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Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

While foraging or during social interactions, animals may benefit from judging relative quantity. Individuals may select larger prey or a patch with more food and, likewise, it may pay to track the number and type of individuals and social interactions. We tested for spontaneous quantity discrimination in the gidgee skink (Egernia stokesii), a family-living lizard. Lizards were presented with food quantities differing in number or size and were able to select the larger quantity of food items when they differed in number but not when items differed in size. We show, for the first time, superior spontaneous discrimination of items differing in number over size in a lizard species, which contrasts with previous findings. Our simple method, however, did not include controls for the use of continuous quantities, and further tests are required to determine the role of such information during quantity discrimination. Our results provide support for the use of the parallel individuation system for the discrimination of small quantities (four or fewer items). Lizards might, however, still use the approximate number system if items in larger quantities (more than four) are presented. Overall, we uncovered evidence that species might possess specific cognitive abilities potentially adapted to their niche with respect to quantity information (discrete and/or continuous) and the processing system used when judging quantities. Importantly, our results highlight the need for testing multiple species using similar testing procedures to gain a better understanding of the underlying causes leading to differences across species.

Urban wildlife faces a novel set of challenges resulting in selective pressure that can lead to population-level changes. We studied Australian water dragons (Intellagama lesueurii) from urban and natural populations to test if urban populations differed in body size, shape, and performance capacity. If urban-derived morphology has arisen through selection, we predicted distinct morphological differences between wild dragons from urban and natural areas in both adult and hatchling life-stages. Urban hatchlings were morphologically distinct (shorter body lengths and longer limbs) from natural populations, while urban adult males continued this trend but only for body size (shorter body lengths). We then experimentally reared hatchlings originating from urban and natural populations within urban- and natural-style enclosures (2 × 2 factorial design) for a year to determine if differences in morphology and performance capacity (sprint speed, endurance, and clinging ability) were related to either the individual’s origin population or developmental environment. Yearlings reared in urban-style enclosures, irrespective of population origin, had smaller body sizes compared to those from natural-style enclosures, suggesting developmental environment was affecting their morphology. Despite this difference in body size, yearling dragon performance capacity was not significantly different between treatments. Overall, this study provides evidence of a complex relationship driving urban-divergent morphology – whereby urban dragons emerge as smaller hatchlings with longer limbs (innate traits) and are then further influenced by the urban environments that they develop in (phenotypic plasticity); however, and potentially owing to behavioral, ecological, and demographical differences, these changes appear to be sex-specific.

Early developmental environments influence life-history traits and survival of reptiles. In fact, rising global temperatures have already caused widespread extinctions among lizards. Viviparous species might be more susceptible to increasing temperatures because of their inability to meet their energetic demands following rapid environmental changes. Nevertheless, we do not yet fully understand how lizards with different reproductive modes can respond to climate change. We investigated the effect of both maternal thermal environment during pregnancy and incubation temperature on hatchling morphology and physiological performance of two populations of the lizard Saiphos equalis differing in their mode of reproduction, to test whether reproductive mode affects the ability to buffer against rising temperatures. Gravid females from both populations were subjected to current or projected end-of-century (future) thermal environments, to evaluate differences in the body size, growth rate, thermal preference, and locomotor performance of their offspring. Our results show that independently of the mode of reproduction, high temperatures accelerated gestation periods. Thermal environments did not affect hatchling thermal preference, but viviparous hatchlings consistently preferred lower temperatures. Unlike viviparous lizards, oviparous hatchlings incubated under future temperatures were smaller and had a lower growth rate compared to current-incubated hatchlings. Finally, thermal environments did not affect hatchling endurance and speed when controlling for body size. Our results show that global warming is likely to have a negative impact on S. equalis, but suggest that some of its effects may be ameliorated by maternal responses during pregnancy, particularly in viviparous populations.

We tested learning and behavioral flexibility in family-living gidgee skinks (Egernia stokesii) using a multistage visual discrimination task that included acquisition and reversal stages using simple and compound stimuli composed of black shapes superimposed on a colored background. We evaluated how lizards learn compound cues through a probe test. Lizards showed behavioral flexibility through reversal learning using simple stimuli (only color or shape). Our lizards used compound stimuli to learn a discrimination but had problems reversing and generalizing across novel compound stimuli. In the probe test, lizards chose the correct stimulus in a novel pairing with a distractor feature even without previous experience with compound stimuli. Our results suggest that some lizards are likely able to attend selectively to the relevant features of our compound stimuli while ignoring irrelevant features instead of using the configuration of a cue card as a whole to learn to discriminate between compound stimuli. We hope that our work will spark interest in further studies looking at how lizards (and reptiles in general) learn to solve visual discrimination problems. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Biological invasions are a contemporary global threat because invasive species can have substantial negative economic and ecological impacts. Invasive species can outcompete native species through two main mechanisms: interference competition (direct, negative interactions like aggression) and/or exploitative competition (indirect, negative interactions resulting from species using the same, limited resources like food). The invasive Italian wall lizard (Podarcis siculus) was introduced into Lisbon, Portugal, 20 years ago, and is believed to be locally displacing the native green Iberian wall lizard (Podarcis virescens). We experimentally tested for competition between these two lizard species by establishing heterospecific (one pair of each species) and conspecific (two pairs of the same species; control) treatments in enclosures containing a high- and a low-quality refuge. Lizards were fed from food dishes every other day. We tested if species showed interference (aggressive behaviour, stealing food and shelter exclusion) or exploitative competition (tolerance between species but differences in food consumption efficiency). We found evidence for exploitative competition: the invasive species arrived first at food stations, consumed more food and gained more weight than the native species. We suggest that exploitative competition may, in part, explain the observed displacement of P. virescens from contact areas with the invasive P. siculus. Deciphering the competitive mechanisms between invasive and native species is vital for understanding the invasion process. To become successful invaders, alien species must often outcompete native species they encounter in a new location. But how can an alien species outcompete a resident with a long evolutionary history in an environment in which the resident is expected to be better adapted? We studied an invasive and native congeneric pair of sympatric lizards to understand how they interact and potentially compete in a controlled environment. The invasive Italian wall lizard and a native congener were very tolerant of each other; however, the invasive species was first to arrive at food, ate more and grew faster, suggesting exploitative competition. This contrasts with previous studies in other introduced locations where the Italian wall lizard was more aggressive towards native lizards, suggestive of interference competition. Our results help explain why the Italian wall lizard is so successful and suggests it may compete in different ways, possibly in response to local environmental conditions and which species it may be competing with, but with the same outcome: the displacement of native species.

Inhibitory control, the inhibition of prepotent actions, is essential for higher-order cognitive processes such as planning, reasoning, and self-regulation. Individuals and species differ in inhibitory control. Identifying what influences inhibitory control ability within and between species is key to understanding how it evolved. We compared performance in the cylinder task across five lizard species: tree skinks (Egernia striolata), gidgee skinks (Egernia stokesii), eastern blue-tongue skinks (Tiliqua s. scincoides), sleepy lizards (Tiliqua r. asper), and eastern water skinks (Eulamprus quoyii). In our task, animals had to inhibit the prepotent motor response of directly approaching a reward placed within a semi-transparent mesh cylinder and instead reach in through the side openings. Additionally, in three lizard species, we compared performance in the cylinder task to reversal learning to determine the task specificity of inhibitory ability. Within species, neither sex, origin, body condition, neophobia, nor pre-experience with other cognitive tests affected individual performance. Species differed in motor response inhibition: Blue-tongue skinks made fewer contacts with the semi-transparent cylinder wall than all other species. Blue-tongue skinks also had lower body condition than the other species which suggest motivation as the underlying cause for species differences in task performance. Moreover, we found no correlation between inhibitory ability across different experiments. This is the first study comparing cylinder task performance among lizard species. Given that inhibitory control is probably widespread in lizards, motor response inhibition as exercised in the cylinder task appears to have a long evolutionary history and is likely fundamental to survival and fitness.SignificanceThe study of lizard cognition is receiving increasing attention. Lizards are a diverse group with a wide range of ecological attributes and represent a model system through which we can test a wide range of hypotheses relating to cognitive evolution. Furthermore, considering their evolutionary history, studying non-avian reptile cognition can help understand the evolution of different cognitive abilities including inhibitory control. Here, we provide a comparison of inhibitory control ability in five lizard species. Consequently, we are able to, firstly, validate a method (the cylinder task) initially developed for the use in mammals and birds, for use in lizards, and secondly, collect valuable data on inhibitory control in a poorly studied group with respect to cognitive ability. Our study suggests non-cognitive factors as a major influence on cylinder task performance, which is in agreement with previous studies of other vertebrates.

Magnetic resonance imaging (MRI) is an established technique for neuroanatomical analysis, being particularly useful in the medical sciences. However, the application of MRI to evolutionary neuroscience is still in its infancy. Few magnetic resonance brain atlases exist outside the standard model organisms in neuroscience and no magnetic resonance atlas has been produced for any reptile brain. A detailed understanding of reptilian brain anatomy is necessary to elucidate the evolutionary origin of enigmatic brain structures such as the cerebral cortex. Here, we present a magnetic resonance atlas for the brain of a representative squamate reptile, the Australian tawny dragon (Agamidae: Ctenophorus decresii), which has been the subject of numerous ecological and behavioral studies. We used a high-field 11.74T magnet, a paramagnetic contrasting-enhancing agent and minimum-deformation modeling of the brains of thirteen adult male individuals. From this, we created a high-resolution three-dimensional model of a lizard brain. The 3D-MRI model can be freely downloaded and allows a better comprehension of brain areas, nuclei, and fiber tracts, facilitating comparison with other species and setting the basis for future comparative evolution imaging studies. The MRI model and atlas of a tawny dragon brain (Ctenophorus decresii) can be viewed online and downloaded using the Wiley Biolucida Server at wiley.biolucida.net.

This project was funded by an ARC Discovery grant (DP130102998) to Martin Whiting and Richard Byrne and by Macquarie University. Behavioural flexibility, the ability to adjust behaviour to environmental change by adapting existing skills to novel situations, is key to coping with, for example, complex social interactions, seasonal changes in food availability or detecting predators. We tested the tree skink, Egernia striolata, a family-living skink from eastern Australia, in a set-shifting paradigm of eight colour/shape discriminations including reversals, an intradimensional acquisition of a new colour/shape and extradimensional shift from colour to shape (and vice versa). Skinks could learn to discriminate between colour/shape pairs and reverse this initial stimulus–reward association; however, they showed no significant decrease in the probability of making a correct choice in the extradimensional shift suggesting that they did not form an attentional set. Subjects appear to have learnt each stage as a new problem instead of generalizing stimuli into specific dimensions (set formation). In conclusion, tree skinks solved a discrimination reversal by focusing their attention towards visual stimuli and flexibly adjusting their choice behaviour accordingly. These lizards learned to use multidimensional visual stimuli to find a food reward but did not generalize stimuli into dimensions. Furthermore, this study is the first to test for set shifting in a lizard species and thereby allows us to extend set-shifting theory to a new taxon for comparison with primates, rodents, a bird and a turtle. Postprint

Some of the best evidence for rapid evolutionary change comes from studies of archipelagos and oceanic islands. City parks are analogous systems as they create geographically isolated green spaces that differ in size, structure and complexity. Very little, however, is known about whether city parks within a single urban centre drive selection and result in the diversification of native species. Here, we provide evidence for the rapid genetic and morphological differentiation of a native lizard (Intellagama lesueurii) at four geographically close yet unconnected parks within one city. Year of establishment of each city park varied from 1855 (oldest) to 2001 (youngest) equating to a generation time range of 32 to three generations. Genetic divergence among city park populations was large despite the small pairwise geographic distances (

The brain plays a critical role in a wide variety of functions including behaviour, perception, motor control, and homeostatic maintenance. Each function can undergo different selective pressures over the course of evolution, and as selection acts on the outputs of brain function, it necessarily alters the structure of the brain. Two models have been proposed to explain the evolutionary patterns observed in brain morphology. The concerted brain evolution model posits that the brain evolves as a single unit and the evolution of different brain regions are coordinated. The mosaic brain evolution model posits that brain regions evolve independently of each other. It is now understood that both models are responsible for driving changes in brain morphology; however, which factors favour concerted or mosaic brain evolution is unclear. Here, we examined the volumes of the 6 major neural subdivisions across 14 species of the agamid lizard genus Ctenophorus (dragons). These species have diverged multiple times in behaviour, ecology, and body morphology, affording a unique opportunity to test neuroevolutionary models across species. We assigned each species to an ecomorph based on habitat use and refuge type, then used MRI to measure total and regional brain volume. We found evidence for both mosaic and concerted brain evolution in dragons: concerted brain evolution with respect to body size, and mosaic brain evolution with respect to ecomorph. Specifically, all brain subdivisions increase in volume relative to body size, yet the tectum and rhombencephalon also show opposite patterns of evolution with respect to ecomorph. Therefore, we find that both models of evolution are occurring simultaneously in the same structures in dragons, but are only detectable when examining particular drivers of selection. We show that the answer to the question of whether concerted or mosaic brain evolution is detected in a system can depend more on the type of selection measured than on the clade of animals studied.

