Showing papers by "R. J. van Aarde published in 1987"
TL;DR: It was shown that the distribution pattern of the grazing-path could intuitively reflect the characteristics of the habitat utilization by livestock, being in accordance with the results of tracking grazing, and the major factors affecting the features of grazing- path were screened by redundancy analysis.
Abstract: Taking the Berberis aggregate shrubs in the ecotone of dry valley and montane forests in upper reaches of Minjiang River as study objects, and by the methods of tracking grazing and field survey, this paper studied the characteristics of habitat utilization by livestock and the features of grazing-path. The major factors affecting the features of grazing-path were screened by redundancy analysis (RDA), and the relationships of the grazing-path features with the coverage, size class, and distribution pattern of the shrubs were analyzed. It was shown that the distribution pattern of the grazing-path could intuitively reflect the characteristics of the habitat utilization by livestock, being in accordance with the results of tracking grazing. The Morisita index at 5 m scale could objectively reflect the distribution type of the grazing-path. Sample plots 1, 2 and 6 presented a contagious distribution of grazing-path, while the other plots showed regular distribution. In slope scale, the coverage and height of the shrubs were the notable affecting factors, which had negative correlations with the grazing-path features. There was a significant negative correlation between the coverage of B. aggregate population and the area of grazing-path. The population structure of B. aggregate had a close correlation with the distribution of grazing-path. The ratio of the long axis to short axis of the shrubs was averagely 1.29, and the shape of the shrubs approached to round. It was considered that the grazing-path landscape and the livestock on the grazing-paths had the function of reconstructing the shape of the shrubs. The directionality of the population pattern of B. aggregate was generally in line with the distribution type of grazing-path, but actually, they were opposite in distribution. The patches of the shrubs were in aggregated or uniform distribution in the areas deviated from the grazing-path.
71 citations
TL;DR: Examination of age-specific survival, mortality and fecundity rates in a population, evaluates the roles of possible density-dependent changes of population parameters in the regulation of porcupine numbers, and describes the life history strategy of the species.
Abstract: The Cape porcupine is a large (12.0 kg), nocturnal hystricomorph rodent and widely distributed throughout southern Africa. The present paper examines age-specific survival, mortality and fecundity rates in a population, evaluates the roles of possible density-dependent changes of population parameters in the regulation of porcupine numbers, and describes the life history strategy of the species. The study is based on data sets obtained from animals collected during 1977/78 and during 1981/82. Changes in demographic characteristics are ascribed to an artificial reduction in density, resulting in the relaxation of social factors inhibiting reproduction in young adults.
17 citations
15 citations
TL;DR: The observations and data on the age structure, obtained from skulls in the paddock, were used to construct a model of the population changes over the first 10 years and the population was severely depleted in the 11th year.
Abstract: SUMMARY The changes in a population of springbok confined to a paddock on a farm in the Karoo were observed for 12 years. The observations and data on the age structure, obtained from skulls in the paddock, were used to construct a model of the population changes over the first 10 years. In the 11th year the population was severely depleted as a result of drought. Possible reasons for the magnitude of the population decrease are discussed in relation to the model and the losses in other paddocks on the same farm.
4 citations