Showing papers in "African Journal of Ecology in 1970"

Elephants and habitats in north bunyoro, uganda

Abstract: Summary The paper is concerned with the changing relation between elephant populations and vegetation in north Bunyoro, Uganda. The history of the area over the past 100 years is briefly described, particularly in terms of changing human populations and contraction of the elephant range. The main features of the environment, including vegetation types and distribution, annual burning, other species of large mammals (including the results of aerial counts) and birds are described. The main results of investigations on the elephant populations in the area, dealing with numbers, distribution and movements, population density distributions, and social organisation iocluding group size frequencies and structure, are presented. From a population of about 10,000 elephants over 1,000 have been cropped or shot on control in the area since 1965. The results of detailed analyses of material derived from these operations are presented and discussed. Material from the cropping operations represents a cross-section of the population and all animals sampled have been aged from the dentition. It is concluded that the mean daily food intake (wet weight) is 4% of live weight for all classes except lactating females; results of studies of food quality are discussed and a possible explanation for the de-barking of trees presented. The physical condition of elephants in several populations has been compared and appears to be poorer when less browse is available. Growth equations are presented for height and weight; the male shows a post-pubertal growth spurt. Various reproductive parameters are examined including age at puberty, pregnancy rate, and the seasonal cycle. Seasonal conceptions are delayed in North Bunyoro in relation to their timing north of the River Nile and it is suggested that the delay is nutritionally-induced. Recruitment has been falling in this population and this decline is likely to continue in the absence of effective management. Some undesirable consequences of extensive control-shooting are mentioned. The analysis of the elephant populations indicates that they are at densities in excess of the carrying capacities of the habitats, and the continuing changes in these habitats are described. In the grassland and wooded grassland areas the destruction of woodland has progressed radially, a zone of damage about 15–20 km wide having moved outwards through the range. This is consistent with destruction mainly by elephants rather than by fire. The influence of elephants on the forest edge and on the areas of regeneration inside the forest, created by management, is described. Finally specific proposals that have been presented to the National Parks and Forest Department are discussed. These involve rational cropping of over 4,000 elephants over the range and the construction of elephant-proof barriers, the control of fire, and the declaration of a Conservation Area with a statutory Authority on which the various interests concerned would be represented.

Age criteria and vital statistics of a black rhinoceros population

Abstract: Summary Tsavo National Park, in Kenya, probably contains the largest population of black rhinoceros (Diceros bicornis (L.)) left in existence. Large-scale damage of the vegetation initiated by elephants and aggravated by fire has changed considerable areas of the park. The ecology of the black rhinoceros in this changing environment has been studied; the present status and population structure is considered here, including the development of detailed ageing criteria for the species, an analysis of natural mortality and survivorship, and a record of the structure of the living populations within the major habitat types. Crania and mandibles were collected from 506 rhinoceros found dead in all areas of the park. This material was divided into 20 relative age classes based on dental characteristics. Crude chronological ages, based on an estimate of the maximum expectation of life and the examination of seven known-age dental records of captive animals, were assigned to each age class. These crude ages were then refined by examination of 16 dental records of known-age wild rhinoceros, and a chronological age scale established. A survivorship curve of the population was thus constructed. Annual mortality during the first and second year of life is about 16%, and the indicated mean annual mortality from 5–25 y is 9.8%. A theoretical model of the population structure is shown, and analysis of the annual mortality and recruitment at birth suggests that the population was stable during the 1960's. Assuming the data represent a stable population the mean expectation of life at birth is 8.4 y. Thirteen major habitat types are described. The characteristics of the rhinoceros population within each habitat type were established both from ground studies and aerial observations. Nearly 700 rhinoceros were identified and catalogued on the ground, in sample areas selected for intensive study. Population structures, cow: calf ratios, and recruitment appear to be average in most habitat types. The analysis of recruitment at birth and mortality during the first year of life, both from computations from the survivorship curve and from the structure of the living populations, support the validity of the ageing criteria, and further suggest that the population was stable during the 1960's. Finally, the relationship between the elephant and the rhinoceros in the changing environment is discussed with reference to recent findings in elephant ecology. In conclusion it is recommended that population reduction of the Tsavo elephants should be initiated.

