Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Cervidae

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).
Previously published Red List assessments:
2002 Vulnerable (VU)
1996 Vulnerable (VU)
1994 Vulnerable (V)
1990 Vulnerable (V)
1988 Vulnerable (V)
1986 Vulnerable (V)
1982 Vulnerable (V)

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.
Countries occurrence:
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).
Current Population Trend: Decreasing
Additional data:
Population severely fragmented: No

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.

Citation: Duarte, J.M.B., Varela, D., Piovezan, U., Beccaceci, M.D. & Garcia, J.E. 2008. Blastocerus dichotomus. The IUCN Red List of Threatened Species 2008: e.T2828A9486864. . Downloaded on 09 October 2015.
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