Blastocerus dichotomus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Blastocerus dichotomus
Species Authority: (Illiger, 1815)
Common Name(s):
English Marsh Deer
Spanish Ciervo De Los Pantanos, Ciervo Marismeño
French Cerf Des Marais

Assessment Information [top]

Red List Category & Criteria: Vulnerable A4acde ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Duarte, J.M.B., Varela, D., Piovezan, U., Beccaceci, M.D. & Garcia, J.E.
Reviewer(s): Black, P. & Gonzalez, S. (Deer Red List Authority)
This species is considered to be Vulnerable due to an ongoing decline estimated from habitat loss in the past, and suspected habitat loss in the future based on direct and indirect threats. Based on rates of current decline, and considering a time period of three generations (15 years), including both past (10 years) and future (five years), this species is projected to have declined by more than 30%. Despite the lack of evidence of decline in the Pantanal population (Mourão et al. 2000, Rodrigues et al. 2005), the species may be considered to be declining throughout its geographic distribution. Although no data on demography are available for other populations, it is realistic to expect an overall decline due to poaching, habitat loss and disease. Habitat loss due to hydroelectric dams has been documented, but wetland drainage for agricultural purposes is also important in the floodplains of many rivers. Flooding by large reservoirs completely eliminates the best marsh deer habitats and isolates populations. Additionally, the retention of water by these dams causes deep changes in the flooding regime of wetlands downstream, which may cause disruption in the aquatic-plant communities, consequently reducing the carrying capacity of these habitats for Marsh Deer (Tomas et al. 1997, Tomas and Salis 2000). Drainage of the wetlands and its conversion into agricultural landscapes, also reduces its carrying capacity for the species. The main direct effects of habitat loss have been the fragmentation and isolation of marsh deer populations (Tomas et al. 1997), which may lead to demographic and genetic consequences. In Uruguay the species is thought to be extinct: the last record from this country was in 1958 (Ximenez et al. 1972).
2002 Vulnerable
1996 Vulnerable

Geographic Range [top]

Range Description: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.
Argentina; Bolivia, Plurinational States of; Brazil; Paraguay; Peru
Regionally extinct:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: The species is declining throughout much of its range (Nowak and Paradiso 1983) although recent surveys in Brazil have revealed higher populations than had been previously recorded (Mauro 1995). Information gathered at a PHVA workshop indicates that approximately 41,000 Marsh Deer still survive in Brazil (Pinder 1995). In Argentina, population estimates are around 2,000 animals in Iberá marshes, other important populations are known from Formosa and the Paraná River Delta (Varela et al. 2001). In Bolivia, several populations are known from the Beni savannas and Noel Kempff National Park, and a recent population survey in Pampas Heath estimates 700 deer in the north of Madidi National Park (Gomez and Ríos-Uzeda 2004).

The principal population in Paraguay is in the Yacyretá region where density is low. Most populations in Paraguay were reported to be declining in the 1970s (Jungius 1974, 1976). In Peru the species occurred in small numbers in Pampas del Heath (Hofmann et al. 1976, Montanbault 2002, Escamilo pers. comm.). The last record of the species in Uruguay dates back to 1958 (Ximenez et al. 1972, González 1994).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: 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).
Systems: Terrestrial; Freshwater

Threats [top]

Major Threat(s): The species is declining throughout its range due to excessive hunting and wetland conversion for agriculture, tree plantations, and dams. In Brazil and Argentina, hydroelectric projects have eliminated floodplain habitat along many large rivers, including the Tiete, Paraná, and Rio Grande (DSG 1991), and cattle ranching has severely reduced and fragmented habitats. Competition with domestic livestock may be a major threat (Schaller and Vasconcelos 1978) and pollution of waterways associated with gold mining is a serious threat in the Pantanal. Accidental introduction of bovine diseases may account for large losses reported in Bolivia during the 1970s when reproductive failure was reportedly common (Mann and Schuerholz 1977). Beccaceci (1994) also mentioned disease, hunting, and competition with livestock as possible limiting factors in the Ibera Natural Reserve, Argentina. In the Paraná River Delta, the conversion of marshes for exotic tree plantation and hunting threaten the population in Argentina (Varela 2003). In Brazil, tick infestation was one of the most important causes of death after habitat loss in the Parana River basin (Szabo, et al. 2003).

Conservation Actions [top]

Conservation Actions: 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.

Bibliography [top]

Beccaceci, M. D. 1994. A census of marsh deer in Iberá Natural Reserve, its Argentine stronghold. Oryx 28: 131-134.

Duarte, J. M. B. and Merino, M. L. 1997. Taxonomia e Evolução. In: J. M. B. Duarte (ed.), Biologia e conservação de cervídeos Sul-americanos: Blastoceros, Ozotoceros e Mazama, pp. 1-21. FUNEP, Jaboticabal, São Paulo, Brazil.

