior, posterior, and lateral semicircular canals, the vestibule, the cochlear recess, and the canal for the endolymphatic duct. The fossa subarcuata is visible anteromedial to the anterior semicircular canal. The presumed endolymphatic fossae occur in the dorsal wall of the posteromedial portion of the supraoccipital. Both the fossa subarcuata and the fossa endolymphatica lie in the cerebellar portion of the cranial cavity. In order to investigate the phylogenetic position ofL. dynatiswe used a recently published data matrix, including characters of the braincase, and subjected it to maximum parsimony analyses under a variety of character weighting schemes and to a Bayesian analysis.Limnoscelis dynatisemerges as sister taxon toL. paludis, and both species form the sister group to remaining diadectomorphs. Synapsids and diadectomorphs are resolved as sister clades in ∼90% of all the most parsimonious trees from the unweighted analysis, in the single trees from both the reweighted and the implied weights analyses, as well in the Bayesian tree.

In an era of global warming, the negative effects of temperature stress on fertility could intensify predicted losses of biodiversity. Male fertility is particularly sensitive to temperature stress, yet we have an incomplete understanding of when, during reproductive ontogeny, spermatogenesis is most affected. Here, we used a temperature-switch protocol to identify when during development temperature affects the expression of sperm length and testes size in the bruchid beetle Callosobruchus maculatus. Egg-to-adult development took place at 17°C, 27°C or 33°C for either the full duration of pre-imago development or it was switched at different stages during development. Full development at 17°C or 33°C resulted in significantly shorter sperm than at 27°C. However, when developing larvae were switched to higher or lower temperatures, we observed switch-specific phenotypic expression of sperm length and testes size. Our key finding was that sperm length was sensitive to high-temperature stress during the early stages of ontogeny and to low-temperature stress during the latter stages of ontogeny. Such age-specific developmental sensitivity suggests that infertility resulting from transient heat stress (i.e. heatwaves) could be mitigated by age-related developmental heterogeneity within populations. Those individuals able to avoid severe effects of heat stress on fertility, through serendipitously being at less-sensitive stages of development, could potentially compensate for the loss of fertility experienced by those individuals at more sensitive stages of development.

Over the last 50 years, sperm competition has become increasingly recognised as a potent evolutionary force shaping male ejaculate traits. One such trait is sperm swimming speed, with faster sperm associated with increased fertilisation success in some species. Consequently, sperm are often thought to have evolved to be longer in order to facilitate faster movement. However, despite the intrinsic appeal of this argument, sperm operate in a different biophysical environment than we are used to, and instead increasing length may not necessarily be associated with higher velocity. Here, we test four predictive models (ConstantPower Density, Constant Speed, Constant Power Transfer, Constant Force) of the relationship between sperm length and speed. We collated published data on sperm morphology and velocity from 141 animal species, tested for structural clustering of sperm morphology and then compared the model predictions across all morphologically similar sperm clusters. Within four of five morphological clusters of sperm, we did not find a significant positive relationship between total sperm length and velocity. Instead, in four morphological sperm clusters we found evidence for the Constant Speed model, which predicts that power output is determined by the flagellum and so is proportional to flagellum length. Our results show the relationship between sperm morphology (size, width) and swimming speed is complex and that traditional models do not capture the biophysical interactions involved. Future work therefore needs to incorporate not only a better understanding of how sperm operate in the microfluid environment, but also the importance of fertilising environment, i.e., internal and external fertilisers. The microenvironment in which sperm operate is of critical importance in shaping the relationship between sperm length and form and sperm swimming speed.

