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Image courtesy of The Happy Cappy

Diet

Capybaras are highly selective grazers whose eating habits change with the seasons and from day to day. In fact, 4-6 species of plants compose 75% of the diet of most wild capybaras (Quintana et al.). Capybaras graze both on land and in water, and capybaras never follow the same grazing route on consecutive days. They've even been observes to leave an area in their territory untouched for long periods at a time (Barreto et al.). This allows the plant life some time to recover, and at the same time it may reduce predation. Capybaras behave like optimal consumers, and will select individual leaves of one species that are surrounded by another species (Barreto et al.). Capybaras are caecum fermenters, and they consume almost exclusively the grasses with the most protein and fiber. In fact, capybaras will spend the same amount of time grazing two different species, even if both species have different caloric content, as long as both have the same fiber or protein content (Barreto et al.).

Capybaras eat a wider range of plant life during the dry season, in part because there is less total plant life available, but also possibly due to a changing nutritional value. They eat predominantly grasses during the wet season, and shift to the less nutritious but more abundant reeds during the dry season (Barreto et al.). It has also been discovered that the plants which capybaras consume in the summer but not the winter, lose most of their nutritional value in the winter, making them not worth consumption (Quintana et al.).

To analyze the capybara's effect on surrounding plant life, Barreto et al. set up an experiment with three different areas; a control, a capybara-only area, and a full wildlife area. Because it had nothing trimming the grass, the control naturally had the tallest grass. The capybara-only and the third area had similar heights, indicating that capybaras are responsible for most grass height control in any area they reside. This would make sense as capybaras are the dominant herbivore in most of the areas where it is found. More interesting, however, was the finding that the capybara only area had a significantly higher level of protein in its grasses. This seems to suggest that capybaras are "gardeners" and via their eating habits actually coax grass into a higher nutritional value. This hidden talent is not their only asset, however. Capybaras manage to survive and flourish on a remarkably small variety of fauna. Their secret lies in their stomach. Quintana et al. found that capybaras have a very efficient digestive system. A capybara can extract far more nutrients from the same amount of plant life than can a white tailed deer for instance. This may be related to how capybara thrived while most other large herbivores in the region disappeared. Finally, capybaras have been found to have both a regurgitory and a cecotrophic behavior.

Regurgitation and Cecotrophy

Similar to a cow chewing its cud, only without the additional stomach, Capybaras have been observed to regurgitate their food and continue to masticate it before swallowing it a second time (Lord-Rexford). Additionally, the same experimenter observed juveniles eating the regurgitate of an adult. Many observers have also seen cecotrophy performed by capybara. Cecotrophy or coprophagy is the process of eating one's own feces in order to pass the same material through the digestive tract a second time, and therefore extract a higher percentage of nutrients from the substance. Cecotrophy allows capybaras to maintain a very high level of protein extraction from the plant life they consume. As was mentioned above, the limited diet of a capybara makes such efficient extraction vital. Like rabbits, capybaras excrete two types of feces (Mendes et al.). one is a collection of hard oval pellets, the other is pasty and considerably clearer in color. The second type contains an average of 37% more protein than the first type, while the first type has more cell wall and cellulite constituents. This difference becomes greater as the protein level of a capybara's diet decreases (Mendes et al.). Besides appearance and texture, this second type of excrement differs from the first in another vital way. Namely, the second type is produced by the capybara's caecum, which acts as a natural fermenter (Mendes et al.).