SummaryThis paper presents a description of the temporal and spatial distribution of rainfall within the Serengeti Ecosystem, Tanzania. Ecosystem and Regional patterns are discussed with respect to synoptic processes, vegetation zonation, phases of primary production and the distribution and migrations of large mammals.

Interspecific competition and facilitation have both been proposed as processes promoting species separation and co-existence in African ungulates. In one group of grazers on the Serengeti plains, comprising wildebeest (Connochaetes taurinus), zebra (Equus burchelli), and Thomson's gazelle (Gazella thomsoni), these processes have also been suggested to regulate the populations. Censuses of these populations over 20 years have shown changes that allow a test of which, if either, process regulates population numbers. Wildebeest numbers have levelled off as a result of intraspecific competition for food following a five-fold increase due to release from disease and an increase in food supply. Zebra numbers have remained stationary throughout the same period. Gazelle numbers have declined in the last 10 years. These results are contrary to the facilitation hypothesis, which predicts that wildebeest numbers should not have increased if those of zebra did not, and that gazelle numbers should have increased since the wildebeest population increased. The gazelle results are consistent with the interspecific competition hypothesis, but the zebra results are contrary to it. We propose an alternative hypothesis that predation regulates the zebra population, and we suggest ways of testing this.

No abstract

No abstract

Summary A method for sample counting the Serengeti migratory wildebeest using vertical aerial photography to sub‐sample randomly located transects is described. The population estimate achieved was 754 028 animals, with 95% confidence limits of ± 8‐5% of the population estimate. The application of this method to other wildlife populations is considered.

No abstract

I. The transport and presentation of food to the young Oystercatcher is described. The parents will present food to the young either on their own initiative or in response to the approach of the young. 2. The auditory and tactile interactions between the hatching eggs and the incubating parents are described. As hatching proceeds both the parents and young become more responsive to each other, and both show marked selective responsiveness. These pre-hatch interactions lead to the transition from incubation behaviour to brooding behaviour and to the onset of parental feeding. It is suggested that the young may learn to respond to the call of the parent before hatching. 3. Both non-breeding and breeding birds show the same cyclical pattern of total feeding activities and it is suggested that self-feeding and parental feeding are part of the same motivational system. Once the food has been presented to the young, the subsequent behaviour of the parent is dependent upon the speed with which the young seizes and eats the food. If the young reacts within a certain time (the Waiting-Time Threshold) then the parent will present more food, and will continue to do so for as long as the young reacts within the threshold time. In this way feeding trains are initiated and maintained. The feeding train is broken off once the young fails to react within the threshold time. As the young grows older the parent plays an increasingly minor part in the initiation of feeding trains, the role of the young becoming more important. This leads to the eventual breakdown of parental feeding which is closely correlated in time with how long it takes the young to learn to feed itself. A model of the motivation and control of parental feeding is described. 4. It is suggested that parental feeding evolved in the Oystercatcher subsequent to the evolution of a specialised feeding behaviour which very small young were unable to

No abstract