Field Guide to the Mammals of Southern Africa [antikvár]

Introduction Compared with the birds (8 900 species) or the fish (30 000 species) the mammal group is a small one. It contains between 4 000 and 4 500 living species, of which some 337 species are currently known to occur in the Southern African Subreglon. Some of these, however, are known from very few, or even single, records. The richest period of mammal diversity was during the late Tertiary, when an estimated three times as many mammal species roamed the earth than do so today. Taxonomlsts are constantly revising and reassessing the scientific status of many mammals, particularly the smaller species such as bats, shrews and small rodents. This often results in scientific names being changed and, on occasion, new species being described; Juliana's Golden Mole, for example, was described from the Transvaal In 1972 and the Long-tailed Forest Shrew from the southern Cape as recently as 1978. The bats are especially mobile, and It is very likely that additional species from this group will be discovered and added to the faunal complement of southern Africa In due course. Mammals have a number of common characteristics that set them apart from other vertebrates: they breathe with lungs; they possess a four-chambered heart; they have three delicate bones In the middle ear; females have mammary glands that produce milk for suckling the young; and nearly ail species have a covering of body hair. The Southern African Subreglon - defined as that part of the African Continent and Its coastal waters south of the Cunene and Zambezi rivers -can be divided Into six major blotic zones (see below and map), each differing In climate and vegetation. This does, however, present an oversimplified picture, and each of these zones can be further subdivided Into many different habitat and vegetation types. 1. Desert Desert Is characterized by Its very low rainfall (usually less than 100 mm per year) and sparse plant growth. Extensive areas may be devoid of any vegetation, being covered by sand-dunes or consisting of flat gravel plains and rugged hill country. Several species of mammal have evolved mechanisms that help them to survive In this harsh environment. In the Southern African Subreglon this blotic zone is represented by the Namib Desert of South West Africa/Namibia. 2. Arid zone Areas classed as 'arid' receive higher rainfall than true desert, but this rarely exceeds 500 mm per year. In southern Africa, rainfall Is at its lowest in the west, gradually Increasing towards the east. The Kalahari, Karoo, Bushmanland, Namaqualand and Damaraland fall within the arid zone. The southern section, viz. Bushmanland, Namaqualand and the Karoo, consists mainly of extensive rocky plains and isolated hills and hill ranges, with a vegetation comprising low, woody shrubs and succulents. Much of the area is veined with river courses which are vegetated along their banks with bushes and low trees. In the northern parts, for example the Kalahari 'Desert' of the northern Cape and Botswana, sandy soils are more prevalent with low (often acacia) trees and bushes, and relatively good grass cover. This zone once supported vast numbers of ungulates, but the free-roaming herds of Springbok, Red Hartebeest, Blue Wildebeest, Eland and Burchell's Zebra have diminished greatly and are now restricted to the more sparsely populated parts of Botswana. 3. Savanna woodland and 4. Savanna grassland The savanna blome can be divided into two zones, viz. savanna woodland mostly In the north, and savanna grassland In the south. Savanna woodland,