Small mammal ‘critters’ of the greater Kloof region

Terrestrial small mammals (definition)

The majority of the 6400 mammal species comprise “small mammals” that include members of the Orders Afrosoricida (golden moles), Chiroptera (bats), Eulipotyphla (hedgehogs, shrews), Hyracoidea (hyraxes), Lagomorpha (hares, rabbits), Macroscelidea (elephant shrews), and Rodentia (rodents). They typically weigh less than 1 kg, with the exception of the Cape Porcupine (Hystrix africaeaustralis) – the largest southern African rodent that weighs approximately 10 – 20 kg. For the purposes of this article, we refer to terrestrial small mammals as those species that are non-flying.

Figure 1. Proportion of mammalian species that comprise “small mammals” in eThekwini Municipality. In general, rodents are more numerous than bats. However, in the eThekwini context, there are more bat species than rodent species.

Increasing numbers

There has been a marked increase in the number of mammal species described in the last decade (~420 new species), most notably from the rodents. The majority of these newly described species has resulted from the ‘splitting’ of species once considered widespread, into two or more taxa. For example, the Four-striped mouse (Rhabdomys pumilio), a ubiquitous southern Africa rodent species, has been split into four different taxa. The Mesic Four-striped mouse (R. dilectus), as the name suggests, occurs in the moister eastern regions of South Africa, including the KwaZulu-Natal province. The other species (R. bechuanae, R. intermedius and R. pumilio), are associated with the Karoo and Fynbos regions.

The same applies to the genus Otomys, commonly known as Vlei Rats. A species that can routinely be found in moist grassland habitats of the greater Kloof area, Otomys irroratus, was recently split into two species. Otomys auratus is associated with mesic high-lying grasslands of the eastern half of South Africa, whilst the distribution of O. irroratus has been relegated to the south-western semi-Karoo and fynbos environments of South Africa.

Figure 2. African Vlei Rat (Otomys auratus) recorded from Giba Gorge. This species was once considered synonymous with O. irroratus, however genetic data has shown them to be two distinct species. Another species, Angoni Vlei Rat (O. angoniensis), is also found in the area.

Threatened status

Of the various terrestrial small mammal species, those belonging to Afrosoricida more commonly known as “golden moles”, are the most threatened by possible extinction in the wild. There are approximately 18 species of golden mole in South Africa with only one species recorded from the greater Kloof region (Hottentot’s Golden Mole, Amblysomus hottentotus). Sixteen of the 18 species carry a Threatened status (Critically Endangered, Endangered or Vulnerable).

Golden moles are a gardener’s best-friend as they remove underground invertebrates that can harm plants. Their burrowing activities, which result in tunnel-like pathways immediately under the surface of the ground, assist with aerating the soil and churning up soil nutrients from lower layers. Unfortunately, they are often persecuted by home-owners and gardeners who mistake their burrowing activities for that of mole-rats (Cryptomys spp.), which have an affinity for the underground tubers and roots of plants.

At least half of the 17 species of shrews recorded from South Africa are considered threatened. Eight of the 17 species can be found in Kloof and its surrounding regions. These eight species belong to three genera: Dwarf Shrews (Suncus), Forest Shrews (Myosorex), and Musk Shrews (Crocidura). One of the more common shrew species, the Greater Red Musk Shrew (C. flavescens), is also regarded as the largest of the South African shrews.

Figure 3. Dark-footed Forest Shrew (Myosorex cafer-left) – a forest-dependent species that is currently listed as Vulnerable. The most commonly encountered shrew species in the Greater Kloof area is the larger Greater Red Musk Shrew (Crocidura flavescens-right). Shrews, in general, are more sensitive to habitat disturbance than rodents.

Three species of hyrax occur in South Africa, one of which is currently listed as Endangered (Tree Hyrax, Dendrohyrax arboreus). Two hyrax species are known to occur in Kloof, the commonly sighted Rock Hyrax (Procavia capensis) and the rare and “Endangered” Tree Hyrax (Dendrohyrax arboreus). Tree hyraxes, as the species name “arboreus” suggests, is mostly an arboreal and nocturnal species. They have a characteristic eerie call that they use to advertise their presence to other individuals at night. Sadly, due to their dependence on forests, their numbers are dwindling as more of our forested areas disappear. In recent years, Rock Hyrax population numbers throughout South Africa were reported to have been reduced due to a suspected viral infection.

Other factors, including the clearing of indigenous forest, have resulted in colonies of hyraxes exploiting urban habitats including culverts and waste water systems. Whilst they are typically associated with rocky outcrops with woodland / forest, they have been recorded from unusual places including abandoned buildings near Durban’s Addington Hospital, City Hall car park, and even the Durban Country Club near the beach front.

