The marsh deer ( Blastocerus dichotomus) is a species of deer native to South America. It is the largest living species of South American deer. This is the monotypic taxon in the genus Blastocerus.
Distribution
It is found in
Argentina,
Bolivia,
Peru,
Brazil,
Uruguay and
Paraguay. Formerly found in much of tropical and
subtropical South America, it ranged east of the
Andes, south from the Amazon rainforest, west of the Brazilian Atlantic rainforest and north of the Argentinian
Pampa. Today it is largely reduced to isolated populations at marsh and lagoon zones in the Paraná,
Paraguay River,
Araguaia River and Guapore river basins. Small populations also occur in the southern Amazon, including Peru where protected in Bahuaja-Sonene National Park.
[Thornback, J., and M. Jenkins. 1982. The IUCN mammal red data book, Part 1: Threatened mammalian taxa of the Americas and the Australian zoogeographic region (excluding Cetacea). IUCN. 516 pp.][Cabrera, A. 1961. Catalogo de los mamiferos de America del Sur. Rev Mus Argentino Cien Nat Bernardino Rivadavia. 4:1-732.][Tomas, W.M., M. Beccaceci, and L. Pinder. 1997. Cervo-do-pantanal (Blastocerus dichotomus). Biologia e Conservacao de Cervideos Sul Americanos. 24–38.] It is listed as a vulnerable species by the
IUCN and is protected under CITES Appendix I.
Description
Marsh deer resemble the North American
mule deer or
blacktail deer. They possess very large ears lined with white hairs, red-gold to tawny brown fur, blackish eyes and long dark legs. The hair turns darker during winter. There are also white marks on the hips and around the eyes. The legs are black below the tarsal as is the muzzle. The tail is of a paler reddish tone than the rest of the body on its upper part and black on the under part. The head-and-body length is , while the tail adds a further . The height at the shoulder can range from .
[[1] (2011).]
The hoof, which is large in relation to the body, has elastic interdigital membranes which are useful for swimming and walking on marshy surfaces. Only the males possess antlers which are ramified and reach a length of . An adult typically grows to a weight of , although an occasional big male can weigh up to ,[[2] (2011).] making it the largest species of living South American deer,
Ecology and behavior
They are solitary animals or living in groups with less than 6 individuals with only an adult male. Their main predators are the
jaguar and the
Cougar.
Habitat
The marsh deer lives only in marsh areas, notably the
Pantanal and
Gran Chaco, in which the level of water is less than deep. They are swift swimmers. The marshes with their high vegetation density protect them from
and provide them with food. These deer also have a small migratory pattern, they follow the water levels between the dry season and flooding season. With the fluctuation in water levels, they are able to find new food sources that the water uncovers during the dry season. Some freshwater ponds on the Pantanal Wetland, Brazil reported low densities of individuals dictating that those ponds are not able to support large populations of marsh deer.
[Tomas, W.M., S.M. Salis, M.P. Silva, and G.M. Mourao. 2001. Marsh deer (Blastocerus dichotomus) distribution as a function of floods in the Pantanal Wetland, Brazil. Studies on Neotropical Fauna & Environment. 56:9-13.]
Diet
Since marsh deer live near aquatic habitats, they eat a majority of their diet in aquatic plants. A study was conducted and they found 40 different species of plants in which they ate. The main food component was
Graminae which took up 22% of their diet,
Pontederiaceae took up 12%,
Leguminosae was about 11%, and the rest was filled in with
Nymphaeaceae,
Alismataceae,
Marantaceae,
Onagraceae, and
Cyperaceae. They also enjoy eating aquatic flowers and shrubs that grow in the swamps and the floating mats.
[Tomas, W.M., and S.M. Salis. 2000. Diet of the marsh deer (Blastocerus dichotomus) in the Pantanal wetland, Brazil. Studies on Neotropical Fauna & Environment. 35:165–172.] They can be best classed as a grazer-browser for food. Their diet also changes between the dry season and the flood season.
Reproduction
Usually the rutting season coincides with the dry season but can change from animal to animal. They may use this to their advantage for breeding or finding mates because the densities of marsh deer are significantly higher on the Rio Negro marshland boundary during the dry season compared to the less dense, more distributed population during the flooded season.
[ Gestation lasts approximately 271 days.][Duarte, J.M.B. & Garcia, J.M. (1995). Reprodução assistida em Cervidae brasileiros. Revista Brasileira de Reprodução Animal 19(1-2): 111–121.] The offspring (normally one per female, though occasionally twins are born) are born between October and November. The infant deer are whitish which becomes more adult-like after a year.
Conservation
The natural predators of the marsh deer – the jaguar (locally called onça or yaguaraté) ( Panthera onca) and the cougar ( Puma concolor)— have almost completely disappeared from its habitat. The former major threat was poaching for its antlers, but this is somewhat under control. Destruction of its habitat presents nowadays the major threat to marsh deer. The Yacyretá Dam altered an area in which several hundred individuals lived and the draining of marshes for farmland and cattle farming threaten hundreds of hectares every year in Argentina and Brazil. Contagious diseases from cattle are also a problem, though it has been shown that the deer is not affected by brucellosis. In October 2018, Argentina established the Ciervo de los Pantanos National Park to help protect this species.
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