Successive negative contrast (SNC) effects are changes in anticipatory or consummatory behaviour when animals unexpectedly receive a lower value reward than they have received previously. SNC effects are often assumed to reflect frustration and appear to be influenced by background affective state. However, alternative explanations of SNC, such as the functional-search hypothesis, do not necessarily imply an aversive affective state. We tested 18 dogs in a SNC paradigm using a patch foraging task. Dogs were tested in two conditions, once with the low value reward in all of five trials (unshifted) and once when reward value was altered between high and low (shifted). Following a reward downshift, subjects showed a SNC effect by switching significantly more often between patches compared to the unshifted condition. However, approach latency, foraging time and quantity consumed did not differ between conditions, suggesting non-affective functional search behaviour rather than frustration. There was no relationship between strength of SNC and anxiety-related behaviours as measured in a novel object test and a personality questionnaire (C-BARQ). However, associations with the C-BARQ scores for Trainability and Stranger directed aggression suggest a possible link with behavioural flexibility and coping style. While reward quality clearly affects incentive motivation, the relationship between SNC, frustration and background affective state requires further exploration.

Honeybees [1] and bumblebees [2] perform learning flights on leaving a newly discovered flower. During these flights, bees spend a portion of the time turning back to face the flower when they can memorise views of the flower and its surroundings. In honeybees, learning flights become longer, when the reward offered by a flower is increased [3]. We show here that bumblebees behave in a similar way and we add that bumblebees face an artificial flower more when the concentration of the sucrose solution that the flower provides is higher. The surprising finding is that a bee’s size determines what a bumblebee regards as a 'low' or a 'high' concentration and so affects its learning behaviour. The larger bees in a sample of foragers only enhance their flower facing when the sucrose concentration is in the upper range of the flowers that are naturally available to bees [4]. In contrast, smaller bees invest the same effort in facing flowers, whether the concentration is high or low, but their effort is less than that of larger bees. The way in which different sized bees distribute their effort when learning about flowers parallels the foraging behaviour of a colony. Large bumblebees [5, 6] are able to carry larger loads and explore further from the nest than smaller ones [7]. Small ones with a smaller flight range and carrying capacity cannot afford to be as selective and so accept a wider range of flowers.

Conservation measures providing food-rich habitats through agri-environment schemes (AES) have the potential to affect the demography and local abundance of species limited by food availability. The European Turtle Dove Streptopelia turtur is one of Europe’s fastest declining birds, with breeding season dietary changes coincident with a reduction in reproductive output suggesting food limitation during breeding. In this study we provided seed-rich habitats at six intervention sites over a 4-year period and tested for impacts of the intervention on breeding success, ranging behaviour and the local abundance of territorial turtle doves. Nesting success and chick biometrics were unrelated to the local availability of seed-rich habitat or to the proximity of intervention plots. Nestling weight was higher close to human habitation consistent with an influence of anthropogenic supplementary food provision. Small home ranges were associated with a high proportion of non-farmed habitats, while large home ranges were more likely to contain seed-rich habitat suggesting that breeding doves were willing to travel further to utilize such habitat where available. Extensively-managed grassland and intervention plot fields were selected by foraging turtle doves. A slower temporal decline in the abundance of breeding males on intervention sites probably reflects enhanced habitat suitability during territory settlement. Refining techniques to deliver sources of sown, natural and supplementary seed that are plentiful, accessible and parasite-free is likely to be crucial for the conservation of turtle doves

The long-term accumulation of biodiversity has been punctuated by remarkable evolutionary transitions that allowed organisms to exploit new ecological opportunities. Mesozoic flying reptiles (the pterosaurs), which dominated the skies for more than 150 million years, were the product of one such transition. The ancestors of pterosaurs were small and probably bipedal early archosaurs1, which were certainly well-adapted to terrestrial locomotion. Pterosaurs diverged from dinosaur ancestors in the Early Triassic epoch (around 245 million years ago); however, the first fossils of pterosaurs are dated to 25 million years later, in the Late Triassic epoch. Therefore, in the absence of proto-pterosaur fossils, it is difficult to study how flight first evolved in this group. Here we describe the evolutionary dynamics of the adaptation of pterosaurs to a new method of locomotion. The earliest known pterosaurs took flight and subsequently appear to have become capable and efficient flyers. However, it seems clear that transitioning between forms of locomotion2,3—from terrestrial to volant—challenged early pterosaurs by imposing a high energetic burden, thus requiring flight to provide some offsetting fitness benefits. Using phylogenetic statistical methods and biophysical models combined with information from the fossil record, we detect an evolutionary signal of natural selection that acted to increase flight efficiency over millions of years. Our results show that there was still considerable room for improvement in terms of efficiency after the appearance of flight. However, in the Azhdarchoidea4, a clade that exhibits gigantism, we test the hypothesis that there was a decreased reliance on flight5–7 and find evidence for reduced selection on flight efficiency in this clade. Our approach offers a blueprint to objectively study functional and energetic changes through geological time at a more nuanced level than has previously been possible. Phylogenetic statistical analyses, biophysical models and information from the fossil record show that an evolutionary signal of natural selection acted to increase the flight efficiency of pterosaurs over millions of years.

