Acacia Woodland Research Articles

Space use in lions, Panthera leo , in the Selous Game Reserve: social and ecological factors

Habitat qualities, such as food supply or access to refuges, often influence home-range size. Furthermore, such qualitative differences usually lead to conspecific competition over space, which can be an important factor in determining the distribution of individuals within populations. In carnivores, patterns of resource dispersion are hypothesized to determine home range-size and group size. But in contests over space (or other resources), larger groups usually dominate smaller ones, and group size should therefore also affect home-range size. Here I describe the space use of lions, Panthera leo, in the Selous Game Reserve, Tanzania, and ask whether space use is related to pride size, habitat, or relatedness. Home ranges varied in size, but size showed no correlation to number of adult females in the pride or to habitat type. Lions exhibited a significant preference for riverine and short-grass habitat, and a significant avoidance of acacia woodland. Habitat preference ratios largely reflected prey availability in each habitat. Outer areas, as well as core areas of home ranges, were often used by two or more prides. Overlaps showed no correlation to relatedness among prides or habitat type. Thus, whereas home-range sizes and overlaps were determined by factors that could not be revealed by demographic factors or analyses of habitat composition or genetic structure, lion space use within each home range seemed driven mostly by prey availability, which mainly varies with habitat type.

Avian assemblages in native Acacia and alien Prosopis drainage line woodland in the Kalahari, South Africa

Plant and bird species richness and abundance in two patches of native Acacia karroo and two patches of alien Prosopis species drainage line woodland in the southern Kalahari, South Africa, were compared using 37 plot (100 m2) samples for the plants and 12 line transects (ca. 1 km long) for the birds. Vertical distribution of canopy cover differed among the four sites in all four strata. The densest Prosopis woodland had less herbaceous understorey cover, and more cover between 1 and 5 m above-ground than Acacia woodlands or the relatively openProsopis woodland. The tallest Acacia woodland differed from other sites in having 40% canopy above 5 m. The densities of all trees >50 mm basal diameter (mainly A. karroo and Prosopis, but including a few A. hebeclada and Ziziphus mucronata) did not differ among sites, but abundance of A. karroo andProsopis species differed greatly among sites. Mean plant species density per 100 m2 plot differed among sites, being greater in the Acacia woodlands than in Prosopis -dominated vegetation. The densest Prosopis woodland was the least diverse site botanically, and was also least similar to the tallest Acacia woodland, sharing only 11 plant species. The ratio of fleshy fruited plant species to all others encountered differed between woodland types being lower in Prosopis than in Acacia woodland. Individual A. karroo trees differed from size-matchedProsopis trees in being less multi-stemmed and having fewer branches in contact with the soil when mature. The numbers of species of sub-canopy plants and fleshy fruited plant species increased with the size of the trees, but tended to be lower for large Prosopis than for large A. karroo.Sorenson's similarity index for bird species assemblages forAcacia sites compared with both Prosopis sites was 0·61. All species that occurred in Prosopis, with the exception of Red-eyed Bulbul Pycnonotus nigricans, were a subset of species that occurred in Acacia woodland. Bird species assemblages were least similar between the densest Acacia site and the most open Prosopis site. The Shannon indices for the Acacia and Prosopis communities showed some variation between patches and between counts. Indices for the Acacia sites were significantly higher than indices for the Prosopis sites, indicating that the bird communities in the native woodland sites are consistently more species-rich and more diverse. In terms of guilds, raptors were absent from Prosopis woodlands, in general frugivores were sparse in Prosopis woodlands, and insectivores were about half as abundant, but there were no large differences between nectarivores, mixed feeders (seeds and insects) and granivores in both types of woodland.