Waiting for the right moment to strike, avoiding the ingestion of harmful foods, or ignoring stimuli associated with ephemeral or depleted resources requires the inhibition of prepotent responses. Good response inhibition facilities flexibility in behaviour which is associated with survival in unpredictable environments. To investigate differences in behavioural flexibility in lizards, we tested reversal learning in the sleepy lizard (Tiliqua rugosa asper) and compared its performance to the relatively closely related eastern blue-tongue skink (Tiliqua scincoides scincoides). We presented both species with a choice between either a light and dark blue stimulus or a triangle and X shape. Both species were able to learn to discriminate between these stimuli and showed similar learning ability during the acquisition of the discrimination. Sleepy lizards, however, demonstrated a higher probability of making a correct choice at the start of the reversal, hinting towards enhanced stimulus response inhibition. Sleepy lizards and blue-tongue skinks inhabit different environments and show differences in ecology and sociobiology, all of which could possibly lead to adaptive specialisation in cognitive ability. Although further research is required, we propose that selection might have led to a change in stimulus response inhibition in the arid-adapted sleepy lizard, because better response inhibition may help them avoid the costs of repeated choices towards stimuli which no longer predict a beneficial outcome.

This project was funded by an ARC Discovery grant (DP130102998) to M.J.W. and R.W.B. and by Macquarie University. In altricial species, young rely on parental care and brain maturation mainly occurs after birth. In precocial species, young are born at a more advanced developmental stage in need of less or no parental care and brain development is mostly completed at the time of birth. We therefore predicted early maturation of learning ability in precocial species. We used a series of visual discrimination and reversal stages to investigate the ability of the precocial eastern blue-tongue lizard, Tiliqua scincoides scincoides, a long-lived Australian lizard species with slow-developing young, to respond to changes in stimulus relevance and test for behavioural flexibility. To test whether age affects learning in this species, we compared juveniles (23–56 days) with adults (sexually mature, at least 2 years). In accordance with our expectations, adults and juveniles performed similarly well in all stages, suggesting that juveniles of this precocial species learn at adult levels from an early age. Both age classes performed well during reversals showing good behavioural flexibility. This is the first study in lizards to directly compare juvenile and adult behavioural flexibility. Importantly, we demonstrate that precocial lizards can begin life with an advanced cognitive ability already in place.In altricial species, young rely on parental care and brain maturation mainly occurs after birth. In precocial species, young are born at a more advanced developmental stage in need of less or no parental care and brain development is mostly completed at the time of birth. We therefore predicted early maturation of learning ability in precocial species. We used a series of visual discrimination and reversal stages to investigate the ability of the precocial eastern blue-tongue lizard, Tiliqua scincoides scincoides, a long-lived Australian lizard species with slow-developing young, to respond to changes in stimulus relevance and test for behavioural flexibility. To test whether age affects learning in this species, we compared juveniles (23–56 days) with adults (sexually mature, at least 2 years). In accordance with our expectations, adults and juveniles performed similarly well in all stages, suggesting that juveniles of this precocial species learn at adult levels from an early age. Both age classes performed well during reversals showing good behavioural flexibility. This is the first study in lizards to directly compare juvenile and adult behavioural flexibility. Importantly, we demonstrate that precocial lizards can begin life with an advanced cognitive ability already in place.In altricial species, young rely on parental care and brain maturation mainly occurs after birth. In precocial species, young are born at a more advanced developmental stage in need of less or no parental care and brain development is mostly completed at the time of birth. We therefore predicted early maturation of learning ability in precocial species. We used a series of visual discrimination and reversal stages to investigate the ability of the precocial eastern blue-tongue lizard, Tiliqua scincoides scincoides, a long-lived Australian lizard species with slow-developing young, to respond to changes in stimulus relevance and test for behavioural flexibility. To test whether age affects learning in this species, we compared juveniles (23–56 days) with adults (sexually mature, at least 2 years). In accordance with our expectations, adults and juveniles performed similarly well in all stages, suggesting that juveniles of this precocial species learn at adult levels from an early age. Both age classes performed well during reversals showing good behavioural flexibility. This is the first study in lizards to directly compare juvenile and adult behavioural flexibility. Importantly, we demonstrate that precocial lizards can begin life with an advanced cognitive ability already in place.In altricial species, young rely on parental care and brain maturation mainly occurs after birth. In precocial species, young are born at a more advanced developmental stage in need of less or no parental care and brain development is mostly completed at the time of birth. We therefore predicted early maturation of learning ability in precocial species. We used a series of visual discrimination and reversal stages to investigate the ability of the precocial eastern blue-tongue lizard, Tiliqua scincoides scincoides, a long-lived Australian lizard species with slow-developing young, to respond to changes in stimulus relevance and test for behavioural flexibility. To test whether age affects learning in this species, we compared juveniles (23–56 days) with adults (sexually mature, at least 2 years). In accordance with our expectations, adults and juveniles performed similarly well in all stages, suggesting that juveniles of this precocial species learn at adult levels from an early age. Both age classes performed well during reversals showing good behavioural flexibility. This is the first study in lizards to directly compare juvenile and adult behavioural flexibility. Importantly, we demonstrate that precocial lizards can begin life with an advanced cognitive ability already in place. Postprint

We have a poor understanding of differences in learning performance between male and female non-avian reptiles compared to other vertebrates. Learning studies in non-avian reptiles have greatly increased in the last 10 years providing an opportunity to test for sex-based learning using a meta-analysis. Although, we initially considered all reptiles, only lizard studies (N = 11) provided sufficient data to calculate effect sizes. We found weak evidence for sex-dependent learning and moderate heterogeneity in effect sizes across studies. Although, our hypothesized moderator variables (stimulus or task type, species, genus and family) explained little variation. Indeed, our results show that only one species (Egernia striolata) exhibited a sex-dependent learning difference, with males learning faster than females. Together, our meta-analysis indicated a general lack of effective reporting on attributes of study methodology (i.e., animal sex, sample sizes). We propose that future research improve reporting by openly sharing their data for the use in similar analyses. The limited sample currently constrains our ability to effectively disentangle whether sex differences vary across different tasks and stimuli. We urge authors to incorporate both sexes in experimental designs and test them on ecologically relevant cognitive assays to improve our understanding of the degree of sex differences in non-avian reptile learning.

Response inhibition (inhibiting prepotent responses) is needed for reaching a more favourable goal in situations where reacting automatically would be detrimental. Inhibiting prepotent responses to resist the temptation of a stimulus in certain situations, such as a novel food item, can directly affect an animal’s survival. In humans and dogs, response inhibition varies between contexts and between individuals. We used two contextually different experiments to investigate response inhibition in the eastern water skink (Eulamprus quoyii): reversal of a visual two-choice discrimination and a cylinder detour task. During the two-choice task, half of our lizards were able to reach an initial learning criterion, but, thereafter, did not show consistent performance. Only two individuals reached a more stringent criterion, but subsequently failed during reversals. Furthermore, half of our animals were not able to inhibit a pre-existing side preference which affected their ability to learn during the two-choice task. Skinks were, however, able to achieve a detour around a cylinder performing at levels comparable to brown lemurs, marmosets, and some parrot species. A comparison between the tasks showed that reaching the initial criterion was associated with low success during the detour task, indicating that response inhibition could be context-specific in the water skink. To the best of our knowledge, this is the first study to examine inhibitory control and motor self-regulation in a lizard species.