The use of acoustics in predator evasion is a widely reported phenomenon amongst invertebrate taxa, but the study of ultrasonic anti-predator acoustics is often limited to the prey of bats. Here, we describe the acoustic function and morphology of a unique stridulatory structure – the Ander's organ – in the relict orthopteran Cyphoderris monstrosa (Ensifera, Hagloidea). This species is one of just eight remaining members of the family Prophalangopsidae, a group with a fossil record of over 90 extinct species widespread during the Jurassic period. We reveal that the sound produced by this organ has the characteristics of a broadband ultrasonic anti-predator defence, with a peak frequency of 58±15.5 kHz and a bandwidth of 50 kHz (at 10 dB below peak). Evidence from sexual dimorphism, knowledge on hearing capabilities and assessment of local predators, suggests that the signal likely targets ground-dwelling predators. Additionally, we reveal a previously undescribed series of cavities underneath the organ that probably function as a mechanism for ultrasound amplification. Morphological structures homologous in both appearance and anatomical location to the Ander's organ are observed to varying degrees in 4 of the 7 other extant members of this family, with the remaining 3 yet to be assessed. Therefore, we suggest that such structures may either be more widely present in this ancient family than previously assumed, or have evolved to serve a key function in the long-term survival of these few species, allowing them to outlive their extinct counterparts., Highlighted Article: Motion tracing, acoustic recording and micro-CT imaging reveal a unique ultrasonic organ in a relict insect. Statistical quantification of organ morphology reveals sexually driven loss of the organ in males.

Behavioral predispositions are innate tendencies of animals to behave in a given way without the input of learning. They increase survival chances and, due to environmental and ecological challenges, may vary substantially even between closely related taxa. These differences are likely to be especially pronounced in long-lived species like crocodilians. This order is particularly relevant for comparative cognition due to its phylogenetic proximity to birds. Here we compared early life behavioral predispositions in two Alligatoridae species. We exposed American alligator and spectacled caiman hatchlings to three different novel situations: a novel object, a novel environment that was open and a novel environment with a shelter. This was then repeated a week later. During exposure to the novel environments, alligators moved around more and explored a larger range of the arena than the caimans. When exposed to the novel object, the alligators reduced the mean distance to the novel object in the second phase, while the caimans further increased it, indicating diametrically opposite ontogenetic development in behavioral predispositions. Although all crocodilian hatchlings face comparable challenges, e.g., high predation pressure, the effectiveness of parental protection might explain the observed pattern. American alligators are apex predators capable of protecting their offspring against most dangers, whereas adult spectacled caimans are frequently predated themselves. Their distancing behavior might be related to increased predator avoidance and also explain the success of invasive spectacled caimans in the natural habitats of other crocodilians. Supplementary Information The online version contains supplementary material available at 10.1007/s10071-020-01461-5.

