The need for Milkweed: report on the international initiative to address the decline of the Monarch Butterfly (Danaus plexippus)

摘要

Because they make regular and predictable annual migrations, monarch butterflies (Danaus plexippus) are considered a mobile species. The migratory generation of mon-archs travels thousands of kilometers along flyways from breeding to non-breeding grounds, stopping to rest and feed along the way. Every aspect of the journey is crucial, and they may face multiple threats in each habitat. Relatively few monarchs that begin the journey south from North America to Mexico survive the six- to nine- month migration cycle to lay their eggs on the return journey north. In a complex, intergenerational relay, their progeny in two or three relatively short-lived subsequent generations have the task of rebuilding the population so that the next migratory generation starts out in robust numbers. A major challenge when attempting to conserve a mobile species is that the effectiveness of a conservation action takenat one site depends on the condition of other sites that may be geographically and politically distant (Runge et al, 2014). You will see below how this applies to efforts to address the monarch butterfly population decline.