Caviidae
Caviidae, the cavy family, is composed of rodents native to South America and includes the domestic guinea pig, wild cavies, and the largest living rodent, the capybara. They are found across South America in open areas from moist savanna to thorn forests or scrub desert. This family of rodents has fewer members than most other rodent families, with 19 species in 6 genera in 3 subfamilies.
Traditions and student activities at MIT
"Brass Rat" refers to the MIT class ring, which prominently features the school mascot beaver on the top surface. The ring is traditionally made of gold, the beaver is the largest North American rodent, hence "gold beaver" has informally become "Brass Rat" in student lingo.