Effects of two courtship display components on female reproductive behaviour and physiology in the sagebrush lizard

Behavioural plasticity in activity and sexual interactions in a social lizard at high environmental temperatures

Sexual selection often shapes social behavioural activities, such as movement in the environment to find possible partners, performance of displays to signal dominance and courtship behaviours. Such activities may be negatively influenced by increasing temperatures, especially in ectotherms, because individuals either have to withstand the unfavourable condition or are forced to allocate more time to thermoregulation by increasing shelter seeking behaviour. Thus, they "miss" opportunities for social and reproductive interactions. Moreover, behavioural displays of ectotherms closely depend on temperature; consequently, mate choice behaviours may be disrupted, ultimately modifying sexual selection patterns. Therefore, it would be interesting to elucidate how increasing temperatures associated with global warming may influence activity and social interactions in the species' natural habitat and, specifically how high temperatures may modify intersexual interactions. Consequently, our aim was to explore differences in the daily pattern of social interactions in an ectotherm model, Tropidurus spinulosus, in two thermally different habitats and to determine how high temperatures modify mate choice. High environmental temperatures were found to be associated with a bimodal pattern in daily activity, which was closely linked to the daily variations in the thermal quality of the habitat; whereas the pattern and frequency of social displays showed less plasticity. The time allocated to mate choice generally decreased with increasing temperature since individuals increased the use of thermal refuges; this result supports the hypothesis of "missed opportunities". Moreover, at high temperatures, both sexes showed changes in mate selection dynamics, with females possibly "rushing" mate choice and males showing an increase in intermale variability of reproductive displays. In our ectotherm model, plastic adjustments in the behavioural activity pattern induced by high temperatures, plus the modification of the displays during courtship may ultimately modify mate choice patterns and sexual selection dynamics.

Alteration of the temporal association between courtship audio and visual components affects female sexual response

Some multimodal signals-that is, occurring in more than one sensory modality-appear to carry additional information which is not present when component signals are presented separately. To understand the function of male ring dove's (Streptopelia risoria) multimodal courtship, we used audiovisual playback of male displays to investigate female response to stimuli differing in their audiovisual timing. From natural courtship recordings, we created a shifted stimulus where audio was shifted relative to video by a fixed value and a jittered stimulus, where each call was moved randomly along the visual channel. We presented 3 groups of females with the same stimulus type, that is, control, shifted, and jittered, for 7 days. We recorded their behavior and assessed pre- and post-test blood estradiol concentration. We found that playback exposure increased estradiol levels, confirming that this technique can be efficiently used to study doves' sexual communication. Additionally, chasing behavior (indicating sexual stimulation) increased over experimental days only in the control condition, suggesting a role of multimodal timing on female response. This stresses the importance of signal configuration in multimodal communication, as additional information is likely to be contained in the temporal association between modalities.

Female preferences for discrete and continuous male colour expression may help reinforce colour polymorphism in a desert lizard

Despite recognition that colour can vary continuously, colour expression in colour polymorphic species is usually treated as discrete. We conducted three experiments to evaluate the extent that discrete and continuous male coloration influenced female mating preferences in long-tailed brush lizards (Urosaurus graciosus). Each experiment provided females with a different social context: a dimorphic choice between a yellow and an orange male (coloration treated as discrete), and a choice between either two orange males or two yellow males (coloration treated as continuous variation). Females preferred orange males over yellow males in the first experiment, and the findings of our second experiment suggested that males with moderate orange coloration were most preferred. In contrast, females behaved randomly with respect to two yellow males. Our findings show that females in colour polymorphic species can evaluate both discrete and continuous aspects of morph coloration during mate assessment, which may help maintain their polymorphism.

Male mate choice as differential investment in contest competition is affected by female ornament expression

High male mating effort and high variation in female quality select for male mate choice, which may be expressed as differential investment of reproductive effort based on female value. Male reproductive effort includes investment in direct contest competition with rival males for access to females, yet variation in male-male contest behavior is rarely examined in the context of male mate choice. We examine such male response to variation in female body size, reproductive state, and female-specific ornamentation in the striped plateau lizard, Sceloporus virgatus. We housed lizards in trios of 2 size-matched males and one female for 5 days, such that all 3 lizards were physically isolated and the males could see the female but not each other. We then placed males simultaneously into the female's cage and scored the interaction. Male-male aggression was not significantly affected by female body size, reproductive state, nor ornament color, but was influenced by ornament size which reliably signals the phenotypic quality of the female and her offspring. In the presence of larger-ornamented females, males engaged in more male-male aggressive display behavior more quickly, and performed fewer high-intensity contact behaviors but were equally likely to escalate to this riskier level of fighting. Our data suggest that males adjust their energetic investment during intrasexual competitive interactions in response to variation in the contested female which, assuming males gain direct or indirect benefits from their strategic allocation of reproductive effort, fits the modern understanding of male mate choice.

