About Galea musteloides Meyen, 1833
The common yellow-toothed cavy, scientifically Galea musteloides Meyen 1833, is a rodent species in the family Caviidae, closely related to domesticated guinea pigs. It has a karyotype with 2n = 68 and FN = 136, and it has yellow teeth. It is the most common and most widely distributed member of the genus Galea, found across Argentina, Bolivia, Chile, and Peru at elevations ranging from 20 to 5000 meters above sea level, with an overall range stretching from southern Peru to central Argentina. It occurs most often in moist areas including stream edges and croplands. One recent study recognizes five subspecies of G. musteloides: boliviensis, demissa, leucoblephara, littoralis, and musteloides. These subspecies are distinguished by differences in fur coloration, skull size and shape, auditory bullae size, and tooth shape. Growing evidence suggests that the lowland form previously classified as G. musteloides is an independent species, which should be named G. leucoblephara. This species is described as a diurnal, group-living herbivore of squirrel size that occupies open habitats. At birth, male and female common yellow-toothed cavies have average weights of 36.4 g and 37.6 g respectively. Individuals reach reproductive maturity between one and three months of age, with a recorded minimum breeding age of twenty-eight days. Gestation lasts fifty-three days, lactation lasts three weeks, and average litter size is 2.7. In Peru, G. musteloides sometimes associates with tuco-tucos of the genus Ctenomys; Galea individuals use tuco-tuco burrows and respond to tuco-tuco alarm calls, as documented by Sanborn and Pearson. In captive groups, G. musteloides develops separate hierarchical social structures for males and females. Alpha males regularly guard receptive females, but this guarding has little effect: usually other males also mate with the same female, and over 80% of litters have multiple fathers. Females in captivity are clearly promiscuous, always mating with several males in the group. In the wild, the species is clearly territorial, but it remains unclear whether similar hierarchical social structures exist in natural populations, or whether wild G. musteloides live solitarily. Aggression between adult males occurs regularly. Adult male G. musteloides never take part in parental care, and are aggressive toward subadult males even when the subadults are their own very young offspring. Males are not aggressive toward females. Adult females will lactate and nurse the offspring of other females during the first week of the offspring’s life, and nearly all offspring receive some milk from females other than their biological mother. Females still preferentially care for their own offspring, and continue caring for their own offspring beyond the first week of life. Closely related Galea species display a range of mating systems from monogamy to promiscuity, making the genus suitable for comparative studies. Two general trends have been identified from this work: relative to body size, testis size is larger in promiscuous species; and higher social tolerance in captive groups is linked to greater promiscuity and higher testosterone levels in males. Testosterone levels and aggression levels in males are not correlated, and females consistently avoid males with higher than average aggression.
