469.

Chacoan Marsh Rat

Holochilus chacarius

French: Oryzomys du Chaco / German: Chaco-Sumpfratte / Spanish: Rata de marisma del Chaco

Other common names: Chaco Marsh Rat

Taxonomy. Holochilus chacarius Thomas, 1906, “Chaco 1 league [= 5-6 km] N.W. of Concepcion [Concepcion], Paraguay.”

This species is treated here as monotypic, although several authors recognized two subspecies, H. c. chacarius widespread in the Parana-Paraguay fluvial system and H. c. balnearum associated to Yunga environments.

Distribution. S & E Bolivia, Paraguay, SW Brazil, and N Argentina .

Descriptive notes. Head-body 140-201 mm, tail 148-183 mm, hindfoot 37-46 mm; weight 70-240 g (mean 165 g). See general characters of the genus under the Venezuelan Marsh Rat ( H. venezuelae) account. Dorsum of the Chacoan Marsh Rat is reddish to cinnamon, sides are ocherous buffy, and venter is buffy. Throat, chest, and inguinal regions are white. Mystacial vibrissae are short and do not reach ear tips. Tail is unicolor and sparsely haired. Hindfeet have interdigital webbing. Skull is heavily built. Interorbital margins have moderately well-developed supraorbital crests. Incisors are opisthodont; molars are tetralophodont. Chromosomal complement is 2n = 48-56, FN = 57-60.

Habitat. Marshes, swamps, and grasslands in mostly non-forested regions, associated with Pantanal, Chaco, and Yungas biomes.

Food and Feeding. Diet of the Chacoan Marsh Rat consists basically of leaves and other items of plant origin. It can cause extensive damage to several types of crops, such as rice and sugarcane.

Breeding. Captive Chacoan Marsh Rats had average gestation of 27-8 days, and average number of embryos was 3-3/litter. Nest are built with grass up to 1-4 m aboveground and are 20-30 cm in diameter and 25-95 g in weight.

Activity patterns. Trapping data suggests that Chacoan Marsh Rats are nocturnal. They can swim, dive, and climb very well, characteric of an amphibiouslifestyle.

Movements, Home range and Social organization. Chacoan Marsh Rats are frequently found in owl pellets and feces of small carnivores.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. D’Elia, Hanson et al. (2015), Goncalves et al. (2015), Hershkovitz (1955), Massoia (1970, 1971c, 1976), Piantanida (1993), Voglino et al. (2004).