- Santa Catarina's guinea pig <i>Cavia intermedia</i
- Brazil ()
The rarest species of guinea pig is the Santa Catarina's guinea pig Cavia intermedia, which is found exclusively on the tiny island of Moleques do Sul, in the Brazilian state of Santa Catarina. This island has a total area of only 10.5 hectares, out of which just 4 hectares are occupied by this species, making it one of the smallest geographical distributions on record for any species of mammal. No more than 60 individuals exist, and the species itself was described as recently as 1999. It is categorized as "Critically Endangered" by the IUCN.