The Monarch Migration

A monarch butterfly never makes the full journey. The migration that carries it from Mexico to Canada and back is a relay across several successive generations, none of which knows the journey’s starting point or its destination.

This map animates, month after month, nearly 400,000 monarch observations recorded in GBIF across North America, grouped on a one-degree grid: the more opaque a cell, the more observations it holds at that time of year. The wave moves north from Mexico in spring, reaches southern Canada in summer, then flows back south in autumn, without any single individual having lived it in full. A caveat: these are observations, not a census. The density also reflects observation effort, not only where the butterflies are.