What historical human action can quickly establish a strong local population of black squirrels due to the gene's nature?

Answer

Intentional translocation of a few individuals

Because the melanistic gene is dominant, moving just a few black squirrels to a new area can rapidly establish a noticeable population due to the nature of genetic inheritance.

What historical human action can quickly establish a strong local population of black squirrels due to the gene's nature?
colorvariationsquirrelMelanismeastern gray squirrel