Deimatic displays are a type of anti-predator behaviour that startles the predator. They have received much recent theoretical attention, enabling the empirical study of this phenomenon within a predictive framework. It has long been known that bluetongue skinks (Tiliqua spp.), when approached by predators, open their mouth widely and expose a conspicuously coloured tongue. Here, we test whether such ‘full-tongue’ displays are triggered by an imminent predatory attack in the Northern Bluetongue skink Tiliqua scincoides intermedia and examine whether this display behaviour is consistent with the predictions from deimatic display theory. First, we demonstrate that luminance at the rear of the tongue, which is only exposed during full-tongue displays, is almost twice as high for lizard and bird receivers compared to the tip of the tongue, and that tongue colouration is generally more conspicuous to a bird than a lizard visual system. Second, staged predatory encounters using model predators reveal that lizards primarily exhibit full-tongue displays in the final stages of a predatory attack. Lizards performed full-tongue displays congruent with the predictions associated with deimatic displays, i.e. rapid exposure of conspicuous elements from a previously inconspicuous state concurrently with aggressive defensive behaviour, most frequently during the final stages of a predatory encounter. Surprisingly, we also found that lizards vary the area of the tongue exposed during chemoexploratory tongue-flicks depending on whether a predator is present or absent. Bluetongue skinks have long been known to expose their large blue tongue in response to predatory threats. However, this behaviour has never been investigated empirically. Here, we use Northern Bluetongue skinks (Tiliqua scincoides intermedia) to test whether this behaviour is consistent with predictions associated with deimatic displays. We show that the rear of their tongue is UV-blue and more conspicuous to predators compared to the tip and that this ‘full-tongue display’ is only triggered in the final stages of a predatory attack.

Measures of physiological performance capacity, such as bite force, form the functional basis of sexual selection. Information about fighting ability may be conveyed through a structural feature such as a rostrum (i.e. horn) or a colour signal and thereby help reduce costly conflict. We quantified sexual dimorphism in key traits likely to be the targets of sexual selection in Tennent’s leaf-nosed lizard (Ceratophora tennentii) from Sri Lanka, and examined their relationship to bite force and body condition. We found body length and bite force to be similar for males and females. However, head length was significantly greater in males and they had significantly more conspicuous throats and labials (chromatic contrast and luminance) than females. Males also had a proportionally larger rostrum, which we predicted could be an important source of information about male quality for both sexes. Rostrum length was correlated with throat chromatic contrast in males but not females. Nonetheless, the rostrum and aspects of coloration did not correlate with bite force or body condition as we predicted. We have no information on contest escalation in this species but if they rarely bite, as suggested by a lack of difference in bite force between males and females, then bite force and any associated signals would not be a target of selection. Finally, males and females had similar spectral reflectance of the mouth and tongue and both had a peak in the ultra-violet, and were conspicuous to birds. Lizards only gaped their mouths during capture and not when threatened by a potential predator (hand waving). We hypothesize that conspicuous mouth colour may act as a deimatic signal, startling a potential predator, although this will need careful experimental testing in the future. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 00, 000–000. ADDITIONAL KEYWORDS: bite force ‐ colour ‐ deimatic signal ‐ horns ‐ performance capacity ‐ reptile ‐ sexual selection ‐ sexual dimorphism.

Signal diversification is often the product of sexual and/or natural selection and may be accompanied by genetic differentiation or simply reflect a plastic response to social and environmental variables.We use an agamid lizard endemic to Australia, the Jacky dragon (Amphibolurus muricatus), to examine the relationships between population relatedness, morphology and signalling behaviour. We also tested whether males are able to discriminate among rivals from different populations and whether they respond more aggressively to more closely related populations. We studied three populations, two of which belong to the same genetic clade. Individuals from the two most closely related populations were also more similar in morphology than lizards from the third, more distant, population. However, all three populations differed in characteristics of their signalling behaviour including latency to display and the interval between displays. In addition, animals from all populations showed similar levels of aggression when matched with individuals from the same or different populations in staged trials and thus did not show evidence of population-level discrimination. We argue that display variation might be a consequence of behavioural plasticity and that, despite difference in genetic structure, morphology and behaviour, this species retains a cohesive communication system. Macquarie University Universidad de Costa Rica Consejo Nacional para Investigaciones Científicas y Tecnológicas de Costa Rica/FI-252-11/CONYCIT/Costa Rica UCR::Sedes Regionales::Sede del Caribe

This is the peer reviewed version of the following article: [Leu ST, Burzacott D, Whiting MJ, Bull CM (2015) Mate familiarity drives long-term monogamy in a lizard: evidence from detailed biologging and a thirty one year field study. Ethology 121(8) pp. 760-768], which has been published in final form at DOI:10.1111/eth.12390. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving (http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms). This article is under embargo for a period of 12 months from the date of publication, Long-term monogamy is most prevalent in birds but is also found in lizards. We combined a 31-year field study of the long-lived, monogamous Australian sleepy lizard, Tiliqua rugosa, with continuous behavioural observations through GPS data logging, in one year, to investigate the duration of pair bonds, rates of partner change and whether either the reproductive performance hypothesis or the mate familiarity hypothesis could explain this remarkable long-term monogamy. The reproductive performance hypothesis predicts higher reproductive success in more experienced parents, whereas the mate familiarity hypothesis suggests that effects of partner familiarity select for partner retention and long-term monogamy. Divorce ratios were below 34% over a five year period and most sleepy lizards formed long-term pair bonds: 31 partnerships lasted for more than 15 years, 110 for more than 10 years, and the recorded maximum was 27 years (ongoing). In the year when we conducted detailed observations, familiar pairs mated significantly earlier than unfamiliar pairs. Previous pairing experience (total number of years paired with previous partners) had no significant effect. Early mating often equates to higher reproductive success, and we infer that is the case in sleepy lizards. Early mating of familiar pairs was not due to better body condition. We propose two suggestions about the proximate mechanisms that may allow familiar pair partners to mate earlier than unfamiliar partners. First, they may have improved coordination of their reproductive sexual cycles to reach receptivity earlier and thereby maximise fertilisation success. Second, they may forage more efficiently, benefiting from effective information transfer and/or cooperative predator detection. Those ideas need empirical testing in the future. Regardless of the mechanism, our observations of sleepy lizard pairing behaviour support the mate familiarity hypothesis, but not the reproductive performance hypothesis, as an explanation for its long-term monogamous mating system

We studied tree agama (Acanthocercus a. atricollis) habitat use in the Magaliesberg mountain range in northern South Africa using sightings of marked individuals, and in a few cases, radio-telemetry. Acanthocercus a. atricollis preferentially selected thorn trees (46%; Acacia karroo), followed by common sugarbush (10%; Protea caffra) and dead trees (9%). The type of tree selected was unrelated to lizard age class or sex. Multivariate analysis failed to show any age class or sex effects for specific tree physical characteristics, but did reveal a preference for trees with greater diameter, canopy cover and incidence of parasitic plants. We suggest that more ‘complex’ trees may enhance crypsis, facilitate escape from predation, or provide a foraging advantage. Acanthocercus a. atricollis selected night-time perches higher than those used during the day, possibly further offsetting predation risk.Keywords: tree selection, age-sex differences, nocturnal retreat sites, lizard, reptile

