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When different modes of communication are used in combination and for example convey visual and acoustic information, they form a multimodal signal. Frogs are best known for using acoustic communication, but many species also use visual or colour signals, some of which are dynamic, and may be combined with acoustic signals. In this context, the question of whether these two modes of communication reinforce the same message or offer different information is poorly understood. Male whirring tree frogs, Litoria revelata, use a multimodal signal during courtship, which combines a vocalisation and dynamic sexual dichromatism, with nuptial display colours shifting from brown or grey to bright yellow. Here, we examined the properties of the advertisement call and nuptial colour of vocalising male whirring tree frogs and tested whether the two signals were likely to reinforce each other or convey independent information. We found only weak associations between elements of male colouration and vocalisations, suggesting that advertisement calls and nuptial colour do not reinforce each other and that the signals may instead convey different information. Significance statement: Dynamic nuptial colour and vocalisation in combination is a relatively common multimodal signal in frogs but is unstudied. We looked for relationships between properties of colour and vocalisation in an Australian tree frog to explore whether the two sensory modes formed backup signals or multiple messages. We did not find predictive relationships between nuptial colour and vocalisation, supporting the multiple messages hypothesis and suggesting that nuptial colour is not necessarily directed at females for the purposes of mate attraction, potentially differing from the assumed function of the vocalisation. Our study is also the first to formally characterise aspects of dynamic sexual dichromatism in the whirring tree frog (Litoria revelata) and the first to describe the advertisement call of this species in its southern distribution. Whilst we do not specifically address the function of dynamic sexual dichromatism in this species, our findings do not contradict the existing literature in respect to it being a male-male directed signal. [ABSTRACT FROM AUTHOR]

Early developmental temperatures influence the physiology and behavior of reptiles, with important consequences for their fitness and survival. For example, many viviparous lizards are cold adapted which may restrict their activity times during the reproductive season, increasing their susceptibility to global warming. However, it is unclear if and how lizards with different reproductive modes (oviparity vs. viviparity) can respond to rising temperatures by modifying their life-history traits. We examined the effect of developmental temperatures on hatchling behavior and learning in viviparous and oviparous populations of the lizard Saiphos equalis to test whether their reproductive behavior can 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 exploratory, foraging and antipredator behavior, and spatial learning ability of their offspring. We found that viviparous lizards were more exploratory and had a less-pronounced antipredator response than oviparous lizards. Regardless of the mode of reproduction, elevated temperatures reduced the exploratory behavior of hatchling lizards. Elevated temperatures also reduced the foraging efficiency of oviparous, but not viviparous, hatchlings. Finally, future-gestated oviparous hatchlings were more likely to choose the correct refuge and made fewer mistakes in a spatial learning task; however, we found only weak evidence of spatial learning in S. equalis. Our results suggest that although global warming is likely to have a negative impact on phenotypic traits, in S. equalis, some of these effects may be ameliorated by maternal behavior and/or physiological responses during pregnancy, particularly in viviparous populations. Significance statement: Computational modeling studies suggest that live-bearing lizards (viviparous) are more vulnerable to global warming compared with egg-laying ones (oviparous). However, there is little experimental evidence showing that viviparous species are indeed at a greater risk of extinction. Using a lizard species that has both oviparous and viviparous populations, we tested the effect of high developmental temperatures (projected for 2100) on the behavior and learning of their offspring. We found that elevated temperatures had a stronger negative effect on egg-laying lizards by producing hatchlings with lower foraging efficiency. Our results suggest that viviparous mothers can ameliorate some of the effects of global warming on their offspring. Moreover, our study suggests that if live bearers are indeed more vulnerable to global warming, it is likely not due to maladaptive behavior in offspring, but rather, to other causes that affect pregnant females. [ABSTRACT FROM AUTHOR]

