Unfortunately, there is no easy way to distinguish the two. Wild pigs (Sus scrofa) include both feral hogs (domestic swine that have escaped captivity) and wild boars, native to Eurasia but introduced to North America to interbreed with feral hogs. Like domestic hogs, they may be any color. Their size and conformation depend on the breed, degree of hybridization with wild boars, and level of nutrition during their growing period.
Wild boars have longer legs and larger heads with longer snouts than feral hogs. The color of young boars is generally reddish brown with black longitudinal “watermelon” stripes. As the young develop, the stripes begin to disappear, and the red changes to brown and finally to black. Both the male feral hog and wild boar have continuously growing tusks. Wild boars and feral hogs hybridize freely; therefore, the term wild pig is appropriate as a generic term for these animals.
Resources: (online)
Wild Pigs