in the dry season, (2)bajios,areas covered with short, highly
palatable grasses which flood in the wet season, and (3)ban-
cos,areas vegetated with tall grasses or bushes, which rarely
flood.
The mara, also known as the Patagonian cavy, is a 7 to
9 kg cursorial member of the Caviidae. Its habitat contrasts
with that of the capybara, being the dry scrub deserts and
grasslands of south and central Argentina. Maras have been
most intensively studied in the wild on sheep ranches on
the Valdés Peninsula in Argentina (e.g., Taber and Mac-
donald 1992a, 1992b; Parkhurst 2002 provides parallel
observations in captivity). These areas consist of semiarid
thorn scrub, broken by ephemeral lagoons of a few ha in
size. Bushes predominate, growing to a height of around
1 m, and sparse grasses and forbs grow in the spaces be-
tween them. There is a clear seasonality, with winter (June –
August) being the wet season, and summer (December –
February) the dry season. Summer temperatures average
17 oC, while winter temperatures rarely drop below freezing.Habitat Use, Home Ranges, and TerritorialityHerrera and Macdonald (1987, 1989) marked and ob-
served groups of capybaras in the Venezuelan Llanos, where
social group sizes varied between four and sixteen adult an-
imals (mean ten, but see the following). Capybaras use a
progression of habitats, with animals following the avail-
ability of water, grasses, and dry land as the season pro-
gresses. The areas of highest primary productivity, the grassy
ponds and flooded bajios (Escobar and Gonzalez-Jimenez
1976), typically support Leersia hexandraand the Hymen-
achnespecies. These species are nutritious for grazers and
predominate in the capybaras’ diet (Ramia 1974; Escobar
and Gonzalez-Jimenez 1976). Consequently, capybaras feed394 Chapter Thirty-Three
Table 33.1 Comparative behavior, ecology, and life history of capybaras and maras
Capybara MaraOrder Rodentia Rodentia
Family Hydrochaeridae Caviidae
Weight 35 – 66 kg; average 50 kg 7– 9 kg; average 8 kg
Range South America: Venezuela, Brazil, Colombia, Argentina South America: Central and southern Argentina
Habitat Flooded savannah or grassland next to waterholes; also along Dry scrubland deserts
ponds and rivers in tropical forests
Habitat Use Changes seasonally to follow the availability of water, grasses Changes seasonally to follow food availability
and dry land
Home range size 2 –200 ha; average 10 –20 ha Up to 200 ha; average 98 ha
Territoriality Minimal overlap between groups. Territories are defended by all Drifting territories, with a high degree of overlap between pairs.
adult members of a group against conspecific intruders.
Social structure Mixed sex groups-dominant male, females and young and Monogamous pairs, although settlements of several pairs may
subordinate males form in resource rich areas
Group size 10 –30 Male-female pair
Diet Grasses Grasses and herbs
Scent marking Males have snout gland used to signal their dominance. Anal Males mark daily ranges using anal dragging. Enurination and
glands in both males and females used to mark territories anal dragging by both sexes is greatest during breeding season
Breeding season Year round with seasonal peaks that varies according to area Twice a year, June –July and September – October
Reproduction Group living, allosuckling, Communal denning, allosuckling uncommon
Gestation period 150 days 90 days
Litter size 1– 8, average 4 1–3, average 2
Resource Dispersion Group size is determined by size, heterogeneity and richness of Monogamous pairs form when resources are sparse, groups of
Hypothesis habitat patch pairs may form when resources are clumped and plentiful
Figure 33.1 Capybara male. The small size of the capybara’s eyes and ears
may be adaptations to their semi-aquatic lifestyle, whereas the prominence of
the male’s morrillo gland indicates the importance of social odors. Jacanas have
a commensal relationship with capybaras, which act as “beaters,” disturbing in-
sects that the birds catch (Macdonald 1981b). Photo by D. W. Macdonald.