Knights in shining armour are not necessarily bold: defensive morphology correlates negatively with boldness, but positively with activity, in wild threespine stickleback, Gasterosteus aculeatus
Background: The threespine stickleback (Gasterosteus aculeatus) varies in armour phenotype from fully armoured to non armoured morphs. Aim: Investigate the connection between individual variation in behaviour and armour morphology within and across populations. Study organism and site: During the Spring of 2015, we assayed the behaviour of 250 sticklebacks from seven populations on the Scottish island of North Uist, located in the Outer Hebrides. Hypotheses: The 'phenotypic compensation' hypothesis holds that individuals with poorer defences should behave more timidly. Yet the energetic costs associated with bearing armour should reduce both the activity and exploration behaviour of more heavily armoured individuals. Methods: We assayed individual stickleback for boldness, exploration, and activity. We then stained the fish with Alizarin red, which allowed the characterization of the armour phenotype of each fish. Results: Across populations, bold fish were less armoured than their shy counterparts and active fish were more armoured. Exploratory behaviour was not correlated with armour