Marsh Deer (Blastocerus dichotomus) are the largest type of deer from South America. Though they originally thrived in tropical and subtropical environments in the rain forest, today small units of Marsh Deer inhabit the swamps and low river basins in Brazil, Uruguay, Paraguay, Peru, Bolivia, and Argentina.
Marsh Deer loosely resemble the North American Mule Deer, and their primary threat (apart from development of their natural habitat) is the jaguar or puma.
On this page we’ll share facts and information about Marsh Deer, including their size, physical description, range and preferred habitat, as well as notable behavior of the Blastocerus dichotomus.
Marsh Deer Size
- Head & Body Length – 145 to 200 cm
- Shoulder Height – 100 to 115 cm
- Tail Length – 25 cm
- Weight – 100 to 120 kg
What do Marsh Deer Look Like?
The Marsh Deer is the largest native species of deer found in South America.
It is similar in size to the Red Deer / North American Elk. Its alternative name of the Swamp Deer reflects the types of habitat this deer lives in.
The Marsh Deer has a shaggy coat, which is a distinctive red chestnut color. The under parts and lower parts of the neck are paler in color. The coat darkens during the winter months.
The lower legs are often a black or dark brown color. There are no distinct rump markings. The tail is long and bushy and has a reddish brown color.
Head & Face
The ears are large and prominent and stand out well against the coat being lined with white colored fur.
The lips, and the lower parts of the muzzle are black and also stand out well against the coat.
Around the edge of the eyes of this deer is a slight ring of whitish fur.
The Unique Hooves of the Marsh Deer
Of note are the Marsh Deer’s hooves, which are very distinctive in this species of deer.
The Marsh Deer is well adapted to living in wetland swampy areas, and as such the hooves are especially wide and broad. This prevents the deer from sinking into muddy ground.
The hooves of Blastocerus dichotomus can spread out to over 10 cm in width. They hooves have a special membrane between them; this is elastic in nature and may give the hooves greater surface area.
The dew claws of Marsh Deer are especially large and add even further surface area to the foot when walking through swampland. These can grow to up to 7 cm in length.
Marsh Deer Antlers
Males have large antlers that have many tines. Mature males often have antlers with 10 tines, but animals with more than 12 may be observed.
The antlers grow to over 60 cm in length and weigh about 2 kg. As the Marsh Deer is a tropical species of deer, there is no season of growth for the antlers, and they are grown and cast throughout the year and not on a set schedule as is the case of some other types of deer.
Some animals may keep their antlers for up to 2 years before they are lost and new ones are grown.
Where do Marsh Deer Live?
Now let’s discuss where the Marsh Deer live – their preferred habitat, where they thrived historically, and where they can be found in the world today.
As its name suggests, this is a wetland living deer and this species is happiest in swampy and marshy areas of grassland.
Marsh Deer can be found on South American grasslands that flood seasonally, and in areas that are marshy all year round.
This deer prefers areas which offer it good cover — for example areas where grass stands are high or where reed beds grow.
Marsh Deer are primarily found close to permanent sources of water, and to see this type of deer in dry habitats is very rare.
They are excellent waders and prefer areas with water levels of about 50 cm, although they will wade in areas where the water level reaches over a metre.
When the water level gets too high they move to dry, higher locations, and often they are more susceptible to hunting in these areas.
The Decline of Marsh Deer in South America
Formerly they had a large distribution across South America. Marsh Deer could be found over a large part of the central Brazil, southwards to northern Argentina.
However, due to the expansion of agriculture in the area after the Spanish colonization of the area, numbers of this species fell to reflect their diminished habitat.
The grasslands Marsh Deer once had to themselves began to be used to keep cattle on large ranches. This squeezed out native deer.
Hunting also played a part in the decline of this species. The range and numbers of the species today remain unclear, but it is certain that it has disappeared from much of its former range.
Remaining populations of Marsh Deer are small and highly fragmented.
Habitat loss and competition from domestic livestock continues to threaten this species. When they come into contact with domestic animals they may pick up the diseases that they carry.
Only a small number of Blastocerus dichotomus live in captivity. A small herd of about 30 animals resides in Brazil, but the numbers of this herd are proving difficult to preserve for some of the reasons we’ve mentioned here.
In Europe the only specimens are kept at the Berlin zoo. They are classified as being vulnerable by the IUCN.
Diet of the Blastocerus dichotomus
The Marsh Deer feed mainly on grasses and on water living plants.
Mating Habits & Reproduction
Little is known about the mating season. In more southerly locations mating takes place between October and November, but in more tropical areas, the rut for Marsh Deer can occur throughout the year.
It is unknown whether there is any aggression between the males of this species. This deer’s gestation period is 240 to 260 days long, and normally only a single young is born.
At birth the fawns are not spotted the way many young deer are for camouflage.
Young Marsh Deer are suckled for 6 months before being weaned. They remain with their mother for about a year, leaving when she gives birth again.
Females mate soon after giving birth so these does are almost continually pregnant.
The timing of mating and birth for this species of deer depends on the location in which it lives. In more tropical locations births and mating may occur throughout the year. The Marsh Deer’s babies are mostly born between May and November.
Notable Behavior & Habits Unique to Marsh Deer
Little is known about the behavior and lifestyle of this species of deer. There are few studies about its behavior. They are active late in the evenings and in the early mornings. In areas where they are hunted or disturbed by man they are mostly nocturnal in behavior.
Marsh Deer live mostly in pairs or in small family groups that are made up of 3 to 6 animals. However, some animals may be solitary on behaviour. During the wet seasons they become more scattered and widely distributed as available habitat expands, but during the dry seasons they area of suitable habitat decreases and they become more concentrated. Males have larger home ranges than the females.
They are a shy secretive deer, spending most of their time close to reed beds, which act as protective cover. They have a number of predators including jaguars and anacondas, but the main threat to their survival is man.