© 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology Phenotypic traits such as ornaments and armaments are generally shaped by sexual selection, which often favours larger and more elaborate males compared to females. But can sexual selection also influence the brain? Previous studies in vertebrates report contradictory results with no consistent pattern between variation in brain structure and the strength of sexual selection. We hypothesize that sexual selection will act in a consistent way on two vertebrate brain regions that directly regulate sexual behaviour: the medial preoptic nucleus (MPON) and the ventromedial hypothalamic nucleus (VMN). The MPON regulates male reproductive behaviour whereas the VMN regulates female reproductive behaviour and is also involved in male aggression. To test our hypothesis, we used high-resolution magnetic resonance imaging combined with traditional histology of brains in 14 dragon lizard species of the genus Ctenophorus that vary in the strength of precopulatory sexual selection. Males belonging to species that experience greater sexual selection had a larger MPON and a smaller VMN. Conversely, females did not show any patterns of variation in these brain regions. As the volumes of both these regions also correlated with brain volume (BV) in our models, we tested whether they show the same pattern of evolution in response to changes in BV and found that the do. Therefore, we show that the primary brain nuclei underlying reproductive behaviour in vertebrates can evolve in a mosaic fashion, differently between males and females, likely in response to sexual selection, and that these same regions are simultaneously evolving in concert in relation to overall brain size.

In lizards, males are predicted to sprint faster and run for longer than females by virtue of higher testosterone levels and differences in morphology. Consequently, escape behaviour is also predicted to be associated with sex and locomotor performance, yet these links have rarely been explored. Here, we tested whether escape behaviour is associated with locomotor performance in the toad-headed agama, Phrynocephalus vlangalii, and whether it is sex-dependent. This species is also characterized by elaborate tail displays, which we examined as a potential pursuit-deterrent signal. Tail waves were performed by a very small proportion (2/58, 3 %) of individuals during predatory trials, suggesting that tail signalling functions exclusively in a social context. To understand the relationships between sex, escape behaviour and performance, we first measured escape behaviour (flight initiation distance, flight distance—measured differently compared to previous studies of lizard escape behaviour, and refuge use) in the field before measuring maximal sprint speed and endurance on the same individuals in the laboratory. Flight initiation distance did not differ between the sexes and was unrelated to performance capacity (maximal endurance and sprint speed) but was positively related to body size with larger individuals fleeing earlier. Males fled farther than females, but flight distance was also unrelated to either endurance or sprint speed. Interestingly, faster females were less likely to enter a refuge than slower females, whereas sprint speed and the probability of taking refuge were unrelated for males. Our results suggest that when males and females are not obviously sexually dimorphic, they are more likely to overlap in escape tactics.

Understanding underlying physiological differences between the sexes in circulating androgens and how hormonal variation affects morphology–performance relationships may help clarify the evolution of sexual dimorphism in diverse taxa. Using a widely distributed Australian lizard (Eulamprus quoyii) with weak sexual dimorphism and no dichromatism, we tested whether circulating androgens differed between the sexes and whether they covaried with morphological and performance traits (bite force, sprint speed, endurance). Males had larger head dimensions, stronger bite force, faster sprint speed, and longer endurance compared to females. We found that the sexes did not differ in androgen concentrations and that androgens were weakly associated with both morphological and performance traits. Interestingly, high circulating androgens showed a nonlinear relationship with bite force in males and not females, with this relationship possibly being related to alternative male reproductive tactics. Our results suggest that androgens are not strongly correlated with most performance and morphological traits, although they may play an important organizational role during the development of morphological traits, which could explain the differences in morphology and thus performance between the sexes. Differences in performance between the sexes suggest differential selection on these functional traits between males and females. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 834–849.

Alternative reproductive tactics (ARTs) are predicted to be the result of disruptive correlational selection on suites of morphological, physiological, and behavioral traits. ARTs are most obvious when they occur in discrete morphs with concomitant behavioral tactics. However, ARTs driven by behavior in species lacking obvious phenotypic differences are rarely documented and poorly understood. We quantified selection acting on phenotypic traits predicted to characterize ARTs by observing marked lizards in six seminatural populations. We quantified reproductive fitness for each male using six microsatellite DNA loci from 226 offspring born to 56 females. Candidate models containing directional and correlational selection gradients were equally supported. As predicted, large males with large home ranges and large males that were observed frequently had the highest reproductive success. We also found evidence that large males that moved little but that were observed frequently and large males that moved frequently but that were observed little were predicted to have high fitness. Model predictions support our verbal hypothesis regarding the phenotypes characterizing ARTs and suggest that large males may be adopting subtly different tactics to acquire paternity. Our results suggest that disruptive correlational selection between behavioral traits may drive the evolution of ARTs in "cryptic" systems that lack overt polymorphisms.

Multiple paternity is taxonomically widespread, yet the relative role of direct and indirect (genetic) fitness benefits in explaining the evolution of multiple mating is a topic of intense debate. We test whether female Eastern Water Skinks (Eulamprus quoyii) gain direct (fecundity) and/ or indirect genetic (increased offspring fitness) benefits through multiple mating. We maintained 216 (108 males and 108 females) E. quoyii in 6 large outdoor enclosures for a single breeding season before bringing gravid females into the lab to give birth. We classified female clutches as being singly or multiply sired using 6 polymorphic microsatellite DNA loci. To test whether females gain genetic benefits, we measured 5 fitness traits on offspring over their first active season and compared these traits between single paternity and multiple pater nity clutches. Contrary to predictions from genetic benefits models, offspring from multiple paternity and single paternity clutches did not differ significantly in snout–vent length, mass, growth rate, sprint speed, or endurance. Although multiple paternity and single paternity females did not differ significantly in body size, condition, or mass, multiple paternity females invested more heavily in reproduction when body size, mass, and condition were controlled, producing significantly more offspring compared with single paternity females. We suggest that polyandry in E. quoyii possibly evolved as a mechanism to ensure fertilization of ova, similar to what has been reported in some other taxa.

Conspicuous color signals are commonly used by a wide diversity of animals to advertise some specific aspect of their competitive ability. In particular, orange and red colors are often used as an aggressive signal to potential rivals. The iconic Australian frillneck lizard (Chlamydosaurus kingii) has a large and extensible frill that varies geographically in the extent of yellow, orange, and red present. Focusing on the red-orange lizards found in Western Australia, we first established that, in contrast to most lizards studied to date, the red-orange–colored frill is carotenoid rather than pterin based. Second, we measured chromatic and achromatic aspects of male frills before staging dyadic contests between males to determine whether color is used to signal fighting ability. Both chromatic and achromatic measures of the red-orange patches on the lizard’s frills, as well as similarly colored patches on their throats, were reliable predictors of competitive ability; males possessing more colorful displays dominated size-matched competitors in dyadic contests. Apart from large differences in body size and mass (>10%), no other colorimetrics (e.g., white patches), frill traits (e.g., size, relative and absolute patch sizes), or morphological measures (e.g., head size, bite force) were found to predict the outcome of contests. To the best of our knowledge, this is the first example of carotenoid-based patches signaling male fighting ability in a lizard.

