Prairie Dogs Once Covered the Expanses of the Great Plains

Prairie dogs once covered the expanses of the Great Plains. Their grazing made the grass more nutritious for the huge herds of bison, and a variety of snakes, raptors, and mammals preyed on the rodents. In fact, the black-footed ferret (now endangered) specialized in prairie dog predation. Today, growing housing and agricultural developments have covered many prairie dog towns. Which of the following statements about prairie dogs is True?

A) Their realized niche has expanded.
B) They have a mutualistic relationship with bison.
C) They are probably a poor candidate for keystone species.
D) Their fundamental niche is changed.
E) Their fundamental niche has expanded.