habitat_narrative
Terrestrial|Freshwater (=Inland waters)|Marine
Cape Clawless Otters are predominantly aquatic and seldom found far from permanent water. Fresh water is an essential habitat requirement, not only for drinking but also for rinsing their fur. As otters do not have a subcutaneous layer of fat like most other aquatic mammals, they rely on their dense fur for thermoregulation. Thus, rinsing their fur in freshwater followed by rolling in sand, grass or reeds helps them cleanse their fur and restore the thermoregulatory properties. Generally, they will only occur in marine habitats provided there is access to fresh water (coastal rivers or estuaries) and rocky shores are preferred for foraging (van Niekerk et al. 1998), and otter activity is often found near thick vegetation, abundant food supply and fresh water (van der Zee 1982; Arden-Clarke 1986; van Niekerk et al. 1998). Elsewhere, they are found in diverse habitats, from impoundments, estuaries, and mangroves to desert conditions of the upper Doring River in the Western Cape and the Fish River in southern Namibia (Nel & Somers 2007; Somers & Nel 2013); they are also found in many seasonal or episodic rivers in the Karoo, such as the Sak, Vis, Riet, Seekoei and Gamka Rivers, provided suitable-sized pools persist (Nel & Somers 2007; Somers & Nel 2013; Prinsloo 2014). They have been recorded up to 2,900 m asl in the Lesotho Highlands (Lynch 1994; Avenant & du Plessis 2012). Cape Clawless Otters have been found in towns and cities, and can occupy rivers with high pollution and eutrophication levels (Somers & Nel 2013).Somers and Nel (2004) found that in a river ecosystem, otters selected habitat characterised by reed beds, boulders and overhanging vegetation. It has also been found by other authors including Rowe-Rowe (1992a, 1992b) and Perrin and Carugati (2000), that Cape Clawless Otter activity is usually associated with natural riverine habitat, particularly with rocks covered with dense vegetation and large areas of undisturbed long grasses and dense bushes. Kubheka et al. (2013) found less otter sign in areas without stream-bank cover. Deforestation, overgrazing and the deterioration of riparian vegetation is therefore a threat to the key habitat requirements for the species in a river environment.
Cape Clawless Otters are predominantly crepuscular, meaning they are mostly active at dawn and dusk (Somers & Nel 2004). However, this behaviour may differ between disturbed and non-disturbed habitats. In the protected areas of Drakensberg in KwaZulu-Natal they are often seen foraging from mid-afternoon. In the Cape Peninsula and Gauteng, for example, otters are more nocturnal in the urban areas possibly so as to avoid dogs, people and disturbance.
With a wide variety of prey items (for example, Rowe-Rowe 1977; Somers & Purves 1996; Jordaan et al. 2015), this species shows functional responses to temporal or geographical patterns, and can switch between prey items (for example, between fish, crabs, frogs, insects or combinations thereof), thus facilitating a wide distribution (Nel & Somers 2007).
Arden-Clarke (1986) estimated the home range of otters in Tsitsikamma National Park, Eastern Cape of South Africa, and found the minimum home range for a female otter to be 14.3 km (7.5 km core range), and for a male otter to be 19.5 km (12 km core range). In the Western Cape, the home range of otters in rivers was estimated by Somers and Nel (2004). They found that total range length varied from 4.9â54.1 km (linear home range core length from 0.2â9.8 km). The pattern of home range use by females was suggestive of territoriality. Male Cape Clawless Otters had overlapping home ranges in both studies (Arden-Clarke 1986; Somers & Nel 2004), with other males and with females.).
Ecosystem and cultural services: Globally, other otter species are considered to be indicators of water qualityâfor example, in both North American rivers (North American River Otter Lontra canadensis) (Mayack 2012) and coastlines (Sea Otter Enhydra lutris) (Jessup et al. 2004)âor sentinels of environmental health; for example, in Europe (European Otter Lutra lutra) (Chadwick 2007; Lemarchand et al. 2011). Mayack (2012) suggested that the otterâs wide distribution, opportunistic and predatory nature, plus their flexibility in habitat and diet, allow them to serve as a useful upper level consumer component in ecosystem monitoring. Similarly, the Cape Clawless Otter may be a useful flagship species to highlight the importance of river health, and potentially provide information on the contaminant levels in African urban rivers as European Otters do in Europe. However, it is not yet known whether Cape Clawless Otters have an important role in the freshwater ecosystems. Currently, research is underway investigating the health of otters relative to the pollution levels in urban rivers (N. C. Okes unpubl. data). Preliminary results show that certain persistent organic pollutants are present in the tissues of otters found killed on the roads in the Cape Peninsula (N. C. Okes unpubl. data). Further research is needed in order to establish whether they may be a useful indicator species for river health (see, for example, Seaman et al. 2010; Prinsloo 2014).
In the Lesotho Highlands, inhabitants report that Cape Clawless Otters are commonly used for traditional medicine, clothes, hats, and as food (Avenant 2004).
