ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00086.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00087.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryLion population size is investigated by examining the effects of food supply and of aspects of social behaviour, on the factors which determine population size in a given area: the sizes of the lion prides there, and the sizes of the territories they occupy. Data come mainly from 7 years of records of two lion prides in the Serengeti.There is little evidence, but it is probable that territory size alters little. Pride size is best measured in terms of the number of adult females; it does not change in response to short‐term changes in food availability, and appears to be regulated.Factors causing change in pride size are examined in the same way. Reproduction is profoundly influenced by behavioural factors, and to some extent by food; cub mortality is strongly influenced by both. However, these appear to be relatively unimportant in population regulation since in practice whatever the levels of these factors, more than enough female cubs survive to replace adult losses, and only some are recruited, the rest being expelled. This recruitment is influenced possibly by food and certainly by behaviour, and appears to be density dependen

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00088.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryA series of censuses throughout Uganda showed that the population of marabou storks between 1970 and 1972 was of the order of 4000–5000 of which the majority were usually in Ruwenzori (formerly Queen Elizabeth) National Park. There were at least twenty breeding colonies totalling some 1300 nests.Marabous have two main types of food. Firstly, there is what might be termed ‘natural food’, such as insects and amphibia, and the poachings from carcasses. This is assumed to have been the only kind of food available to marabous until comparatively recently. The other type is food obtained as a consequence of human activity. In Uganda, the second category is now far more important than the first.The numbers of marabous at three sites are considered in relation to their food supply, and in each case it appeared that there was usually an excess of food. Against this background, consideration is given to those factors which might be limiting to the rate of increase of this species.Marabous have obviously benefited from human activity and have no doubt increased greatly in numbers as a result. Moreover, they are probably still increasing, and it appears likely that they will continue to

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00089.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryThis study was conducted from June 1968 to July 1969 and from August 1970 to December 1972 with information available for the intervening period as well as for the first half of 1968, giving records for approximately 5 years.The Nairobi Park lion population has averaged thirty animals with a high percentage (about 60%) of juveniles and a preponderance of females among the adults.Matings occurred all through the year but births showed a distinct peak during December and January. The correlation between number of kills one month and births 3 months later proved statistically significant, suggesting that the level of nutrition may influence fertility.Gestation period is about 110 days; litters, when first seen, averaged three cubs, sex ratio was 1:1. Cubs ioined their pride when 6–8 weeks old, but only if no cubs much older than themselves were present; reasons for this are suggested.Young males left their pride around the age of 2 years and so did most young females, although the latter occasionally stay on with their pride.Youngest age to conceive was about 2| years, intervals between litters averaged 2 years. The hypothesis is put forward that lionesses usually refuse to raise single cubs or those that remain sole survivors at less than 3 months of age. Some evidence to support this thesis is submitted.The reproductive performance of the Nairobi Park lions is compared with those in the Serengeti (Schaller, 1972). The Nairobi population's higher performance despite a higher density there suggests that numbers are still within the optimum. However, this balance is dependent upon a large surplus being able to disperse into the area adjo'ning the Park

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00090.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary(1) The population structure and breeding success of the Fish EagleHaliaeetus vocifer(Daudin) at Lake Naivasha was assessed in 1970‐71, as part of a wider pesticide residue survey. The figures obtained have been combined with those of an earlier population and breeding survey in 1968‐69.(2) Population structure was assessed by plumage criteria, dividing the total adults, subadults (early and late), 2 year‐olds, and recent immatures. Between 1968 and 1971 there was an increase of about 40% in the adult population on the lake, but immatures increased by only 11 %. The adult/immature ratio was 83: 17% in 1968‐69 and 85‐6: 14‐4% in 1970‐71.(3) From these data it appears that the age of Fish Eagles as adults lies between 16 and 24 years, with a total age of 20–28 years. This is much longer than observed wild life spans in some other eagles.(4) Although the total population rose, the number of breeding pairs was constant, fifty‐six in each year of survey, with minor changes.(5) Breeding success overall is about 0–47 young/pair/annum for both years combined, varying greatly between different parts of the lake and from year to year. As only two thirds of all pairs lay, and some of these fail, this equals 0–74 young/pair which bred and 1–28/successful nest.(6) Breeding success at Lake Naivasha is considered to be unaffected by human interference, either deliberate or casual.(7) Analysed by habitat, pairs which bred near wide lagoons within the papyrus were markedly more successful than those with access only to open water (0–55 young/ pair/annum overall cf. 0–29). The possibility that this is due to superior food opportunities in the lagoon habitat is discussed. Fish Eagles can catch birds and fish, and pirate other species kills in lagoons, whereas they must catch all their own fish prey in the open lake sites.(8) Preliminary observations of diurnal behaviour do not indicate that Fish Eagles with access only to open water have any more difficulty in catching prey than those in lagoons, so that the relation between food supply, habitat, and nest

