This species is found in the marshy habitats south of the Amazon River into northern Argentina (Pinder and Grosse 1991), with water depth as much as 0.0 m (Tomas et al. 1997). Diet is generally grasses, reeds and aquatic plants, but may include shrubs and vines during prolonged flooding (Nowak and Paradiso 1983). The marsh deer is generally solitary or found in small groups of 2–3. Aggregations of up to six animals have been reported on islands during floods (Schaller and Vasconcelos 1978). The Marsh Deer is the largest cervid species of South America. Male animals can reach up to 150 kg and the females up to 100 kg (Duarte and Merino 1997).

The Marsh Deer, Blastocerus dichotomus, is the largest South American deer. Originally much more widely distributed throughout present range (Nowak and Paradiso 1983), it now occurs in east-central and northeastern Argentina, west-central and southern Brazil, Paraguay, southeastern Peru, and eastern Bolivia. The species has been extirpated from Uruguay.

The species is included on CITES Appendix I. The species occurs in several protected areas throughout its range. A management plan for this endangered deer is urgently needed to assure the survival of populations closely related with the major basin in South America (Mauro 1995). Recommended conservation actions include further population surveys, ecological research, strengthening of existing management of protected areas, creation of new protected areas, establishment of a collaborative captive breeding programme, and enlisting the co-operation of local landowners in maintaining this species.