Comparative foraging ecology of five species of ground-pouncing birds in western Australian woodlands with comments on species decline

In this paper, we compare the foraging ecology of five Australian robins (Petroica multicolor, P. goodenovi, Eopsaltria griseogularis, Microeca fascinans, and Melanodryas cucullata) in woodlands of Western Australia. Australian robins are in- sectivorous and obtain the greatest proportion of their prey by pouncing from a perch to the ground. Data were collected at three different sites in eucalypt (Eucalyptus) woodland and two sites in acacia (Acacia) woodland. The species differed in habitat, structure of the ground substrates where prey were taken, proportion of foraging ma- noeuvres used, height of foraging perches and prey-attack distances, though there were broad overlaps in all foraging dimensions. Within a site, species were more sim- ilar to each other in their foraging behaviour and selection of foraging substrates than they were to conspecific individuals occurring elsewhere. This indicates that potential foraging behaviours were very broad, and their expression is determined by the char- acteristics of the habitat and available prey. At all sites, robins took prey from ground substrates characterised by a mosaic of bare soil, low ground vegetation, and litter. The smallest species, P. goodenovi, used lower perches than the other robins and probably searched for small prey which it located at short distances. P. goodenovi had the widest distribution and was the most abundant of the species studied. The impli- cations of these findings for the conservation of ground-foraging birds in Australia are discussed.

Status and Conservation of Prince Ruspoli's Turaco Tauraco ruspolii

Borghesio, L. & Massa, R. 2000. Status and conservation of Prince Ruspoli's Turaco Tauraco tuspolii. Ostrich 71 (1 & 2): 355–358. Prince Ruspoli's Turaco is an Ethiopian endemic, distributed in a small region at the southern border of the Abyssinian Plateau. Owing to the difficulty of visiting its secluded range, little information is available on its current conservation status. Based on the available data, it is currently considered endangered in the IUCN criteria. In order to evaluate the conservation status of T. ruspolii, field work was carried out during spring 1995. The results of the survey were as follows: 1. the species was found in 26 localities, including all of those previously reported by other authors, and had an area of occurrence about 6 500 km2 2. the population of T. ruspolii was censused by means of linear transects, giving an estimate of about 10 000 individuals. 3. T ruspolii frequents mostly forest margins and relatively dry Acacia woodlands. These habitats are less severely threatened by human activity than true forests in present day Ethiopia. 4. since T. ruspolii and the related T. leucotis usually occur in different habitats (the latter preferring wetter forest) competition is not likely to be a severe threat for T. tuspolii. 5. the species is subject to some egg collecting by local people, but probably not to a severe extent. Other direct human persecution was not recorded. 6. although there is no hint of numerical decrease in the past, this is likely to occur in the future, as consequence of the increasing human pressure in the region. These results are evaluated and discussed. It is consequently proposed that Prince Ruspolii's Turaco should be considered as a Vulnerable species instead of Endangered in the IUCN criteria.

Soil seed flora, germination and regeneration pattern of woody species in an Acacia woodland of the Rift Valley in Ethiopia

The objectives of this study were to determine the composition, density and spatial distribution of the soil seed bank of woody species, as well as their regeneration pattern in two different land use systems, controlled (ranch) and open grazing, in an Acacia woodland of the Rift Valley in Ethiopia. We also compared the species composition of the soil seed bank and the above-ground vegetation to find out if differences exist in the soil seed bank and advance regeneration between the two land use systems. The germination requirements of seeds of the woody species were also investigated under laboratory conditions. Acacia senegal, Acacia seyal, Acacia tortilis, Dichrostacys cinerea and Balanites aegyptiaca were encountered in the above-ground vegetation in both systems. Seeds of only A. tortilis (90±32 seeds m−2) from the ranch, and A. senegal (5±3 seeds m−2) and A. tortilis (72±34 seeds m−2) from the open system were found in the soil seed bank along transects with patchy horizontal pattern. The two systems were not significantly different in density of soil seed banks of A. senegal andA. tortilis . Jaccard's similarity index showed that only a few woody species were common in the soil seed flora and above ground vegetation. However, all of the species accumulated seeds (58±43–331±130 seeds m−2) in/on the soil under the canopy. Very large numbers of seeds of A. tortilis (19382±9722 seeds m−2) and D. cinerea (1278±494 seeds m−2) were also found in barns. Most of the seeds recovered from the soil samples (60–80%) were found in the litter layer. Acid and mechanical scarification improved legume germination (36–99% and 60–99%, respectively) over boiling water (0–48%). Treatment means differed significantly for all the legumes (p<0·001) but not for Balanites. Height and diameter class distribution of regeneration of A. tortilis and D. cinerea in both systems and A. senegal in the open system had a negative exponential correlation (rs=−0·5, −0·25 and −0·86, respectively). A. seyal and B. aegyptiaca showed poor regeneration. Horizontal distribution of advance regeneration of all the species was patchy. Advance regeneration of A. seyal, A. tortilis and B. aegyptiaca were not significantly different, while that of A. senegal and D. cinerea were significantly different between the two systems. Poor representation of species in the soil seed bank along transects and in the different height and diameter classes may be attributed to the low density of mature trees as well as the mode and strategy of seed dispersal. Ungulate and wind dispersed species (e.g. A. senegal, A. tortilis and D. cinerea) were highly favoured. Patchiness in the distribution of seeds and advance regeneration was also a result of endozoochory. Dispersal of non-ungulate dispersed seeds (A. senegal, A. seyal and B. aegyptiaca) was restricted to the canopy zone. Piles of seeds ofA. tortilis and D. cinerea that were found in barns were a result of consumption of their pods by cattle. High concentration of seeds in the litter layer may be due to low soil disturbance and larger size of seeds. The height and diameter class distribution of A. senegal (in the open system), A. tortilis and D. cinerea also indicated that the species have good regeneration. Results from the germination tests indicated that seeds of the legumes require pre-sowing treatments to give a rapid, uniform and improved germination. Intervention through artificial regeneration should be employed to improve the density and regeneration capacity of those species with hampered regeneration at both systems.

Protective efficacy of lambdacyhalothrin-impregnated bednets against Phlebotomus orientalis, the vector of visceral leishmaniasis in Sudan.

Field investigations on the sandfly Phlebotomus orientalis (Diptera: Psychodidae), the vector of Leishmania donovani causing visceral leishmaniasis (VL) in Sudan, were undertaken in two villages (Bellow and Elgamel) and Dinder National Park, to determine the protective value of bednets (polyester, 100 denier) impregnated with lambda-cyhalothrin 10 mg a.i./m2 pyrethroid insecticide. After exposure to treated netting for 30 s, P. orientalis females all died within 1 h. When field-tested in Acacia woodland, treated bednets provided complete protection from bites of the vector. Numbers of P. orientalis females landing on human collectors without bednets or using untreated bednets averaged 32.0 +/- 8.3 or 6.9 +/- 2.7 per man-night, respectively, whereas collectors using treated bednets experienced no sandfly bites during the same period (18.00-06.00 hours, 12 nights in June 1995). Socio-behavioural observations on the bed-time of people living in both study villages indicated that the use of impregnated bednets against P. orientalis would give more potential protection for women and children than for male adults. Overall the proportions of people and their durations of exposure to the risk of sandfly bites (i.e. after sunset until they went to bed) were 40% unprotected for< 1h, 50% for 1-2h and >10% for > or = 2h. Because visceral leishmaniasis in Sudan occurs mainly in children, the use of impregnated bednets (outdoors as well as indoors), and going to bed early could provide a high degree of personal protection against this zoonotic infection.

Tree rings as indicators of growth periodicity of acacias in the Rift Valley of Ethiopia

In many arid and semi-arid parts of Ethiopia, acacia trees are important for the rural economy. However, very little is known about the dynamics of the acacia woodlands. In this study, an attempt was made to find out whether or not tree rings in acacias can be used as indicators of growth periodicity. In such a case, growth and yield models could be developed from tree-ring measurements. The study was made in the central part of the Rift Valley of Ethiopia and included samples from both, naturally regenerated and planted acacias. Standard techniques from tree-ring research were employed to study the relationship between tree-ring patterns and different moisture-related climatic variables (e.g. moisture balance, precipitation). Also, the number of rings in trees with known age was counted. The results indicate that the acacias form one ring per rainy season (year) in the dry parts of this area. In a minor complementary study using X-ray densitometry, the wood density appeared to be correlated with moisture-related climatic variables. However, the technique appeared to be of very limited use for locating growth boundaries.

Abundance of Olivaceous Warblers Hippolais pallida and potential invertebrate prey in unmanaged Acacia woodland

Abundance of Olivaceous Warblers Hippolais pallida and potential invertebrate prey in unmanaged Acacia woodland

Functions for multi-phase assessment of biomass in acacia woodlands of the Rift Valley of Ethiopia

In this article, single-tree biomass functions for acacia woodland tree species are presented. The main aim of developing the functions was for utilizing them in a multi-phase sampling design in estimating the woody biomass in acacia woodlands of the Rift Valley of Ethiopia. Eighty-five trees (5–35 cm diameter) were selected randomly from the five dominant tree species: Acacia tortilis (Forsk.) Hayne, Acacia senegal (L) Willd., Acacia seyal Del., Acacia etbaica Schweif. and Balanites aegyptiaca (L) Del. Four categories of functions were developed. These were (i) functions with crown area as independent variable, to be applied using high resolution satellite images or aerial photos; (ii) functions with crown area and tree height as independent variables, to be applied using data from aerial photos; (iii) functions for quick estimation in ground surveys, based on the diameter at 0.8 m; and (iv) functions for thorough estimation in ground surveys, in which the diameter at 0.8 m, the diameter at stump height, and the crown area were included. Also, two sets of functions were developed, one with and one without species indicator variables. In gathering data for developing biomass functions, the selection of sample discs from trees for determining the ratio between dry weight and fresh weight is important. In addition to the functions, a robust method for the disc sampling is proposed.

Acacia, cattle and migratory birds in southeastern Mexico

Acacia pennatula groves in mid-elevation valleys of southern Mexico supported both the highest density and diversity of migratory birds compared to other habitats in the region. In addition, we found the highest numbers for over half of the common migratory species. Despite the high degree of leaf loss during the late winter, acacia groves do not experience greater declines in insectivorous migratory bird populations than other local habitats. Color-marked individuals of canopy species had a strong tendency to remain resident within a single acacia grove throughout the winter. Management of native acacias on subtropical rangelands for wood products, fodder, and soil improvement would probably directly and indirectly benefit migratory song bird populations. Neotropical acacia woodland is primarily associated with grazing land for livestock which might discourage some from considering acacia management a viable option for migratory bird conservation. However, acacias were probably widespread in recent geologic time under drier conditions with heavy browsing and seed dispersal by a now extinct megafauna. Two observations suggest a foraging advantage for acacia use: the higher density of migratory birds in acacia is a result of higher numbers of canopy insectivores; and acacias are selected by migrants when they occur in mixed habitat. We hypothesize that plant investment in mechanical defenses (thorns) reduces energy available for chemical defenses effective against insect herbivores.

The Reservation Status of Plant Species and Vegetation Types in the Northern Territory