The communities of bacterial species present within a sheep gut microbiota can have varying effects on general host health. It is thought that the microbiota carried by ewes can transfer to offspring and influence their microbial communities, which then could potentially affect the health and production of the animal. Antibiotic resistance has become a major issue worldwide and commensal bacteria can also harbour antibiotic resistance genes. Therefore, transfer of microbiota from ewes to lambs could also transfer resistance, further increasing the problem. There are limited studies monitoring transfer and resistance of bacteria within sheep, even though the processes could have an economic impact on farmers. In this study, faecal samples from 65 ewes and 109 lambs were collected. There were 11 different species of bacteria isolated from the faeces. These species showed most resistance to tetracycline (bacterial species isolated from 77% of ewes and 79% of lambs showed tetracycline resistance)and the blaTEM-1 resistance gene was the most prevalent(found in 25% of the isolated bacteria). The species present as part of the gut microbiota and their resistance levels, in both ewes and lambs, were compared to deduce whether transfer from mother to offspring was likely. The bacterial species in lambs were also measured at repeat sample collections within the first two months of birth, to try and determine whether gut microbiota changed with age. A significant relationship was found between resistance levels of the bacteria isolated and the age of lambs. Similarities could be seen in the composition of gut microbiota in ewes and lambs, suggesting possible transmission of species from ewe to their offspring, however the relationship was not significant. Further analysis, including isolating bacteria from affecting factors other than the ewes, would need to be undertaken to prove direct microbial transfer from mother to offspring.

This commentary arose from a workshop entitled ‘What works, and what doesn’t work? The challenge of creating effective applied conservation research in human-modified habitats’, held during the joint meeting of the European Federation for Primatology and the Primate Society for Great Britain in Oxford, 2019. One discussion point highlighted the different use of terminology between disciplines as a challenge for effective multidisciplinary conservation research. Growing number of publications have drawn attention to the misuse of the terms such as human-wildlife conflict (Marshall et al. 2007, Peterson et al. 2010, Davidar 2018), crop-raiding (Hill 2017), or ecotourism (McKinney 2017). Here we widen this conversation by reflecting on an additional term regularly used in primatology: commensalism. Here, we will give the different definitions of the term ‘commensal’ used across disciplines and the implications of its misuse. We will then discuss whether this term can be used to categorise human-nonhuman primate (afterward primates) relationships, and conclude by proposing alternative terminology.

Traditional methods of assessing human-animal interactions include questionnaires or targeted interviews. More people typically use the internet as their primary source of information and now the a...

Temperate terrestrial species in Europe were hypothesized to have been restricted to southern peninsular refugia (Iberia, Italy, Balkans) during the height of the last glacial period. However, recent analyses of fossil evidence indicate that some temperate species existed outside these areas during the last glacial maximum (LGM). Red foxes (Vulpes vulpes) in particular, could have been distributed across the southern half of the continent, potentially forming one continuous population. To investigate these hypotheses, we used 21 nuclear microsatellite loci and two fragments (768 bp) of mitochondrial DNA to characterize the population structure among a continent-wide sample of 288 European red foxes. We tested whether European red foxes clustered into discrete populations corresponding to the hypothetical peninsular refugia. Additionally, we sought to determine if distinct northern populations were formed after post-glacial recolonization. Our results indicated that only the foxes of Iberia appeared to have remained distinct over a considerable period of time (32–104 kya). Spanish red foxes formed their own genotypic cluster; all mtDNA haplotypes were endemic and closely related, and together both the mitochondrial and nuclear datasets indicated this population contributed little to postglacial recolonization of Northern Europe. In contrast, red foxes from Italy and the Balkans contributed significantly to, or were part of, a wider, admixed population stretching across mid-latitude Europe. In Northern Europe, we identified a Scandinavian population that had an ancestral relationship with red foxes to the south, and a more recent relationship with those to the east, in Russia. We also resolved two distinct populations on the islands of Ireland and Britain that had been separated from one another, and from those on the continent, since the late Pleistocene/mid Holocene (~4–24 kya

The effects of temperature on cellular, systemic and whole-organism processes can be short-term, acting within seconds or minutes of a temperature change, or long-term, acting across ontogenetic stages to affect an organism’s morphology, physiology and behavioural phenotype. Here we examine the effect of larval development temperature on adult copulatory behaviour in the bruchid beetle, Callosobruchus maculatus. As predicted by temperature’s kinetic effects, copulation duration was longest at the lowest ambient temperature. However, where ambient temperature was fixed and developmental temperature experimentally varied, males reared at the highest temperature were least likely to engage in copulation, whilst those reared at the lowest temperature copulated for longer. Previous research has shown males reared at cooler temperatures inseminate fewer sperm. Thus, in this species longer copulations are associated with reduced sperm transfer. We argue that knowledge of preceding ontogenetic conditions will help to elucidate the causes of variation in copulatory behaviour.

