Rodents of Ndola (Copperbelt Province, Zambia)
Duisburg-Essen (2004), 109 Bl.
Dissertation / Fach: Allgemeines, Sonstiges
Fakultät für Biologie » Allgemeine Zoologie
The present thesis deals with rodents of Ndola, capital of the Copperbelt Province, Zambia, and its surroundings. The study area is located approximately 13 o South and 28 o 35 East, about 1,300 m above sea level, is characterised by average monthly rainfall of 1,198 mm (with a highly variable rain: monthly range 0-283 mm, with 5 to 7 virtually rainless months per year). The region exhibits a mosaic of built up areas, cultivated fields, forests and natural habitats of the original Zambezian savannah woodland. The composition of the rodent fauna and its distribution across Zambia is analyzed and discussed here on the basis of a new-attitude analysis of the published data. My analysis reveals that Ndola can be denoted as a Zambian rodent diversity hotspot, as 46% (29 out of 63) rodent species known from Zambia were recorded also in the given area. I analyzed more than 1,200 pellets of the Barn Owl from four different locations. Contents of about 850 owl pellets which could be attributed to particular months and were produced by two owl individuals was analyzed also quantitatively. Most of these pellets, representing a series encompassing 24 months, were collected from one owl nest in the Namboard Silo in a built-up and cultivated area. The rest originates from a nest in a forest habitat and covers four months. The pellet contents was analyzed from the taphonomical point of view, revealing that maxillary bones (either isolated or within the skull) with upper tooth rows, mandibles, femora and humeri were well preserved and gave information about numbers of preyed animals. The species identification and counting were based on maxillary bones. Altogether 44% of pellets contained a single vertebrate prey specimen, 33% rests of two individuals, 16.5 % three specimens, 4% four specimens, up to 12 preyed individuals were represented in a single pellet. Arthropods included in the diet of the Barn owl were mainly sunspiders, locusts and scarabeid beetles. Lizards and frogs/toads were only sporadically represented. Birds constituted up to 6% of vertebrate prey. Small mammals constituted about 93% of vertebrate prey, the most common prey being rodents (83%), mainly Multimammate rats (Mastomys, 54%), Pygmy Mice (Mus minutoides, 10%), Climbing Mice (Dendromus, 10%) and Gerbils (Tatera, 6%). The food composition in the forest was slightly different (Mastomys 38%, Tatera 23%, Mus 4%, birds 0.7%) but the difference may be due to a seasonal bias. The calculation reveals that the Barn Owl consumes about 1.6 kg vertebrates, mostly rodents, per month, about 19 kg per year. This makes an average daily consumption to be about 53 g (31-74 g), and an average weight of a single prey amounts to about 41 g. Changes in abundance of rodents in the course of the year(s) are analyzed. There appear two peaks of maxima of Mastomys rats during the year: in February and November. The pellet analysis revealed at least 27 species of mammals belonging to four orders: 18 species of rodents, 1 species of elephant shrews, 4 species of shrews and 4 species of bats. Rodents Aethomys chrysophilus, Dendromus mesomelas, Praomys jacksoni and bats Scotophilus leucogaster, Tadarida pumilla represent new records for Ndola and surroundings. Preliminary trapping study using traditional live traps is described. Altogether 581 rodents were trapped during 2181 trapnights (27% efficiency) in the course of three months at two localities. About 50 % of caught animals in both areas were Mastomys natalensis, about 20% (more in Mansansa, less in Namboard) were Tatera sp., about 10 % were Mus minutoides; about 10% were Acomys spinosissimus (Spine Mice), which were -apparently due to their diurnal habits - very rarely represented in owl pellets. Furthermore Steatomys, Dasymys and Saccostomus were identified in the sample. Some further specimens were not identified so far. There were no shrews (apparently due to specific rodent bait) in traps. Generally, pellets reflect (apart from relative, but not absolute, absence of Spiny Mice) very well the composition of the small mammalian community in both, qualitative and quantitative aspects. Climbing Mice (Dendromus), which were quite common in pellets were not trapped. This trapping study, though not yet completed, confirms the importance of the study of owl pellets. It is argued that analysis of owl pellets, as presented here, represents a cheap, relatively simple alternative, producing comparable comparative data on small mammal communities and their changes across space and time. Indeed, this is an excellent way of conducting surveys, especially in areas with few resources, and can potentially be used to monitor changes in biodiversity with little effort. It is surprising that thus far, this source of information has remained virtually untapped in Zambia in particular and in most of Africa in general. One problem is surely the lack of suitable identification keys for skulls (and bones in general) of African small mammals. The next part of my thesis summarises results of more than eighteen years of my (more or less intensive) research on distribution, taxonomy, ecology, and the economic impact of the subterranean Giant Mole-Rat Coetomys (Cryptomys) mechowi (Bathyergidae, Rodentia) in Ndola. Much of the findings presented here have been published already in original research papers authored and co-authored by myself and published in international peer-reviewed scientific journals. I have priority in finding that giant molerats) are highly social and live in large families (with more than 20, probably with up to more than sixty members) where only one parental pair breeds. Further aspects of biology (like carnivorous habits) of this previously almost unknown species have been, for the first time, identified by myself. Of behaviour-ecological interest is the fact that giant mole-rats are relative generalists as far as their food choice and habitat (soil and vegetation type) selection are concerned. I have analyzed the sex ratio of giant mole-rats and shown that sex ratio among youngsters in male-biased but near to equality among adults. The fact that among pups born in captivity females prevail calls for an explanation. Some scenarios are suggested. I have contributed to description of the karyotype (2n=40) of Coetomys mechowi. My survey of the occurrence of mole-rats in different areas and my contribution to their karyological examination provided insight into the pattern of distribution and extensive diversification of mole-rats in Zambia. Based on the high proportion of biarmed chromosomes in the karyotype it is argued that C. mechowi represents an ancient lineage of mole-rats. For the first time I have shown how important are the mole-rats as agricultural pests and as a source of animal proteins in many regions. I have demonstrated that locals are very well acquainted with these animals. Tapping their know-ledge is a good source of information and should not be underestimated.