In invasive species, geographically variable evolutionary and ecological pressures can cause the rapid evolution of divergent behavioural phenotypes. Studies on invasive cane toads ( Rhinella marina) in tropical Australia have revealed strong (and heritable) shifts in physiological traits related to dispersal rate. Behavioural phenotypes may have evolved in similar ways. We used standardised arena trials to test field-collected adult female toads from three populations: a range-core area in Queensland (ca. 76 years post-colonisation), a range-front population in Western Australia (<5 years post-colonisation) and an intermediate Northern Territory population (11 years post-colonisation). As predicted, toads from the range-front population were more exploratory and more likely to take risks in a novel arena environment than were conspecifics from the range-core population. We suggest that differential selection on behavioural responses to novel conditions in range-core versus range-front populations has produced a distinctive behavioural phenotype at the range-front that retains a high propensity for exploration and risk-taking (enhancing the ability of range-front toads to locate food and shelter) even when faced with novel environments. In contrast, at the range core where the locations of resources are known, a decrease in exploration and risk-taking in response to a novel environment may be favoured as it assists toads in evading threats. Significance statement: Ongoing biological invasions provide an ideal opportunity to examine which phenotypic traits drive establishment, range-expansion and invasion success. Furthermore, ongoing invasions allow us to investigate if variation in evolutionary and ecological pressures across an invasion range leads to geographical divergence in phenotypic traits. Dispersal ability is a key factor in invasion success. Behavioural traits such as exploration and a propensity to take risks enhance dispersal as individuals with these traits rapidly move out of their existing range and exploit new habitats and resources. We studied geographic divergence of dispersal-related behavioural traits across the Australian invasion range of cane toads ( Rhinella marina) using standardised laboratory trials. We found that range-front toads were more exploratory and more likely to take risks than were conspecifics from range-core areas. Our results suggest that dispersal-enhancing behavioural traits may be important drivers of invasion success in cane toads. [ABSTRACT FROM AUTHOR]

An individual's contest history can have a significant effect on their probability of winning a future contest. These winner-loser effects are likely to be mediated by the level of escalation in a contest, although this is rarely considered in the contest literature. We staged contests between size-matched male water skinks ( Eulamprus quoyii) in a tournament design to investigate how prior contest success indirectly affected contest outcome through its effects on contest behavior. Moreover, we predicted that the effect of behavioral traits on contest outcome would depend on the level of escalation reached by contestants (non-escalated versus escalated contests). Contest initiation was the best predictor of contest outcome in both non-escalated and escalated contests, and whether an individual initiated a contest depended on prior contest experience. Prior winners were more likely to initiate subsequent aggressive encounters, and by doing so, initiators had an 88 % probability of winning compared to non-initiators in non-escalated contests. However, this effect was mediated by the level of escalation. Initiators in escalated contests had only a 59 % probability of winning compared to non-initiators. These results suggest that the strength of the effect of prior contest experience on behavioral traits varies across contest stages and is consistent with the hypothesis that prior contest experience alters an individual's perception of its own fighting ability. Our study highlights the importance of considering the level of contest escalation when examining winner-loser effects in predicting contest outcome. SIGNIFICANT STATEMENT: Our results show that the effect of prior contest experience on contest initiation varies depending on the level of escalation reached by the contestants. We emphasize the importance of considering the level of contest escalation when examining the influence of prior contest experience on contest outcome. [ABSTRACT FROM AUTHOR]

Territorial behaviour, whereby dominant animals gain priority access to critical resources, is widespread in some animal lineages, but rare in others. Theory suggests that territoriality will evolve only when animals can economically defend sites that contain critical resources (typically mates, sometimes food). In striking contrast to their close relatives the lizards, male defence of territories for access to mates has not been reported in snakes. In south-eastern Australia, receptive female small-eyed snakes thermoregulate under 'hot rocks', concentrating mating opportunities and thus, potentially allowing males to enhance their fitness by defending these rocks from rivals. We videotaped staged contests between resident and intruder males and analysed data on cohabitation patterns from a long-term (21 years) mark-recapture study. In staged contests, males actively defended hot rocks from intruder males; and thus, larger males actively displaced their smaller rivals. In the wild, larger males were found under rocks with more or larger females. These results suggest that the thermally driven concentration of female small-eyed snakes has rendered hot rocks economically defensible, and thus favoured the evolution of territoriality in a snake. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The ability of an animal to acquire, process and learn from information in their environment is thought to be fundamental to fitness. We currently have a poor understanding of the learning ability of young animals within the first few months of their life, the types of learning they use and the extent of their learning ability. Furthermore, an animal's developmental environment, such as nest incubation temperature, may profoundly influence motor and cognitive skills. We first tested the ability of hatchling three-lined skinks ( Bassiana duperreyi) incubated at 'hot' and 'cold' temperatures to solve an instrumental (motor) task before assessing their ability to learn colour associations in a multi-stage instrumental task, with a choice reversal. While 53 (88.3 %) lizards successfully completed the training phase, 14 (46.7 %) of the 'hot' incubated and none of the 'cold' incubated lizards successfully completed the instrumental task. Thirteen of these lizards rapidly learnt to discriminate colours, and this culminated in eight individuals successfully completing a choice reversal. Hatchling B. duperreyi demonstrated surprisingly rapid learning, and these results highlight the potentially important role of cognition during development and ultimately, in fitness. [ABSTRACT FROM AUTHOR]

