The resemblance is real but the relationship is distant. True pigs are Suidae, an Old World family; peccaries are Tayassuidae, and the two lineages separated tens of millions of years ago. The differences are structural: a peccary's upper canines point straight down rather than curling outward, the hind foot carries three functional toes instead of four, and the stomach is divided into chambers that ferment fibrous plant matter.
That stomach matters in the desert, where prickly pear is a staple. Collared peccaries eat the pads, spines included, taking both water and bulk from a plant most herbivores avoid. They also carry a musk gland on the rump, rubbed onto herd mates so that a group carries a shared scent.
Genus names for this animal have shifted between Pecari, Dicotyles and Tayassu in recent revisions, so older references and newer ones may disagree while describing the same species.