Food habits of wildebeest, zebra, hartebeest and cattle in kenya masailand

Abstract: Summary A study was conducted of grass selectivity shown by four herbivores on open range lands of Kenya Masailand. At four seasons over one year, wildebeest, zebra and kongoni (Coke's hartebeest) were taken. Stomach materials and faeces were sampled from each animal. Faecal samples were collected from cattle that had been grazing in the same area. Simultaneously, vegetation availability assessments were made. A comparison of techniques for determining the food selectivity indicates that faecal and stomach-content analyses provide similar results when the diets are almost entirely grass. The selectivity exhibited by the four herbivores was determined by faecal analyses. Three grass species were preponderant in all diets as well as in the available menu. In comparing the selectivity shown for the three dominant grasses there is a high degree of similarity even though statistical differences are demonstrated. All animals favoured Themeda triandra over Pennisetum mezianum and Digitaria macroblephara. Kongoni displayed the highest degree of selectivity and cattle and zebra had the greatest similarity in diets. Each animal species had a wide spectrum of grasses in their diets: these contained a greater number of species during the drier seasons than during the rainy seasons. Wild animals had a greater diet variation between seasons than did cattle, the diet of the latter remaining much more consistent than the combination of available grasses.

Food preferences of black rhinoceros in the tsavo national park

Abstract: Summary Food preferences of the black rhinoceros population in Tsavo National Park, Kenya were studied from 1967 to 1969. Feeding rhinoceros were watched for a period of 1 h, and the plants which they selected and rejected were identified, either as they were feeding or when they had moved on. A technique was used which provided an indication of the relative importance of certain plants in the diet during the wet and dry seasons. A total of 70 h was spent actually watching feeding rhinoceros in six habitat types representative of the changing ecosystem; 3,600 feeding stations were examined. Black rhinoceros were observed eating 102 species from 32 botanical families. In all habitat types the rhinoceros is very selective for herbs and shrubs, and shows a marked preference for legumes. Available grasses are very rarely eaten. Results of food preference studies in other areas of East Africa are compared with the present study. It is suggested that the abundance and distribution of certain kinds of leguminose flora may be the key to an optimum black rhinoceros habitat.

Appraisal of condition estimation methods for east african ungulates

Abstract: Summary Previously proposed methods of determining physical condition of game animals are discussed. A total of 286 African ungulates of ten species were collected and autopsied, and several indices of physical condition were calculated. Selected indices were correlated with total fat or total lean percentages or both. Of the methods discussed and evaluated, those based upon fat deposited in particular areas were more accurate or feasible than those based upon blood constituents, adrenal weights, or body weight/skeletal measurement ratios.

The banded mongoose, mungos mungo gmelin

Abstract: Summary The banded mongoose is a social, diurnal, medium-sized carnivore classified in the family Viverridae. Packs of up to 32 animals were found to occupy a single, old termite mound for periods in excess of 2 months. Nine out of ten dens were in termite mounds, the other was in a gully. One den was excavated to show structure. The whole pack occupied the central chamber each night. One group of 32 consisted of 17 adults, 7 juveniles, and 8 babies too small to leave the den with the pack during the day. The animals were strictly diurnal, usually leaving the den about one hour after dawn; time of return was more variable, but was usually during the hour before dark. Senses of sight, smell and hearing were found to be very acute. During the day the packs covered large distances, foraging as they went. During the period of study, food (estimated by dung analysis) consisted almost entirely of Coleoptera (mainly dung beetles) and millipedes. The packs followed the trails of elephant and buffalo and obtained most of their food from their dung. Detailed behaviour is described. Mating was seen on three occasions and two males were seen to copulate with the same female. Family size was not determined, but eight young were seen to be suckled by three females indiscriminately. One mother looked after all eight young during the day when the pack was away. The animals used communal defaecating areas on and around the den, the faeces being scattered over the surface of the ground. Reactions to various animals, including predators, are described. When caught in the open the pack tended to bunch together acting as a single unit. If bushes were near they used them for shelter. Adaptations are discussed.

Some observations on the sitatunga in kenya

Abstract: Summary A 16-month study was made of sitatunga in a swamp in western Kenya, with particular reference to distribution within the habitat, daily activity, and food preferences. Absolute figures for density could not be obtained because of observational difficulties, but there was a minimum of 7.3 animals/linear km of swamp, or c. 55/km2. The sitatunga preferred areas of swamp adjacent to patches of gallery forest, and areas where there was deep water and a dense growth of tall reeds. They were most active during the first five and last two hours of daylight, and at night. Much of this time was spent feeding. Feeding behaviour and food preferences were studied. The sitatunga usually moved along well-marked tracks through the swamp vegetation; some of these led to beds of flattened plants, raised above water level, which were probably used for resting and for breeding. The latter took place in most months of the year, with a possible peak in November. Calves remained hidden for some weeks after birth. Group size and structure were examined; most sightings were of single animals or groups of two. A majority of these two groupings were composed of adult females. The proportion of immature animals seen indicated a healthy population. Courtship behaviour was observed 18 times and mating once.