Gómez, H. and Ríos-Uzeda, B. 2004. Abundancia y distribución del ciervo de los pantanos (Blastocerus dichotomus) en las Pampas del Heath (PN Madidi, La Paz, Bolivia). Technical report. Wildlife Conservation Society – Bolivia. Living Landscapes Program.

Gonzalez, S. 1994. Marsh deer in Uruguay Population and Habitat Viability Assessment. Workshop for the Marsh Deer (Blastocerus dichotomus). CBSG publication Section 4, Apple Valley, Minnesota, USA.

Hoffmann, R. K., Ponce del Prado, C. F. and Otte, K. C. 1976. Registro de dos nuevas especies de mam'iferos para el Peru, Odocoileus dichotomus (Illiger, 1811) y Chrysocyon brachyurus (Illiger, 1811) com notas sobre su habitat. Revista Forestal de Peru 5: 61-81.

Jungius, H. 1974. Beobachtungen am Weisweldelhirsch und an anderen Cerviden in Bolivia. Zeitschrift für Säugetierkunde 39(6): 373-383.

Jungius, H. 1976. National Parks and Indigenous People - A peruvian case study. 1976: 6-14.

Marquez, A., Maldonado, J. E., Gonzalez, S., Beccaceci, M. D., Garcia, J. E. and Duarte, J. M. B. 2006. Phylogeography and Pleistocene demographic history of the endangered marsh deer (Blastocerus dichotomus) from the Río de la Plata Basin. Conservation Genetic 7: 563-575.

Mauro, R. A., Mourão, G. M., Pereira de Silva, M., Coutinho, M. E., Tomas, W. M. and Magnusson, W. E. 1995. Influência do habitat na densidade e distribuição de cervo (Bastocerus dichotomus) durante a estação seca, no Pantanal Mato-grossense. Rev. Bras. Biologia 55: 745-751.

Montanbault, J. R. 2002. Informes de las evaluaciones biológicas de Pampas del Heath, Perú, Alto Madidi, Bolivia y Pando, Bolivia. RAP Bulletin of Biological Assessment Nº 24. Conservation International, Washington, DC, USA.

Mourão, G. M., Coutinho, M., Mauro, R., Campos, Z., Tomas, W. M. and Magnusson, W. E. 2000. Aerial surveys of caiman, marsh deer and pampas deer in the Pantanal wetland of Brazil. Biological Conservation 92: 175-183.

Nowak, R. M. and Paradiso, J. L. 1983. Walker's Mammals of the World. The Johns Hopkins University Press, Baltimore, USA and London, UK.

Pinder, L. 1996. Marsh deer population estimate in Paraná river, Brazil. Biological Conservation 75: 87-91.

Pinder, L. and Grosse, A. P. 1991. Blastocerus dichotomus. Mammalian Species 380: 1-4.

Rodrigues, F. H. G., Medri, I. M., Tomas, W. M. and Mourão, G. M. 2005. Revisão do conhecimento sobre a ocorrência e distribuição de mamíferos do Pantanal. Documentos, Embrapa Pantanal 38: 1- 42.

Schaller, G. B. and Vasconcelos, J. M. C. 1978. A marsh deer census in Brazil. Oryx 14: 345 - 351.

Szabo, M. P. J., Labruna, M. B., Pereira, M. C. and Duarte, J. M. B. Ticks (Acari: Ixodidae) on wild marsh-deer (Blastocerus dichotomus) from southeast Brazil: infestations before and after habitat loss. Journal Medical Entomology, Laham 40(3): 268-274.

Tomas, W. M. and Salis, S. M. 2000. Diet of the marsh deer (Blastocerus dichotomus) in the Pantanal wetland, Brazil. Studies on Neotropical Fauna and Environment 35: 165-172.

Tomas, W. M., Beccaceci, M. D. and Pinder, L. 1997. Cervo-do-pantanal (Blastocerus dichotomus). In: J. M. B. Duarte (ed.), Biologia e conservação de cervídeos sul-americanos, pp. 24-40. FUNEP, Jaboticabal.

Varela, D. 2003. Distribución, abundancia y conservación del ciervo de los pantanos (Blastocerus dichotomus) en el Bajo Delta del río Paraná, Provincia de Buenos Aires, Argentina. Licentiate Thesis, University of Buenos Aires.

Varela, D., Gagliardi, F., D'Alessio, S., Lartigau, B., Aprile, G. and Monaco, C. 2001. Conservation of marsh deer in Paraná delta, Argentina. IUCN Deer Specialist Group News 16: 6-8.

Ximenez, A., Langguth, A. and Praderi, R. 1972. Lista sistematica de los mamiferos del Uruguay. Anales del Museo de Historia Natural, Montevideo 7(5): 1-45.

Citation: Duarte, J.M.B., Varela, D., Piovezan, U., Beccaceci, M.D. & Garcia, J.E. 2008. Blastocerus dichotomus. In: The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 03 September 2015.
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