Inter-sexual selection, or mate choice results in the evolution of expensive and conspicuous traits in many systems. The use of such traits in attracting mates is called sexual signalling. Sexual signalling has largely been studied in the context of indirect competition among males and mate choice by females. Historically, sexual signalling in females was expected to be of limited consequence. However, there is growing evidence of sexual signalling in females that involve energetically costly investments and elaborate conspicuous traits. Do females modulate the use of sexual signals to maximize benefits and minimize costs?

Given the limited understanding of sexual signalling by females in polygynous mating system, we first examined the repertoire of sexual signalling exhibited by females of the Peninsular rock agama Psammophilus dorsalis. We further investigated how females strategically use their sexual signals in response to important factors that may affect the benefits of signalling. In socially polygynous mating systems, males typically invest in elaborate ability-based or honest displays which are intended towards female receivers. Although strategic signalling in males has received greater research attention, here too key questions of how competitors may affect their signalling is poorly understood. Sexual signalling males typically experience male competitors in their environment. We lack a comprehensive understanding of the impact that such unintended audiences have on male sexual signals. We studied how strategies of male signalling are shaped by both mate and competitor environments.

To understand the repertoire of sexual signalling, we set up a context for females to display by simulating the presence of a breeding male by presenting artificial male models to individually tagged female lizards. We found that females use a range of behaviours including stereotypical body postures and dynamic colour signals. We compared the response of lizards to cues of intra-sexual competition and found that distinct signals were used in the contexts of mate attraction and intra-sexual competition.

To understand how females strategically use their sexual signals, we evaluated key hypotheses for how females should modulate their signalling, including male quality, access to high quality mates and breeding season. We simulate male quality using artificial male models to individually tagged, and intensely monitored wild female lizards. We found that females invest

more in signalling towards high quality males and increased their investment towards the later part of their only breeding season. Contrary to that which is typically expected in a polygynous mating system, females not only invest in costly and elaborate sexual signals, but they also modulate their usage to maximise their benefits and minimise their costs. We argue that, even in polygynous mating systems, dispersed distribution of individuals can result in females experiencing limitation in mate availability, resulting in costly sexual signalling.

To understand how males strategically use signals in response to a combination of competitor and mate environments, we collected information on where lizards were found relative to other conspecific lizards. Since Peninsular rock agama change colour states, we then identified how individuals strategically modulate the use of colour signals with respect to other lizards present in their vicinity. We measured the relative size of male neighbours as size can be a measure of competitive ability in contest competitions. We find that individuals appear to modulate the use of sexual signalling in response to both males and females in the vicinity. We found that displays increased with increase in the potential number of mates, and decreased with competing male effect. We found that relative size affects their response to competitor abundance, with smaller males reducing the use of sexual signals in competitor environments.

My thesis highlights the wide repertoire of sexual signals seen in females of a socially polygynous species of lizard and the strategic use of sexual signalling in both males and females. Females exhibit sexual signalling with well-defined sexual signalling postures and colour-based displays that are different from other social contexts. Females, not only use their signals in specific contexts but also use them where they gain maximum benefits. The study emphasizes the scarcity of high-quality males that females may encounter, even in species adhering to conventional sex roles. We demonstrate how female invest in sexual signalling in response to both quality of mates as well as the time of breeding season. We highlight how males flexibly modulate the use of sexual signals through their colour trait in a dynamic environment with breeding females and competing males. My thesis challenges the conventional sex roles in sexual signalling while also investigating the nuanced mating strategies of males and females in a polygynous lizard.