Fortunately for the most speciose group of South African small mammals, the rodents, only four species carry a threatened status. There are about 80 rodent species found in South Africa, with 20 of these occurring in the Greater Kloof Area. They range in size from the tiny African Pygmy Mouse (Mus minutoides) at 5 – 7 g, to the Cape porcupine that can reach a maximum mass of almost 30 kg!

Figure 4. Contenders for the tiniest critter – Least Dwarf Shrew (weighs 3 – 4 g; left) and African Pygmy Mouse (weighs 5 – 7 g; right).

Ecosystem services and functional groups

Terrestrial small mammals are frequently passed over in favour of larger, more enigmatic species. They are vital yet often overlooked component of ecosystems, providing valuable ecosystem services. Some of these ecosystem services include a food source for raptors and other predators, important pollinators of wild flowers and forbs, underground ‘engineers’ (e.g. golden moles) that aerate the soil and control invertebrate population numbers, to mention but a few.

They also occupy various functional guilds or groups based on their dietary preferences. For example, elephant shrews, golden moles and shrews are categorised as insectivores feeding almost exclusively on invertebrates. Herbivorous species include Vlei Rats, Single-striped mice (Lemniscomys rosalia) and Woodland Rats (Grammomys dolichurus). Surprisingly, few rodents are classified as granivores, with only a single granivorous species, the Mesic Four-striped Mouse, known from Kloof. The majority of rodent species are omnivorous, feeding on both plant and invertebrate matter, as opportunities present themselves.

Figure 5. The Single-striped Mouse – a grassland-associated species (above), and Woodland Rat that is more commonly found in wooded habitats (below), are classed as herbivorous. Both species have been frequently recorded from reserves such as Krantzkloof and Springside Nature Reserves.

Smaller mammals as bioindicators

There are several reasons why small mammals make for good biological indicators or bioindicators of environmental health and stability. Firstly, they are better indicators of ecosystem integrity at a finer, local scale – thus providing better resolution. Their population numbers are usually higher than those of larger mammals and they are easier to study than other taxa. Most importantly, they are generally fast-breeding and have a shorter life-span and therefore it is possible for researchers to witness rapid population responses to changes in the environment.

The presence and absence of certain species and/or functional group/s are indicators of environmental health. For example, the presence of high numbers of Natal Multimammate Mice (Mastomys natalensis) is indicative of current or past ecological disturbance. The presence of Vlei Rats indicates to a fairly healthy wetland system with associated grassland habitats. The presence of Climbing Mice (Dendromus spp.) is also indicative of an intact grassland ecosystem. Fairly high shrew population numbers and/or species diversity alludes to an environment that has a rich and ample invertebrate community.

Figure 6. A Grey Climbing Mouse (Dendromus melanotis). These tiny mice are most commonly associated with grasslands with ample cover. It is believed that their presence is indicative of productive and intact grasslands.

More researchers and conservationists are now recognising terrestrial small mammals as potential keystone species in terms of environmental management and conservation planning. Using small mammal assemblages as the basis for comparison, researchers are able to effectively compare local environmental quality across different landscapes and land-use practices. This is becoming increasingly useful in the current Anthropocene era where habitats are drastically altered due to human activities. Evaluating the degree to which changes are apparent in mammalian communities can assist in developing and establishing mitigating measures to halt or minimise further environmental degradation.

Post-graduate studies in the Greater Kloof and Outer West Regions

Based on the above, the Mammal Department of the Durban Natural Science Museum (DNSM) has been conducting small mammal surveys throughout the Maputaland-Pondoland-Albany biodiversity hotspot region that spans the south-eastern region of southern Africa and extends from the southern reaches of Mozambique to the Eastern Cape Province. The eThekwini municipal region lies at the very centre of this biodiversity hotspot.

In the context of survey work in eThekwini, special emphasis has been given to the Endangered KwaZulu-Natal (KZN) Sandstone Sourveld grassland ecosystem. Work conducted over the past few years by DNSM mammal researchers in the Greater Kloof and Outer West regions, has resulted in the compilation of an important small mammal faunal baseline database from which other studies can take root.

One such study is that of the MSc project of Ms Zamawelase Mwelase, technical assistant in the DNSM’s mammal department. Titled “Guild structure and population dynamics of small mammal communities in suburban patches of KwaZulu-Natal Sandstone Sourveld grassland”, Zama’s project is centred on the Krantzkloof and Giba Gorge Nature Reserves and adjacent D’MOSS areas. Through seasonal capture-mark-release-recapture methods, Zama is comparing small mammal assemblages found within the reserves larger tracts of KZN Sandstone Sourveld grassland, with those of smaller and somewhat isolated grassland patches associated with neighbouring D’MOSS. The eThekwini owned Doornrug and Uitkomst conservancy areas serve as reference sites for the study.

