Monarch butterfly populations have declined by over 80% in recent decades due to habitat loss, pesticides, and climate change, affecting both individuals and an iconic migration.
Individual monarchs exposed to sublethal doses of pesticides show disorientation, reduced foraging efficiency, and impaired navigation during migration. Caterpillars developing on milkweed sprayed with systemic pesticides experience developmental disruption. The welfare of individual insects, while debated, is increasingly considered relevant given evidence of nociceptive responses. The loss of migration and the suffering of individuals navigating a degraded landscape represents both a conservation crisis and a welfare concern.