The marsh deer (Blastocerus dichotomus) once thrived throughout much of South America, from Argentina to Bolivia, Paraguay, Brazil and Peru. Today, the species is in decline throughout most of its historical range.
One of the corners of South America where this beautiful reddish-brown, black-legged deer has found a refuge is the wetland habitat contained within Tambopata National Reserve, in the Amazon forests of southeastern Peru.
As its name suggests, this deer favors the marshy conditions found in parts of the continent south of the Amazon River, as far south in fact as Argentina. Such areas offer them better protection against the major predators of the Amazon basin, including the jaguar and puma. Once found in Uruguay also, hunting and habitat loss have led to its total extinction in that country. Historically, wetland drainage for agriculture has had the most dramatic effect upon marsh deer numbers throughout their former range. In some parts of South America, water pollution and the accidental transmission of bovine diseases from cattle have also caused deer numbers to decline.
The vast area of wetland contained within the borders of Tambopata National Reserve favors this timid and rarely seen deer, and its presence has been reported on the Pampas de Heath, where wetland systems are fed by the Heath River. While they tend to favor shallow waters, when necessary they are able swimmers. Equipped with membranes, this deer’s large hooves are well-adapted for swimming and for coping with its preferred wetland habitat.
With a body length of up to two meters (6.5 feet) and shoulder height of 1.2 meters (4 feet), this is one of the largest deer in South America. Adult males can weigh up to 150 kilograms (330 pounds), while females have been reported as weighing up to 100 kilograms (220 pounds). Their appearance resembles that of the North American black-tailed deer. Only the males have antlers, which can be up to 60 centimeters (2 feet) in length. Marsh deer are believed to live for around 15 years in the wild.
In their preferred wetland habitat, marsh deer will tend to feed on grasses, reeds and aquatic plant species. During flooding, when such plant species may be unavailable for extended periods, they have been known to widen their preferences to include shrubs and vines.
Marsh deer are predominantly nocturnal and do not form herds. When they are spotted in southeastern Peru, they tend to be found alone, although they may also roam in small groups of two or three individuals.