Illnesses caused by a variety of micro- and macro- organisms can negatively affect individuals’ fitness, leading to the expectation that immunity is under positive selection. However, immune responses are costly and individuals must trade-off their immune response with other fitness components (e.g. survival or reproductive success) meaning that individuals with intermediate response may have the greatest overall fitness. Such a process might be particularly acute in species with strong sexual selection because the condition-dependence of male secondary sexual-traits might lead to striking phenotypic differences amongst males of different immune response levels. We tested whether there is selection on immune response by survival and reproduction in yearling and adult male black grouse (Lyrurus tetrix) following an immune challenge with a novel antigen and tested the hypothesis that sexual signals and body mass are honest signals of the immune response. We show that yearling males with highest immune response to these challenges had higher survival, but the reverse was true for adults. Adults with higher responses had highest mass loss and adult males with intermediate immune response had highest mating success. Tail length was related to baseline response in adults and more weakly in yearlings. Our findings reveal the complex fitness consequences of mounting an immune response across age classes. Such major differences in the direction and magnitude of selection in multiple fitness components is an alternative route underpinning the stabilising selection of immune responses with an intermediate immune response being optimal. peerReviewed

Skeletal remains of a new early Miocene (Ottnangian, MN 4 mammal zone) monitor lizard, Varanus mokrensis sp. nov., are described from two karst fissures in the Mokrá-Western Quarry (1/2001 Turtle Joint; 2/2003 Reptile Joint), Czech Republic, providing the first documented example of a European varanid for which osteological data permit a well-supported assignment to the genus Varanus. The new species is morphologically similar to the Recent Indo-Asiatic varanids of the Varanus bengalensis group. It differs from all other Varanus species on the basis of a single autapomorphy and a combination of 11 characters. As a distinguishing feature of V. mokrensis, the parietal and squamosal processes of the postorbitofrontal form a narrowly acute angle. The teeth show distinct, smooth cutting edges along the mesial and distal margins of the apical portion of their crowns. This feature is not observed in most extant Asiatic Varanus species and may represent a plesiomorphic condition. The results of parsimony phylogenetic analyses, with and without character reweighting, reveal poor resolution within Varanus. A Bayesian analysis shows V. mokrensis to be closely related to extant representatives of the Indo-Asiatic Varanus clade, with close affinities to the V. bengalensis species group. The topology of the Bayesian tree supports the hypothesis that Miocene monitors from Mokrá are representatives of a lineage that is ancestral to the well-defined clade of extant African varanids, including the early Miocene V. rusingensis. In addition, our results support a Eurasian origin for the varanid clade. The extant African Varanus species probably originated in the late Oligocene. The radiation of African varanids probably occurred during the late Oligocene to early Miocene time interval. The occurrence of Varanus in the early Miocene of Mokrá-Western Quarry corresponds to the warm phase of the Miocene Climatic Optimum. Remains of a diverse aquatic and heliophobe amphibian fauna at the 2/2003 Reptile Joint site indicate more humid conditions than those at the 1/2001 Turtle Joint site.

The known diversity of tetrapods of the Devonian period has increased markedly in recent decades, but their fossil record consists mostly of tantalizing fragments1–15. The framework for interpreting the morphology and palaeobiology of Devonian tetrapods is dominated by the near complete fossils of Ichthyostega and Acanthostega; the less complete, but partly reconstructable, Ventastega and Tulerpeton have supporting roles2,4,16–34. All four of these genera date to the late Famennian age (about 365–359 million years ago)—they are 10 million years younger than the earliest known tetrapod fragments5,10, and nearly 30 million years younger than the oldest known tetrapod footprints35. Here we describe Parmastega aelidae gen. et sp. nov., a tetrapod from Russia dated to the earliest Famennian age (about 372 million years ago), represented by three-dimensional material that enables the reconstruction of the skull and shoulder girdle. The raised orbits, lateral line canals and weakly ossified postcranial skeleton of P. aelidae suggest a largely aquatic, surface-cruising animal. In Bayesian and parsimony-based phylogenetic analyses, the majority of trees place Parmastega as a sister group to all other tetrapods. Three-dimensionally preserved fossils of Parmastega aelidae, a newly described tetrapod from the earliest Famennian (Late Devonian) of Russia, provide detailed insights into the morphology and palaeobiology of the earliest tetrapods.

