Individual-area relationship best explains goose species density in wetlands
Zhang, Y. ; Jia, Q. ; Prins, H.H.T. ; Cao, L. ; Boer, W.F. de - \ 2015
PLoS ONE 10 (2015)5. - ISSN 1932-6203 - 11 p.
human disturbance - habitat heterogeneity - mammalian herbivores - population-density - african elephant - forage quality - barnacle geese - body-mass - diversity - selection
Explaining and predicting animal distributions is one of the fundamental objectives in ecology and conservation biology. Animal habitat selection can be regulated by top-down and bottom-up processes, and is mediated by species interactions. Species varying in body size respond differently to top-down and bottom-up determinants, and hence understanding these allometric responses to those determinants is important for conservation. In this study, using two differently sized goose species wintering in the Yangtze floodplain, we tested the predictions derived from three different hypotheses (individual-area relationship, food resource and disturbance hypothesis) to explain the spatial and temporal variation in densities of two goose species. Using Generalized Linear Mixed Models with a Markov Chain Monte Carlo technique, we demonstrated that goose density was positive correlated with patch area size, suggesting that the individual area-relationship best predicts differences in goose densities. Moreover, the other predictions, related to food availability and disturbance, were not significant. Buffalo grazing probably facilitated greater white-fronted geese, as the number of buffalos was positively correlated to the density of this species. We concluded that patch area size is the most important factor determining the density of goose species in our study area. Patch area size is directly determined by water levels in the Yangtze floodplain, and hence modifying the hydrological regimes can enlarge the capacity of these wetlands for migratory birds.
Optimising investments from elephant tourist revenues in the Maputo Elephant Reserve, Mozambique
Boer, W.F. de; Stigter, J.D. ; Ntumi, C.P. - \ 2007
Journal for Nature Conservation 15 (2007)4. - ISSN 1617-1381 - p. 225 - 236.
wildlife conservation - african elephant - protected areas - incentives - management - people - zambia - damage - kenya
Private enterprises are active in conservation initiatives in Africa. Some of these enterprises have long-term licences for the development of conservation areas. The motivation of these organisations to participate in conservation is ultimately determined by the economic output of their activities. An electric fence is being constructed in the Maputo Elephant Reserve, Mozambique. A costs-benefit analysis was carried out, in order to assist in the optimisation of the management activities of the elephant population, based on elephant population size, fence costs, crop raid costs, elephant poaching, and benefits derived from tourism (game-viewing and hunting). Tourist numbers increased with increasing elephant density through a concave utility function. Optimal harvest/hunting strategies were calculated from optimal control theory, using dynamic optimisation (Pontryagin's Maximum Principle). Poaching and raid costs could be compared to fence construction costs at different elephant population sizes. Costs generated through elephant poaching and elephant crop raid costs were higher than fence construction costs at a population size >100. Elephant hunting was a less favourable activity, economically and ecologically, than elephant viewing, due to the large game-viewing profits per elephant. Only if the licence fee increases from US$6500 to 28,500 would hunting become attractive, although ecological and economical constraints would probably prevent the development of hunting activities in the area. The assumed resource price of elephant (US$5000) was lower than the marginal value derived from tourism, indicating that elephants should be bought until the maximum stocking rate is reached.