Observations on the food habits of tame warthog and antelope in uganda

Abstract: Summary Monthly observations were made of the food habits of tame warthog, reedbuck and kob over a period of a year. Measurements were taken of the shoulder height and size of mouth of the animals at different stages of their growth. Whilst a few species of grass were regularly preferred, the majority showed fluctuations in their preference. Some consistent seasonal differences were apparent. Most herbs were avoided. Large differences in food habits occurred between warthog and antelope; however, there was some overlap during the rains when food was abundant and at the height of the dry season when it was scarce. Some differences were apparent between kob and reedbuck and between individual warthog and reedbuck. Intraspecific differences, however, were less noticeable than interspecific differences. The height of the animal and the size of its mouth were important in determining the portion of the sward available for food and the degree of selection possible within the available food supply.

A quantitative study of the daily activity of the warthog in the queen elizabeth national park, uganda

Abstract: Summary Warthog activity was recorded at 4-min intervals for continuous periods of 14 h on three consecutive days. The major activities were feeding or lying down and walking. The amount of time spent in feeding is related to the size of the animal and maximum-intensity feeding occurs in the early morning and in the late afternoon and evening. The animals drank usually only once each day. Adult females urinate much more often than males and this is thought to be a behavioural adaptation whereby the males can tell whether or not a female is in heat.

Crocodile distribution and status in the major waters of western and central uganda in 1969

Abstract: Summary 1 This report presents the results of a survey into the current status of the Nile crocodile in the major waters of central and western Uganda, made on behalf of the Uganda Fisheries Department and the Trustees of the Uganda National Parks. 2 The waters covered by the survey are described briefy 3 Crocodile numbers and distribution were assessed by diurnal aerial counting and nocturnal ground counts as described by Graham (1968). The major sources of error inherent in these techniques are recognised and discussed. Efforts to reduce bias in results included the use of a light helicopter to obtain data for comparison with those obtained from a conventional aircraft. Comparative costs are also presented. 4 Inaccessible areas of dense papyrus were searched at night from a helicopter equipped with a spotlight. 5 Information was obtained from fishermen in Lake Albert on the status of crocodile to corroborate other results. 6 The analysed results of aerial and ground counts give estimates of less than 100 crocodile outside the Murchison Falls National Park, indicating the species' reduction to the status of an ‘occasional’ or ‘rare’ animal. Within the National Park crocodile occur in two populations separated by the Murchison Falls. Below the Falls it is estimated that there are 1064 crocodile, and above 433. 7 By use of aerial photography 369 crocodile from the larger of the National Park's populations were measured for length. From Graham's (1968) age/length data, age classes are ascribed to those measured. This, together with data from the counts, permitted the computation of a survivorship curve for the population. This is presented with two possible alternatives. From these curves it does not appear that the population is declining through lack of recruitment. 8 From the aerial photographs river banks are classified into four crude categories. By relating crocodile in the photographs to the nearest bank category, it is shown that they have a marked preference for sandy banks over swampy shores, hard flat earth or cliffs. It is also shown that smaller crocodile make more use of swampy areas than larger specimens. 9 Biomass densities for both crocodile populations in the National Park are computed. The larger shows a biomass of 347 kg/km of shoreline which compares with 350.2 kg/km for Lake Rudolf (Graham's (1968) data modified), the smaller 75.3 kg/km. 10 The decline of crocodile in Uganda is attributed to expanding human populations and over-exploitation for skins. 11 Recommendations for the future conservation and management of crocodile are presented. These are based on reducing immature mortality rates by hatching eggs and artificially rearing small crocodiles for a period of 6 months after hatching. Some of these should be used to augment recruitment in the National Park populations, and the surplus placed in other waters until of an exploitable size.