Behavioral asymmetries exhibited by the common octopus, Octopus vulgaris, a cephalopod mollusk, during predatory and exploratory responses were investigated. Animals were tested for eye preferences while attacking a natural (live crab) or an artificial (plastic ball) stimulus, and for side preferences while exploring a T-maze in the absence of any specific intra- or extra-maze cues. We found individual-level asymmetry in some animals when faced with either natural or artificial stimuli, but not when exploring the maze. Our findings suggest that visual lateralization in O. vulgaris is context-dependent.

Mantis shrimp strikes are one of the fastest animal movements, despite their occurrence in a water medium with viscous drag. Since the strike is produced by a latch-mediated spring-actuated system and not directly driven by muscle action, we predicted that strikes performed in air would be faster than underwater due to reduction in the medium's drag. Using high-speed video analysis of stereotyped strikes elicited from Squilla mantis, we found the exact opposite: strikes are much slower and less powerful in air than in water. S. mantis strikes in air have a similar mass and performance to latch-mediated spring-actuated jumps in locusts, suggesting a potential threshold for the energetics of a 1-2 g limb rotating in air. Drag forces induced by the media may be a key feature in the evolution of mantis shrimp strikes and provide a potential target for probing the braking system of these extremely fast movements.

The present study explores the macroevolutionary dynamics of shape changes in the humeri of all major grades and clades of early tetrapods and their fish-like forerunners. Coordinate point eigenshape analysis applied to humeral outlines in extensor view reveals that fish humeri are more disparate than those of most early tetrapod groups and significantly separate from the latter. Our findings indicate sustained changes in humeral shape in the deepest portions of the tetrapod stem group and certain portions of the crown. In the first half of sampled tetrapod history, subclades show larger than expected humeral disparity, suggesting rapid diffusion into morphospace. Later in tetrapod evolution, subclades occupy smaller and non-overlapping morphospace regions. This pattern may reflect in part increasing specialisations in later tetrapod lineages. Bayesian shifts in rates of evolutionary change are distributed discontinuously across the phylogeny, and most of them occur within rather than between major groups. Most shifts with the highest Bayesian posterior probabilities are observed in lepospondyls. Similarly, maximum likelihood analyses of shifts support marked rate accelerations in lepospondyls and in various subclades within that group. In other tetrapod groups, rates either tend to slow down or experience only small increases. Somewhat surprisingly, no shifts are concurrent with structural, functional, or ecological innovations in tetrapod evolution, including the origin of digits, the water–land transition and increasing terrestrialisation. Although counterintuitive, these results are consistent with a model of continual phenotypic innovation that, although decoupled from key evolutionary changes, is possibly triggered by niche segregation in divergent clades and grades of early tetrapods.

The string-pulling test is a classic test of physical cognition which is thought to examine an animal’s understanding of means-end comprehension, but may also result from trial and error learning. Here, we presented Green-winged macaws (Ara chloroptera) with a standard pull-up, and an alternative, pull-down, string pulling test to better understand the processes involved. Birds were divided into two groups: the experimental group were presented with the classic pull-up test and, upon completion, with the pull-down test, while the control group were only presented with the pull-down test. Six experimental birds solved the pull-up test, although none successfully completed the pull-down test; however, birds from the experimental group made significantly more pull-down actions than those from the control group. Together with previous findings on string-pulling behaviour in green-winged macaws, the results from the present study suggest that string-pulling behaviour in this species does not involve means-end understanding.

