In large parts of Africa, wildlife herbivores spill over onto private lands, competing with domestic livestock for forage resources. To encourage private landowners to take into account the externality benefits of wildlife, game cropping is increasingly considered as an important component of conservation policies. In this paper, we employ a bioeconomic model of a private game ranch to examine five potential government policies concerning wildlife conservation, ranging from (strict) preservation to uncontrolled exploitation. 'Intermediate' policies appear to contribute most to wildlife conservation, with costs to landowners of such policies being modest. The model outcomes support recent wildlife policy shifts in Kenya.

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An alternative interpretation is provided of the concepts of carrying capacity and exchange ratios, particularly suitable for game animal species, based on management models for a given area of rangeland or pasture. It involves modelling animal population dynamics as discrete-time logistic equations. Carrying capacity is then generated endogenously using rainfall as a proxy. The model interaction parameters, also generated endogenously, represent the animal exchange ratios. Because these two parameters are generated endogenously, this approach takes into account all the animals' habitat requirements (food, cover, water and space) simultaneously, unlike other approaches that tend to consider food requirements only. This makes the approach amenable to multi-species situations. It also captures the ecological de¢nition of population growth models where the realized rather than the theoretical carrying capacity is determined endogenously.Re¨sumeÖ n apporte une interpre¨tation alternative des concepts de capacite¨de charge et de taux d'e¨changes spe¨ci¢quement adapte¨e aux espe© ces-gibier, base¨s sur des mode© les de gestion pour une zone donne¨e d'habitat ou de paª turage. Elle implique la mode¨lisation de la dynamique des populations animales en e¨quations logistiques de¨limi-te¨es dans le temps. La capacite¨de charge est alors ge¨n-e¨re¨e de manie© re endoge© ne, en utilisant les chutes de pluie comme proxy. Les parame© tres d'interaction mode¨-lise¨s, ge¨ne¨re¨s aussi de manie© re endoge© ne, repre¨sentent les taux de remplacement des animaux. Comme ces deux parame© tres sont ge¨ne¨re¨s de cette fac , on, cette approche tient compte en meª me temps de toutes les exigences de l'habitat des animaux (nourriture, couvert ve¨ge¨tal, eau et espace), contrairement aux autres approches qui ont tendance a© ne tenir compte que de la nourriture. Ceci rend cette approche adaptable a© des situations touchant de nombreuses espe© ces. Elle inte© gre aussi la de¨¢nition e¨cologique des mode© les de croissance de population ou© la capacite¨de charge e¡ective plutoª t que the¨orique est de¨termine¨e de manie© re endoge© ne.

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