Species use multiple defensive strategies aimed at different sensory systems depending on the level of threat, type of predator and options for escape. The core cobra clade is a group of highly venomous Elapids that share defensive characteristics, containing true cobras of the genus Naja and related genera Aspidelaps, Hemachatus, Walterinnesia and Pseudohaje. Species combine the use of three visual and chemical strategies to prevent predation from a distance: spitting venom, hooding and aposematic patterns. Although the functional morphology and mechanisms behind spitting and hooding are understood, few studies have investigated the evolution and variation of hood size. The aim of this thesis is to reconstruct the evolutionary history of defensive strategies in cobras, investigate the reasons why different strategies are used and to identify trade-offs. Focusing on variation in hood size, X-ray radiography was used to visualize and measure ribs of cobra specimens. Hood morphology and occurrence of hood pattern, ventral bands and spitting were analysed in phylogenetic comparative analyses. A single origin of hooding behaviour in core cobras prompted the evolution of extended ribs multiple times in Hemachatus and Naja, trending towards a large hood. Reduction in extended ribs occurred multiple times due to specialization to aquatic, subterranean or arboreal habitats. No trade-offs between spitting and hood pattern were uncovered due to the variation in pattern within Asian spitting cobras. Wide hoods were only associated with a hood pattern when phylogenetic signal was not considered, suggesting that correlation may be due to shared ancestry. In different species, size or distinctiveness of aposematic signals may be more important, leading to smaller hoods with bold patterns or large hoods with faint patterns. This study highlights the diverse morphology within cobras and the need for further investigation into frequency,