Anthropogenic noise is pervasive in terrestrial and aquatic environments, and recognised as a pollutant in national and international legislation. Extensive research in the last 15 years has shown effects of noise across taxa on both physiology and behaviour. However, the majority of that work has only considered the overall effects of noise, reporting responses as a mean cohort effect and ignoring the variation that exists within a species due to both intrinsic characteristics (e.g. size, sex and body condition) and extrinsic factors (e.g. prior experience, context and the existence of other stressors). In this thesis, I consider intraspecific variation in responses to anthropogenic noise, a greater focus on which will help avoid misinterpretations of effects and improve how we manage, monitor, model and mitigate the impacts of noise on wildlife. I start with a systematic and comprehensive review of the peer-reviewed literature pertaining to the causes and consequences of intraspecific variation in responses to anthropogenic noise (Chapter 1). In the first data chapter (Chapter 2), I examine the effects of pile-driving playback on the physiology and behaviour of Atlantic salmon (Salmo salar). I find no effects of pile-driving noise on any response measure, but develop methodology for use in later chapters. In Chapter 3, I begin assessing intraspecific variation in responses by determining the influence of body condition and habitat quality on noise impacts in the blue-green damselfish (Chromis viridis). Habitat quality had no effect on responses to noise, but individuals in poorer body condition performed worse than better-condition conspecifics in an anti-predator experiment. I then start to consider the influence of prior experience by testing the responses of Cynotilapia zebroides, an endemic cichlid fish, from high- and low-disturbance sites to noise exposure (Chapter 4). Fish from high-disturbance sites had a reduced sensitivity to motorboat noise compared to conspecifics from low-disturbance sites. Going a step further, I investigate the impact of chronic noise exposure within a generation using experimental manipulations to determine the potential for behavioural plasticity (Chapter 5). I found no changes in responses of Stegastes nigricans following a month-long manipulation of motorboat noise. However, chronic anthropogenic-noise exposure had effects at the community level. Comparing sites varying naturally in the level of motorboat disturbance, a number of species differed in their abundance (some were more prevalent, some less so, in high- vs low-disturbance sites). Some of these abundance differences were replicated following the month-long experimental manipulation of motorboat noise. Overall, my work emphasises the importance of considering variation in responses to noise if we are to understand fully and mitigate successfully this global pollutant.
|Date of Award||28 Nov 2019|
- The University of Bristol
|Supervisor||Andrew N Radford (Supervisor), Steve Simpson (Supervisor) & Ian Davies (Supervisor)|