The terrestrial conservation reserve system of the Northern Territory comprises 83 reserves covering 3.79% of the land area. This system includes representation of only 63 of the 112 vegetation types recognised in the Northern Territory at 1:1000000 scale. Of these, only 31 are represented to at least 5% of their extent. The reserve system has a strong geographic bias, with very poor representation of vegetation types occurring across a broad band in the mid-latitudes of the Northern Territory. Broad vegetation categories which are particularly poorly reserved include tussock grasslands, chenopod shrublands, Acacia woodland and hummock grasslands: by contrast, closed forests and floodplains have &gt; 20% of their extent reserved. In some contrast to the poor reservation extent of vegetation types, 80% of the 3632 named native vascular plant species known from the Northern Territory have been recorded from reserves. The distribution of the 743 unreserved plants is mapped, and coincides reasonably well with the pattern of unreserved vegetation types. The high proportion of the flora which is reserved is due in part to judicious (or fortuitous) reserve placement-for example, one reserve, Kakadu, contains almost half of the plant species known from the Northern Territory. There are substantial taxonomic and ecological biases in the reported reservation rates for NT plants. Rainforest plants tend to be reasonably well reserved (80% of 585 species), but designated threatened plants are poorly reserved(44% of 553 species). Due to its largely intact environment, the Northern Territory offers an unusually good opportunity for the establishment of a comprehensive reserve network. However, most of the unreserved plants and vegetation types occur on either freehold Aboriginal lands or pastoral leaseholds, suggesting that substantial enhancement of the existing reserve network may not be simple.

Floristic Composition of Dakata Valley, Southeast Ethiopia: An Implication for the Conservation of Biodiversity

Protected areas can help meet societies evolving needs (Leucas, 1984; McNeely et al., 1984; Hamilton, 1992) provided that they are well protected and conserved. They maintain those ecological processes that are essential for the continuation of life and safeguard habitats critical for sustainable use of species. They preserve the diversity of species and the genetic variation within them, thereby preventing irreversible damage to our natural heritage. They provide opportunities for scientific research, education, and training. They also provide places for recreation as well as tourism, and serve the spiritual and cultural needs of people by securing the wilderness and sacred areas on which so many draw for aesthetic, emotional, and religious nourishment. In general, they provide a vital link between us, our past and future. Dakata Valley, also known as the Rock Valley,:' is a part of the Harer (Harar/Harrar or Babille) Elephant Sanctuary in the Harerge Region (southeast Ethiopia) which covers 6,000-7,000 km2 (Stephenson, 1976; Teshome Ashine, 1981; Friis, 1987; Anonymous, 1990; IUCN, 1990; Sayer et al., 1992). The sanctuary was established in 1970, by Imperial order, to provide protection to wildlife, especially elephants and other large mammals. The natural features of the area include rock outcrops spectacularly arranged, rich vegetation, and varieties of wild-animals. It is one of the 24 areas proposed by Beals (1968) for protection in Ethiopia. He categorized these areas into 8 groups based on the types of vegetation. Dakata Valley was grouped in the Acacia woodland; he considered it to be rich in game population, including elephants, and a good example of the Acacia woodland group containing a grass swamp and an extensive Acacia seyal and combretaceous woodland. He also noted that, at that time, the Acacia woodland was rapidly deteriorating all over the country due to expanding human and livestock populations, and also increasing demand for charcoal in cities and villages. The situation of the woodlands in the country, including Dakata Valley, is getting even worse today. They are subjected to severe destruction by cutting, burning, and overgrazing. If this trend continues, there is a great danger that they will either be degraded to a level difficult to regenerate or be wiped out in few years' time. This implies that the wild animals living in them will have the same fate since they depend on these woodlands for food, shelter, and breeding. Hence, the threat is two-fold-the loss of vegetation and of animal diversity. Dakata Valley is habitat of a variety of wildlife, one of which is an endangered endemic elephant subspecies, Loxodonta afticana orleansi. This very distinctive subspecies has been recorded only from northern Somalia, where it has become extinct since 1928, and from adjacent areas of Ethiopia between the Chercher Highlands in the north and the Wabi Shebele to the south (Largen and Yalden, 1987). The only surviving representatives of this race are found south of the city of Harer where they appear to undertake seasonal migrations along the Errer, Dakata, and Fafam valleys, between the headwaters of these rivers and the areas of Ime on the Wabi Shebele (Bolton, 1973; Largen and Yalden, 1987). At least 130 individuals were recorded in 1967 (Ingersol, 1968) but only 60 in 1976 (Stephenson, 1976). Based on information from the Ethiopian Wildlife Conservation Organization (EWCO), Largen and Yalden (1987) reported 300 individuals in 1986. They noted that this figure does not necessarily indicate that populations are increasing since it is an estimate for total populations, where as the earlier figures are direct counts made on specific occasions. It is reported that some elephants still exist in the area (Anonymous, 1990). However, their number and status are not exactly known. All reports (Beadles, 1968; Duckworth, 1974; Stephenson, 1976; Largen and Yalden, 1987; Anonymous, 1990) indicate that this elephant is continuing to decline. Even though they are legally protected from hunting, they receive little additional protection due to the lack of resources presently available for this purpose (Largen and Yalden, 1987; Anonymous, 1990). In his discussion on the natural resources of Ethiopia, Tewolde B. G. Egziabher (1989) noted that to pinpoint areas of conservation of plant and animal resources in Ethiopia, inventories of the conservation areas concerned should be carried out. Although the Dakota Valley is given a sanctuary status, there is no work on its flora and very little is known about its fauna. Friis (1987) indicated that the sanctuary is of special interest from a plant conservation point of view and deserves more attention from botanically-inclined conservationists. The aim of the present work was, therefore, to study the floristic composition of the Dakata Valley to provide a background for the conservation of unique vegetation and one of the habitats of the endangered endemic elephant subspecies, Loxodonta africana orleansi and other animals.

Long‐Term Glades in Acacia Bushland and Their Edge Effects in Laikipia, Kenya

Throughout the Laikipia ecosystem in Kenya, isolated glades occur within acacia bushland and woodland communities. These glades are at least several decades old. They are reported to be old settlement sites of traditional pastoralists no longer present, and their size, location, and orientation are consistent with the settlement sites of related pastoralists studied elsewhere. The purpose of this study was to document the effects of these glades at the local and landscape levels. Working in central Laikipia, we documented differences in vegetation, animal use, and soils at four of these glades, and at increasing distances from glade edges. Four "glade specialists" dominated the plant communities within glades, and were very rare outside of glades. Pennisetum stramineum, one of six glade edge species, formed a ring of dense tall grass around most glade edges. The transition to acacia bushland at the glade edges was not always abrupt (depending on the trait considered), resulting in edge effects that differed in depth and sharpness. Edge depth, defined as the distance required to attain two‐thirds of background levels for a trait, ranged from 0 to 200 m. Understory plant species richness and diversity were lowest inside glades, and gradually increased with distance from glades. However, because glades supported species not found elsewhere, the presence of glades increased overall species diversity. The density of wild and domestic large mammal dung was up to 10 times greater inside the glades, and declined with distance from glad edges. Similarly, soil nitrogen, potassium, carbon, calcium, and sodium were greatest inside glades. Soil phosphorus, magnesium, and manganese were not elevated inside glades or within 100 m of glades, but instead were much more abundant in background samples. These glades may be maintained by high densities of large mammals, either through herbivory or through changes in soil chemistry. Glades may be attractive to mammals because of the high quality of food there, or as part of an anti‐predator strategy. The result is a relatively permanent community mosaic that increases ecosystem heterogeneity and resource use by domestic and wild animals. The spatial nature of this heterogeneity differs among species, depending on their distributions relative to the glades.

Wildlife of Lancewood (Acacia Shirleyi) Thickets and Woodlands in Northern Australia. 2. Comparisons With Other Environments of the Region (Acacia Woodlands, Eucalyptus Savanna Woodlands and Monsoon Rainforests).

