The role of colour and pattern in background matching camouflage

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Camouflage is a phenotypic trait that significantly impacts the likelihood of survival in predators and prey alike. The objective of this thesis is to identify the specific attributes of background-matching camouflage when faced by multiple, differing, backgrounds. Chapter 2 examines the phenomenon of egg camouflage in plovers (Aves: Charadriiformes), utilising colour and texture analysis of calibrated photographs to assess camouflage against beach and saltmarsh habitats. I show that eggs are an excellent colour-match to the subset of backgrounds that are found in both habitats, but the patterning of the maculation makes eggs and backgrounds reliably discriminable at close viewing distances. Chapter 3 focuses on chick camouflage, specifically exploring possible sex differences that might explain higher mortality in female than male chicks. I show that there is no sex difference in plumage colouration but males are found on backgrounds to which they are a better match. Chapter 4 examines camouflage from a different perspective, assessing the discriminability of chicks from different backgrounds using humans as model predators. The results are consistent with the visual modelling of chapter 3, and show that chicks are a better match to mud than vegetated backgrounds, suggesting stronger selection for camouflage against backgrounds where physical hiding is not possible. Chapter 5, moving away from the plovers to ultilise an experimental paradigm of artificial moth-like prey on woodland tree bark, investigates the phenomenon of whether to specialize on a particular background or adopt a camouflage pattern that is a compromise between multiple substrates. I show that matching the average colour of a background is more important than matching the visual texture, but also that a background which has a complex texture is more ‘forgiving’ of mismatches than a texturally simple background.
Date of Award7 May 2024
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorInnes C Cuthill (Supervisor) & Andrew N Radford (Supervisor)

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