摘要:

SummaryMany investigations have made contributions to an understanding of energy flow through large mammals in East African ecosystems. This paper lists references to such works and compiles them according to their application to various segments as they appear in an energy‐flow model. The first part indicates papers on pasture utilization, value of foodstuffs, animal numbers and distribution, population dynamics and secondary production. The second part assembles references dealing with individual animal species, stratifying them according to the subjects of ecology, food habits and nutrient utilization, population dynamics and growt

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00215.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryFour crocodile populations have been examined by aerial photography with a view to assessing their length frequency distributions.The assumptions, and the limitations attached to such assumptions, necessary to convert length frequency information into information on the age structure, and hence the status, of the population are considered.Environmental conditions of value in understanding the status of the populations are listed.The Victoria Nile population is considered to show adequate recruitment, but dispersal of young crocodiles tends to give the converse impression. The population is probably stable and has not been heavily exploited in the past.The Grumeti River population may represent a local aggregation mostly of large males from Lake Victoria, probably retreating from human induced pressures. There is little recruitment through breeding, and the largest crocodile encountered in this study are members of this population.The Lake Rudolf population is a typical healthy population with high recruitment and high juvenile mortality. The population is probably stable, but may be expected to decline as fishing interests on the west shore expand. Growth is retarded in the Rudolf population.The Lorian swamp population is expanding rapidly probably after a period of heavy mortality wrought by hunters shooting for skins. The present conflicts with human/livestock interests is expected to increase, resulting in stabilization and decline of crocodile in the swamp.Some comments are made on the possible influence of various environmental parameters on present status and trends of the populations.

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00216.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryAs part of a broader ecological investigation, in the framework of the Tsavo Research Project, food habits of lesser kudu have been studied during 2 y in Tsavo National Park (East).Free‐ranging lesser kudu were observed, from a Land Rover, while feeding in different habitats and at different times of the year. Each time one animal fed on one individual plant was noted as one “food record”; some 2000 records are analysed in this paper.Leaves of trees and shrubs constitute the main bulk of the diet of lesser kudu. Creepers and vines, herbs, grasses, fruits and tubers of some root succulents contribute variable but relatively small proportions of the food.Pronounced local and seasonal variations in the composition of the diet were found. Local variations are mainly a result of differences in the vegetation of the different habitats. Seasonal variations are caused by changes in the vegetation's condition, depending on rainfall. Deciduous trees and bushes, herbs, climbers and grasses account for much smaller proportions of the diet during the dry season, when evergreen species are crucial for survival.Lesser kudu feed on a wide variety of plants, utilizing all layers of the vegetation that they can reach, at least to some extent. A total of 105 plant species have so far been recorded as being eaten by lesser kudu.With regard to food only, the vegetation changes in Tsavo National Park do not appear to have had any adverse effects on the population of lesser kudu. However, the amount of suitably structured habitat has been substantially reduced in recent years. If present trends continue, it may decrease further, to the point of jeopardizing the future of lesser kudu in large parts of Tsavo National

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00217.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryCoincident with the shooting out of hippopotamus in May 1958 20 permanent 30.46 m line intercept transects were established on the denuded grassland of the Mweya Peninsula, Queen Elizabeth National Park, western Uganda, to assess botanical changes in basal cover, species composition and frequency. Between May 1958 and May 1959, grass basal cover (GBC) decreased from 14.7% to 5.3% and bare ground increased from 78.3% to 83.6%. After four years total ground cover was 10.9% GBC, 27.2% litter, 1.3% dicotyledons and 60.6% bare ground.Changes occurred in grass species composition. The perennial carpet grass,Chrysochloa orientalis, declined from 37.7% GBC (transect frequency 100%) to 6.6% (87%) by May 1962. Bunch grasses showed marked recovery:Sporobolus pyramidalisincreased from 8.0% GBC (60%) to 27.6% (100% frequency).Cynodon dactylon, initially prominent in two lakeside transects only, declined from 9.2% GBC to 2.1%, then became re‐established in inland localities and recovered to 11.7% GBC.The variable rainfall (714 mm annual average) and its influence on plant growth is discussed and the advantage of mechanically increasing effective rainfall mentioned. Authorities for plant names are given in Table

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00218.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryThe paper concerns the circumstances surrounding the collection of ivory from dead elephants, with particular reference to Murchison Falls National Park.The characteristics of the interval between death and complete disintegration of an elephant are described. These, combined with observations of known age skeletons, comprised the criteria used in classifying skeletons found from the air into three relative age classes.Average annual mortality is estimated for the population north of the Nile (MFPN) at 147 animals yielding 1945 kg of ivory, and for that south of the Nile (MFPS) at 474 animals yielding 7497 kg ivory. Park‐found ivory records are analyzed for the 11 y 1959–69. The expected age distribution of deaths is compared with the observed. For MFPN a bias in favour of large (male) tusks is present, explicable by the concentration of ranger search effort in areas of known high male density. For MFPS a bias towards small tusks is thought to be caused by elephants wounded outside the park dying inside it.The National Park recovers an average of 27.6 % of its available ivory per annum, with large annual fluctuations probably correlated with the incidence of wounding outside the park. High losses to poachers are evident.An aerial search for ivory showed a tendency for elephants to die near watercourses. A finding rate of one carcass every 4.3 km of watercourse was obtained. As only 5 % of carcasses still had tusks the aerial searching was prematurely terminated. The results indicated a finding efficiency of 26.4% of the available current year carcasses. Comparative costing suggests that ground searching would be a more efficient method of finding ivory than aerial searching. The high value of the available ivory in Murchison and other areas justifies intensive searching. The low collection rates prevailing in East Africa are largely attributable to the absence of appropriate search effo

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00219.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryNight counts of hares and other animals were made on a disused airstrip in the Queen Elizabeth National Park, Uganda and on the road between Magadi and Nairobi in Kenya.Lepus crawshayiis the only species of hare which occurs in the Queen Elizabeth Park butL. capensisis also found in Kenya. No regular seasonal fluctuations were found in the number of hares recorded due probably to the continuous breeding of these equatorial species. The number of waterbuck seen in Uganda on moonlit nights was significantly greater than that counted on dark nights. This is not thought to be due to better viewing conditions under a full moon since the phenomenon was not found with other species. The number of hares recorded varied inversely with the number of other mammals present but bore no relationship with the number of birds. It is concluded that night counts can be useful in revealing population trends but not for assessing total numbers or for comparing densities in different areas.