In Space and Time: Territorial Animals are Attracted to Conspecific Chemical Cues

Territorial animals lay scent marks around their territories to broadcast their presence, but these olfactory signals can both attract and repel con-specifics. Attraction or aversion can have a profound impact in terms of space use and thereby influence an individual's access to resources and mates. Here, we test the impact of chemical signals on the long-term space use and activity of receivers, comparing the response of males and females, territory holders, and temporary visitors in Sceloporus undulatus lizards in the field. We placed either male femoral gland secretions (chemical) or blank (control) cues on resident male landmarks, repeatedly over 5 d, while monitoring the activity and location of all lizards in the vicinity. We found that resident males and females, but not non-resident males, were active on more days near landmarks treated with chemical cues than landmarks treated with control cues. Non-resident males remained closer to chemical than control cues. These results suggest that territorial scent marks are attractive to conspecifics and impact space use, but that the specific effects depend on receiver sex and residency status. Such subtle or gradual changes in behavior may frequently be overlooked by short-term choice experiments. Future studies investigating the behavioral significance of a communicative signal should consider these finer details of behavior for a more comprehensive assessment.

Evolution and role of the follicular epidermal gland system in non-ophidian squamates

Many lizard and amphisbaenian lineages possess follicular glands in the dermis of the inner thighs and/or the area anterior to the cloaca. These tubular glands produce a holocrine secretion that finds its way to the external world through pore-bearing scales (femoral and/or preanal pores). Secretions are composed of proteins and many lipophilic compounds that may function as chemosignals in lizard and amphisbaenian communication. In recent years, we have begun to develop an understanding of the adaptive significance of these secretions, and they are currently thought to play an important role in a variety of processes in these animals. While it appears that epidermal gland secretions function in intra- and interspecific recognition and territoriality, research has focused largely on their role in mate assessment. Despite these recent studies, our knowledge on the true role of the chemicals found in epidermal secretions remains poorly studied, and there are many possible avenues for future research on this topic. Here, we review the literature on the follicular epidermal glands of non-ophidian squamates and provide a first taxon-wide overview of their distribution.

Melanin-based colouration as a potential indicator of male quality in the lizard Zootoca vivipara (Squamata: Lacertidae)

In many animals, aspects of colouration are hypothesized to convey information on the body condition or quality of individuals. This idea has been tested primarily for the carotenoid-based component of body colouration. The significance of other pigments in this context has received far less attention. In the common lizard, Zootoca vivipara, the degree of black patterning on the ventrum and throats is sexually dimorphic and varies considerably among individuals. In this study, we examine whether this melanin-based component of body colouration may reflect individual differences in quality (SVL, condition, immune response). We find that males (but not females) with a higher degree of ventral patterning mount a stronger phytohemagglutinin-induced immune response. The amount of black patterning does not correlate with body size, body condition, aspects of dorsal colouration or parasite load. We conclude that in male Zootoca vivipara, melanin-based ventral colouration may signal an aspect of immune capacity to sexual rivals or potential partners.

Female goats use courtship display as an honest indicator of male quality

Due to the differential cost of reproduction in promiscuous species, like domesticated goat(s) (Capra hircus), it is expected that females should mate with higher quality males, while males should mate with a greater number of females. Females may use conspicuous secondary sexual characteristics of males such as courtship display to distinguish among high and low quality males. Testosterone (T) controls a large suite of secondary sexual characteristics and variation in T concentrations may account of differences in courtship rates. Two studies were conducted to examine the relationship between T concentrations and courtship rate and its role in mammalian female mate choice. Experiment 1 utilized bucks (intact males) and Experiment 2 utilized T-replaced wethers (castrated pre-pubertally). During the first year of Experiment 2, T-replaced wethers received either vehicle control (CON), 25mg or 100mg testosterone propionate (TP). During the second year of Experiment 2, T-replaced wethers were treated with either 5mg, 15 mg or 25mg TP. For all experiments, mean courtship rates and circulating T concentrations were measured, as well as female preference for males displaying different courtship frequencies. T concentrations and courtship rate were positively correlated for bucks and estrous females preferred high courting bucks. Males receiving 25mg and 100mg TP courted females at a similar rate, but both were significantly higher than courtship rates of the CON wethers. Courtship rates of the 25mg, 15 mg and 5mg TP-treated males were all significantly different. Females did not show a preference between the 100mg or 25mg TP-treated wethers, however both were preferred in comparison to the CON wethers. Females did not show preference between the 25mg or 15 mg TP-treated wethers, however both were preferred in comparison to the 5mg TP-treated wethers. Taken together, these studies suggest that courtship rate is T-dependent. Further, females can use courtship rate to distinguish among males.