Sexual selection theory predicts different optima for multiple mating in males and females. We used mating experiments and genetic paternity testing to disentangle pre- and postcopulatory mechanisms of sexual selection and alternate reproductive tactics in the highly promiscuous lizard Eulamprus heatwolei. Both sexes mated multiply: 30-60 % of clutches were sired by two to four fathers, depending on the experiment. Larger males sired more offspring when we allowed male contest competition: 52 % of large males but only 14 % of small males sired at least one offspring. In the absence of male contest competition, females mated promiscuously and there was no large male advantage: 80 % of large males and 90 % of small males sired at least one offspring, and there was no evidence for last-male precedence. Multiple mating did not yield obvious direct or indirect benefits to females. E. heatwolei represents a complex system in which males attempt to improve their fertility success by limiting rivals from access to females and through adopting alternate reproductive tactics. Conversely, females exhibit no obvious precopulatory mate choice but may influence fitness through postcopulatory means by either promoting sperm competition or through cryptic female choice. Our results support the hypothesis that female multiple mating in nonavian reptiles is best explained by the combined effect of mate encounter frequency and high benefits to males but low costs to females. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Differential treatment of neighbours and strangers (the dear enemy phenomenon) can reduce the costly effects of territory defence. Individual recognition, and by extension the dear enemy phenomenon, was examined in the cordylid lizard Platysaurus broadleyi. I had no knowledge of familiarity between individuals and therefore classed intruders as neighbours or non-neighbours and tested for differences in agonistic response consistent with the dear enemy phenomenon. In the dear enemy phenomenon, levels of aggression are inversely related to degree of familiarity such that residents are more tolerant of immediate neighbours than distant territory holders. A manipulative field experiment in conjunction with field observations of known territory holders revealed that resident males allowed neighbours to approach more closely than non-neighbours before challenging them, residents were more aggressive towards non-neighbours than neighbours, contests between neighbours were significantly longer than between neighbours and non-neighbours and contests between residents and non-neighbours were likely to result in a win for the resident, while neighbours frequently drew contests. These results suggest a level of recognition consistent with the dear enemy phenomenon. I also manipulated front leg colour to test the hypothesis that it alone could serve as a cue for individual recognition. I found no support for this hypothesis and suggest that multiple cues operate in individual recognition. [ABSTRACT FROM AUTHOR]

Flat lizards ( Platysaurus broadleyi) at Augrabies Falls National Park, South Africa, are restricted to rocky terrain where the predominant tree is the Namaqua fig ( Ficus cordata cordata). P. broadleyi readily feeds on Namaqua figs when they are available, and the lizards sometimes form large (maximum recorded=134) congregations under fruiting fig trees. The distance lizards travel to fruiting trees also exceed normal daily foraging distances. Location of fruiting fig trees by a lizard can have a high pay-off because figs are energetically rich and trees fruit irregularly and asynchronously, resulting in a resource that is available, but unpredictable in time and space. The prediction that bird activity in fig trees provides a cue to the presence of ripe figs was tested experimentally. By placing cages containing birds and empty control cages in trees devoid of fruit, we demonstrated that P. broadleyi are drawn to fig trees with high bird congregations. We also tested if the presence of a fig tree was necessary to draw lizards to bird congregations by placing cages containing birds and empty control cages in a matched-pairs design on rock away from trees. Namaqua fig trees were not necessary to draw lizards to bird congregations. [ABSTRACT FROM AUTHOR]