Data generated from the project will provide information on species diversity and abundance across sampling sites and data on seasonal population trends. One of the objectives is to establish the proportion of small mammal species and their population sizes that inhabit D’MOSS grassland patches relative to the reserves. Preliminary data indicate lower species diversity and abundance in D’MOSS grassland patches when compared to the reserves; such biodiversity indices may be correlated with D’MOSS patch size and patch connectivity to larger expanses of grassland.

The project hopes to provide practical, evidence-based data to bridge the divide between researchers, land-managers and those involved with policy development. It will also hopefully feed into municipal land-use practices and management policies and have application in the preservation of faunal biodiversity, fire management practices and urban development and planning.

The research would not be possible were it not for key collaborators. These include eZemvelo KZN Wildlife, Kloof Conservancy, Msinsi Conservancy, eThekwini’s Environmental Planning and Climate Protection Department (EPCPD) and Natural Resource Division (NRD), as well as numerous private land-owners. Watch this space for more information emanating from the study.

Figure 7. Zamawelase Mwelase who is embarking on an MSc study of the rodent and shrew fauna in the Greater Kloof and Outer West regions.

Figure 8. Zama recording biological data from captured rodents and shrews prior to their release, at Krantzkloof Nature Reserve and Uitkomst Conservancy.

New species distribution records

Through Zama’s project we have managed to confirm the presence of a healthy and viable population of Mesic Four-striped mice in Giba Gorge Nature Reserve. Taylor (1998) cited this species as absent from the municipal region and only occurring from higher altitudinal regions starting from the KZN Midlands. Our data thus represents the most easterly-distribution of the species in the KwaZulu-Natal province.

Figure 9. Mesic Four-striped Mouse from Giba Gorge. The area boasts a large population of striped mice and is considered the most easterly distributed population in KZN. They derive their common name from the characteristic four stripes that run the length of their backs. Four-striped mice are usually replaced by Single-striped mice near the KZN coast.

Another welcomed surprise was documenting a hitherto unrecorded species from the municipal area – a species of Fat Mouse, Steatomys spp. We are as yet uncertain of the species identification, but hope to collect genetic samples at a later stage for purposes of confirming taxonomy, once Zama’s fieldwork comes to an end. A list of approximately 30 species recorded from the greater Kloof area is provided (Table 1).

Figure 10. A species of Fat Mouse (yes you read that correctly!), found at the Uitkomst North conservancy area. The closest records of Fat Mice are from the KZN Midlands. Fat Mice look very similar to African Pygmy Mice, yet are almost double the length and triple the weight of the diminutive pygmy mice.

Open-air classrooms

One of the major outcomes of the eThekwini-based small mammal research is its’ human capacity development component. The field volunteer programme, established by the museum’s Mammal Department, has provided practical field-based skills training to at least 20 young adults over the past seven years. Utilising eThekwini reserves as “open-air classrooms”, the programme aims to provide small mammal field research training to nature conservation students that are part of the museum’s larger volunteer programme. The programme provides dual benefits to both museum staff as we are able to cover more ground with a larger team, as well as the volunteers who gain valuable new skills. Our research would not have achieved as much as it has, were it not for the contribution and dedication of our volunteers.

Figure 11. Some of the Durban Natural Science Museum volunteers that have joined the field volunteer programme and have been trained in field-based small mammal sampling techniques. To-date at least 20 young adults, most with a former nature conservation background, have been trained.

References 

Avenant N (2011) The potential utility of rodents and other small mammals as indicators of ecosystem ‘integrity’ of South African grasslands. Wildlife Research, 38(7):626-39.

Burgin CJ, Colella JP, Kahn PL, Upham NS (2018) How many species of mammals are there?. Journal of Mammalogy, 99(1):1-11.

Child MF, Roxburgh L, Do Linh San E, Raimondo D, Davies-Mostert HT, editors. The 2016 Red List of Mammals of South Africa, Swaziland and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa.

Skinner JD, Chimimba CT (2005) The mammals of the southern African sub-region. Cambridge University Press.

Taylor P (1998) The Smaller Mammals of KwaZulu−Natal. University of KwaZulu-Natal Press.

Terrestrial smaller mammals of the greater Kloof region

Non-exhaustive listing of the terrestrial smaller mammal species recorded from the greater Kloof region (as based on records of three natural science museums and 2016 Mammal Red Data List).

Dr Leigh Richards is the current Curator of Mammals at the Durban Natural Science Museum, a position she has occupied since 2010. She curates the rapidly growing Mammal Collection of the DNSM that holds 17000 specimens. She obtained her PhD in biosystematics in April 2014 from the University of KwaZulu-Natal (UKZN) and currently co-supervises post-graduate students at UKZN, Stellenbosch University, University of Western Cape and UNISA. Her research interests are aimed at understanding the evolutionary history and biogeography of southern African small mammal taxa from the Afrotropics.