The common blue butterfly is one of the UK's most widespread blue species but has declined significantly. Its welfare is tied to the availability of bird's-foot trefoil and other larval foodplants.
Common blue welfare is tied to the availability of specific microhabitat conditions that grassland intensification has reduced dramatically. Females require warm, south-facing patches of short grassland with abundant bird's-foot trefoil for egg-laying. Without the specific thermal and botanical conditions they require, eggs are laid on unsuitable plants or in suboptimal conditions where larval survival is low. The ant associations that protect larvae from predation depend on the presence of appropriate ant species, which themselves require undisturbed grassland structure. The welfare chain from egg to adult depends on habitat quality at every stage.