Income and capital breeding describe two dichotomous breeding strategies that characterise the allocation of resources to reproduction. Capital breeders utilise stored endogenous resources (typically lipids) to finance reproduction, whereas income breeders use exogenous resources (typically carbohydrates). The basis for such characterisation has mainly come from studying females, yet for many species, male and female reproductive success may be determined by substantially different factors. Females allocate resources to offspring production, whereas males typically allocate resources to accessing mating opportunities, e.g. from contests or displays. The primary metabolic fuel (lipids or carbohydrates) in males appears to be dependent on the type of activity being performed (i.e. high versus low intensity or long versus short duration), rather than capital or income breeding strategy per se. Males performing sustained, long-duration effort typically utilise lipids, whereas those undergoing intense activity more often utilise carbohydrates. As a result, either fuel type can be used in either strategy. Breeding season duration can constrain strategy choice; lipids and carbohydrates can be used in short breeding season species, but only lipids provide a viable fuel source for long breeding season capital breeders. Both capital- and income-breeding males must manage their resource use during the breeding season, but capital breeders must also cope with physiological stressors associated with extended fasting. Overall, the capital–income breeding concept applies equally to male reproduction, but compared with females, there are different physical and physiological constraints that shape choice of strategy. This Commentary also highlights some key future areas that need to be investigated to further understand how capital–income breeding strategies shape male mating strategies.

As animals get smaller, their ability to generate usable work from muscle contraction is decreased by the muscle’s force-velocity properties, thereby reducing their effective jump height. Very small animals use a spring-actuated system, which prevents velocity effects from reducing available energy. Since force-velocity properties reduce the usable work in even larger animals, why don’t larger animals use spring-actuated jumping systems as well? We will show that muscle length-tension properties limit spring-actuated systems to generating a maximum 1/3 of the possible work that a muscle could produce – greatly restricting the jumping height of spring-actuated jumpers. Thus a spring-actuated jumping animal has a jumping height that is 1/3 of the maximum possible jump height achievable were 100% of the possible muscle work available. Larger animals, which could theoretically use all of the available muscle energy, have a maximum jumping height that asymptotically approaches a value that is about 3 times higher than that of spring-actuated jumpers. Furthermore, a size related ‘crossover point’ is evident for these two jumping mechanisms: animals smaller than this point can jump higher with a spring-actuated mechanism, while animals larger than this point can jump higher with a muscle-actuated mechanism. We demonstrate how this limit on energy storage is a consequence of the interaction between length-tension properties of muscles and spring stiffness. We indicate where this crossover point occurs based on modelling and then use jumping data from the literature to validate that larger jumping animals generate greater jump heights with muscle-actuated systems than spring-actuated systems.

Anthropogenic hybridization is widely perceived as a threat to the conservation of biodiversity. Nevertheless, to date, relevant policy and management interventions are unresolved and highly convoluted. While this is due to the inherent complexity of the issue, we hereby hypothesize that a lack of agreement concerning management goals and approaches, within the scientific community, may explain the lack of social awareness on this phenomenon, and the absence of effective pressure on decision-makers. By focusing on wolf x dog hybridization in Europe, we hereby (a) assess the state of the art of issues on wolf x dog hybridization within the scientific community, (b) assess the conceptual bases for different viewpoints, and (c) provide a conceptual framework aiming at reducing the disagreements. We adopted the Delphi technique, involving a three-round iterative survey addressed to a selected sample of experts who published at Web of Science listed journals, in the last 10 years on wolf x dog hybridization and related topics. Consensus was reached that admixed individuals should always be defined according to their genetic profile, and that a reference threshold for admixture (i.e., q-value in assignment tests) should be formally adopted for their identification. To mitigate hybridization, experts agreed on adopting preventive, proactive and, when concerning small and recovering wolf populations, reactive interventions. Overall, experts' consensus waned as the issues addressed became increasingly practical, including the adoption of lethal removal. We suggest three non-mutually exclusive explanations for this trend: (i) value-laden viewpoints increasingly emerge when addressing practical issues, and are particularly diverging between experts with different disciplinary backgrounds (e.g., ecologists, geneticists); (ii) some experts prefer avoiding the risk of potentially giving carte blanche to wolf opponents to (illegally) remove wolves, based on the wolf x dog hybridization issue; (iii) room for subjective interpretation and opinions result from the paucity of data on the effectiveness of different management interventions. These results have management implications and reveal gaps in the knowledge on a wide spectrum of issues related not only to the management of anthropogenic hybridization, but also to the role of ethical values and real-world management concerns in the scientific debate.