Male sexual behavior does not require elevated testosterone in a lizard (Coleonyx elegans, Eublepharidae)

Male sexual behavior depends on gonadal androgens in species of all major vertebrate lineages, including reptiles. However, male sexual behavior includes distinct appetitive and consummatory phases, typically denoted as courtship and mounting, with potentially different hormonal control. Different proximate controls of courtship versus mounting could enable disconnected evolutionary losses and gains of various aspects of male sexual behavior. Male courtship display, which is activated by testosterone (T) in many species, is an ancestral trait in the lizard family Eublepharidae. However, Coleonyx elegans (Yucatan Banded Gecko) lost the courtship display, while retaining a highly simplified male sexual behavior that involves only mounting for copulation. We performed surgical manipulations (castration with and without T replacement in adult males; implantation of adult females with exogenous T) to investigate hormonal mechanisms involved in this evolutionary novelty. Our results indicate that the expression of simplified sexual behavior in C. elegans does not require elevated circulating levels of T, a finding that is previously unreported in lizards. In females, however, exogenous T induced male-like mounting. Thus, the mounting phase of sexual behavior is not activated by T in the traditional sense of this term but probably requires post-natal, maturational organization (if not periodic reorganization) by androgens. We conclude that the simplification of male sexual behavior and its independence from elevated levels of circulating androgens in C. elegans evolved via 1) evolutionary loss of the androgen-activated courtship display and 2) retention of the mounting phase, which has a longer "functional memory" for the effects of androgenic steroids.

Food supplementation and testosterone interact to influence reproductive behavior and immune function in Sceloporus graciosus

The energetic resources in an organism's environment are essential for executing a wide range of life-history functions, including immunity and reproduction. Most energetic budgets, however, are limited, which can lead to trade-offs among competing functions. Increasing reproductive effort tends to decrease immunity in many cases, and increasing total energy via supplemental feedings can eliminate this effect. Testosterone (T), an important regulator of reproduction, and food availability are thus both potential factors regulating life-history processes, yet they are often tested in isolation of each other. In this study, we considered the effect of both food availability and elevated T on immune function and reproductive behavior in sagebrush lizards, Sceloporus graciosus, to assess how T and energy availability affect these trade-offs. We experimentally manipulated diet (via supplemental feedings) and T (via dermal patches) in males from a natural population. We determined innate immune response by calculating the bacterial killing capability of collected plasma exposed to Escherichia coli ex vivo. We measured reproductive behavior by counting the number of courtship displays produced in a 20-min sampling period. We observed an interactive effect of food availability and T-patch on immune function, with food supplementation increasing immunity in T-patch lizards. Additionally, T increased courtship displays in control food lizards. Lizards with supplemental food had higher circulating T than controls. Collectively, this study shows that the energetic state of the animal plays a critical role in modulating the interactions among T, behavior and immunity in sagebrush lizards and likely other species.

Sex-specific visual performance: female lizards outperform males in motion detection

In animal communication, complex displays usually have multiple functions and, male and female receivers often differ in their utilization and response to different aspects of these displays. The perceptual variability hypothesis suggests that different aspects of complex signals differ in their ability to be detected and processed by different receivers. Here, we tested whether receiver male and female Sceloporus graciosus lizards differ in visual motion detection by measuring the latency to the visual grasp response to a motion stimulus. We demonstrate that in lizards that largely exhibit complex motions as courtship signals, female lizards are faster than males at visually detecting motion. These results highlight that differential signal utilization by the sexes may be driven by variability in the capacity to detect different display properties.

Pheromone communication in amphibians and reptiles

This selective review considers herpetological papers that feature the use of chemical cues, particularly pheromones involved in reproductive interactions between potential mates. Primary examples include garter snake females that attract males, lacertid lizards and the effects of their femoral gland secretions, aquatic male newts that chemically attract females, and terrestrial salamander males that chemically persuade a female to mate. Each case study spans a number of research approaches (molecular, biochemical, behavioral) and is related to sensory processing and the physiological effects of pheromone delivery. These and related studies show that natural pheromones can be identified, validated with behavioral tests, and incorporated in research on vomeronasal functional response.

Courtship attention in sagebrush lizards varies with male identity and female reproductive state

Previous experiments suggest that males spend more time with the more receptive of 2 novel females or the one with the higher fitness potential. However, males often court individual females repeatedly over a season; for example, male lizards sequentially visit familiar females as they patrol territorial boundaries. It may benefit males to vary display intensity as they move between multiple females. In this study, we explored the factors influencing amount of male courtship to familiar females in the sagebrush lizard, Sceloporus graciosus. We tested whether males vary the amount of courtship exhibited due to individual differences among males, female reproductive state, or female fitness potential. Each male was allowed to interact separately, but repeatedly, with 2 females until both females laid eggs. Male courtship behavior with each of the 2 females was assayed at an intermediate point, after 3 weeks of interaction. We found that individual differences among males were considerable. The number of male courtship displays was also positively correlated with female latency to lay eggs, with males displaying more often toward females with eggs that had not yet been fertilized. Courtship behavior was not well predicted by the number of eggs laid or by female width, both measures of female quality. Thus, male S. graciosus appear to alter courtship intensity more in response to signals of female reproductive state than in response to variation in potential female fitness.