Pregnancy is a challenging period for egg laying squamates. Carrying eggs can encumber females and decrease their locomotor performance, potentially increasing their risk of predation. Pregnant females can potentially reduce this handicap by selecting higher temperatures to increase their sprint speed and ability to escape from predators, or to speed up embryonic development and reduce the period during which they are burdened with eggs (‘selfish mother’ hypothesis). Alternatively, females might select more stable body temperatures during pregnancy to enhance offspring fitness (‘maternal manipulation hypothesis’), even if the maintenance of such temperatures compromises a female's locomotor performance. We investigated whether pregnancy affects the preferred body temperatures and locomotor performance of female velvet geckos Amalosia lesueurii. We measured running speed of females during late pregnancy, and one week after they laid eggs at four temperatures (20°, 25°, 30° and 35 °C). Preferred body temperatures of females were measured in a cost-free thermal gradient during late pregnancy and one week after egg-laying. Females selected higher and more stable set-point temperatures when they were pregnant (mean =29.0 °C, Tset =27.8–30.5 °C) than when they were non-pregnant (mean =26.2 °C, Tset =23.7–28.7 °C). Pregnancy was also associated with impaired performance; females sprinted more slowly at all four test temperatures when burdened with eggs. Although females selected higher body temperatures during late pregnancy, this increase in temperature did not compensate for their impaired running performance. Hence, our results suggest that females select higher temperatures during pregnancy to speed up embryogenesis and reduce the period during which they have reduced performance. This strategy may decrease a female's probability of encountering predatory snakes that use the same microhabitats for thermoregulation. Selection of stable temperatures by pregnant females may also benefit embryos, but manipulative experiments are necessary to test this hypothesis. Fil: Dayananda, Buddhi. University of Technology Sydney; Australia Fil: Ibarguengoytía, Nora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Whiting, Martin J.. Macquarie University; Australia Fil: Webb, Jonathan K.. University of Technology Sydney; Australia

Environmental contaminants from anthropogenic activity such as mining can have profound health effects on the animals living in adjacent areas. We investigated whether inorganic contaminants associated with gold-mining waste discharges were accumulated by a threatened species of lizard, Smaug giganteus, in South Africa. Lizards were sampled from two mining sites and two control sites. Blood samples from the most contaminated mining site had significantly greater concentrations of lithium, sodium, aluminum, sulfur, silicon, chromium, manganese, iron, nickel, copper, tungsten, and bismuth than the remaining sites. Contaminant concentrations were not significantly related to lizard body condition, although these relationships were consistently negative. The adult sex ratio of the population inhabiting the most contaminated site also deviated from an expected 1:1 ratio in favour of female lizards. We demonstrate that lizards at these mining sites contained high concentrations of heavy metals that may be imposing as yet poorly understood costs to these lizards.

Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizardPlatysaurus broadleyibecause it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev–Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this.

In externally fertilizing animals in which females mate with multiple males at the same time (simultaneous polyandry), the possibility that females accrue genetic benefits that improve offspring viability remains largely unexamined. Here, we investigate whether simultaneous polyandry influences offspring fitness in a wild population of the Grey Foam Nest Treefrog Chiromantis xerampelina. Simultaneous polyandry in this frog is the most extreme reported for any vertebrate, with more than 90% of females mating with 10 or more males during the deposition of a single clutch. We compared growth (using age and size at metamorphosis as proxies) and survival of offspring produced by females that naturally mated with either 1 male (monandrous females) or 10‐12 males (polyandrous females). Polyandry did not influence size or age at metamorphosis, but we found that offspring from polyandrous matings had both significantly higher mean survival and reduced variance in offspring survival. These findings implicate a genetic mechanism, but targeted cross-classified breeding experiments that control for both maternal and material effects will be required to conclusively determine whether elevated offspring viability is linked to enhanced genetic diversity, intrinsic sire effects, or genetic compatibility. Irrespective of the causation, the findings provide the first evidence that naturally formed polyandrous matings have increased offspring viability in an anuran amphibian. Key words: anuran amphibian, genetic benefits, offspring viability, polyandry, sexual selection. [Behav Ecol]

Species that are able to solve novel problems through social learning from either a conspecific or a heterospecific may gain a significant advantage in new environments. We tested the ability of a highly successful invasive species, the Italian wall lizard Podarcis sicula , to solve a novel foraging task when social information was available from both a conspecific and an unfamiliar heterospecific ( Podarcis bocagei ). We found that Italian wall lizards that had access to social information made fewer errors, regardless of whether the demonstrator was a conspecific or a heterospecific, compared to Italian wall lizards that individually learnt the same task. We suggest that social learning could be a previously underappreciated, advantageous mechanism facilitating invasions.

We investigated the thermoregulatory abilities and behavior of Pseudocordylus melanotus melanotus (Drakensberg crag lizard) in terms of the relationship between the operative temperature (Te), selected temperature (Tsel), set-point range (Tset) and field active body temperature (field Tsel), exposure to low temperature, body posture and activity. The Te range for P. m. melanotus was about 58 C (23.20 C in winter to 54.94 C in summer). In a laboratory thermal gradient, in a setting that is independent of ecological costs or thermal constraints, lizards maintained Tset (defined as the interquartile range of Tsel, after Hertz et al., 1993) between 29.00 6 0.36 C and 31.78 6 0.16 C in winter and 29.61 6 0.28 C and 32.47 6 0.18 C in summer. The mean Tsel was 30.08 6 0.14 C in winter and 30.99 6 0.11 C in summer. In the field, however, lizards achieved significantly lower Tb, which suggests that the thermal environment limited the Tb that lizards were able to achieve. Lizards were active for significantly longer and selected significantly higher Tb in summer than in winter. During winter, lizards spent a significant amount of time at Tb below their lower critical limiting temperature (defined by loss of righting). The most frequently assumed body postures in summer were those where the head or body were raised, whereas, in winter, lizards usually lay with head and body flat on the rock substrate. We suggest that these differences reflect the physiological requirements of the lizards: Head-up postures in sit-and-wait foragers are consistent with scanning for prey while head-down postures are likely motivated by thermoregulatory needs. It is clear that P. m. melanotus can thermoregulate efficiently, but the Tb maintained may be constrained by the range of Te available to the lizards in their natural environment. Pseudocordylus m. melanotus currently appears to be geographically constrained by low environmental temperatures at the edge of its range. Should global warming become a reality in southern Africa, this species could inadvertently benefit by occupying new habitat that was previously unavailable because of thermal constraints.

