摘要:

SummaryThe results are presented of a 2‐month study of the Mara River hippopotamus population in the Serengeti National Park and the Maasai Mara Game Reserve. A method for correcting aerial counts of hippos in turbid rivers and based on herd behaviour characteristics is described. There were an estimated 1927 hippos at an average density of 16‐1/km in the area censused. The population became more dispersed and the mean group size decreased from thirty to fifteen after a rise in water level. The value of comparisons between populations in various terms of expression of density, and mean group sizes, are discussed. The amount of day living space, defined as areas preferred or utilizable by hippo during the day, and productivity of the food plants are seen to be very important factors in hippo habitat utilization, and as constraints on population increase.Hippo use of the habitat and the effects of hippo on the vegetation at various distances from the river were quantified, and a cycle of vegetational changes suggested which may be associated with the effects of hippo grazing and fire in other parts of Africa.Groups were found to consist of nearly equal numbers of males and females. There was no evidence of territorial behaviour either on land or in the water. A number of observations on social interactions and defaecating behaviour are described and indicate that olfactory communication is very important in interactions between hippos. Hippo society is unstable due to climatic influences, but a dominance hierarchy including males and females exists in the groups. Males appear less firmly attached to groups than females, but a male is normally the dominant animal in a gr

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1974.tb01036.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryEighteen elephants were followed individually in the Rwenzori National Park, Uganda for varying periods and their activity noted at 4‐min intervals. Continuous data extending over 24 h or more were collected from seven of these elephants. About 75% of the total time was spent in feeding and about 75% of the feeding activity consisted of grazing or feeding at ground level. There were three feeding peaks, one in the morning, another in the afternoon and the third around midnight. The feeding rate tended to increase during the day. The proportion of the total feeding time spent in browsing increased in the dry season. Walking took place mainly at dusk. The principal sleeping period occurred during the small hours of the morning with a shorter rest period in the early afternoon. The elephants defaecated about eleven times in the 24 h and drank an average of 1–3 times. The rate of progress through the bush averaged 0–5 km/h. Comparisons are made with published data concerning the activity patterns of waterbuck and warthog in the Rwenzori Park and of elephants in the Tsavo National Park,

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1974.tb01037.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryEvidence is presented to show that both the quality and quantity of food available to a buffalo population falls below the minimum maintenance requirements of that population at certain times of the year. In the Serengeti grasslands there was a shortage of the only good quality component, grass leaf, in the dry season, with the result that the animals consumed an increasing proportion of poor quality food such as grass stem. By the end of the dry season the diet had dropped in quality below the minimum maintenance level. In areas such as Mt. Meru where there was a more continuous growing season, the high density of animals kept the standing crop of leaf at a low level. During the cooler dry season the growth of leaf became insufficient in quantity for the maintenance requirements of the population. These two quite different situations suggested that food shortage was a more general phenomenon in eastern Africa.Various measurements of feeding behaviour were made. Total grazing time per 24 h did not differ between seasons but ruminating time may have increased as the season became drier and could have been a response to the more fibrous food. Analysis for cycles of activity showed that there was more temporal organization during the dry season. These changes in activity cycles appeared to be related to the increase in energy expenditure produced by heat stress and sweating. Old animals with poor teeth did not compensate for the poor food supply by changing their feeding behaviour.There was a positive relationship between annual rainfall and mean crude density in different areas of eastern Africa, indicating that regulation was taking place. Since rainfall determined the amount of available food, it could have operated through the food supply. On a finer scale it was found that the extent of the preferred riverine habitats was also related to density. Thus rainfall, the extent of riverine habitat and perhaps soil moisture were three limiting factors that determined mean density and all could have taken effect through the food supply.As a result of initial selective grazing the amount of available leaf declined as the dry season progressed to the extent that by the end of the season the proportion of this component in the diet fell to a very low level. The impact of the population on its limited food supply indicated that intra‐specific competition was acting as the cause of regulation. Measurements of wildebeest eating the same food in the same habitats as buffalo showed that inter‐specific competition was also taking place. A small proportion (7“) of the wildebeest population could have reduced the buffalo population by approximately 18o,‘, from its potential population size.The buffalo population in the Serengeti was regulated by adult mortality which was caused by undernutrition as a result of food shortage. This food shortage was caused by intra‐ and inter‐specific competition. The effect of predation and disease was to hasten the response of the population to changes in the food supply. The limiting factors determining the mean level of the available food were, amongst others, rainfall, soil moisture and the extent of the preferred riverine habitat. The effect of interspecific competition could result in a complex regulation of populations through their food supply. There appears to be no foundation for hypotheses which invoke over‐utilization or damage as a consequence of regulation

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1974.tb01038.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1974.tb01039.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0141-6707    

DOI:10.1111/j.1365-2028.1974.tb01040.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY