The common yellow-toothed cavy (Galea musteloides) is a species of rodent in the family Caviidae, closely related to the domesticated guinea pig.

[2] G. musteloides is the most common and widely found member of Galea, and is present at elevations ranging from 20 to 5000 m above sea level.

[4] It is a "diurnal herbivore of squirrel size that lives in groups and occupies open habitat.

In the wild G. musteloides is clearly territorial, and it remains unclear if a similar hierarchical social order exists, or if they live solitarily.

[4][7] As closely related Galea species show a range of mating systems from monogamy to promiscuity, comparative studies are possible in these groups.

General trends have been identified: a) testis size increases relative to body size in promiscuous species and b) higher social tolerance in captive held groups is associated with greater promiscuity and higher testosterone levels in males.