Whether general patterns of signal evolution can be explained by selection for signal efficacy (detectability) has yet to be established. To establish the importance of signal efficacy requires evidence that both signals and their detectability to receivers have evolved in response to habitat shifts in a predictable fashion. Here, we test whether habitat structure has predictable effects on the evolution of male and female display coloration in 21 lineages of African dwarf chameleon (Bradypodion), based on a phylogenetic comparative analysis. We used quantitative measures of display coloration and estimated signal detectability as the contrast of those colors among body regions or against the background vegetation as perceived by the chameleon visual system. Both male and female display colors varied predictably with different aspects of habitat structure. In several (but not all) instances, habitat-associated shifts in display coloration resulted in habitat-associated variation in detectability. While males exhibit a remarkable variety of colors and patterns, female display coloration is highly conserved, consisting in all populations of contrasting dark and light elements. This color pattern may maximize detectability across all habitat types, potentially explaining female conservatism. Overall, our results support the view that selection for signal efficacy plays an important role in the evolution of animal signals.

Aggregations are a common feature of many species although for most taxa, the mechanisms underlying these aggregations are poorly understood. The Augrabies Flat Lizard (Platysaurus broadleyi) is a sexually dimorphic lizard that experiences intense conflict as a result of sexual selection. In the wild, P. broadleyi share communal crevices and aggregate in the presence of large insect plumes. We experimentally tested whether lizards aggregate as a result of social factors. We also tested whether aggregative behavior differed between the sexes and depends on density. We found no evidence that Augrabies Flat Lizards preferentially group for social reasons in the absence of resources or thermoregulatory benefits. This was true for both sexes and at both densities (two-lizard and four-lizard trials). Although social factors did not promote grouping, males sheltered alone significantly more often than expected by chance, suggesting that males actively avoid one another. Therefore, social factors may wor...

Some aspects of escape predicted by theoretical models are intended to apply universally. For example, flight initiation distance (distance between an approaching predator and prey when escape begins) is predicted from predation risk and the costs of escaping. Escape tactics and refuge selection are not currently predicted by theoretical models, but are expected to vary with structural features of the habitat. One way of studying such variation is to compare aspects of antipredatory behavior among sympatric species that differ in habitat or microhabitat use. In an assemblage of lizards in northwestern Namibia, we conducted experiments to test predictions of escape theory for three risk factors in representatives of three families and observed escape tactics in additional species. As predicted by escape theory, flight initiation distance increased with directness of a predator’s approach and predator speed in Agama planiceps, Mabuya acutilabris, and Rhotropus boultoni, and with distance from refuge in M. acutilabris. As predicted by theory, the probability of entering refuge increased with risk in R. boultoni. All available data indicate that flight initiation distance and refuge entry by lizards conform to theoretical predictions. Escape tactics varied greatly as a function of habitat type: (1) arboreal species fled up and around trees and sometimes entered tree holes; (2) saxicolous species used rock crevices as refuges, but differed in tactics prior to entering refuges; and (3) terrestrial species fled into bushes or other vegetation, often to the far sides of them. Some M. acutilabris entered small animal burrows or buried themselves in sand beneath bushes. Escape tactics varied even among congeners in Mabuya, highlighting the important effect of habitat structure on them. Although habitat partitioning has traditionally been viewed as favoring species coexistence, an interesting by-product appears to be structuring of escape tactics in lizard communities.

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85 mm SVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17–19 mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL....

1. An organism's thermal tolerance to the environment may indicate a thermal limit to its geographical distribution. 2. We measured the lower critical minimum (CTMin) and lower lethal temperature in the lizard Pseudocordylus melanotus melanotus . 3. CTMin was 10.17±0.48 °C and the lower lethal temperature was −5.15±0.31 °C. 4. All lizards that froze did not survive. This suggests that these lizards are restricted to areas where the microclimate allows them to avoid freezing. 5. Pseudocordylus m. melanotus can allow their body temperatures to drop well below CTMin without any ill effect.

Many species possess multiple sexually dimorphic traits, which incorporate different sensory modalities (e.g., acoustic, olfactory and visual), although their relative roles in sexual selection and in determining reproductive success are still poorly understood for most taxa. We assessed the role of multiple male traits, including one acoustic (dominant call frequency) and one visual (yellow throat patch) trait, in residency advertisement, contest behavior, and breeding success in barking geckos (Ptenopus garrulus garrulus). We show that male barking geckos maintain largely exclusive home ranges, with a trend for larger males to maintain larger home ranges. We also show that larger males have a lower dominant calling frequency. When aggressive behavior was elicited in the field using a recorded call of average frequency, resident males with low frequency calls were more likely to respond aggressively and charge the speaker compared to males with high frequency calls. However, body size and small relative throat patch size, rather than call frequency, were the best predictors of overall aggressiveness. Body size was also the best predictor of whether males bred. We suggest that call frequency in this crepuscular species constitutes an effective long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries in low-light environments.

Understanding the role of multiple colour signals during sexual signalling is a central theme in animal communication. We quantified the role of multiple colour signals (including ultraviolet, UV), measures of body size and testosterone levels in settling disputes between male rivals in an elaborately ornamented, African lizard, played out in a large ‘tournament’ in the wild. The hue and brightness (total reflectance) of the UV throat in Augrabies flat lizards, Platysaurus broadleyi, as well as body size, were consistent and strong predictors of ‘fighting ability’. Males with high fighting ability were larger and displayed a UV throat with low total reflectance. In contrast, males with low fighting ability were smaller and had violet throats with broader spectral reflectance curves (higher total reflectance). As fighting ability is associated with alternative reproductive tactics in this system (territorial versus floater), we also examined the role of colour signals in predicting male reproductive tactic. Territorial males had UV throats with higher chroma but had poorer body condition than floater males, probably because of the energetic costs of maintaining a territory. Although testosterone was not a significant predictor of fighting ability or reproductive tactic, it was correlated with the hue of the UV throat, suggesting that testosterone may impose some constraint on signal expression. Lastly, we show that within the context of the natural signalling environment, UV-reflective throats constitute a conspicuous, effective signal that male Augrabies flat lizards use to advertise their status honestly to rivals.

Ultraviolet (UV) signals are used in female mate choice in numerous taxa; however, the role of UV signals in male contests remains relatively unexplored. We experimentally reduced throat UV of free-ranging lizards ( Platysaurus broadleyi ) to test whether UV acts as a signal of fighting ability during male contests. We found that UV-reduced males were more likely to be challenged than control males. However, contest outcome was not influenced by UV-reduction, and this was despite other obvious asymmetries between opponents, such as body size and residency. Throat UV was confirmed as a signal of fighting ability because contests were more likely to escalate when one contestant had reduced UV. Therefore, throat UV, not body size or residency, was used during the initial stage of opponent assessment, but this did not influence contest outcome. The results suggest that UV overrides other traits that could function as signals during rival assessment.

