A Field Study of a Population of Leopard Toads (Bufo regularis regularis)

Abstract

An ecological study was made in the Rukwa Valley, Tanganyika Territory. Movement and growth were studied by marking and recovery. Monthly samples were dissected. There was a nightly movement of toads to and from the pool. Movement began soon after nightfall and appeared to be stimulated by the low light intensity. Toads found the pool as a result of their general familiarity with the area, but they were also guided by the calls of their fellows already in the water. Apart from nightly fluctuations, the number of toads in the pool increased as the dry season advanced but fell sharply as soon as the rains began, remaining low so long as the rains lasted. These changes were related to the availability of water elsewhere than in the pool. Oviposition occurred mainly from Nov. to Jan.. during the rainy season. Some males were mature at all times of year. Egg-laying was seen only in the mornings in shallow water all round the edge of the pool. Growth was mainly during and after the rainy season when food was abundant and desiccation at a minimum. The food consisted almost entirely of insects. The fat bodies constituted at their maximum about 5% of the total body weight. Their development, reached a maximum in June. Growth of the testes was allometric and even in old males there was seasonal variation in size. The greatest development was reached during the rainy season. Males matured in their 1st year. The ovaries each contained an average of 19 lobes which increased in size as the eggs developed. Development was maximal during the rains and may have been associated with high temperatures or with increasing day length. Bidder''s organ was present in both sexes but was reduced or absent in old individuals.