ISSN:0035-919X    

DOI:10.1080/00359198609520111

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Bullia digitalisis a sandy-beach whelk which displays a well-defined series of reactions to most pollutants. A marked sub-lethal response is cessation of burrowing, the animals either refusing to burrow or emerging from the sand if already buried. The concentrations of a series of organic substances eliciting the latter response are reported and a correlation is demonstrated between these concentrations and the first-order molecular valence connectivity indices of the substances concerned.

ISSN:0035-919X    

DOI:10.1080/00359198609520112

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The distributions of springbok and Merino sheep in a 350 ha paddock on a game ranch in the Karoo were monitored over 16 periods of 5 days throughout one year. Limited forage resulted from high stocking rates and drought. This necessitated the provision of supplementary feed which was utilised solely by Merino sheep. Springbok were at all times more dispersed than Merino sheep especially so when pasture conditions deteriorated and feed was provided. Springbok preferred a ‘rand’ vegetation where favourite food plants such asPentziaspp. andPteroniaspp. predominated. Merino sheep were largely dependent on the close proximity of feed and watering sites and exhibited a preference for a ‘pan’ vegetation. Temporal variation in these distribution patterns is discussed. Levels of association between the two species changed through the year. Observed inter-specific differences suggest that a combination would lead to a better utilisation of the vegetation.

ISSN:0035-919X    

DOI:10.1080/00359198609520113

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The daily activity patterns of springbok and Merino sheep were studied under open-range conditions in the Karoo for 80 days spanning one whole year, during a period of drought. Springbok spent a greater amount of time foraging (in more frequent bouts) than Merino sheep perhaps as a consequence of their greater dietary selectivity. Springbok had more time available for resting behaviour during optimal conditions for plant growth. As the pasture deteriorated, springbok devoted more time to foraging while diurnal behaviour rhythms disappeared. Major springbok mortality occurred when resting behaviour was restricted to one hour per day. Supplementary feed was supplied and utilised solely by Merino sheep which subsequently devoted more time to resting behaviour. Merino sheep spent less time foraging on hot days.

ISSN:0035-919X    

DOI:10.1080/00359198609520114

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Productivity data were collected over a period of seven years of low rainfall on a farming enterprise in the Karoo. Merino sheep were the more important component producers in this enterprise and were 46% more efficient than springbok at converting estimated food energy into net rands profit. Both springbok and Merino sheep populations exhibited recruitments in excess of 30%. Springbok had a lambing percentage of 87% compared with 75% for Merino sheep. Nearly 50% of the springbok population died as a result of critical shortage of nutrients in 1984 representing a severe loss of capital. Merino sheep incurred large feed bills. Management costs for Merino sheep were thus higher (51,1% gross income) than for springbok (31,3% gross income) resulting in a favourable contribution of springbok to net profit. Moreover, springbok were more efficient at converting food energy into kg saleable meat. An increase in the role of the springbok in Karoo farming concurrent with Merino stock reductions is recommended. A combination should help in the reclamation of Karoo vegetation and has the potential of improving overall productivity. Reasons are given why springbok should be stocked at lower rates than Merino sheep.

ISSN:0035-919X    

DOI:10.1080/00359198609520115

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Rumen and vegetation analyses were employed to investigate the diets of springbok (Antidorcas marsupialis) and Merino sheep (Ovis aries) on Karoo vegetation during a period of low rainfall. Supplementary feeds (maize) were utilised by Merino sheep, not by springbok. Karoo shrubs predominated in the veld and were preferred by springbok, but not by Merino sheep. Grasses, in a state of lignification, were preferred by Merino sheep but not by springbok. A choice of some ‘less palatable’ shrubs (esp.Pentziaspp.) was apparent in the diet of springbok; palatable shrubs and geophytes were also preferred while most unpalatable shrubs were not. Springbok showed a preference for certain plant species which are considered unpalatable to Merino sheep. Variation between the diets of springbok rams and ewes is believed to be related to social structure. Findings on diet tally with the activity patterns, habitat selection and vegetation impact of the two species. A combination of springbok and Merino sheep should assist in veld reclamation schemes.

ISSN:0035-919X    

DOI:10.1080/00359198609520116

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359198609520117

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359198609520118

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359198609520110

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor