found living in large groups. Reproduction Females weigh 700-800 g and give birth to only one or two young, but several litters per year are common. The gestation period averages 75 days. The newborn cavies weigh 90 g. The placenta for a rock cavy is similar to other hystricomorph rodents: They have several lobes that are lined with blood vessels and undergo a counter-current blood flow. Blood vessels run from the mother along the placenta and then vessels run from the fetus back over the mother's vessels. This allows for a better flow of oxygen between the mother and the fetus. Parental care The young are able to eat solid food at 3 days old, but continue to nurse for up to 7 weeks. The milk produced for these young is very dense in energy. This may be due to the lack of water availability in their environment. Both male and female rock cavies care for their young. When both parents are present, the females spend more time with their young than the males do. When the male is absent, the females spend more time with their young than they do when the male is present. Females that raise young on their own are more aggressive than females that raise the young with a partner. The young raised by single mothers also gain more weight while nursing compared to those raised by both parents. Threats and protection Rock cavies are endemic to several protected areas, and reproduce quickly, so they are currently listed as "least concern" on the IUCN Red List. They are frequently hunted as food by local human populations, which resulted in population decline of 30% in the last 10 years. Their range is also being reduced due to deforestation. Efforts are underway to breed rock cavies in captivity as a potential food source. Footnotes References Further reading External links Cavies Mammals of Brazil Endemic fauna of Brazil Mammals described in 1820