Embedded in the extensive Eucalyptus open forests and savanna woodlands that dominate the northern Australian landscape are patches of monsoon rain forest and Acacia thickets and woodlands. In this paper, the vertebrate species composition of patches of lancewood (Acacia shirleyi) thickets and woodlands of the Northern Territory was compared with that of other environments of this region: pindan woodlands (A. eriopoda and A. tumida), gidgee woodlands (A. georginae), patches of monsoon rain forests and the extensive Eucalyptus open forests and woodlands. The vertebrate fauna of lancewood thickets is distinct for that of Eucalyptus open forests, and has fewer species. Differences in species composition and richness are associated with substantial differences in resource availability, with lancewood thickets having far less grass cover (and hence relatively few granivorous birds and rodents, but more ground-feeding insectivorous and omnivorous birds), fewer nectar-bearing flowers (and hence fewer nectarivorous birds) and lower structural and floristic diversity than Eucalyptus forests. There was little difference in species richness or total abundance between the three types of Acacia woodlands sampled. Lancewood thickets had fewer species than monsoon rain forests to coastal dry monsoon rain forests to inland dry monsoon rain forests to lancewood thickets to pindan woodlands to gidgee woodlands, in accord with the pronounced rainfall gradient of this region and with canopy cover and height. Within this broad continuum the three Acacia woodlands were most closely grouped. Species turnover along this gradient consisted of substantial decrease or loss of some foraging groups (e.g. frugivorous birds) or replacement of species within broad foraging groups. The faunal relationship of the monsoon rain forests and Acacia communities provides some support for considering these fire-sensitive environments as fragments of a formerly extensive continuum. Three species (Pomatostomus temporalis, Struthidea cinerea and Melanodryas cucullata), all ground-foraging insectivorous or omnivorous birds, were significantly associated with lancewood in this region, but all three have extensive ranges beyond this area.

Linear regressions for canopy cover estimation in Acacia woodlands using Landsat-TM, -MSS and SPOT HRV XS data

Abstract The aim of the study was to establish remote sensing models for the estimation of canopy cover in Acacia woodlands. The models were established using Landsat-TM and MSS data and SPOT HRV XS data and based on field data from eastern Sudan. The models were derived using the Reduced Major Axis (RMA) method. Correlation coefficients between NDVI and canopy cover are for Landsat-TM 0-552, for Landsat-MSS 0-698 and for SPOT HRV XS 0-718. The confidence intervals of predicted canopy cover are also presented.

REPRODUCTIVE FAILURE AND NEST SITE SELECTION OF TWO ESTRILDID FINCHES INACACIAWOODLAND

Summary Barnard, P. & Markus, M.B. 1990. Reproductive failure and nest site selection of two estrildid finches in Acacia woodland. Ostrich 61:117-124. Reproductive output of Blue Waxbills Uraeginthus angolensis (BWs) and Melba Finches Pytilia melba (MFs) was extremely low in the central Transvaal, South Africa, despite strict measures to limit observer disturbance. Eggs were laid in 5741% of nests built in 1985, and 2&Z% of nests in 1986. Between 0% and 20% of nests with eggs were successful, and &25% of individual eggs resulted in fledged young Predation, nest desertion and storm damage accounted for most failures. A substantial proportion of nests failed before they were visited, indicating a high rate of natural failure, and the number of nest visits did not appear to influence nest outcome. Both BWs and MFs chose well-protected, camouflaged sites, especially in the tree Acacia tortilis. However, neither dense thorns nor dense foliage, nor the presence of commensal wasps (Polistes and Ropalidia), safeguarded nests from failure.

A landscape taphonomic model of the scale of prehistoric scavenging opportunities

The character of degreased mammal bones scattered over modern East African landscapes is shown to provide a measure of competition among carnivores for fresh carcasses. The number of bones by which individuals are represented, skeletal part profiles, and the completeness of surviving bones are shown to differ among three settings: Ngorongoro Crater, the Acacia woodlands and grass plains of the Serengeti, and riparian woodlands of the Serengeti. These differences are correlated directly to the scale of scavenging opportunities previously documented for these ecosystems and habitats. The results are explicable through reference to the sequence in which spotted hyenas consume carcass parts, and their competitively-induced motivation to destroy bone before its edible contents decompose. The landscape assemblages provide a taphonomic model for estimating the degree of competition for carcasses in prehistoric settings. Such estimates are a prerequisite for assessing the frequency by which prehistoric hominids may have acquired and consumed food from scavenged carcasses.

The population ecology of Glossina pallidipes Austen (Diptera: Glossinidae) in the Lambwe Valley, Kenya. I. Feeding behaviour and activity patterns

AbstractInvestigations into feeding behaviour and activity patterns, basically by biconical trap sampling, were carried out as part of a study of the population ecology and dynamics of Glossina pallidipes Austen in the Lambwe Valley, Kenya. Host-preference determinations from blood-meal analyses showed that over 80% of feeds constantly derived from bushbuck, buffalo and bushpig, in roughly equal proportions. Activity cycles in relation to feeding and pregnancy, investigated by mark-release-recapture and physiological methods, indicated four-day feeding intervals for males and three-day ones for females. The periodicity was more variable in males, and in females was contingent upon reproductive events, with feeding mainly taking place just before the in-utero moult of the second-instar larva to the third instar, just after larviposition and again at a more variable time during pregnancy. Comparisons of nutritional status from size, weight, and fat and haematin levels showed that flies from thicket had consistently greater fat reserves than flies from Acacia woodland and conifer plantation. No seasonal differences were found, nor any relationships between other variables. Based on hourly sample data, both sexes showed unimodal diel activity patterns, but with clear differences. Activity was most closely correlated with temperature, to a lesser extent with saturation deficit and least with light intensity, and better correlations were obtained with females than males. Diel activity patterns in both sexes were also age-related, and from the close similarity found between male and virgin female activity patterns it was inferred that male activity around traps was partly sexually oriented. Using electric screens in conjunction with biconical traps, comparisons between flies attracted to traps and those actually caught showed that traps were relatively more efficient in catching males than females, but captures were representative of the active population in terms of age and pregnancy.

Assessment of Competitive Interactions between Two Iguanid Lizard Species

In riparian mesquite acacia woodland in SE Arizona, we found tree lizards (Urosaurus ornatus) occupying trees with yearling spiny lizards (Sceloporus magister). To examine possible short-term effects of the larger spiny lizard on the smaller tree lizard, we analyzed the joint distribution of resident lizards, and dry season growth rates and residency times of tree lizards in the presence and absence of spiny lizards. Despite a significant positive association in the distribution of lizard species, we could detect no reduction in growth rate or residency time of male and female tree lizards that were resident with spiny lizards. To investigate changes in tree lizard behavior in association with spiny lizards we enclosed 1-m lengths of mesquite branches to confine lizards to a restricted area of their natural habitat. Control tree lizards were introduced to the enclosure and their occupation time on the branch was recorded. Lizards could leave the branch by attempting to climb the metal partition or by jumping from the branch. The same (control) tree lizard was introduced to the branch enclosure with a spiny lizard; however, for each tree lizard the order of control and treatment was randomized. In another set of trials we increased ant density on the branch enclosure and recorded the feeding rate of tree lizards. Spiny lizard yearlings had no effect on either the time tree lizards were on the enclosed branches or the feeding rate of tree lizards.

Diagramme pollinique d'un sondage Pleistocene superieur—Holocene du Lac Bogoria (Kenya)

This paper presents the palynological results obtained from Late Pleistocene-Holocene deposits of Lake Bogoria (990 m), Kenya. It documents the floristic and climatic environment of the lake for the periods between 28,000 and 14,680 B.P., between 15,000 and 11,000 B.P. and after 4500 B.P. These pollen data confirm the geological, sedimentological and limnological data on the hydrological evolution of the lake and the relationship between high level stages-rainfall. The results show a humid episode somewhere in the period between 28,000 and 14,680 B.P., a cold and dry one between 15,000 and 12,000 B.P. and a humid phase again between 12,000 and 11,000 B.P. Another major vegetation change, as witnessed by the extension of coniferous forests and of Acacia woodland after 4500 B.P., is related to the onset of drier conditions over East Africa.