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. Significance: The 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. [ABSTRACT FROM AUTHOR]

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. Significance statement: 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. [ABSTRACT FROM AUTHOR]

Urban environments are novel landscapes that markedly alter animal behavior. Divergence in behavior in response to urbanization may provide advantages in navigation, exploiting resources, and surviving under a novel suite of selective pressures. Relatively few studies, however, have identified population-level behavioral changes in response to urbanization that are not confounded by rearing environment and prior experience (e.g., an urban upbringing). To address this, we used the Australian water dragon (Intellagama lesueurii) to test whether populations under varying levels of urbanization (urban, semi-natural, and natural populations) differ in their innate behavioral traits; acquired either heritably or due to population-specific maternal effects. Eggs were collected from wild mothers and hatched in the lab. Hatchlings were then reared in the lab under standardized conditions (a common-garden experiment). We then assayed individual behavioral traits (boldness, exploration, and neophilia) five times across their first year of development. We compared behavioral traits, as well as their expression (repeatability), between urban, semi-natural, and natural populations. Neophilia and explorative behavior was similar among all populations. However, dragons from semi-natural populations were significantly bolder than those from natural populations. Urban dragons were also bolder than dragons from natural populations, although this trend was not significant because of high variance in boldness. Dragons from semi-natural and urban populations had similar boldness scores, suggesting a potentially biologically relevant difference in boldness between them and natural populations. We also saw some differences in the consistency of the expression of behavior. Boldness in individuals from urban environments was also the only repeatable trait. Overall, our study suggests that boldness is an innate, urban-derived divergent behavioral trait that likely contributes to the success of these lizards in anthropogenically altered environments. Significance statement: Lizards from human-modified areas are innately bolder than ones from natural habitats. To determine this, we raised lizards from eggs collected from urban, semi-natural, and natural populations in a standardized environment, removing the effects of prior experience and developmental environment, and examined their behavioral traits over time. The difference we found in boldness was related to their origin population, rather than being shaped through experience, suggesting this trait may be heritable and is being selected for in anthropogenic landscapes. Our study addresses an important gap in studies of urban behavioral ecology by examining behavioral differences among replicated, differently urbanized, sites after experimentally accounting for both rearing environment and prior experience. [ABSTRACT FROM AUTHOR]

Female-female aggression and its effect on fitness are poorly understood compared to male-male aggression. We quantified female-female aggression in the viviparous toad-headed agama, Phrynocephalus vlangalii, and tested the mate limitation and resource competition hypotheses, to explain the driving forces behind heightened female-female aggression. We established populations in outdoor enclosures and separately manipulated mate and food availability while quantifying aggressive interactions between known females. Female mass and offspring quantity and quality were monitored for 2 years and used as an index of female fitness. Interestingly, female-female aggression was highest outside the mating season, when females were pregnant. Also, male availability did not significantly influence female-female aggression. Consequently, we found no evidence in support of the mate limitation hypothesis. Female-female aggression, however, was greatest during periods of low-food availability. Greater food availability did have positive fitness consequence for females: high-food treatment females were more likely to gain mass and give birth than females from the low-food treatment, and offspring from high-food treatment females were more likely to survive the first winter. However, we did have an effect of year: female mass was negatively associated with female-female aggression in year 1 but positively associated in year 2, although the association was not significant. The same pattern appeared in the association between offspring sprint speed and female-female aggression: higher levels of female-female aggression in year 1 were associated with slower offspring, while in year 2, higher female-female aggression was associated with faster offspring. Overall, our results demonstrate a link between female-female aggression and competition for resource (food) and highlight the potential importance of female aggressive behavior as a mechanism that influences female fitness. Significance statement: Male-male contest competition has been a cornerstone of sexual selection theory for decades because dominant males can control more space and access to females. Conversely, female aggression is poorly understood and sometimes considered a paradox, especially in species lacking parental care. We tested whether female-female aggression in the viviparous lizard P. vlangalii is best explained by competition for males (mate limitation hypothesis) or competition over food (food limitation hypothesis). Interestingly, female aggression peaks after mating, while females are still pregnant. Heightened aggression at this time supports the food limitation hypothesis because any advantage females have in terms of access to resources will benefit offspring born into her home range. Likewise, access to additional food resources may improve female survival and future reproductive investment through greater energy storage. [ABSTRACT FROM AUTHOR]

Abstract: 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.Significance statement: 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. [ABSTRACT FROM AUTHOR]

Abstract: Innate antipredator responses are integral for survival in many species, particularly those which lack parental care. Antipredator responses include both active (fight or flight) and passive behaviours (immobility). As the success of antipredator responses directly relates to survival and fitness, investigating the drivers that explain variance in these traits is key to understanding how predation shapes the instinctive behaviour of animals. We quantified innate antipredator behaviour of hatchling Australian water dragons (Intellagama lesueurii) immediately after hatching using a model snake to simulate a series of attacks, and scored their behaviour using a fight or flight index. Then we explored which factors were related to dragon antipredator behaviour, such as habitat disturbance, origin population, morphology, and parental genetic effects and phenotype (clutch effects). We developed multiple hypotheses and used model selection to determine which factors drive variation in hatchling antipredator behaviour. Clutch effects explained a significant proportion of variation in innate antipredator responses, suggesting a heritable component. We also found an effect of body size on innate antipredator behaviour: larger hatchlings were more prone to flight behaviour (e.g. short-distance runs and long-distance sprinting), while smaller individuals were more prone to standing their ground and being aggressive (e.g. throat puffing, mouth gaping, biting). Clutch effects also explained a significant proportion of the variance in dragon body size. Our study provides evidence that the innate antipredator responses of water dragons are heritable in origin (directly through clutch effects, and indirectly through body size) and not associated with particular populations or habitat types. We suggest future research examine the survival implications of these responses.Significance statement: The action an animal takes in response to a predator is a life or death decision, and can be required immediately after birth. These innate antipredator behaviours may be genetically linked, and enable individuals to emerge into their environment with the necessary behaviour to promote survival. We examined what factors drive hatchling lizards to exhibit different innate antipredator behaviour. Our study found that body size affected their innate behaviour: larger hatchlings were more prone to flee and smaller hatchlings were more likely to fight. Interestingly, parental genetics and phenotype (clutch effects) also significantly explained the variation in innate antipredator behaviour, which supports the hypothesis that these behaviours are heritable. Understanding what drives variation is a cornerstone of evolutionary biology, and our findings raise questions about how selection acts on antipredator behaviour and the degree to which they are plastic. [ABSTRACT FROM AUTHOR]

Abstract: The social environment during development can affect learning; for example, raising an obligate social mammal in isolation can hinder their learning ability. However, we know little about how the social environment impacts learning in less-studied, facultatively social taxa, like family-living lizards. We reared tree skinks (Egernia striolata) in two treatments, either with a conspecific or in isolation. We used three tasks to quantify skink learning ability (motor, discrimination, and reversal). Skinks performed these tasks under two learning treatments: either after demonstration (social learning) or without social information (individual learning). We did not find any evidence that tree skinks used social information. The majority of skinks learnt our motor (91%) and discrimination tasks (100%), and a third learnt our reversal task (34%). Contrary to our predictions, and the majority of previous literature, we detected no negative effect of rearing treatment on learning in any task. Our surprising findings are likely due to this skink’s variable social system, and we suggest that birds and mammals with facultative sociality may not be affected by isolation rearing in the same way as taxa with obligate sociality.Significance statement: Survival can be impacted by an animal’s ability to learn, but many factors can influence this ability (i.e., age, sex, stress, and developmental environment). In this study, we examined how social environment across ontogeny impacts the learning ability of a facultatively family-living animal, the tree skink. Traditionally, the relationship between social environment and learning has been examined in obligate social species. But, examining this relationship in species across all social systems aids in our understanding of the evolution of sociality, and the consequences and limitations of each social system. We found the social environment tree skinks were raised in did not affect their social or individual learning abilities across three foraging tasks. Our findings provide an initial examination of how social environment impacts learning in a facultatively social species. [ABSTRACT FROM AUTHOR]

A correction to the article "Use of Heterospecific Cues by the Lizard Platysaurus Broadleyi for Food Location" that was published in the 1999 issue is presented.