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Blastocerus dicotomus - Marsh Deer


The marsh deer is an animal that lives in the wet marshy areas of South America.  The hide can vary in color from a bright chestnut in the summer to a brown red during the winter months.  Along with these colors the marsh deer also has black and white in various areas such as the tail and the underside of the legs.  The hair on marsh deer is quite long and very tangled; it is like this all over the deer including the white hairs in the deer’s ears.  Males grow antlers that develop and increase in size, as they get older.  Adult males will have four tines on each side.  Usually the older the animals have more tines and can be asymmetrical.  The body size of the marsh deer is similar to the large Wisconsin northern whitetail deer, they can range from 176lbs or 80kg to 275lb or 125kgs (Pinder 1991).


The marsh deer is a South American species.  The range of the marsh deer is shrinking considerably, now it is only found in 6 major countries; these are Paraguay, Peru, Uruguay, Bolivia, Brazil, and Argentina (Walfrido 2001).  Marsh deer are typically found in the floodplains of large rivers, some of these include the Paraguay, Guapore, Parana, and the Araguaia river systems.  The largest population of marsh deer is located in the Pantanal.  This huge lowland or marshland is located in the northeastern part of Paraguay; however the majority of it lays in Brazil and some in Bolivia (Mauro 1998).  The deer’s range shrinks and expands as the dry and wet seasons alter water levels which in turn alter the marsh deer’s location (De-Salis 2001).  

Ontogeny and Reproduction:

The marsh deer can be found alone, which is the common occurrence, or up to groups of five.  During the peak mating periods, which are October and November, the breeding usually occurs.  The gestation period of the marsh deer is 271 days.  Most fawns are born from May to September however they are not restricted to this and sometimes fawns can be seen at any time of the year.  The fawns are born with no spots and they are the same mature color as the adults (Pinder 1991).

Ecology and Behavior:

The marsh deer lives in flood plain areas that are usually marshy and often inundated with water. They stay out of forested areas and prefer areas of standing water in the marsh.  They feed mostly on semi-aquatic plant species, however when this food supply is hard to find they will feed on the leaves of vines and shrubs (Pinder 1991).  Some plant species that the deer have been observed eating are “Aeschynomene sensitiva (Leguminosae), Discolobium pulchellum (Leguminosae) and Rhabdadenia pohlii (Apocynaceae)” (Walfrido 2001).

The marsh deer is most active during the night hours however some are seen during the day, but they are usually bedded or ruminating.  The deer come out around dusk and are active all hours of the night and early morning.  This is when they will feed on marsh plants.  They prefer wading in water around two feet and less.  When extreme flooding occurs the marsh deer takes to higher ground.  The marsh deer have an excellent ability to use there hind legs to jump with power; this helps the deer to move fast in deep water.  The antlers on the marsh deer are just for eye appeal; these deer do not fight for breeding privileges (Brent Huffman 2004).  Antlers are not shed at the same time of the year and it can vary with the individual.  Some males carry there antlers for almost two years before shedding them (Epps 2000).   


There is not a lot known about this particular deer species.  The populations are decreasing due to poaching, disease and from habitat loss.  They are very susceptible to catching diseases from the cattle that are farmed in there areas.  When high flooding occurs the marsh deer are forced to higher ground and in closer contact with these cattle (Pinder 1991).                

Literature Cited:

De-Salis,-Suzana-Maria.,Pereira-da-Silva,-Marta., De-Miranda, Mourao, Guilherme.
2001. Marsh deer (Blastocerus dichotomus) distribution as a function of floods in Pantanal Wetland, Brazil. Studies-on-Neotropical-Fauna-and-Environment. 2001; 36(1): 9-13.

Walfrido M. Tomas, Salis,-Suzana-M.,. Diet of the marsh deer  
(Blastocerus dichotomus) in the Pantanal wetland, Barzil.  Studies-on-Neotropical-Fauna-and-Environment. 2001; 35(3): 165-172.

Epps, Clinton. 2000. “Blastocerus dichotomus”, Animal Diversity Web. Accessed
September 29, 2004. < information/Blastocerus_dichotomus.html>

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

Huffman, Brent. The Ultimate Ungulate Fact Sheet. Blastocerus dichotomus.
10-19-04. 2004 <Http:// _dichotomus.html>

Mauro, R.A.;Mourao, G.M., Coutinho, M.E., Silva, M.P. & Megnusson, W.E.
Abundance and Distribution of Marsh Deer Blastocerus dichotomus In the Pantanal, Brazil. Vol. 5. pp13-20, 1998.

Reference written by Ben Nelson, Biol 378 (Mammalogy), University of Wisconsin – Stevens Point:  Edited by Christopher Luddington. Page last updated March 4, 2005.

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