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00091.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary(1) The insectivorous batT. pumilaliving at Entebbe latitude 0o6'N breeds throughout the year. However, it exhibits peaks in its breeding cycle which appear to coincide with the two rainfall peaks which occur at Entebbe and in Uganda generally; a low one in October‐November and a higher one in April‐May.(2) The other insectivorous batT. condyluraliving at Bukalasa latitude 0o43'N exhibits a bimodal breeding rhythm also closely correlated with the rainfall pattern at Bukalasa which is similar to that at Entebbe.(3) Rain may therefore be an important proximate factor in the breeding of these bats while food (insects) may play an important ultimate role.(4) One young per bat is the rule and implantation which always takes place in the right horn of the bicornuate uterus of both species is unilateral.(5) The gestation period inT. condylurais about 2 months and inT. pumila, it may be shorter than this.(6) Both species develop and mature rapidly and as they are often found living together, the difference in their breeding patterns is advantageous in that it helps to reduce competition between t

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00092.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryA brief review of published data is presented, outlining the intensive exploitation of African elephants for ivory. Records suggest that this began in the early seventeenth century in western Africa, and that hunting pressure was sufficient to eliminate, or drive out, populations over wide areas. In eastern Africa intensive exploitation ensued between 1840 and 1890, leading to a sudden collapse of the ivory supply from over‐exploitation. Subsequent protection has apparently enabled surviving elephants to enter an exponential phase of population increase. Elephant population cycles, if they can be shown to have occurred, are probably reflections of over‐exploitation, followed by population recovery when hunting was no longer profitable. If cycles of scarcity and abundance were a natural feature of elephant populations, then they could have been masked by the intensity of hunt

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00093.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryA survey of the vegetation was undertaken in order to ascertain the browse production and its utilization by the existing community of animals in the park. The most prevalent types of woody vegetation areAcaciawoodlands in the drainage lines andCommiphora‐Combretumdeciduous woodlands on the uplands. As these formations are considered to provide the bulk of the available browse, the animal impact on the woody plants (mainly shrubs and young trees) in relation to replacement growth and regeneration, is the principle theme of the present paper.The method used for collecting field data is explained. The intention was to collect meaningful information on the composition and dynamic status of the vegetation in relation to the course of plant succession and possible causes of disturbance.For the present purpose, the data are treated so as to elucidate the effect of browsing on growth and growth on browsing. The main factors considered include, the distribution, status and structure of the vegetation; possible disturbances that may have caused changes from the state of naturalness; the distribution, frequency and density of the commoner species of shrubs and trees; the intensity and effect of browsing on woody plants, and the influence that utilization may have on the course of plant succession or decline.Conclusions are discussed in the light of conservation. On the one hand it is accepted that browsing animals have to be catered for. On the other, that the productivity and diversity of the vegetation should be maintained.A balanced situation is one in which utilization is replaced by growth. In these circumstances, both the primary and secondary productivity of the ecosystem is maintained. Both over‐utilizationandunder‐utilization would indicate an imbalance as a result of which productivity will be lowered.The survey indicates that only about half the available browse is currently utilized, and of this amount, most is replaceable by growth. On the average, not more than 1 % of any common species is so damaged that recovery is unlikely. Most of the species that are severely damaged are deciduous; those that are least damaged, but at the same time sustain the highest overall impact, are evergreen. Furthermore there is no conclusive evidence that the course of succession is impeded by utilization.The results of the survey do not, therefore, indicate that there is over‐utilization of the available browse. Other conditions being equal, the browse potential in the park should be sufficient to support the existing community of animals. However, the environment is not stable. The rainfall is low and variable. The vegetation is degraded and because grassy types of vegetation are extensive, the fire hazard is high. Undoubtedly there has been over‐burning for years and a programme of fire management is overdue.In these circumstances, the following recommendations are made. (1) Further field data should be obtained by using the method explained in this paper. (2) A programme of fire management should be initiated and carried out. (3) Utilization, replacement growth and the progress of plant succession should be monitored in order to ensure that the productivity of the area is being maintained or increased. In this way the goals of management in the park will be assured and it is expected that the browse potential in the park will be able to support a healthy and varied community o

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00094.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SummaryBy annual measurements of population size, fertility and recruitment on a buffalo population in the Serengeti it has been possible to construct a model that predicts the equilibrium level of this population. This model also suggests that the population is increasing towards an equilibrium position, and that adult mortality is the only regulating mortality needed to achieve this equilibrium. Juvenile mortality shows large fluctuations from year to year and potentially is the most important mortality in causing fluctuations in population size.By extrapolating the model population backwards in time it is possible to observe that the real population has experienced a higher mortality or lower fertility in the past, and there is evidence from the rinderpest disease at that time which suggests that this could have been a possible cause. The models can be adapted to incorporate changing conditions either from habitat change due to the population itself or from environmental change and hence this approach is potentially useful in solving certain population problems.

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1973.tb00095.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY