Chacoan Mara

Exhibiting a distinctive cursorial morphology resulting from convergent evolution with lagomorphs, this medium-sized caviomorph rodent possesses a body mass typically ranging between 1.8 and 2.5 kg, with a head-body length of 42 to 45 centimeters. It is characterized by exceptionally long, slender limbs adapted for high-speed running, with the hind legs being visibly longer than the forelegs. The dorsal pelage is a finely speckled grayish-brown or olive-gray, transitioning to a clean whitish or pale cream tone on the venter, throat, and lower flanks. A key diagnostic feature distinguishing it from its larger congener, Dolichotis patagonum, is the absence of the prominent, broad white rump patch; instead, its rump is a uniform grayish hue, occasionally bordered by a subtle, pale margin. The ears are large, erect, and pointed, playing a crucial role in thermal regulation and the early detection of predators within its open habitats.

Geographical distribution: It is strictly endemic to the Gran Chaco ecoregion of south-central South America. Its geographic range encompasses western Paraguay, southeastern Bolivia, and extends widely into northern and central Argentina, including the provinces of Formosa, Chaco, Santiago del Estero, Salta, Tucumán, Catamarca, La Rioja, San Juan, Córdoba, and northern Santa Fe. Its distributional boundaries are tightly constrained by the climatic and vegetational shifts of this semi-arid region.

Habitat: It primarily frequents dry, thorny deciduous forests, xerophytic shrublands, and alluvial plains characteristic of the Chaco region. The species displays a strong affinity for areas with loose sandy or clayey soils that facilitate burrowing activities, as well as habitats adjacent to salt flats and saline depressions where halophytic, sparse vegetation dominates. It avoids dense, closed-canopy forests, preferring ecotones, open woodland clearings, and areas moderately degraded by livestock grazing, where its long-range vision and running capabilities are not hindered by dense undergrowth.

Feeding: It is a generalist herbivore whose diet consists mostly of leaves, tender shoots, bark, fruits, and seeds of woody plants and shrubs native to the Chaco, showing a marked preference for species within the genera Prosopis and Acacia. During the wet season, it opportunistically consumes a higher proportion of grasses and ephemeral annual herbs. Throughout the prolonged dry season, when free water is virtually non-existent, it exhibits a specialized physiological adaptation by consuming cacti and other succulent plants from the Cactaceae and Bromeliaceae families, deriving both essential nutrients and necessary hydration directly from these plants.

Behavior: This species is strictly diurnal and crepuscular, with activity patterns peaking during the cooler morning and late afternoon hours to avoid the intense midday heat, during which it seeks refuge under the shade of dense shrubs. Highly cursorial, it relies on its acute visual and auditory senses to detect potential threats from afar. It lives in long-term monogamous pairs, a social structure rarely observed among rodents, although temporary aggregations may form around localized, high-quality food resources. For shelter and rearing offspring, it utilizes underground burrows, which may be excavated by the pair or acquired by modifying abandoned tunnel systems of the plains vizcacha (Lagostomus maximus).

Reproduction: The mating system is defined by strict monogamy, with pair bonds often persisting across multiple breeding seasons. The gestation period is unusually long for a rodent of this size, lasting between 75 and 77 days. Females produce litters of one to three pups, and under optimal environmental conditions, they can produce up to three litters per year. The young are highly precocial at birth, delivered fully furred, with open eyes, and capable of coordinated locomotion within hours of parturition. While the pups remain sheltered inside the deep safety of the burrow during their first weeks, the parents take turns acting as sentinels outside the entrance to deter potential predators.

Conservation status: It is currently assessed as Least Concern (LC) on the IUCN Red List of Threatened Species. Although it remains relatively common and displays a moderate tolerance to human-modified landscapes, local populations are increasingly threatened by rapid habitat loss, fragmentation, and degradation driven by agricultural expansion, deforestation, and overgrazing by domestic livestock. Additionally, localized hunting pressure and ecological competition with introduced European hares (Lepus europaeus) present ongoing challenges to the long-term conservation of the species across its natural range.