Animals facing threats from human encroachment are featured in these offerings from the Our Wild World series. Prairie Dogs looks at critters considered a keystone species by scientists, linked to the survival of about 40 other species. Horse-lovers will gravitate to the doe-eyed bays on the cover of Wild Horses, which introduces readers to the scattered herds of mustangs still roaming the U.S. Both books spend a great deal of time on these animals'...