There is growing evidence that achromatic plumage can act as honest indicators of male quality. In some species with areas of white plumage, black melanin spots can be found on parts of the feathers. The functional significance of these spots and the relationship with male quality is yet poorly understood. We investigated the relationship between black melanin spots in an otherwise totally white ornament, the undertail covert, in relation to age, fitness and covariance with past and present expression of sexual traits, in the lekking black grouse Lyrurus tetrix. We found that spots at tips of feathers (tip spots) were negatively related to survival and reproductive success, and covaried negatively with current fighting rate. They also covaried positively with past fighting rate, suggesting high investment in fighting leads to carryover effects on male condition. In contrast, spots found further down the feather (vane spots) were unrelated to fitness and morphological and behavioural trait expression. Our results show that melanin spots can indicate some relationship with male quality and that the location of the spots has some importance in this relationship. However, the exact drivers of melanin spot expression and how these link to male quality, are currently unknown.

Dietary changes linked to the availability of anthropogenic food resources can have complex implications for species and ecosystems, especially when species are in decline. Here, we use recently developed primers targeting the ITS2 region of plants to characterise diet from faecal samples of four UK columbids, with particular focus on the European turtle dove (Streptopelia turtur), a rapidly declining obligate granivore. We examine dietary overlap between species (potential competition), associations with body condition in turtle doves, and spatiotemporal variation in diet. We identified 143 taxonomic units, of which we classified 55% to species, another 34% to genus and the remaining 11% to family. We found significant dietary overlap between all columbid species, with the highest between turtle doves and stock doves (Columba oenas), then between turtle doves and woodpigeons (Columba palumbus). The lowest overlap was between woodpigeons and collared doves (Streptopelia decaocto). We show considerable change in columbid diets compared to previous studies, probably reflecting opportunistic foraging behaviour by columbids within a highly anthropogenically-modified landscape, although our data for non-turtle doves should be considered preliminary. Nestling turtle doves in better condition had a higher dietary proportion of taxonomic units from natural arable plant species, and a lower proportion of taxonomic units from anthropogenic food resources such as garden bird seed mixes and brassicas. This suggests that breeding ground conservation strategies for turtle doves should include provision of anthropogenic seeds for adults early in the breeding season, coupled with habitat rich in accessible seeds from arable plants once chicks have hatched.

Secondary sexual trait expression can be influenced by fixed individual factors (such as genetic quality) but also by dynamic factors (such as age and environmentally induced gene expression) that may be associated with variation in condition or quality. In particular, melanin-based traits are known to relate to condition and there is a well-characterized genetic pathway underpinning their expression. However, the mechanisms linking variable trait expression to genetic quality remain unclear. One plausible mechanism is that genetic quality could influence trait expression via differential methylation and differential gene expression. We therefore conducted a pilot study examining DNA methylation at a candidate gene (agouti-related neuropeptide: AgRP) in the black grouse Lyrurus tetrix. We specifically tested whether CpG methylation covaries with age and multilocus heterozygosity (a proxy of genetic quality) and from there whether the expression of a melanin-based ornament (UV blue chroma) correlates with DNA methylation. Consistent with expectations, we found clear evidence for age- and heterozygosity-specific patterns of DNA methylation, with two CpG sites showing the greatest DNA methylation in highly heterozygous males at their peak age of reproduction. Furthermore, DNA methylation at three CpG sites was significantly positively correlated with UV blue chroma. Ours is the first study to our knowledge to document age- and quality-dependent variation in DNA methylation and to show that dynamic sexual trait expression across the lifespan of an organism is associated with patterns of DNA methylation. Although we cannot demonstrate causality, our work provides empirical support for a mechanism that could potentially link key individual factors to variation in sexual trait expression in a wild vertebrate.