habitat_narrative
Terrestrial
Brantsâ Whistling Rat is a largely crepuscular species (Jackson 1998), with additional short bouts of activity during the night and day (du Plessis 1989). It has a patchy habitat distribution (reflecting forage availability and the need for deep soils). It is restricted to areas with consolidated sands in semi-desert landscapes, with a low percentage plant cover (plant cover = 34â40%) (du Plessis & Kerley 1991; Malan 2001). These open areas probably provide it with a clear view of approaching aerial and terrestrial predators. In the Kalahari, it occurs in dune swales associated with Driedoring (Rhigozum trichotomum) (Jackson 2013). It is not associated with grass patches in Goegap Nature Reserve (C. Schradin unpubl. data). It can also occur in rangelands or old fields. It feeds on a variety of annuals in spring, and mostly perennial succulents, grasses and shrubs in summer and winter (Jackson 1998, 2001). Perennial succulents may function as key resource areas for this species and it is thus potentially sensitive to destruction of these areas. It is a central place forager; smaller food items are eaten in situ whilst larger items are eaten at burrow entrances or stored underground (Jackson 2001).It lives in small colonies in extensive tunnel systems or warrens in sandy soils (De Graaff 1981; du Plessis et al. 1991), especially in the relatively stone-less soil of Mima-like mounds or heuweltjies (Lovegrove & Siegfried 1986; Cox et al. 1987). It relies on the cooler temperatures of burrows to escape high temperatures (du Plessis & Kerley 1991; Jackson et al. 2002). Heuweltjies are earth mounds, 25â32 m in diameter and 1.25â2.25 m in height, and are dispersed in a uniform fashion 41â51 m apart (measured centre to centre) (Cox et al. 1987; Lovegrove & Siegfried 1989). The highest heuweltjie density recorded in its Western Cape distribution range was in the eastern Little Karoo at 500 mounds / km (Lovegrove & Siegfried 1989). Densities of heuweltjies accounted for 56% of the variation in the density of P. brantsii warrens (Malan 2001). In the shallow soils (< 40 cm) of the central Little Karoo, it is an obligatory burrower that prefers deeper soils (77 cm) (du Plessis & Kerley 1991). In this area, 58% of heuweltjies surveyed contained active warrens (N = 524), whereas 97% of warrens not on heuweltjies were inactive (N = 145) (Malan 2001). The relationship between heuweltjie and P. brantsii densities can therefore be explained by the dependence of P. brantsii on the suitable heuweltjie soils.
It has a range of aerial and terrestrial predators and uses an âurgency-basedâ alarm call to alert conspecifics of predators depending on the immediate threat (Jackson 2001).
Ecosystem and cultural services: Desmet and Cowling (1999) suggested that the nutrient-rich soil patches around P. brantsii burrows may facilitate the re-vegetation of mine dumps. This should be interpreted with some caution as the rats require forage and would only recolonise areas where there is at least some plant cover. It is a key prey species for Pale Chanting Goshawks (Melierax canorus) and Booted Eagles (Aquila pennatus) in the Little Karoo, where the reproductive fitness of the latter is associated with the Karoo Broken Veld vegetation type that contains the tall shrubs and heuweltjies necessary for high Otomyine density (Malan 2001). Pale Chanting Goshawks catch P. brantsii individuals in proportion to the warren densities, as the birds may find it easier to catch P. brantsii on or near their warrens that are normally devoid of any vegetation (Malan 2001). At high rodent densities, Jackal Buzzard (Buteo rufofuscus), Black Harrier (Circus maurus) and Lanner Falcon (Falco biarmicus) move into the area to hunt P. brantsii (Malan 2000). Reptiles found in warrens include the Cape Cobra (Naja nivea) and Mole Snake (Pseudaspis cana) (G. Malan pers. obs. 2014).
