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Despite a long history of study showing that male courtship signals influence female mate choice in many species, we lack a good understanding of how females choose. What are the mechanisms of mate choice, and how do these mechanisms shape the evolution of courtship signals and traits? In this thesis, I use the peacock’s iridescent eyespots to link signal perception with female mate choice decisions and the behaviours males use during courtship. I begin by investigating how a peacock’s eyespot colours influence his mating success, using models of avian colour vision and measurements of eyespot plumage colours taken at light angles that mimic the way the feathers are displayed during courtship. My results suggest that a substantial portion of the variation in peacock mating success can be explained by these plumage colours, demonstrating that signal function is best understood by considering the context in which signals are presented. Next, I examine how females choose to visit different males for courtship. I show that a female’s familiarity with a male as a result of previous courtship encounters affects how she responds to his signals, including his eyespot colours. Lastly, I examine the visual effects of the peacock’s iridescent eyespot colours under different light conditions, and show that typical male courtship behaviours might enhance the eyespots in a way that influences female choice. I also find evidence that light conditions and female sensory biology together may have shaped the evolution of the eyespot colours in two species of peafowl. Overall, the results of this thesis demonstrate that by understanding how animals perceive colour signals, we can gain a better understanding of the function of behaviour on both sides of the courtship signaling exchange. / Thesis (Ph.D, Biology) -- Queen's University, 2013-03-22 14:23:48.991

Polymers are increasingly used in structures that have to withstand impact conditions. This thesis describes an investigation of strain rate properties at room temperature of four engineering polymers; polyethylene (high density, HDPE and ultra high molecular weight, UHMWPE), nylatron and polyetheretherketone (PEEK 150g). A split Hopkinson pressure bar (SHPB) system was used to study the response of these polymers in compression tests at high strain rates up to 10' S-1. Stress equilibrium in SHPB samples was studied theoretically by examining multiple reflection effects during the initial elastic loading of the polymers; this study proved very useful in the analysis of SHPB tests. To cover a wide range of strain rate, compression studies were also made at low strain rates (10-3 _10-2 S-1) using a Hounsfield screw machine. Viscoelastic models have been applied to these results. These models fit quite well with the experimental results of HDPE, UHMWPE, and nylatron, but not to the PEEK due to the yield drop in the stress - strain curves, especially at high strain rates. An exploding wire technique was used as an axial impulsive loading system for hollow cylindrical samples. An image converter camera at framing intervals of 21ls or 10 Ils recorded the radial expansion of the cylinder. The expanding cylinder was used as a driving system for a new technique called the freely expanding ring method, which was used to obtain the stress - strain behaviour of polymeric thin rings placed as a sliding fit on the cylinder. This method produced very high tensile strain rates up to fracture (> 10' S-1). Comparisons have been made between results obtained from the quasi-static, SHPB, and expanding ring tests. The freely expanding ring and SHPB results were in good agreement indicating similar tensile and compressive high strain rate behaviour. The mechanical properties of the above polymers are strongly dependent on strain rate. The Young's modulus and the flow stress increase with increasing strain rate. Nylatron showed high strain rate strain softening at high strain, this was due to the high temperature rise during loading, when the transition temperature (Tg) of the material (50 QC) was exceeded. However, the other materials showed continuous hardening behaviour. Plots of the flow stress at 5% and 10% strain vs log strain rate showed a linear increase up to a strain rate of about 103 S-1. Above 103 s-1, the stress rose more rapidly, but then showed significant drops for nylatron and PEEK. These drops in stress are probably due to both micro crack initiation in the sample and also high temperatures around the crack tips.