Doctoral Degrees (Zoology)

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The analysis of erythropoiesis and other early developmental events in the chick embryo using mesodermal-inducing factors.
(1994) Gordon-Thomson, Clare.; Fabian, B.
The causal and temporal aspects of blood tissue specification in the chick embryo were investigated in this study. The main focus was on the role of basic fibroblast growth factor (bFGF) in the determination of the erythropoietic tissue, particularly in context with its representation as a non-axial mesodermal derivative which arises in the posterior domain of the chick embryo. The initial strategy employed in this study was the use of agents that are known to block the activity of bFGF, and to determine their effects on erythropoiesis. Treatment of unincubated chick embryo explants with heparin, which binds specifically to the FGF family, was found to inhibit primitive streak formation and erythropoiesis, and also inhibited the formation of other mesodermal tissues. These initial findings suggested that one or more growth factors had become bound to the heparin, and that their activity is important for the specification of primitive streak formation and mesodermal patteming. The development of the erythropoietic tissue was assayed by a cytochemical test for haemoglobin using 0dianisidine; and by histological examination for blood islands and red blood cells in serial sections of the embryos after 48 hours incubation. Microscopic examination of the embryos at the stages of gastrulation on the first day of incubation revealed that heparin caused holes to appear in the ventral layer; and although a primitive streak did not form, a middle layer of mesenchymal cells were seen to accumulate between the ectodermal and ventral "endodermal" layers. It was significant that heparin's inhibitory effect on erythropoiesis could be reversed after the addition of a recombinant bovine bFGF to the heparin-treated embryos. However, the exogenous bFGF did not neutralize the inhibitory effect of heparin on the primitive streak and other mesodermal derivatives (Chapter Two). The inhibition of erythropoiesis by heparin was also reversed by the addition of a mesodermal-inducing factor extracted from a Xenopus embryonic cell line, namely XTC. The XTC mesodermal-inducing factor (MIF), which belongs to the transforming growth factor-B family and is a homologue of activin, could also reverse the inhibitory effect of heparin on primitive streak formation; but no recognizable axial mesodermal structures subsequently developed. Of consequence, was that both bFGF and XTC-MIF blocked heparin's effect on the ventral layer, preventing the gaps forming. Therefore, it is suggestive that the VI development of an intact ventral layer is important for the determination of the erythropoietic sequence (Chapter Three). By taking a more specific approach using antisera to bFGF (anti-FGF) and the bFGF receptor (anti-FGFR) on whole embryo explants, it was found that anti-FGP and anti-FGFR were able to inhibit erythropoiesis, but not primitive streak formation. However, these antisera caused defects in the posterior region of the embryonic axis. These embryos not only lacked posterior blood tissue, but heart and somites were missing; whereas the anterior head structures were well formed. These results therefore suggest that bFGF signalling is important for the development of the posterior body plan, which includes erythropoiesis (Chapter Four). Further evidence for the role of bFGF in the determination of the blood mesodermal tissue line was reached in an in vitro bioassay. In this part of the investigation, specific pieces of the blastoderm, namely pieces dissected from the posterior marginal zone (PMZ) and inner core of the central disc (lCD) were able to form haemoglobin under particular conditions. The PMZ components were found to have the capacity to form haemoglobin when dissected from blastoderms of stages X to xm when cultured in serum-free medium. This commitment to form haemoglobin could be blocked by treatment with anti-FGP at stages X and XI, but not at the later stages of xn and XIII. The ICD components were found to have a commitment to form haemoglobin only if this component was dissected from embryos at stage XIT and XITI, but not before. These results suggest that a determinative event for the haemoglobin differentiative pathway occurs between stages XI and XII. It was also found that the stage X central disc component could be induced to form haemoglobin if a stage xm hypoblast was added to it in tissue recombination sandwich cultures, or if bFGF (75 - 150 ng/ml) was added to the medium. These results lend further support that bFGF plays an important role in the determination of erythropoiesis; and furthermore, suggest that the hypoblastic tissue is the source of this induction (Chapter Four). Finally, immunocytochemical labelling with a polyclonal antibody to bFGF has revealed that bFGF increases significantly from stage XI in cells within the developing hypoblast layer and in the middle mesodermal layer. These cells are located predominantly in the posterior domain of the embryo. This polarized distribution of bFGF with the high value of bFGF concentration in the posterior area, is presumably responsible for inducing the overlying epiblast to form the posterior horseshoe-shaped region from which blood tissue is seen to arise. An immunocytochemical analysis of the distribution of the FGF receptor was vu assessed, as an indicator of the possible competence of the cells to respond to the bFGF signal. The bFGF receptor was found to be expressed at stage XII in cells that appeared to be in register with those immunoreactive to the bFGF ligand; therefore suggesting an autocrine function. It was interesting that at stage Xli an intense immunostaining with the anti-FGFR developed in the nuclei of cells within the epiblast layer (Chapter Five). In conclusion, this study has demonstrated that the initial determination of the erythropoietic cell lineage in the chick is at the time when the hypoblast is in the process of forming beneath the epiblast, Le. between stages XI and XII. Furthermore, it was found that an induction by an FGF-like signal from the hypoblast layer (or middle mesodermal cells that may be closely associated with the hypoblast) induces "competent" cells (Le. FGFR-positive cells) in the epiblast to form blood tissue in the posterior domain of the chick embryo.
The Anostraca (crustacea : Branchiopoda) of southern Africa.
(1994) Hamer, Michelle Luane.; Appleton, Christopher Charles.
The Anostraca are a group of crustaceans belonging to the class Branchiopoda. They are predominantly restricted to temporary, inland waterbodies, which in southern Africa, include rockpools, animal wallows, and large "pans". The anostracan fauna of southern Africa was last examined in detail in 1929 by Barnard, and recent collecting in a number of areas indicated the need to update earlier work. A total of four genera, each belonging to a separate family, and forty-six species, some of which had not previously been described, are presented in this thesis. The monogeneric family Streptocephalidae is well represented in Africa, and the fauna of Africa south and north of the Zambezi and Kunene Rivers, as well as Madagascar is reviewed. The Streptocephalus species are characterised by having an S-shaped antennal process, terminating in a cheliform "hand" region. The species were divided into ten groups based on similarities in antennal process morphology. The descriptions of five new species have been published, and an update on distribution and specimen data for a number of species are presented. An additional, as yet unpublished new species from Zimbabwe is presented. The genus Artemia, although well researched in other parts of the world, has been largely ignored in southern Africa. Bisexual populations occur along the Cape coast, and a set of specimens from Namibia, which includes only females, may indicate that A. parthenogenetica is also present on the subcontinent. The frontal knob morphology of the Cape specimens is similar to that of A. tunisiana from northern Africa and the Mediterranean. The family Branchipodidae is characterised by the fusion of the basal joints of the male antennae to form a so-called "clypeus". This family is represented in southern Africa by a diverse fauna of the genus Branchipodopsis. Eleven previously described species, as well as five new species are presented. An attempt was made to divide the sixteen species into species groups, as was done for the streptocephalids, but this proved difficult. The taxonomically useful characters in this genus are largely restricted to the basal processes. An additional character, the presence of expansions of the posterior thoracic segments in the females of some species could be useful. Much intraspecific variation in clypeus morphology was evident, particularly in two of the widespread species. Branchipodopsis species commonly occur in small pools which fill a number of times during the wet season and this has probably led to the development of localised adaptations, and intraspecific variation, or even species endemic to very restricted areas. Three sets of specimens which belong to the family Branchipodidae, but to no known genus, were recently collected from north-eastern Natal, the eastern Cape and the Namib desert in Namibia. These specimens share a single, large process positioned medianly on the fused basal joints, as opposed to a pair of processes in this position. However, the morphology of the penes, and the position and form of other antennal processes could indicate that the specimens are not congeneric. Unfortunately, more material is necessary before the descriptions of two of these possible new genera can be published. Three species of the genus Branchinella, of the family Thamnocephalidae, occur in southern Africa. These species have a well developed frontal process, and fully retractible penes. Bran chin ella spinosa was recorded from the Makgadikgadi Pan in northern Botswana, and was probably introduced to this area from north Africa, or Europe, where it has a wide distribution. The other two southern African species have been collected from few localities, and in small numbers, and this may be connected to cyst hatching processes. The southern African anostracan fauna exhibits distinct distribution patterns and these . appear to be influenced by climate, with rainfall having the dominant influence in the western half of the subcontinent, and temperature influencing distribution in the eastern half. The high altitude Escarpment forms a barrier to the movement of species between the coastal margin and the central plateau region. The formation of the Escarpment could have resulted in vicariance speciation in some anostracans, but in most cases, allopatric speciation appears to have occurred. The type of habitat also influences species distribution in a number of ways. The great anostracan species richness in southern Africa is probably related to the climatic heterogeneity of the subcontinent, as well as the possible origin of two genera in Gondwanaland, and the absence of a Pleistocene glaciation in Africa. Large parts of southern Africa have not been sampled, and the exact status and distribution of many species is uncertain.
Aspects of the biology and ecology of the estuarine fishes of the east coast of South Africa.
(1974) Wallace, John Henry.; Heydorn, A. E. F.
No abstract available.
Aspects of the biology and population dynamics of freshwater mussels in Lake Kariba and Lake McIlwaine.
(1980) Kenmuir, Dale Harold Stafford.; Heeg, Jan.
Following preliminary observations in 1975 the Lake Kariba Fisheries Research Institute implemented a research program in March 1976 to investigate various aspects of the biology and population dynamics of the mussel crop of Lake Kariba, with a view to greater understanding of their status in the lake, and establishing a basis for management, if required. Aspects investigated were densities, distribution, species composition, predation by fish, reproduction, age and growth, gross biochemical composition and crude production rates. The mussel community comprised four species, a small pill clam, Corbicula africana, and three mussels, Caelatura mossarnbicensis, Aspatharia wahlbergi and Mutela dubia. Only the latter three were studied. Mussel beds occupied all the gently shelving cleared and uncleared areas, and the bulk of the populations occurred from 3 m - 9 m depth, but extending to 11 m. Predation by fish was found to be extremely low. The reproduction study showed two species bred all year C. mossambicensis and M. dubia, whereas A. wahlbergi bred seasonally during the rainy season. The two year-round breeders were repetitive spawners, capable of breeding several times a year. Indications are that A. wahlbergi is essentially a fluviatile species, with a life cycle adapted to taking advantage of riverine conditions. Sex ratios in all three species were approximately 1 : 1 , with females predominating slightly. Fecundity in one species, C. mossambicensis, was investigated. The complete parasitic cycle of M. dubia was elucidated and found to be similar to that of M. bourguignati, as described by Fryer (1961). Host species were noted amongst the cichlid and mormyrid families, and the conclusion drawn that the species is not host specific. various aspects of the life-cycles of the other two species were noted, but complete life-cycles were not successfully elucidated. population composition according to age showed the most common species, c. mossambicensis, to be comprised mainly of 2 - 5 year-old individuals, indicating a young and vigorous population. Juvenile pre-adult mussels were very scarce. In the population of A. wahlbergi, older mussels formed a greater proportion of the biomass than in the population of c. mossambicensis, and young were also scarce. M. dubia were not recorded in sufficiently large numbers to estimate age composition accurately. The production rate (whole wet mass) of the most common species, c. mossambicensis, was calculated to be 2,45 kg ha¯¹ day¯¹ in the sanyati East cleared area (30,5 km²), while the overall production rate of all three species was calculated to be 3,34 kg ha¯¹ day¯¹. Calorific values of all three species were obtained, while gross body composition in terms of water, fat, protein, ash and amino acid composition were determined. The ash component of A. wahlbergi was analysed. The Lake Kariba results were supplemented by a follow-up study of the composition of the mussel population of a eutrophic, highveld dam, Lake McIlwaine, in 1978/1979. This much smaller lake was populated by only two mussel species, M. dubia and C. mossambicensis, although A. wahlbergi and Unio caffer were recorded in the riverine upper reaches. Observations on seasonal breeding of the two lake species were made. A detailed study on the draw down zone of a gently shelving beach showed that at the time the extreme shallows had been dominated by C. mossambicensis, whereas from a depth of approximately 1,6 m M. dubia dominated very significantly. Fulling lake level was found to trigger off migratory responses, thus placing a proportion of individuals in deeper water and improving chances of survival. The mussel composition of Lake Kariba and Lake McIlwaine was considered in conjunction with preliminary observations of mussel distribution a nd composition in other water bodies, and some inferences drawn regarding the ecological factors which appear to influence the composition and diversity of the mussel fauna in rivers and lakes.
Aspects of the biology of the red bishop Euplectes orix and other Euplectes species.
(1977) Craig, Adrian John Fergus Knott.; Maclean, Gordon Lindsay.
The breeding biology and the annual cycle of the Red Bishop Euplectes orix was studied over a two year period in Natal. Some comparative data were also gathered for the related species the Red-shouldered Widow E. axillaris and the Red-collared Widow E. ardens, and additional data from a ringer in Rhodesia have been analysed. The breeding season of these polygynous ploceids coincides with the summer rainy season, and the amount of breeding activity in the Red Bishop appeared to be correlated with the amount of rain during the previous year. Breeding success at the colony studied was low; predation was the major cause of nest failure. In all three species the entire population, including the juveniles, undergoes a complete moult at the end of the breeding season. There is some evidence that the birds may make local movements during the winter dry season. These species are sexually dimorphic, the males being larger than the females. The population sex ratio was Significantly biased in favour of males in the Red Bishop and the Red-shouldered Widow but not in the Red-collared Widow. However, about half the male birds are subadults which do not breed, so that there is an excess of females in the breeding population. Adult males undergo a partial moult at the start of the breeding season and acquire a distinctive nuptial plumage. This is shed again at the post-nuptial moult, and in eclipse plumage they resemble the females. There is a similar pattern of weight change in all three species, with peaks early in the breeding season and again during the moult. The lowest annual weights are recorded during the dry season. The mortality rate of the Red Bishop is not high for a small passerine. The findings of this study are compared with the available information on other members of the genus, and discussed in relation to the evolution of polygyny in the Euplectes species.
Aspects of the biology, specific status and control of the bedbugs Cimex lectularius and Cimex hemipterus in northern Natal and KwaZulu.
(1989) Newberry, Keith.; Appleton, Christopher Charles.
The bedbugs Cimex lectularius and C. hemipterus (Hemiptera: Cimicidae) have been identified from a study area in northern Natal and KwaZulu. South Africa, between 26° 45' S and 28° 45' S, and 32° 00 ' E and 32° 52' E. Morphological behavioural data suggest that the pigeon bug, C. columbarius, which closely resembles C. lectularius, is not present in Zulu huts. Two characters are suggested to supplement Usinger's (1966) key for distinguishing the nymphal stages of C. lectularius, and a key is presented for the case of G. hemipterus. Distinguishing features between the nymphal stages of the two species are also given. The two species were found to be sympatric over most of the study area, with C. hemipterus the more plentiful species in the north and apparently still in the process of invading the study area. Evidence was found that C. hemipterus replaces C. lectularius in huts where initially both species were found, and this agrees with laboratory findings that interspecific mating tends to shorten the life span and reduce the egg production of female C. lectularius females. Interspecifically mated female C. lectularius can be recognised by an easily visible morphological change in the reproductive system (Walpole, 1988b) and this character was used to prove that interspecific mating takes place in the wild. The size and life-stage composition of bedbug infestations were investigated together with factors likely to affect their growth. Cimex hemipterus was found not to be at a disadvantage as regards rate of egg production despite low temperatures in the wild, which suggested that such interspecific differences apparent in the laboratory may be an artifact. The specific status of C. lectularius and C. hemipterus are discussed, with particular reference to their cross-mating in the wild and the production of a hybrid. The acceptability of the Recognition Concept of species (Paterson, 1985) is considered in detail. The susceptibilities of wild bedbugs of both species to DDT, dieldrin and fenitrothion were tested in comparison with a susceptible strain of C. lectularius. Field trials of bendiocarb, deltamethrin and fenitrothion were carried out involving monitoring by bioassay and insecticidal knockdown. Subsequent to successful bedbug control operations, reinfestation rates and rates of replastering of mud walls of huts (an indigenous method of attempted bedbug control inimicable to malaria control operations) are assessed.
Aspects of the ecology and exploitation of the fishes of the Kosi Bay system, KwaZulu, South Africa.
(1986) Kyle, Robert.; Blaber, Steven J. M.; Heeg, Jan.
ln this study the exploitation of the fish fauna of the Kosi estuarine system by man and natural predators is described and estimates made of the off-take and its species composition. The most important human exploitation, that by the traditional Zulu fish traps, was monitored over a four year period and the data collected were used to give an insight into the marine fish populations of the system. All the physical parameters, which it was thought could influence the migrations of fish, were monitored and correlations between these and the daily and monthly fish trap catches were used to interpret fish movements into and out of the system. Reasons for the annual migrations and day to day movements of fish were investigated. In order to establish relative off-takes by local fishermen and sport anglers fish were tagged inside the system and the recovery rates by the various fishing methods were used to calculate estimates of the percentage off-takes of these principal human exploitation methods. These data were also used to obtain estimates of the population sizes of the major marine fish species inside the system. Catch data were used to indicate the levels of estuarine dependence of these species. Where possible comparable data from other areas were used to indicate whether or not similar trends in catch abundance were obvious. The ecological and economic importance of the Kosi system is discussed and its value to the local inhabitants stressed. Competition between the various fishing techniques is described and recommendations are made concerning future fish exploitation. Natural predation rates are also discussed and levels compared with those of other systems. The fish food resources of the systems are considered in the light of recently declining salinities, destruction of swamp forests and increasing numbers of hippopotami. The implications of these changing factors are discussed as is their impact on the Kosi Bay fisheries.
Aspects of the ecology of invasive rose-ringed parakeets (Psittacula krameri) in eThekwini Metropolitan, KwaZulu-Natal Province, South Africa.
(2021) Shivambu, Tinyiko Cavin.; Downs, Colleen Thelma.
Globally, the rose-ringed parakeet Psittacula krameri (Scopoli, 1769) has been cited as one of the world’s worst gregarious invasive parrot species, having established breeding colonies successfully outside its native distribution range. The rapid expansion of its breeding population has been considered a major threat to the economy, agricultural production, biodiversity, human health and social life. To date, the rose-ringed parakeet’s population has been reported in ca. 35 countries and the pet trade is the main introduction pathway of this species across the globe. In South Africa, rose-ringed parakeets were introduced as pets in the 1900s. Their breeding population has successfully established in several cities, particularly in Johannesburg and eThekwini Metropole. Although their population seems to be expanding at an alarming rate, little is currently known about their population size, breeding status, and feeding biology. This includes public knowledge and perception towards them as invasive species. Moreover, impacts (environmental and socio-economic) and areas that are at risk of becoming invaded by rose-ringed parakeets and other selected invasive bird species are unknown. This study conducted monthly surveys in the greater Durban (eThekwini) Metropole, KwaZulu-Natal Province, South Africa, from August 2018 to December 2019, to determine the rose-ringed parakeet’s population size, feeding biology and breeding status. A questionnaire survey was developed to determine the public knowledge and perception of parakeets. The species distribution modelling and Generic Impact Scoring Scheme were also used to investigate areas that are likely to be invaded and potential impacts (environmental and socio-economic) associated with rose-ringed parakeets, and other selected introduced bird species. A total of five major roost sites with an overall mean monthly population size of 1,783 rose-ringed parakeets were located. Most of these roost sites were found around urban (public) parks and shopping centres. Seven bird species were found sharing communal roosting sites with rose-ringed parakeets, with the common myna Acridotheres tristis recorded the most. We identified 72 nests within 39 breeding sites, with the first breeding season accounting for 53 active nests and the second breeding season with 59 active nests. Rose-ringed parakeets used four tree species for nesting, with white milkwood Sideroxylon inerme being the most preferred tree species (71%). The recorded rose-ringed parakeet fledglings ranged between 1 – 3 per nest, and their numbers differed significantly between the seasons. A total of 63 feeding sites were identified, with most of them in the urban built land-use cover type. Rose-ringed parakeets were observed feeding on 31 fruiting/flowering trees and one insect species, with fleshy fruits (58%) and flowers (19%) primarily relied on. For our survey questionnaire, a total of 312 participants responded to the survey, with 92.5% being familiar with parakeets. A large population of rose-ringed parakeets were seen in shopping centres (38.5%), suburbia (26.3%), and golf courses (19.6%). Most survey respondents (58.3%) indicated that they provide feeding stations for these parakeets, and 57.7% did not consider them pests. In terms of invasion risk, the rose-ringed parakeets were found to have large areas in South Africa with high climatic suitability, and their impacts were both socio-economic and environmental. Agricultural production was the main impact through socio-economic, while competition and impact on other animals were the main environmental impacts. In general, this study showed continuous growth in the rose-ringed parakeets’ numbers in eThekwini Metropole, indicating that their population is breeding at an average rate. Our study also showed that rose-ringed parakeets feed on various food items, suggesting that they are generalist-opportunistic feeders. As a result, this plasticity in feeding behaviour may likely enhance competitive interactions with other species, contribute to seed dispersal, and increase damage to crops. Parakeets are not perceived as pests by most of the respondents in the eThekwini Municipality. This positive perception may have been exacerbated by the public’s poor knowledge regarding their impacts on biodiversity, economy, human social life, and health. Therefore, we recommend introducing environmental education, which involves the engagement with the community members and eThekwini Municipality. This may assist in making an informed decision regarding the control of this species in the area. Monitoring of rose-ringed parakeet’s population size, breeding status, feeding biology, and movement patterns should continue so that adequate information can be acquired on their biology. In conclusion, our results highlight the importance of studying rose-ringed parakeet’s ecology, which provides reliable data that can be considered in decision-making, management and eradication plans for parakeets in South Africa.
Aspects of the thermal physiology and fruit digestion of Knysna (Tauraco Corythaix) and Purple-crested (Gallirex porphyrelophus)
(2010) Wilson, Amy-Leigh.; Downs, Colleen Thelma.
Chapter 2: Avian frugivores have been somewhat poorly studied with regards to the effects that different fruit sugar types and concentrations have on their digestive efficiencies. Digestion of sugars in equicaloric and equimolar artificial fruit of different sugar types at varying concentrations and molarities were therefore investigated in two relatively large South African frugivores, the Knysna (Tauraco corythaix) and the Purple-crested (Gallirex porphyreolophus) Turaco. Artificial fruits of 6.6, 12.4 and 22% sucrose and glucose respectively and artificial fruits of 0.42, 0.83 and 1.66 mol L-1 sucrose and glucose respectively were used to determine daily food and energy intake, digestive efficiencies and digestive transit times. Digestive transit times of both Turaco species were slower with an increase in sugar concentration and molarity, irrespective of sugar type. Food intake of both Turaco species increased with decreasing concentration and molarity, irrespective of sugar type suggesting compensatory mechanisms for energy requirements. Apparent assimilation efficiencies of both Turaco species ranged from 61.4-90.0% and 60.2-92.4% for equicaloric and equimolar artificial fruit diets respectively. Consequently these two frugivores appear to be tolerant of sugar type and would be expected to select fruits based on energy yields. Future studies of the composition of indigenous forest fruit sugars may give insight into food preferences of the Turaco species and their role as potential seed dispersers of fruiting tree species. Chapter 3: The effects that different fruit sugar types and concentrations have on food preferences of avian frugivores have been relatively poorly studied. Although it has been recently advocated that preference is based on equicaloric energy it is also important to note whether preferences change as energy content changes. Therefore, sugar preferences of equicaloric and equimolar artificial fruit of different sugar types at varying concentrations and molarities were investigated in two relatively large South African frugivores, Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos. Artificial fruits of 6.6, 12.4 and 22% sucrose and glucose respectively and artificial fruits of 0.42, 0.83 and 1.66 mol L-1 sucrose and glucose respectively were used to determine sugar preferences. Knysna Turacos preferred the sucrose to the glucose equicaloric artificial fruit diet at low concentrations whereas Purple-crested Turacos showed no preference for either diet. Both Turacos species preferred the sucrose equimolar artificial fruit diet to the glucose at low concentrations. At high concentrations neither species showed a preference for either equicaloric or equimolar artificial fruit diets. This suggests that energy requirements influence food preferences more than sugar type and that birds will select fruit that is higher in energy irrespective of sugar type. This complements an earlier study on digestion of sugars at varying concentrations of differing equicaloric and equimolar artificial fruit sugar types. It again emphasizes the need for future studies looking at the composition of indigenous forest fruit sugars in order to obtain insight into the role of these avian frugivores as potential seed dispersers of fruiting tree species. Chapter 4: Avian frugivores may select fruit based on their seed loads and pulp to seed ratios and this may have important implications for their role as seed dispersal agents. Consequently the effect of different seed packaging was investigated in two relatively large South African frugivores, Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos. Small-seeded artificial fruits containing on average five black plastic beads (2.24 mm diameter) and large-seeded artificial fruits containing one average one single black plastic bead (3.85 mm diameter) were used to investigate transit rates and food preference. Total seed volume in the two fruits was on average approximately equal (29.42 mm3 and 29.88 mm3 for small- and large-seeded fruits, respectively). Bead transit rates ranged from 38-45 min for Knysna Turacos and 36-50 min for Purple-crested Turacos with faster transit rates on the small-seeded diet. Pulp transit rates ranged from 25-39 min for Purple-crested Turacos and 34-40 min for Knysna Turacos. Purple-crested Turacos had significantly shorter pulp transit rates on the large-seeded than the small-seeded diet whereas Knysna Turacos had no significant difference between diets. Knysna Turacos preferred the small-seeded to the large-seeded artificial fruits whereas Purple-crested Turacos showed no preference for either diet. Further studies on avian dispersers will contribute to a greater understanding of their evolutionary relationship with fruiting plants. In particular, future studies establishing suitable seed sizes and volumes for use in determining the effect of seed packaging on larger birds are required as well as studies looking at seed packaging of indigenous forest fruit and the effects of seed packaging on digestion and food preference in indigenous avian frugivores may give insight into the role of avian frugivores as fruit consumers and seed dispersers. Chapter 5: Fleshy-fruited plants and frugivores share a mutualistic relationship with plants offering the frugivores a reward of fleshy fruit pulp in order to disperse their seeds. In return frugivores receive a food source and consequently a source of energy. However all fruits are not equal in terms of available energy and consequently the digestion efficiency of six indigenous tree species was investigated in an avian frugivore, the Knysna Turaco (Tauraco corythaix). It was predicted that the Turacos would process these indigenous fruits efficiently and have fast transit rates and high intake rates irrespective of species. Fruits were fed to the Turacos in separate trials to determine daily food and energy intake, digestive efficiencies and digestive transit times. Digestive transit times of Knysna Turacos (c. 12-28 min) fall within the range of published examples for other frugivorous birds. Apparent assimilation efficiencies of the Turacos ranged from c. 15-84% and were generally lower than those observed in other avian frugivores. Future studies looking at the nutritional composition of indigenous forest fruit may provide insight into the Knysna Turacos digestive efficiency and consequently their food preferences and role as potential seed dispersers of fruiting tree species. Chapter 6: Seed dispersal plays an important role in the persistence, regeneration and maintenance of plant communities. It is therefore not surprising that much attention has been paid to the germination potential of seeds ingested by frugivorous animals. Consequently the aim of this study was to determine what effect ingestion of seeds by Knysna Turacos (Tauraco corythaix) has on the germination rate and germination percentage of indigenous South African tree species. Fruits from twelve tree species were fed to the Turacos in separate trials and seed retention times were determined as it has been suggested that a longer seed retention time may increase germination rates. At the end of each trial, seeds were extracted from excreta of individual birds and planted in trays containing potting soil. Germination was recorded daily until 14 days post of no germination. Knysna Turacos seed retention times were in the range of those obtained by other studies with Ficus sur seeds having the fastest retention times (12.4 ± 0.8 min) and Celtis africana the slowest (34.6 ± 5.6 min). Mean percentage germination of ingested seeds was not significantly different to pulp removed and whole fruit seeds indicating that ingestion by Knysna Turacos did not enhance percentage germination through either seed coat abrasion or pulp removal. Seed ingestion by Knysna Turacos did not influence the rate at which seeds germinated in 75 % of the tree species while it did for ingested F. lutea, F. natalensis and F. sur seeds which germinated significantly sooner than whole fruit seeds. Future studies relating the composition of indigenous forest fruits to food preferences of Knysna Turacos may give insight into their role as potential seed dispersers of indigenous fruiting tree species. Chapter 7: Frugivorous animals play a major role in dispersing tropical, and to a lesser extent, temperate tree species. In order to attract potential seed dispersers, plants generally offer a reward of fleshy fruit pulp. Criteria for fruit choice by avian frugivores are influenced by a number of non-nutritive (e.g. fruit size and colour) factors; and nutritional composition of the fruit. There is a paucity of nutritional composition and other fruit trait data of indigenous South African fruit. This information is necessary in order to determine which frugivores are likely to ingest which fruits and consequently act as potential seed dispersal agents. This information would provide us with an understanding of the inter-relationships between indigenous fruit and frugivores in South Africa. Consequently nutritional composition was investigated in various indigenous fruit species that avian frugivores feed on. Fruits were collected from 38 indigenous tree species found in KwaZulu-Natal afromontane and coastal forests. Pulp was freeze-dried to constant mass and then analyzed for sugar, lipid and protein content; and for water content determination. Fruit width in this study ranged from 4 mm (Searsia rehmanniana and Trema orientalis) to 40 mm (Annona senegalensis, Ficus sur and Xylotheca kraussiana). Of the fruits examined in this study 29% were black and 43% red when ripe. Most (84%) fruit species analysed for sugar content were hexose dominant with 50% being fructose and 34% being glucose dominant. Only 16% of the fruit species analysed were sucrose dominant. Fruits in this study were generally observed to be high (mean: 68.1 ± 3.3%; n = 30) in water content; and low in protein and lipid content respectively (mean: 8.2 ± 0.5%; 9.3 ± 2.2%; n = 30) indicating that these fruits species could be considered as nutrient-dilute. Future studies need to determine the nutritional composition of the remaining indigenous South Africa fruit in order to develop a comprehensive database as well as examining non-nutritive factors. Together this information would play a key role in understanding fruit preferences and consequently seed dispersal and would therefore be useful in developing management plans for forest conservation. Chapter 8: Many seasonal thermoregulation studies have been conducted on Holarctic birds that live in predictable, highly seasonal climates with severe winters. However, relatively few studies have been conducted on their southern hemisphere Afrotropical counterparts that encounter less predictable climates with milder winters. These latter birds are expected to conserve energy in winter by down-regulating their metabolic rates. Therefore in this study, metabolic rate was measured during summer and winter in Knysna Turaco, Tauraco corythaix (Musophagiformes, Musophagidae) (c. 310 g), a non-passerine, in order to test whether there is energy conservation in winter. No overall significant differences in resting metabolic rates over a range of ambient temperatures were observed between winter and summer. However, whole-organism basal metabolic rates were 18.5 % higher (p = 0.005) in winter than in summer (210.83 ± 15.97 vs. 186.70 ± 10.52 O2 h-1). Knysna Turacos had broad thermoneutral zones ranging from 20-28 oC in winter and 10-30 oC in summer. These results suggest that Knysna Turacos show seasonal thermoregulatory responses that represent cold defense rather than energy conservation, which is contrary to what was expected. Keywords: sugar digestion, sugar preference, seed packaging, basal metabolic rate (BMR), resting metabolic rate (RMR), phenotypic flexibility, indigenous fruit, germination percentage, germination rate, fruit sugars, protein, lipids, fruit size, fruit colour, Knysna Turaco, Purple-crested Turaco.
Assessing the risk of non-native small mammals in the South African pet trade.
(2021) Shivambu, Ndivhuwo.; Downs, Colleen Thelma.; Willows-Munro, Sandi.
Humans have introduced non-native small mammalian species for various purposes, including hunting, biological control, farming, fur markets, ornamental, and pet trade. The latter has been cited as one of the main invasion pathways for some small mammals through accidental escapes and intentional releases of pets. In addition, the pet trade has been cited as one of the major threats to biodiversity loss and human health through the spreading of zoonotic diseases. The trade of non-native pets is growing in South Africa, and this is of great concern as some of these species may become invasive should they escape or be released from captivity. There is also a lack of information regarding which non-native small mammalian species are sold in South Africa. As a result, two primary sources of trade (online and pet shops) were assessed to determine the extent of small mammal trade in South Africa. A list of the traded small mammalian species was compiled online and physical pet shops to determine which species pose an invasion risk and have potentially high impacts. Mitochondrial gene regions were used to assess the taxonomy and genetic diversity of 156 rodent specimens collected in the South African pet shops. We also determined if their genetic diversity follows a geographically correlated pattern. A total of seven websites and 122 pet stores in South Africa were recorded, with 24 non-native small mammalian species traded. Three provinces, Gauteng, Western Cape and KwaZulu-Natal, had the highest number of websites and pet shops selling these species. Overall, online trade had more species diversity when compared with pet shops. Rodents and primates dominated the trade; however, the European rabbit Oryctolagus cuniculus, guinea pig Cavia porcellus, Norwegian rat Rattus norvegicus and house mouse Mus musculus were the most available species in both online and pet shops. In terms of the potential impacts, traded small mammalian species were associated with both socio-economic and environmental impacts. Impacts on agricultural and animal production (livestock) prevailed for the socio-economic category, while the impacts on animals (predation) and competition were the main mechanisms in the environmental impacts. Of the species recorded, 14 had potential climatic suitability; however, species such as Guinea pig Cavia porcellus, sugar glider Petaurus breviceps, domesticated ferret Mustela putorius furo, M. musculus, O. cuniculus, European grey squirrel Sciurus carolinensis, and R. norvegicus are likely to become invasive given their popularity in the trade, large climatic suitability, and history of invasion through releases and accidental escapes. A total of 156 rodent samples were identified using molecular analyses, with 115 specimens identified as M. musculus, 35 as R. norvegicus and six as Southern multimammate mouse Mastomys coucha. Phylogenetic trees showed that the three species were monophyletic, and there was a genetic diversity within M. musculus and R. norvegicus. The specimens for M. musculus and R. norvegicus were more geographically diverse when compared with the specimens for M. coucha. As a result, this suggests that most of the provinces comply with the trade regulations as native species are prohibited from trade. The combined data recovered 19 unique haplotypes for M. musculus and eight haplotypes for R. norvegicus. However, the genetic diversity for M. musculus did not show a clear geographical pattern, while R. norvegicus showed a subtle geographic structure. Unique haplotypes in these species may be explained by the desire to breed rare varieties or introduce new strains from different pet trade sources. In conclusion, small mammalian species with high trade volume, suitable climate, potential environmental and socio-economic impacts are likely to become invasive and cause impacts in South Africa. In addition, M. musculus and R. norvegicus individuals may establish feral populations if released from captivity, given that their haplotypes were unique. Therefore, it is recommended to further monitor the pet trade (both online and physical pet shops), including surveillance, to determine if there are any escapes and releases from the trade.
An autecological study of bushbuck and common duiker in relation to forest management.
(1986) Allen-Rowlandson, Timothy Simon.; Hanks, John.
Frequent reports of damage caused by bushbuck and common duiker browsing on commercially important timber seedlings, and an interest in the potential and feasibility of hunting these two species on State land were the primary factors responsible for the Directorate of Forestry's motivation of this study. The study area at Weza State Forest comprised approximately 21 000 ha of plantations, grasslands and indigenous forests which were considered representative of timbered areas throughout the Natal midlands. Several methods of age determination were investigated and these findings permitted assessments of growth, fecundity and population structure. The physiological condition of both antelope species was examined in relation to age, sex, reproduction and management strategies, and the results discussed in conjunction with mortality patterns. Principal foods of both bushbuck and duiker were determined from rumen analyses while 112 marked animals were regularly monitored to facilitate assessments of habitat selection and levels of spatial and social organisation. of these largely solitary and Estimates of the abundance nocturnal antelope were influenced by local movements in response to the availability of food and cover which varied seasonally and also fluctuated dramatically with forest succession and timber management activities. Although bushbuck and duiker bred throughout the year and had almost identical rates of reproductive performance, different factors were responsible in limiting the sizes of these two populations. All the available evidence gathered in this study indicated that food resources during winter and early spring were inadequate for bushbuck, particularly in 1983 when 33% of the marked population died from starvation and/or exposure. Notable differences in forage utilization and habitat selection inferred little interspecific competition at this time of the year. In contrast, territorial duiker appeared to be susceptible to highly localised habitat modifications (including the availability of food and cover) which occurred throughout the year and resulted from silvicultural and timber harvesting practices. Rumen analyses and quantitative damage assessment surveys revealed that browsing on timber seedlings was usually confined to localised areas during the winter months and was much less severe than had been originally suggested. Conifers were regarded as a starvati~n food and methods of reducing damage to these young trees were recommended for potential problem areas. Both antelope species were considered overabundant at Weza and recommendations for the future management of these populations included the limited utilization of surplus animals, by sport hunting on a sustained yield basis, and methods of manipulating and improving forest habitats.
Behaviour and social organization of the African Jacana Actophilornis africanus.
(1997) Bonkewitzz, Americo Nestor.; Maclean, Gordon Lindsay.
The behaviour, nesting, food resources and mating system of the African Jacana Actophilornis africanus were studied at Muzi Swamp, northern KwaZulu-Natal and at Darvill Sewerage Works, KwaZulu-Natal. African Jacanas show highly polyandrous behaviour associated with a marked reversed sexual size dimorphism. A high clutch loss was recorded because of predation and weather conditions. Contact behaviour was recorded, which is unusual in Charadriiformes. Vocalization and visual displays were distinctive and closely related to territorial and sexual behaviour. Unlike the Wattled Jacana Jacana jacana, the African Jacana practises male guarding behaviour. Rich food concentration in the African Jacana habitat was shown by field tests and this may be a reason for this species evolving in a floating environment. The presence of simultaneous polyandry in the African Jacana was analyzed mathematically and by computer modelling in order to determine possible advantages of polyandry.
The behavioural thermoregulation and ecophysiology of the leopard tortoise (Geochelone pardalis) in the Nama-Karoo.
(2007) McMaster, Megan Kay.; Downs, Colleen Thelma.
The leopard tortoise (Geochelone pardalis) is the largest of the southern African tortoise species and has a wide distribution range. However, there is a lack of ecological and physiological information about the species, especially arid and semi-arid regions. The Nama-Karoo, an arid region of South Africa, is subject to large fluctuations in rainfall, food availability and ambient temperatures (Ta). This study focused on the thermal behaviour, thermoregulatory, digestive and metabolic plasticity of the leopard tortoise within the Nama- Karoo biome. Seasonal changes in activity patterns and body temperature (Tb) were investigated in free ranging leopard tortoises in the Nama-Karoo. Leopard tortoises had unimodal daily activity patterns in winter, bimodal in summer, and there were daily and seasonal differences in the extent to which certain behaviours were practiced. Daily activity behaviours were executed at lower Tb and at lower Ta in winter compared to summer. In summer, core Tb of all tortoises oscillated on a daily basis well below maximum Ta, while core Tb of all tortoises in winter oscillated well above the daily Ta range. Tortoises were therefore able to maintain their Tb independently of Ta. Differences in Tb as measured from various positions on the tortoises body was investigated in relation to Ta. There was a strong seasonal and temporal influence on the relationship between various Tb’s, with the skin and external shell temperatures being more variable in response to fluctuating Ta’s compared with cloacal and core Tb. Cloacal temperatures were significantly different to other Tb measurements suggesting that it should be treated with circumspection as an exclusive measure of Tb. Heating and cooling rates of leopard tortoises were investigated in the field and under controlled laboratory conditions to determine if the tortoises maximise operational daily activity periods, and to determine the effect of behaviour and size on the rate of heat flux. In the laboratory, cooling rates were faster than heating rates in summer and winter for all size classes and decreased with increasing body mass. Leopard tortoises had significantly faster heating and cooling rates in winter than in summer. Free-ranging leopard tortoises had faster heating rates than cooling rates and their heat flux was largely independent of Ta. Heating and cooling rates were dependant on body mass and surface area-to-volume ratio of individuals. Under experimental conditions, tortoises physiologically adjusted their rate of heat flux, while free-ranging tortoises used physiological and behavioural mechanisms to minimise the risk of overheating, to aid thermal inertia and maximise operative activity time. Seasonal climatic cycles and fluctuating daily temperatures influence the oxygen consumption (VO2) of reptiles, however the result of these effects on metabolism in chelonians is poorly understood. The effect of seasonal and daily differences in Ta on VO2 was investigated. Leopard tortoises’ VO2 was slightly higher than reported for other chelonians. There were significant differences in tortoise VO2 at different Ta’s during the day and night and in different seasons. This metabolic plasticity is possibly an adaptive mechanism to cope with unpredictable environmental conditions. Unpredictable climatic conditions lead to unpredictable food and water availability. Little is known how tortoises adjust dietary parameters in response to food type and water availability, and if this affects body mass, energy and water balance. Therefore this study also considered whether leopard tortoises adjusted food transit rate, food intake and water loss to cope with a diet fluctuating in fibre and water content, and whether body mass, energy and water balance were maintained. Leopard tortoises fed a high fibre, low water content diet had lower food intake rates, longer food transit times, but lower daily energy assimilation compared with tortoises fed a low fibre, high water content diet. Tortoises fed a high fibre, low water content diet had lower urine osmolality, but similar total water loss to those fed a high fibre, low water content diet. The results indicate that tortoises can adjust digestive parameters according to diet composition and exercise some control over energy and water balance. It is concluded that leopard tortoises show a high degree of plasticity in their thermal behaviour and physiology which allows survival in an unpredictable environment, particularly where there are fluctuations in rainfall, food availability and Ta’s. Seasonal and daily variation in thermoregulation, metabolic rate and the uptake of energy allows the leopard tortoise to maximise the duration of operative temperature, to minimise energy loss and to use variable and unpredictable seasonal resources.
Beyond DNA sequencing : integrative approaches to resolving selected higher and lower taxonomic problems in Afrotropical Chiroptera.
(2013) Richards, Leigh Rosanne.; Lamb, Jennifer Margaret.; Taylor, Peter John.; Schoeman, Marthinus Cornelius.; Goodman, Steven Michael.
Of the approximate 300 currently recognised bat species known from the Afrotropics, very few have been studied in sufficient detail to a) provide accurate species and distributional limits for extant taxa, b) identify possible cryptic species, and c) ascertain the closest sister lineage of numerous taxonomic groups. For those species where DNA-based phylogenies are available, the use of additional taxonomic markers and methods has provided further insights into the evolutionary history of certain extant chiropteran groups. This work comprises a series of systematic studies of African and Malagasy Chiroptera aimed at investigating sequence-based evolutionary hypotheses of higher and lower level taxa using comparative molecular cytogenetic and morphometric techniques. Efforts were directed at resolving taxonomic inconsistencies of chiropteran taxa from the African subregion and/or Madagascar, for which there is a general paucity of comprehensive and/or resolved phylogenies. Taxa belonging to the families Pteropodidae, Hipposideridae, Myzopodidae, and Molossidae were chosen for study because molecular-based have failed to provide consensus regarding evolutionary relationships amongst the above-mentioned taxonomic groups, or are in stark contrast to phylogenies based on morphological data. In addition, molecular cytogenetics and geometric morphometric approaches were used because they have had been applied in few evolutionary studies of Afrotropical bats. With the exception of a few karyotypic descriptions, scant data are available that details the chromosomal diversity and karyotypic evolution of bats from Madagascar in relation to their conspecifics or congenerics on other continents. To understand better the mechanisms that may have structured the karyotypes of extant Malagasy Chiroptera and the utility of chromosomal characters in retracing their evolutionary history, eight species from seven families were analysed using G- and C-banding and chromosome painting. Robertsonian (Rb) fusions and fissions were the dominant mode of genome restructuring amongst taxa and, for the most part, proved useful characters for investigations of phylogenomic relationships amongst families and genera. Chromosomal data generated from painting studies employing Myotis myotis (MMY) chromosomal probes, produced phylogenetically important characters that supported two conflicting hypotheses regarding the evolutionary affinities of the Myzopodidae, a family of bats endemic to Madagascar. The Rb fusion MMY 9+11 detected in Myzopodidae, also common to Phyllostomidae, could suggest a close association of Myzopoda aurita with the superfamily Noctilionoidea. However, the Rb fusion MMY 3+4 that is also present in vesper bats, suggests closer evolutionary ties between M. aurita and the Vespertilionoidea. A sex-autosome translocation, a cytogenetic character previously confined to phyllostomid and vespertilionid bats, was also detected in M. aurita casting further uncertainties on the evolutionary origins of this deep-branching species. This study highlighted the need for more refined cytogenetic investigations based on human-derived chromosomal paints and the application of highresolution bacterial artificial chromosomal (BACs) probes to map intrachromosomal breakpoints and/or subchromosomal rearrangements in the genome of Myzopoda. Heterochromatic polymorphisms and inversions appear to be important mechanisms of karyotypic evolution amongst pteropodid genera. Painting data revealed that at least five structural arrangements might be linked to the evolutionary divergence of pteropodine and rousettine fruit bats. A cryptic pericentric inversion was detected in the genome of Pteropus rufus corresponding to the homologue of MMY 4+19 (equivalent to HSA3+21); an ancestral syntenic character proposed for eutherian mammals. Proposed synapomorphies of the rousettine clade, as defined by molecular DNA studies, include the derived state of the MMY 4+19 homologue and the non-centric fusion of MMY 16/17+24 homologue. Integration of painting data on Hipposideros commersoni with published comparative maps of other hipposiderids enabled a brief revision of the postulated ancestral hipposiderid chromosomal complement. These data disputed previously proposed chromosomal synapomorphies of Hipposideridae and supported the basal position of H. commersoni within the genus. The inclusion of other hipposiderid genera, in particular Malagasy Paratriaenops and southern African Cloeotis, in chromosome painting studies may allow for further inferences regarding the evolutionary history of this diverse family. Morphometric approaches were employed to resolve uncertainties concerning species-level relationships within Afrotropical Otomops. Multivariate analyses delineated three well-supported morphological groups that corresponded to recently described genetic lineages and revealed several species-specific morphological traits for taxonomic diagnoses. Otomops from Djibouti, Ethiopia, Kenya, and Yemen constitute an undescribed morphologically and genetically cohesive group that requires a formal taxonomic description. Understanding the ecological and possible physiological adaptive value of morphological variation can provide valuable insights into the evolutionary history of this Afrotropical species complex. This work has provided further insights into the systematics of certain Afrotropical Chiroptera through the use of molecular cytogenetic and geometric morphometric techniques. Specifically, it has facilitated the interpretation of ancestral, independent and convergent chromosomal characters in the evolution of Afrotropical taxa belonging to the families Pteropodidae, Hipposideridae, and Myzopodidae, and has also elucidated lineage-specific morphological attributes in members of the genus Otomops thereby advancing our understanding of chiropteran diversity within the region.
Biological studies of bottlenose dolphins from Natal coastal waters.
(1989) Cockcroft, Victor Gavin.; Ross, Graham.
The biology of bottlenose dolphins from the east coast of southern Africa is investigated. Births occur predominantly in summer, after a one year gestation period. Calves are born at a length of approximately 103 cm and a mass of nearly 14 kg. Neonates are closely attended by the mother, she determines the calf's respiration rate and behaviour as it swims in a negative pressure vortex high on her flank. The initial weeks are marked by the calf's acquisition of swimming skills and its ability to regulate its own respiration rate. Although the calf takes solid food between six months and one year, suckling may continue for as much as three years. Initial growth is rapid but slows with the approach to puberty. Females reach sexual maturity at about ten years of age and may undergo a series of rapid ovulations before fertilisation occurs. Subsequently, the mean ovulation rate indicates a three year calving interval. Males show a mass growth spurt at the onset of puberty, between 10 and 12 years, and reach sexual maturity between 12 and 15 years of age. In both sexes, physical maturity and asymptotic size are reached at about 15 years and maximum life-span is in excess of 40 years. Although a wide variety of fish and cephalopods are taken, the fishes Pomadasys olivaceum, Scomber japonicus, Pagellus bellotti, Trachurus delagoae, and the cephalopods Sepia officinalis and Loligo sp. contribute some 60 % by mass of all prey taken. Different sex and maturity classes of dolphins consume differing sizes and species of prey, implying a partitioning of food resources within the group. Comparisons of stomach volumes with estimates of prey mass and nutritional requirements suggest that calves and lactating females may need to feed more often than other sex and maturity classes. Examination of shark stomachs indicates that shark predation may be an important component of dolphin natural mortality. Four species of shark, the Zambesi (Carcharhinus leucas), the tiger (Galeocerdo cuvien), the great white (Carcharodon carcharias) and the dusky shark (Carcharhinus obscurus) are implicated as dolphin predators. Estimates from the number of these four species caught annually and the frequency of occurrence of dolphin flukes and vertebrae in their stomachs suggest that a minimumof 20 bottle nosed dolphins or 2.2 % of the estimated population in southern Natal coastal waters are killed each year by sharks. Some 32 bottlenose dolphins, about 4 % of the estimated population, are captured in shark nets annually. Calves of two years or less constitute nearly 45 % of the catch, while lactating females make up a further 15 %. An analysis of biological, environmental and physiographic factors associated with each capture, suggest that feeding and probably prey movement and distribution are directly associated with capture. PCB, t-DDT and dieldrin concentrations in the blubber of male bottlenose dolphins increase with age and reach levels that may impair testosterone production. In females, there is an 80 % decline in residue concentrations after the first or second ovulation. Evidence presented suggests that first born calves receive possibly lethal doses of residues within two months of birth. Residue concentrations in dolphins from different geographical areas varied significantly, implying a degree of isolation of sections of the population. Investigation of reproductive parameters indicates that mortality of bottlenose dolphins off Natal probably equals or exceeds the replacement rate. The necessity for and requirements of further research on the natural history of bottlenose dolphins off the east coast of southern Africa are summarised.
The biology and systematic relationships of Crowned, Blackwinged and Lesser Blackwinged Plovers.
(1987) Ward, David Mercer.; Maclean, Gordon Lindsay.
Plovers was compared with particular reference to breeding biology, feeding ecology and habitat preference. Crowned and Blackwinged Plovers coexisted in mixed flocks in grasslands which aided predator detect ion and defence against predators. Lesser Blackwinged Plovers were opportunistic in their use of habitat and were found in habitats ranging from the muddy edges of pans to woodlands. Body size was found to have an important effect on the breeding biology of these birds, affecting incubation behaviour and reproductive pattern. The behaviour of Lesser Blackwinged Plovers differed considerably from that of Crowned and Blackwinged Plovers. Crowned and Blackwinged Plovers appear to constitute a superspecies on account of their behavioural and morphological similarities while the Lesser Blackwinged Plover is possibly closely related to the ancestral stock of the genus Vanellus.
The biology, ecology and conservation of four Flufftail species, Sarothrura (Aves: Rallidae)
(1994) Taylor, Peter Barry.; Maclean, Gordon Lindsay.
The distribution, status, biology and ecology of four flufftail species were investigated in South Africa and Zimbabwe. The Redchested Flufftail is a successful and widely distributed species, occupying a wide range of dense vegetation, from seasonally wet grassland and sedges to permanently shallowly flooded reedbeds. It colonizes artificially created wetland patches and occupies very small patches of suitable habitat. Redchested Flufftails maintain a permanent pair bond and are permanently territorial and entirely sedentary. Their habitat is relatively stable but unpredictable catastrophic events such as burning may force temporary emigration in winter or spring. Displaced birds move a short distance, occupy often marginally suitable habitat and recolonize burned areas as soon as vegetation cover becomes adequate. Periodic burning improves habitat quality, and recommendations are formulated for the management of wetland habitats by burning. The size of the winter territory is larger than the minimum required for survival and provides an insurance against forced emigration, while immatures often share parental territories in winter. The Striped Flufftail's grassland habitats in Natal are decreasing and its numbers are declining. Striped Flufftails are sedentary in low-altitude grassland habitats, but in high-altitude sourveld the decrease in invertebrate food forces emigration in April-June, when the birds move to unknown wintering destinations (movements are possibly altitudinal). Return time to unburned vegetation is dependent upon invertebrate food availability. Return time to burned vegetation is governed by the development of suitable cover, which may occur too late in the breeding season to permit occupation. The species is well adapted to frequent burning of its habitats, which serves to maintain suitable fire-climax grassland, but is also adapted to post-fire-climax vegetation types. The Whitewinged Flufftail is rare but its occurrence was regularly noted during the summer at four sites in Natal and the Transvaal. Habitat preferences and movement patterns were clarified, as was the bird's ecological segregation from the Redchested Flufftail. No conclusive evidence was found for breeding in South Africa and it is suggested that lack of suitable breeding habitat (possibly as a result of its being occupied by breeding Redchested Flufftails) may account for this. Some aspects of the bird's behaviour and calling were investigated. In view of this bird's threatened status and the continuing destruction of its wetland habitats, further surveys are urgently required to clarify the bird's status and the full extent of suitable habitat in South Africa, while a captive breeding programme is recommended to study breeding behaviour. The Buffspotted Flufftail inhabits a wide variety of forested and bushed habitats, and in Natal is a successful colonist of exotic vegetation in gardens. Its breeding biology, territorial and aggressive behaviour, and feeding ecology, were investigated in detail. It has regular seasonal movements in Natal, probably both altitudinal and coastal, although birds may remain throughout the year in areas where conditions are suitable. Seasonal departures are correlated with decreasing invertebrate food availability, while return time is largely governed by food availability, although cover development in exotic vegetation delayed recolonization at one site. The pair bond and the territory are maintained throughout the breeding season, and possibly throughout the year under suitable conditions. Adult mortality is probably high and the species' breeding strategy emphasises fecundity, this being achieved by a large clutch size, a very restricted period of parental care and rapid re-nesting. Juvenile mortality is high. The plumage, behavioural and vocal development of the young were studied in detail.
Black rhinoceros (Diceros bicornis) habitat selection and movement analysis.
(2010) Morgan, Simon.; Slotow, Robert Hugh.