Lizards that forage from ambush do not exhibit prey chemical discrimination, but might enhance foraging efficiency by staying longer at ambush posts bearing chemical prey cues. By presenting chemical stimuli to free-ranging lizards, we tested whether Platysaurus broadleyi had longer giving-up time (i.e., time at an ambush post) in the presence of insect prey stimuli. The lizards remained no longer at tiles labelled by prey chemicals than control substances, but giving-up times were greater at tiles labelled by a plant food (fig). Ambush foragers may not use prey chemicals to assess the quality of ambush posts.

Lizards use visual and/or chemical cues to locate and identify food. The ability to discriminate prey chemical cues is affected by phylogeny, diet, and foraging mode. Augrabies flat lizards (Platysaurus broadleyi) are omnivorous members of the lizard clade Scleroglossa. Within Scleroglossa, all previously tested omnivores are capable of both prey and plant chemical discrimination. At Augrabies Falls National Park, P. broadleyi feed on both insects (black flies) and plant material (figs), and as scleroglossans, are predicted to discriminate both plant and prey chemicals. However, Platysaurus broadleyi use visual, not chemical cues, to detect and capture black flies, which occur in large concentrations in the study area. We tested free-ranging individuals for the ability to discriminate insect and plant chemicals from controls. There was a significant stimulus effect such that lizards tongue-flicked fig-labelled tiles significantly more than the remaining stimuli, spent more time at the fig-labelled tile, and attempted to eat fig-labelled tiles more often than tiles labelled with control or insect stimuli. Platysaurus broadleyi is exceptional in being the first lizard shown to possess plant chemical discrimination but to lack prey chemical discrimination. We suggest that an absence of prey chemical discrimination may be a consequence of foraging behaviour and environmental effects. Because insect prey are highly clumped, abundant, and aerial, profitable ambushing using visual cues may have relaxed any selective pressure favouring insect prey chemical discrimination. However, a more likely alternative is that responses to figs are gustatory, whereas as prey chemical discrimination and plant chemical discrimination are usually mediated by vomerolfaction.

Flat lizards Platysaurus intermedius wilhelmi occur on small discrete rock outcrops in Mpumalanga Province, South Africa. These rock outcrops are structurally simple and this, combined with the lizard’s behaviour (ambush foraging in the open), make them ideal for field studies of anti-predatory behaviour. Lizards were approached in the field and how escape behaviour was influenced by habitat and age-sex class was recorded. Juveniles (c .4m onths of age) responded quite differently to an approaching human ‘predator’ compared with adult males and females (which responded similarly). Compared to adults, juveniles allowed a closer approach by the investigator; took longer to find a refuge and therefore fled further; were more likely to remain visible in the open and maintain visual contact with the investigator; and more likely to flee into vegetation when given the opportunity to take refuge in a crevice. We suggest that because a greater suite of predators (including arthropods living in rock crevices) feed on small juvenile lizards, this may affect their choice of refuge and result in the avoidance of crevices when chased. Finally, because juveniles were frequently found on small rock outcrops, the influence of rock outcrop area on anti-predatory behaviour was tested. Escape behaviour (time to refuge) was independent of rock outcrop area.

Multiple mating in female animals is something of a paradox because it can either be risky (e.g., higher probability of disease transmission, social costs) or provide substantial fitness benefits (e.g., genetic bet hedging whereby the likelihood of reproductive failure is lowered). The genetic relatedness of parental units, particularly in lizards, has rarely been studied in the wild. Here, we examined levels of multiple paternity in Australia's largest agamid lizard, the eastern water dragon (Intellagama lesueurii), and determined whether male reproductive success is best explained by its heterozygosity coefficient or the extent to which it is related to the mother. Female polyandry was the norm: 2/22 clutches (9.2%) were sired by three or more fathers, 17/22 (77.2%) were sired by two fathers, and only 3/22 (13.6%) clutches were sired by one father. Moreover, we reconstructed the paternal genotypes for 18 known mother–offspring clutches and found no evidence that females were favoring less related males or that less related males had higher fitness. However, males with greater heterozygosity sired more offspring. While the postcopulatory mechanisms underlying this pattern are not understood, female water dragons likely represent another example of reproduction through cryptic means (sperm selection/sperm competition) in a lizard, and through which they may ameliorate the effects of male-driven precopulatory sexual selection.

Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new information by another, is taxonomically biased towards mammals, especially primates, and birds. However, social learning need not be limited to group-living animals because species with less interaction can still benefit from learning about potential predators, food sources, rivals and mates. We trained male skinks ( Eulamprus quoyii ), a mostly solitary lizard from eastern Australia, in a two-step foraging task. Lizards belonging to ‘young’ and ‘old’ age classes were presented with a novel instrumental task (displacing a lid) and an association task (reward under blue lid). We did not find evidence for age-dependent learning of the instrumental task; however, young males in the presence of a demonstrator learnt the association task faster than young males without a demonstrator, whereas old males in both treatments had similar success rates. We present the first evidence of age-dependent social learning in a lizard and suggest that the use of social information for learning may be more widespread than previously believed.

Understanding individual differences in cognitive performance is a major challenge to animal behaviour and cognition studies. We used the Eastern water skink ( Eulamprus quoyii ) to examine associations between exploration, boldness and individual variability in spatial learning, a dimension of lizard cognition with important bearing on fitness. We show that males perform better than females in a biologically relevant spatial learning task. This is the first evidence for sex differences in learning in a reptile, and we argue that it is probably owing to sex-specific selective pressures that may be widespread in lizards. Across the sexes, we found a clear association between boldness after a simulated predatory attack and the probability of learning the spatial task. In contrast to previous studies, we found a nonlinear association between boldness and learning: both ‘bold’ and ‘shy’ behavioural types were more successful learners than intermediate males. Our results do not fit with recent predictions suggesting that individual differences in learning may be linked with behavioural types via high–low-risk/reward trade-offs. We suggest the possibility that differences in spatial cognitive performance may arise in lizards as a consequence of the distinct environmental variability and complexity experienced by individuals as a result of their sex and social tactics.

Mistaken identity and competitive exclusion are two alternative hypotheses proposed to explain interspecific aggression between males. We examined agonistic behaviour in males of two lizard species: Platysaurus minor and P. monotropis. In each of nine outdoor field enclosures, we maintained a male and a female of both species (i.e., four total) and observed the dominance relationship between the males. Interspecific aggression was intense and P. monotropis was dominant in eight of nine enclosures. Furthermore, P. minor males received significantly more bite marks than P. monotropis males during the course of the experiment. To distinguish among the two hypotheses for interspecific aggression (mistaken identity and competitive exclusion), we presented P. minor males from sympatry and allopatry with model lizards of both taxa and measured aggressive responses. All trials with models were conducted in field enclosures where males were kept alone for the duration of the experiment. The model experime...