Freshwater Life - A field guide to the plants and animals of southern Africa

1	Text by Gary Bronner

Mammals

Class Mammalia

Mammals are a diverse, warm-blooded class of vertebrates distinguished by giving birth to live young that are nourished with milk produced by mammary glands, and by having hair (sometimes reduced, but always present somewhere on the body). The group includes 159 families and over 5,400 species, with 50 families and 350 species found in southern Africa. Many mammals depend partially on wetlands as sources of drinking water, or because they supply an abundance of food resources. However, only the 14 southern African mammal species that are most closely and permanently associated with water bodies are included here.

1 Hippopotamus

Hippopotamus amphibius

Body rotund with short thickset legs and large four-toed feet; massive head with small ears and eyes, broad snout with slit-like nostrils and cavernous mouth containing four enlarged tusks. Skin smooth and naked, greyish black above with pinkish folds around eyes and ears, greyish pink below. Emits distinctive, loud, deep-pitched grunts and snorts. Size: 3–5m in length, 1,000–2,000kg in mass. Biology: Restricted to northern and eastern parts of southern Africa, southwards to northern KwaZulu-Natal. Requires fresh water deep enough for total submergence during the day and prefers shallow waters with sandy substrates and sandbanks to bask on in cooler weather and in winter. Lives in pods of up to 15 cows and calves associated with a dominant territorial bull. Emerges at night (1a) to feed on grasses near home pool, travelling up to 10km to preferred grazing lawns. Social groups and territoriality dissolve during nocturnal foraging. Defecating in water is important for nutrient transfers between land and freshwater ecosystems. Occasional vagrant, moving far from its normal home range.

2 Sitatunga

Tragelaphus spekii

Medium-sized antelope with a shaggy water-resistant coat; hindquarters higher than forequarters, giving a hunched appearance. In southern Africa, adult male is drab dark brown without body stripes. Female (2a) smaller, generally redder, with a dark band down the back, vertical stripes on back, whitish flank bands and white haunch patches. Both sexes have a white chevron marking extending from below the eyes to the top of the muzzle, and white cheek spots. Hooves elongated (16–18cm long) and widely splayed (inset), with extended false hooves and enlarged footpads to facilitate walking on soggy substrates and floating reed mats. Adult male has shallow-spiralled, keeled horns about 60cm long. Size: 1.15–1.75m in length, 50–115kg in mass. Biology: Prefers dense papyrus or reed beds and swamps with water up to 1m deep. Occurs only in the Okavango Delta and Chobe River in southern Africa. Feeds on freshly sprouted reeds and aquatic grasses. Lives in small herds of up to six animals associated with a dominant male, but sometimes occurs singly or in pairs. An excellent swimmer, taking to deep water to escape predators. Mainly diurnal, resting on floating reeds mats, or in cover during hottest hours.

3 Waterbuck

Kobus ellipsiprymnus

Large sturdy antelope with shaggy coat; upperparts greyish brown, grizzled with white or grey hairs. Has characteristic white ring on rump, white bands on lower legs, a white collar and white patches extending down the muzzle to surround nose. Adult male bears long (75–90cm), heavily ringed and curved horns. Size: 1.4–2.4m in length, 250–270kg in mass. Biology: Closely associated with water, because of high water requirements and need for nutritious green grasses for fodder. Prefers wetland habitats within 2km of water, mostly in the northern and eastern parts of southern Africa. Occurs in herds of 5–12 individuals. Adult male defends a territory, through which nursery herds may pass. RELATED SPECIES: Red lechwe (K. leche) (3a) occurs marginally in southern Africa in the Okavango Delta, along the Chobe River and in the Zambezi Region of Namibia (formely eastern Caprivi). Takes to water to escape predators and feeds on semiaquatic grasses. Prefers inundated floodplains and nearby reed beds, seldom moving more than 3km from open water. Puku (K. vardonii) (3b) occurs on the Chobe River floodplain and in eastern Zimbabwe. Small herds favour floodplains and grasslands near water.

1 Reedbuck

Redunca arundinum

Medium-sized antelope with greyish-brown upperparts, usually darker on the back and lighter on the neck, throat and upperparts of bushy tail; underparts white. Front of each foreleg has vertical black stripe. Ears broad, rounded and whitish inside. Adult male has forward-curving, heavily ridged horns up to 46cm long. Size: 1.4–1.8m in length, 32–68kg in mass. Biology: Characteristically associated with reed beds, marshes and tall dense grassland close to permanent water, as these offer a year-round supply of nutritious fodder and concealment from predators. Distribution patchy owing to specialised habitat preferences; occurs mostly in wetter northern and eastern parts of southern Africa. Predominantly nocturnal, with occasional diurnal activity. Lives in pairs or small family groups in territories defended by dominant males. A male proclaims his territory with a characteristic loud whistle; same whistle given by both sexes when alarmed.

2 Cape clawless otter

Aonyx capensis

Large otter with elongated body, long and thickset tail, short legs with finger-like digits and partially webbed hindfeet. Coat dense, upperparts light to blackish brown, underparts lighter with off-white lips, chin, neck, chest and belly. On land, ambles with arched back, progressing to a bounding gait or undulating gallop. Size: Body 1.1–1.8m in length (including 44–54cm tail), 10–18kg in mass. Biology: Usually found close to water bodies. Feeds on crabs and frogs and, to a lesser extent, fish, insects, molluscs and small vertebrates. Often wanders far from aquatic habitats, but absent from dry areas lacking open water. Also occurs in estuaries and rocky intertidal habitats. Active mainly in early mornings and late afternoons; lies up under shelter or cover during heat of day, occasionally also active at night. Latrines with small accumulations of faeces containing large quantities of crab shells and fish scales (2a) indicate its presence near water bodies; scats may be confused with those of Marsh mongoose (see 3, below), but are usually paler, without rodent hair. Usually solitary, but sometimes in pairs or small family groups. RELATED SPECIES: Spotted-necked otter (Lutra maculicollis) (2b) is smaller at 1–1.1m in length, 3–6kg in mass, and has a more slender build with distinctive creamy-white spots and mottling on throat and neck, and fully webbed paws. Has small teeth, adapted for feeding mainly on fish, but also takes frogs and crabs if fish are scarce. Avoids estuaries and marine habitats and requires permanent water bodies with high fish densities. Rarely seen far from water; sometimes occurs in social groups that swim together. Distribution patchy; numbers may be declining owing to habitat destruction, pollution, and soil erosion leading to muddied waters and reduced hunting visibility.