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00220.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryAt least ten major mineral licks occur along the Gaji River which bisects the Yankari Game Reserve. The licks show varying degrees of utilization and have craters of up to 1200m3in volume. Three hundred and eighty five hours of observation were kept at one of the licks. Its use by different species was highly variable. Some species occurring in the reserve made no visits to the lick, whereas Western hartebeest (51 groups), waterbuck (53 groups) and warthog (276 groups) made frequent visits. Lick use was much greater in the daytime than at night, with the peak occurring around 1400 h. A limited number of soil samples (29) were analysed but no single element can be considered as the factor attracting wildlife. However, the lick areas were richer in most minerals than were samples of soil from drier habitat in the open woodland. It is possible that significantly increased lick use might in the future indicate degrading environmental conditions in the drier parts of the reserve. If hides are constructed, the commonly utilized licks will provide excellent opportunities for behaviour observatioii and photography by tourists.

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00221.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryData collected from 265 cropped Thomson's gazelle in northern Tanzania have permitted development of ageing criteria based on weights, horn growth and dentition.Most deciduous teeth are replaced between 12 and 15 months of age and the third molar becomes fully functional at nearly 2 y. Asymptotic horn length of about 32 cm is reached by males at 20–24 months. Dressed carcass weights were about 60 per cent of live weights, being slightly higher in males and higher in January than February. Females are capable of breeding before 1 y. Only single foetuses were found and these only in the right uterine horn. There was evidence of lambing every month but with May and November peak

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00222.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Summary1. Aerial and ground counts in the Queen Elizabeth National Park from 1963 to 1969 indicate that the number of elephants has more than doubled. The increase appears to be the result of immigration rather than reproduction.2. Elephant food habits were studied for 10 months in two areas of the Park. In the short‐grass/thicket area, browse intake rose markedly whenever the rainfall fell below 50 mm/month. In the tall‐grass area without thicket, herbs were eaten frequently during the rains andCymbopogongrass bases in the dry season.3. Food availability had an important influence on the diet of elephants. Sometimes, however, elephant were very selective, e.g. forPanicum maximum, Azima tetracantha, Securinega virosa, andTribulus terrestris. Certain grass inflorescences were selected during the rains, and bases in the dry season.4. Most browse was consumed in the thicket area during the dry season and most grass was eaten in the tall‐grass area of the Park.5. Stomach and faecal samples gave a similar result and indicated that the diet in the tall‐grass area was comparable to that of elephant in Murchison Falls National Park.6. Analyses of important plant species showed that, in general, tall‐grass had a lower crude protein content than short‐grass, herbs and browse. Browse leaves had a relatively high crude‐protein content in the dry season. Differences were less marked in the rains.7. Ether extract, or fat content, was high in browse leaves and inCymbopogon, in particular its bases. These may have been selected in the dry season for this reason.8. Grass and browse stems were very fibrous and this may have contributed to their being avoided.9. High carbohydrate levels probably enhanced the palatability of grass bases and browse leaves.10. Grasses were very siliceous, in particular their bases when contaminated with soil. Elephant took considerable trouble to remove soil. Browse leaves had little silica but were rich in other minerals, and this may have contributed to their greater palatability.11. Studies of woodland dynamics show a decline in large trees which corresponds to the increase in elephants. In some cases trees have been almost eliminated. Damage to trees indicates that a most important factor in their decline is the elephant. There is some evidence that the trees are eliminated selectively.12. In the tall‐grass area there has been an increase of 46.3% in elephant numbers, but a decline of 80.3 % in buffalo, over the past 15 years. An overall decline in combined biomass of 36.9 % is calculated. Estimates of energy utilization of the annual vegetation production by elephant and buffalo indicates a decline from 6.1 % to 3.9% o

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00223.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SummaryThis study surveyed the use made by springbok, hartebeest, wildebeest and gemsbok, in particular, of mineralised artificial waterholes along the Nossob river in the southern Kalahari and the effects of this use on the delicate surrounding habitats, as a basis for evaluating the uses and limitations of such water in the management of these species. Taking into account the chemical composition of the dissolved salts in the water; the status of the vegetation and conservation trends near water holes; the relative use made of the waterholes by the antelopes; and land use history, it was concluded that: (a) the animals made regular use of the water, some of which was more mineralised than that recommended for domestic stock, including sheep; (b) there was no relationship between the total dissolved salts and animal use, although there may have been some association between gemsbok use and certain ions; (c) wildlife attracted to boreholes had very little effect on the stability of some surrounding habitats, but may have retarded recovery in areas downgraded by past land use, and (d) under these circumstances the effects of this land use were still amply evident after 21/2decades.From this and other evidence, it is suggested that, at the present level of knowledge, mobile wildebeest populations can be stabilised by the provision of relatively potable water, and mineralised water may be used to raise the levels of springbok, hartebeest and gemsbok populations. However, as the water is less of a limiting factor than for species requiring regular drinking water, the increase in density may be relatively limited and so less of a danger to the maintenance of surrounding habitats.

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1971.tb00224.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY