The Population dynamics of Rodents at Pongola, Northern Zululand, exposed to Dieldrin coverspraying

[摘要] Four grids, each 3,42 ha (4 morgen) in size, were livetrapped from April 1967 through May 1969 in two soil and vegetationtypes (black turf~ Acacia nigrescens community, andbrown reddish soil: Acacia tortilis community) at Pongola,northern Zululand, to determine the effect of dieldrin coverspraying,at a dosage of 87,4 g/hectare (2,64 oz/morgen), onrodents. Low population numbers before and especially at thetime of spraying made clear-cut conclusions impossible toreach. Rodent populations (mainly Praomys (Mastomys) natalensis,Saccostomus campestris, and Lemniscomys griselda) wereapparently not adversely effected, although L. griselda numbersshowed a decline which was not in correspondence withthat on the control area. This might be ascribed to dieldrinspraying. Relatively higher numbers of s. campestris andL. griselda were observed during periods of lower P.( M.) ~talensisnumbers. Decreases in P.( Me) natalensis populationscoincided with times of food scarcity. Praomys (Mastomys)natalensis are thus found in association with other rodentswhen abundant food is available, but seems to give way whencompetition due to food scarcity occurs.Reproductive data obtained from the study were too meagreto allow any conclusions concerning the effect of sprayingthereon. The method involving the calculation of maximum distancebetween captures was used to express movement patterns ofthe species studied.Populat~on structure is express~d in terms of sexratios, and frequency per mass class for each season.The size of animals was investigated by measuringtotal length, tail length, and head and body length.Behavioural features of the species captured were also noted.

[发布机构] University of Pretoria