3 Marsh mongoose (Water mongoose)

Atilax paludinosus

Medium-sized mongoose, with shaggy and grizzled dark reddish-brown coat; hairs short on face and feet, but longer on tail. Head pointed and broad, muzzle short with moist black nose, rounded ears lying close to the head. Size: Body 0.7–1m in length (including 31–41cm tail), 2.5–5.5kg in mass. Biology: Closely associated with well-watered habitats, but may move up to 1km from water in search of food. An excellent swimmer, submerges itself completely when hunting for aquatic prey. Feeds opportunistically on whatever prey is abundant, particularly crustaceans and frogs, but also other small vertebrates (especially rodents), insects, molluscs and occasionally fruit. Widespread in southern Africa wherever there are wetlands, but absent from the arid interior. Mainly crepuscular, with some nocturnal activity. Usually solitary and territorial, sometimes found in pairs; an adult female may be accompanied by young. Latrine located near edge of water body indicates its presence; droppings usually darker than those of otters, with an abundance of crab shells and rodent hairs. Feeding grounds marked by the discarded unbroken carapaces of crabs; otters, by contrast, crunch the carapaces when eating crabs.

1 Vlei rat

Otomys irroratus

Medium-sized rodent with a stocky physique, blunt face, and large, rounded, well-haired ears. Tail short (about two-thirds the body length) and well haired. Coat dense and shaggy; upperparts slate grey suffused with buff and brown, flanks and underparts paler. Size: Body 15–18cm in length (including 8–12cm tail), 102–206g in mass. Biology: Abundant in marshy habitats near water bodies, but also occurs at lower densities in drier grassland, fynbos and savanna habitats >1km from open water. Widespread in southeastern South Africa, central and eastern Zimbabwe, but distribution patchy owing to preference for damp habitats. Terrestrial or semiaquatic, but seldom swims. Exclusively herbivorous; prefers succulent stems of grasses, reeds and forbs, discarding less palatable parts in distinctive small piles that mark feeding grounds. Diurnal and territorial, usually solitary, but sometimes in small groups. Constructs small saucer-like nests above ground in dense cover, sometimes uses burrows made by other species. Well-defined communal runways (used also by other small mammals) link nests and feeding grounds. Breeding aseasonal, peaking in the warm wet summer months. Litter size 1–4. RELATED SPECIES: Angoni vlei rat (O. angoniensis) (1a) externally indistinguishable from the Vlei rat, and often coexists in same habitats. The Water rat (Dasymys incomtus) (1b) resembles Vlei rat in both external morphology and habits, and often coexists with it in wetland habitats, but the fur is generally darker, and the tail relatively longer (as long as body), hairless and heavily scaled. Particularly dependent on reed beds and stands of semiaquatic grasses or sedges, the Water rat is generally rare, especially along the southern coastal belt and in Western Cape, where numbers may be declining owing to destruction of wetlands. Unlike the Vlei rat, readily takes to water, nests in burrows, and sometimes consumes insects to supplement its largely herbivorous diet.

2 Greater cane rat (Grasscutter)

Thryonomys swinderianus

The second-largest rodent in southern Africa. Body stocky, with small, well-haired ears held close to the head, a blunt snout bearing a fleshy extension used for butting during aggressive encounters, and a short tapering tail with bristly hairs. Fur coarse, greyish brown, speckled with buff yellow above; underparts slightly paler. Size: Body 49–60cm in length (including 17–20cm tail), 3.2–5.2kg in mass. Biology: Closely associated with reed beds and dense grasses with cane-like stems, near open water. Feeds on roots, shoots and stems of grasses and reeds. Discards unpalatable leftovers in piles (larger than those left by Vlei rats) that, together with its characteristically grooved droppings, mark its feeding grounds. Mainly nocturnal, usually solitary, but sometimes in groups of up to 10. Makes distinct runs and usually nests and rests in dense cover above ground, but burrows if cover is scarce. May move far from open water, especially when agricultural lands abut water bodies, where its predilection for maize, sugar cane and pineapples brings it into conflict with humans. Breeds mainly in wet summer months, litters small (usually four), maturation slow. Favoured as a delicacy throughout sub-Saharan Africa, owing to its soft veal-like flesh; actively hunted and now also farmed extensively, but on a small scale, owing to slow reproduction rates.

3 Swamp musk shrew

Crocidura mariquensis

A smallish species, with long wedge-shaped snout, small eyes, prominent facial vibrissae (stiff hairs), short legs, relatively short tail bearing long, soft and scattered hairs, and strong musky odour. Upperparts blackish brown, underparts paler, with a silvery sheen. Size: Body 8–9cm in length (including 4–7cm tail), 9–16g in mass. Biology: Closely associated with swamps, dense grassland and reed beds near water bodies, particularly clumps of semiaquatic grasses and litter deposited by receding waters, but sometimes occurs in drier areas away from water. Insectivorous. Active day and night. Breeds aseasonally, with a dip in the drier winter months, litter size 2–5.