The rock cavy or mocó (Kerodon rupestris) is a cavy species endemic to eastern Brazil, from eastern Piauí state to Minas Gerais state. It has been introduced to the oceanic island of Fernando de Noronha.
The rock cavy is a fairly large rodent weighing up to 1 kg (2.2 lb), and like other species of cavies the tail is vestigial or absent. The dorsum is grey and the venter light brown. They are hystricomorphs, which means they have porcupine-like jaw muscles.
The rock cavy belongs to the order Rodentia and the family Caviidae. This group has two subfamilies: Dolichotinae and Caviinae. The rock cavies belong to the subfamily Caviinae along with the guinea pig, desert cavy, and cuis.
Distribution and habitat
Rock cavies are found in dry, rocky areas with low, scrubby vegetation, and they like to reside close to stony mountains and hills. In appearance and habits they closely resemble the unrelated rock hyrax of Africa (an example of convergent evolution). They usually shelter in crevices. They are reportedly seen at day and night, but are most active at dawn or dusk. Animals most active at this time are known as crepuscular.
Studies show that there is a direct link between the retina and the mediodorsal nucleus, a large nucleus in the thalamus, which may provide the rock cavy with strong emotional learning, visual recognition, and object-reward association memory. This may explain why the animals are found to live in large groups.
They can sometimes display homosexual behavior, with males courting males. Some paedophilical behavior has also been displayed, with adult males courting juvenile males. Each group has an alpha or dominant male and several females. The males are territorial, defending rock pile shelters against other adult males. These rock piles are built to impress the females. Once a females chooses a rock pile, she indirectly chooses the builder as her mate.
Females weigh 700-800 g and give birth to one or two young only, 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.
The most unique feature of the placenta is the presence of a subplacenta. The function is not completely known. The vessels from the mother and fetus occur at different times in the subplacenta, so it is not used for counter-current exchange. It may have a role in hormone secretion.
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 males are absent, the females spend more time with their young than they do when the father is present. 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 occurrence. Females who raise young on their own are more aggressive than females that raise the young with a partner.
Rock cavies are herbivorous. They feed on seed and leaves of the scrubby vegetation that grows in their territories. This vegetation consists of tender leaves and certain species of creeper. They are able to climb which makes reaching leaves, seeds, and even occasional fruits easy.
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.
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 also efforts to breed rock cavies in captivity as a potential food source. They are currently listed as "least concern" on the IUCN Red List. There are several protected areas that these animals reside in.
- Catzeflis, F.; Patton J.; Percequillo, A. & Weksler, M. (2016). "Kerodon rupestris". The IUCN Red List of Threatened Species. IUCN. 2016: e.T10988A22190269. doi:10.2305/IUCN.UK.2016-2.RLTS.T10988A22190269.en. Retrieved 13 December 2017.
- Gasparini et al., 2007, p. 30
- Tasse, Judy (1986). "Maternal and Paternal Care in the Rock Cavy,Kerodon Rupestris, a South American Hystricomorph Rodent". Zoo Biology. 5 (1): 27–43. doi:10.1002/zoo.1430050105.
- Nascimento, Expedito Silva Do; et al. (2010). "Retinal Afferents to the Thalamic Mediodorsal Nucleus in the Rock Cavy (Kerodon Rupestris)". Neuroscience Letters. 475 (1): 38–43. doi:10.1016/j.neulet.2010.03.040.
- Miglino, M.a., et al. “Vascular Organization of the Hystricomorph Placenta: a Comparative Study in the Agouti, Capybara, Guinea Pig, Paca and Rock Cavy.” Placenta, vol. 25, no. 5, 2004, pp. 438–448., doi:10.1016/j.placenta.2003.11.002.
- Oliveira, M.f.; et al. (2006). "Placentation in the Rock Cavy, Kerodon Rupestris (Wied)". Placenta. 27 (1): 87–97. doi:10.1016/j.placenta.2004.11.012.
- Derrickson, Elissa Miller, et al. “Milk Composition of Two Precocial, Arid-Dwelling Rodents, Kerodon Rupestris and Acomys Cahirinus.” Physiological Zoology, vol. 69, no. 6, 1996, pp. 1402–1418., doi:10.1086/physzool.69.6.30164266.
- Instituto de Chico Mendes de Conservação da Biodiversidade. http://www.icmbio.gov.br/portal/faunabrasileira/lista-de-especies/6106-especie-6106
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- Bruce Bagemihl, 2000. Biological Exuberance: Animal Homosexuality and Natural Diversity.
- Gasparini, J.L., Peloso, P.L. and Sazima, I. 2007. New opportunities and hazards brought by humans to the island habitat of the skink Euprepis atlanticus. Herpetological Bulletin 100:30–33.
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