SummaryDropping counts were used to assess elephant abundance in the remote forests of northeastern Gabon where there are few people and no logging. Elephants prefer the secondary forest which grows on abandoned villages and plantations, but avoid roads and villages. Thus elephant distribution is governed by the distribution of both past and present human settlement, even in the remotest and least disturbed forests of equatorial Africa.RésuméOn a évalué l'abondance des éléphants en comptant les excréments, dans les forêts reculées du nord‐est du Gabon, là où il n'y a que peu de gens et aucun abattage d'arbres. Les éléphants préférent les forêts secondaires qui poussent dans les villages et les plantations abandonnés, mais évitent routes et villages. Donc, la distribution des éléphants est régie par la répartition des installations humaines présentes et passées, même dans les forêts les plus reculées et les moins troublées d'Afrique équatoriale.
The number of elephants living in the forests of Gabon was estimated by a stratified dung survey. The forest zone was stratified according to the distribution of the human population. The density of dung-piles was estimated for each stratum by the line-transect method. The total number of dung-piles in the forests of Gabon was estimated to be 52.43 × 106 ± 13.25 × 106. This gave an elephant estimate of 61,800 ±20,200. This survey shows Gabon to have one of the largest elephant populations on the continent.
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Download date: 11 May 2018Experimental & Applied Acarology, 8 (1990) Optimal foraging theory predicts that predators prefer those prey species that are most rewarding in terms of reproductive success, which is dependent on prey quality and prey availability. To investigate which selection pressures may have moulded prey preference in an acarine system consisting of two prey species and three predator species, we tested whether prey preference of the predators is matched by the associated reproductive success.The predators involved are Amblyseius finlandicus (Oudemans), Am. potentillae (Garman) and Typhlodromus pyri Scheuten. The prey species are the apple rust mite (Aculus schlechtendali (Nalepa)) and the fruit-tree red spider mite (Panonychus ulmi (Koch)).Reproductive success was assessed in terms of intrinsic rate of increase and for one predator also in terms of diapause induction. All three predator species reached highest reproductive success on the same prey species: apple rust mite. This was most pronounced for the predator Am. finlandicus, because its larval stage suffered severe mortality when feeding on P. ulmi.An independent study on prey preference of the three predator species revealed that Am. finlandicus prefers Ac. schlechtendali to P. ulmi, whereas the other two predator species have the reverse preference.Thus, on the basis of current data, prey preference of Am. finlandicus can be understood in terms of reproductive success. However, this is not so for prey preference of T. pyri and Am. potentillae. Investigations needed for a better understanding of prey preference of the last-named two predator species are discussed.
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