Marsh Deer Male (Blastocerus dichotomus). This surprisingly shy and secretive deer is actually the largest native deer species in South America. Marsh deer have large, primarily ornamental antlers, which are usually impressively forked, growing to about 60 centimetres in length and weighing, on average, about two kilograms. They are shed irregularly and may be retained for up to two years. Marsh deer have long, broad hooves that are particularly adapted to the marshy environment, as they are joined by a special membrane and can spread out, giving the hooves a greater surface area, to prevent the deer from sinking into swampy ground.