Rurik List began studying wildlife south of the U.S.-Mexico border in 1994, doing research in the expansive grasslands of the Janos Valley in the Mexican state of Chihuahua. Back then, the international boundary was pretty porous there, marked only by barbed wire fencing. Most animals could easily pass over, under, or if they were bison, bust right through it, in their quest for food, water, mates, or suitable habitat as they moved between Chihuahua and New Mexico. (Source: Mongabay)