The head of the forest hog, hylochoerus meinertzhageni

Abstract: Summary A description is given of the external features, the muscles moving the rhinarium and lower lip, the jaw muscles and the muscles attached to the occiput in a yearling male Hylochoerus. Rubbing places and scrapes made by the animals in their natural habitat, possibly in search of small invertebrates, are described and certain features of the skull architecture and musculature are considered in relation to the chewing mechanism.

Preliminary observations on food hawits of gerenuk in tsavo national park, kenya

Abstract: Summary In the context of widespread vegetation changes in Tsavo National Park, food habits of gerenuk are being investigated; the present paper gives an account of the results obtained during the first year of the study. Feeding of free-ranging gerenuk was observed from a landrover in two study areas with different vegetation types. Plant species eaten were determined in the field or collected for identification. Gerenuk feed almost exclusively on leaves, shoots, flowers, and a few fruits of trees and shrubs, as well as some climbers and vines, the latter mainly during the rainy seasons. No small herbs or grass were found to be eaten. The composition of the diet differed considerably between the two study areas, largely as a result of differences in the available vegetation. Seasonal variations in the diet are brought about mainly by variations in the availability of different food plants, notably the ratio between deciduous and evergreen species at different seasons. On the basis of a preliminary quantitative survey of the vegetation in the study areas, actual preferences have been evaluated. Some common plant species were found to be rejected altogether, although they are eaten by other browsing animals. A total of 68 plant species has so far been recorded as food plants, indicating that gerenuk are able to utilize a wide range of plants. In view of this adaptability, and of the abundance of preferred food plants in the study areas, the vegetation changes in Tsavo National Park do not, at present, appear to endanger the continued existence of the gerenuk.

The reaction of a group of rothschild's giraffe to a new environment

Abstract: Summary The behaviour of a translocated group of 11 Rothschild's giraffe (Giraffa camelopardalis rothschildi Lydekker) was studied for 9 weeks in 1968. A comparison was made between their new and former habitats, the food plants eaten in both places, and behaviour. For 3 1/2 months after release, they appeared to have settled in the area, but they suddenly started extending their range. Possible reasons are suggested for their failure to stay in the release area and their eventual disappearance.

The ageing of impala from a population in the kenya rift valley

Abstract: Summary Material from 100 impala from a mainly grazing population in the Kenya Rift Valley was investigated to establish age criteria applicable in both the field and the laboratory. Methods relate to tooth eruption, replacement and attrition; horn development; skull and long bone growth and ossification. Determinations are related to the main calving seasons, which occur with two peaks at the time of the long and short rains. All results are approximations which have an accuracy of ±2 months up to physical maturity at an age of c. 2 y. Age determination in animals from 3–8 y appears to yield reliable results with an accuracy of ±6 months at the lower end of the scale, and ± 1 y or even 2 y in older animals.

The diet of duck and coot on lake naivasha

Abstract: Summary 1 The diet of coot and duck on Lake Naivasha has been investigated to provide information on the duck/coot interaction. 2 Some 79 duck and coot were shot in a limited area over a period of 24 h, and their stomach contents preserved in 4% formalin. 3 The analysis of stomach contents was performed in two stages: large particles being completely identified and counted, small particles being sampled. 4 The results of the analyses are considered to be most usefully expressed as proportions of food component by number of particles. 5 Identification of components has been made by matching epidermal characters with collected plants, by matching shape and structures of seeds with collected seeds, and by recognition of such materials as arthropod exoskeletal fragments and molluscan shell. Some components have not been specifically identified. 6 A discussion has been presented on the problem of relating the results of stomach-content analysis to ecologically significant differences in feeding. The discussion hinges on four questions: (a) Is the result of a stomach-content analysis an accurate and appropriate indication of the stomach-contents of a bird when shot, and, if so, do the results presented indicate differences between stomach contents? (b) What is the relationship between stomach-contents at the time of shooting and food ingested over the immediately preceding period, and do differences between stomach contents indicate differences in food intake? (c) How far do differences in diet so deduced apply to the whole population of birds concerned in the study? (d) Are the differences in diet relatable to availability of food, and can any valid inferences be made concerning the birds' interaction? 7 It is concluded that at the time of the shooting, over the limited area examined, there was little overlap in diet for important components, and therefore probably little competition for food among the duck species and coot. 8 Some general observations have been made on the feeding biology of duck and coot, and it is pointed out that the feeding apparatus of coot differs from that of all duck species in having shearing edges. This difference is related to the dietary differences in a predictable manner.