The rock cavy is a fairly large rodent weighing up to. Like other cavy species, their tails are vestigial or absent. Their backs are grey-brown and their bellies tan to light brown. In appearance and habit, they closely resemble the unrelated Africanrock hyraxes. They are herbivorous, feeding on seeds and leaves of the scrubby vegetation that grows in their territories. This vegetation consists of tender leaves and certain species of creeper.
Distribution and habitat
Rock cavies are found in dry, rocky areas with low, scrubby vegetation, and they prefer to reside close to stony mountainsides and hills. They are native to eastern Brazil, from eastern Piauí state to Minas Gerais state, and have been introduced to the island of Fernando de Noronha, off the eastern coast of Brazil.
Phylogeny
Rock cavies belong to the order Rodentia, sub-order Hystricomorpha, based on their porcupine-like jaw muscles. They are in the family Caviidae which has three subfamilies ; rock cavies have recently been placed in a new subfamily Hydrochaerinae, with the capybaras, and with the closely related rainforest-dwelling acrobatic cavy.
Behavior
Rock cavys usually shelter in crevices. They may be seen resting at all times of day, but are crepuscular – active mostly at dawn and dusk. They are able to climb which makes reaching leaves, seeds, and occasional fruits easier. Rock cavys live in groups, centered around rock-sheltered dens. Each rock cavy group has an alpha or dominant male and several females. The males are territorial, defending rock pile shelters against other adult males. The rock piles are chosen to impress the females; once a female chooses a rock pile, she indirectly chooses its guardian as her mate. They can sometimes display homosexual behavior, with males courting other males. Some paedophilic behavior has also been displayed, with adult males courting juvenile males. Studies show that rock cavys have a direct link between their retina and the mediodorsal nucleus in the thalamus, which may provide them with strong visual recognition, emotional learning, and / or enhanced object-reward associative memory. This may partly explain why they are 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. There are blood vessels running from the mother along the placenta and then vessels running from the fetus back over the mothers 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 three days old, but continue to nurse for up to seven 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 father is present. Females who 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 less than those raised by both parents. There is no explanation for this trend.
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. Rock cavies are frequently hunted as food by local human populations, which resulted in population decline of 30% in the last ten years. Their environment is also being destroyed due to deforestation. There are efforts underway to breed rock cavies in captivity as a potential food source.