Many aspects of habitat selection have been largely ignored in conservation planning of large mammals, including variation between day and night movement patterns, inter-individual niche variation of conspecifics and translocated individual‟s responses to new environments in relation to the influence of ecogeographical variables. Being a solitary moving animal with a known tendency to move through the night, the black rhino Diceros bicornis is a perfect species to test theories about individual spatial and temporal variation in habitat utilisation. I tested the appropriateness of using carrying capacity (CC) estimates as a tool for population conservation planning, and as an indicator of habitat utilisation for black rhino. I found individual selection was not related to the value of the habitat according to modelled CC. I therefore do not recommend the use of a priori calculations of resource quality and abundance of habitats (CC estimates), which do not take into account the factors that influence an animal‟s selection of a habitat, as indicators of species habitat use. Secondly I tested whether current methods of analyzing mainly diurnal location data of animals result in accurate ecological or conservation conclusions. I found a circadian variation in habitat use for different behaviours, and that excluding nocturnal data from home and browsing range analyses would provide inaccurate results for black rhino habitat use. I then tested for inter-individual niche variation amongst two populations of black rhino at various scales of selection, ranging from habitat through to browse selection. I showed that black rhino, a selective browser, had a significant degree of inter-individual habitat and dietary niche variation. Consequently, pooling habitat location data and diet selection data for black rhino individuals in a population does not reflect the actual selection of any, or many, individuals. To clarify which ecogeographical variables might influence this selection I ran maximum entropy models on individual‟s diurnal locations across the landscape. I was then able to develop a habitat suitability model which was based on the individual rather than population, providing a more accurate prediction. I repeated the individual models in phases, from the initial post-release phase after the release of individuals onto a new reserve through to their „settled‟ phase, allowing me to explore the effect of habitat variables on different settling phases of translocated animals. The results indicate that all the rhinos‟ acclimation phase lasted no longer than 25 days and that to minimize disturbance to the settling process all individuals in a newly released cohort should be released within this period. This study as a whole provides conservation managers with a better ecological understanding of black rhino in conjunction with a number of management tools. This will enable conservation managers to better understand the way animals utilise and perceive their environment, allowing for better monitoring and analyses of animal movements. This will aid in the development of strategic management plans in the conservation of not only animal species but also the ecosystems that they reside in and the identification of suitable areas for future conservation of animal species.
Chromosomal evolution in the Vlei Rat Otomys irroratus.
(1996) Contrafatto, Giancarlo.; Meester, Jurgens Anthonie Jansen.; Campbell, Glen Kerry.; Grace, James H.
Proponents of the recognition concept of species hold that isolating mechanisms, including chromosome rearrangements, play no role in speciation while the more commonly accepted biological species concept proposes that isolation mechanisms are instrumental in the formation of new species. Moreover, some adherents of the biological concept of species, reject the hypothesis that chromosomal rearrangements can be instrumental in causing reproductive isolation and, hence, speciation. Evidence to the causative role played in speciation by chromosome changes can be obtained from cytogenetic investigations of sibling species, in parallel with analyses of gene products, DNA polymorphism and premating behaviour. This study reports the results of a cytogenetic investigation of 97 specimens of the vlei rat 0. irroratus, from 18 South African localities, and 11 samples of the Angoni vlei rat 0. angoniensis from two geographically distant populations. All 0. angoniensis individuals showed a constant karyotype with 56 acrocentric chromosomes but extensive variation was detected in 0. irroratus. Five cytotypes could be recognized within the latter. In the south-eastern parts of its South African range, 0. irroratus had a diploid number (2n) of 30 chromosomes in whicll all autosomes were acrocentric (cytotype A) while further east (cytotype A2), the diploid number was 30-32 with, again, acrocentric autosomes, A further acrocentric cytotype (AI) with 2n = 24-27 occupied the southern and south-eastern slopes of the Drakensberg range. A type with 2n = 28-30 (cytotype B), with eight pairs of biarmed autosomes, was found in the southern Cape region while in the Cape of Good Hope and in the north-eastern parts of South Africa, 0. irroratus had 2n = 28 with only four pairs of biarmed autosomes (cytotype C). Most of the numerical changes were due to variation in the number of copies of Bchromosomes which were small, biarmed and partly heterochromatic. C-banding analysis revealed that the short arms of bianned autosomes were totally heterochromatic. On the other hand, G-banding patterns of acrocentric autosomes were, with two exceptions (AI and A2 types), similar in all cytotypes while G~banding of the long arms VII of biarmed chromosomes matched the pattern of their homologues in acrocentric cytotypes. A potentially heterotic rearrangement was detected in the Al localities where a unique acrocentric autosome was identified as the product of a fusion between chromosomes 7 and 12. The geographic distribution of these groups of karyotypes correlated, by Discriminant Function Analysis, with bioclimatic regions of South Africa. The Al cytotype was shown to occupy the coldest and wettest region of the montane Drakensberg while the B type is found in the hot area of the eastern Cape with an unpredictable rainfall pattern: group C occupies regions of intermediate climate. Gene product analysis was carried out using the novel approach of subjecting liver homogenates to "Western blotting". This method was first assessed at supraspecilic level using specimens of various southern African rodents, and allowed the generation of phylogenies essentially similar to those produced by allozyme studies of the same taxa. At intraspecilic level, immunobloHing analysis did not reveal synapomorphies congruent with karyotype groups. This was interpreted, in conjunction with available allozyme data from the same populations, as evidence of low genetic differentiation between 0. irroratus cytotypes, A measure of genetic divergence was indicated in two populations from the Cape province and this was in agreement with existing data from allozyme electrophoresis and mitochondrial DNA polymorphism. The cytogenetic results were related to available data on breeding and premating behaviour concerning some of the O. irroratus populations investigated here. The presence of the 7/12 chromosome fusion in the Al cytotype correlated with a dramatic reproductive impairment of FI individuals originated from Al/A2 and Al/B cytotype crosses. Evidence of partial premating behavioural barriers has been reported by others, but information on premating behaviour between populations which are not chromosomally isolated is lacking. Therefore, it was not possible to establish if behavioural premating barriers preceded, or followed, the fixation of negatively heterotic chromosomal rearrangements. It was, nevertheless, suggested that the existence of such impaired mate recognition may be an example of reproductive character displacement which may have followed the fixation of the t(7: 12) typiVIII cal of the Al populations. In conclusion, the existence of chromosome changes in the AI, and possibly A2, populations accompanied by low genetic divergence and severely impaired hybrid reproductive success, are consistent with a hypothesis whereby chromosomal reproductive isolation causes speciation. Nonetheless, other speciation mechanisms mediated by genetic divergence and/or mate recognition failure, are possible in other populations where no chromosome changes of negatively heterotic potential were found.
Comparative feeding and foraging behaviour of the biocontrol agents Chilocorus spp. (Coccinellidae)
(1991) Hattingh, Vaughan.; Samways, Michael John.
This study focuses on the effective biocontrol agent Chilocorus nigritus (Fabricius). Its behaviour and ecology were compared with other Chilocorus spp. where appropriate, to elucidate why this species is such an effective biocontrol agent, and how to improve methodology for its deployment as a natural enemy. An artificial diet for C. nigritus was developed, but was still sub-optimal. Asterolecanium miliaris (Boisduval) was a suitable prey for all life stages of C. nigritus and the adults of Chilocorus bipustulatus (Linnaeus) and Chilocorus infernalis Mulsant, but was inadequate for larvae of the last two species. Adult weight, measured at one day after adult eclosion, was an appropriate indicator of the effects of larval treatment on their development and on the fitness of subsequent adults. There was no improvement in culture vigour due to a behavioural response of individuals within one generation to fluctuating as opposed to constant temperature. starvation for between 10h and 24h was appropriate for standardisation of hunger. Measuring feeding rate at a range of static temperatures did not reflect differences in the climatic adaptations of six Chilocorus spp., but mortality rates at increasingly high temperatures were useful. Chilocorus spp. showed little ability to choose between prey species. Prey substitutions adversely affected adults and larvae. Introduction of adults was the most effective method for field establishment. Giant bamboo Dendrocalamus giganteus Munro was a valuable site for field releases of C. nigritus, but less useful for C. bipustulatus and C. infernalis. Counter to assumptions on which interference models have been based, no significant intraspecific interference, reducing predatory efficiency, was observed. Visually prominent features on the horizon and a specific leaf shape, were attractive to foraging C. nigritus. The location of prey patches by adults was facilitated by prey odour, but not so for larvae. Adults detected individual prey olfactorily and visually over short distances, but physical contact was required for detection by larvae. Prey location by larvae and adults was facilitated by alterations in movement patterns in response to prey consumption. Differences in prey detection and the effects of prey substitutions, between the life stages, were related to field behaviour. The relevance to biological control, of responses to rearing conditions and feeding and foraging behaviour, was investigated.

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