Department of Ecology, Evolution and Environmental Biology, 10th floor Schermerhorn Extension, 1200 Amsterdam Avenue, New York, New York 10027, USA.
Ecol Appl. 2011 Jun;21(4):1296-307. doi: 10.1890/09-1099.1.
In many previously remote regions in the world, increasing and often unregulated access is leading to dramatic increases in hunting pressure and declines in the densities of prey species, sometimes to the point of local extinction. Not surprisingly, numerous studies have found a correlation between the distance to the closest access point and prey densities. Here we hypothesized that, for many wide-ranging species, local abundances are reduced by hunting associated with multiple access points as opposed to just the closest access points. We also hypothesized that the distribution of hunter access determines both patterns of occupancy and abundance in occupied areas and that these two patterns (occupancy and abundance) respond to access at different spatial scales. Using data on the distribution of abundances of African forest elephant (Loxodonta africana cyclotis) in and around five national parks in Central Africa, we tested these hypotheses using a model comparison framework. We found that models including an index based on the distance to multiple roads outperformed models including other access-based covariates, including a model based on distance to the closest road only. We also found that models that allowed us to model occupancy and abundance separately outperformed simpler models. Occupancy responds to access at the same scale as previous estimates of average maximum displacement in the subspecies, while the scale of the response of abundance is more ambiguous, but appears to be greater. Lastly, we show that incorporating indices based on multiple access points and modeling abundance and occupancy has important practical consequences for our understanding of overall regional abundances and the distribution of abundances within regions.
在世界上许多以前偏远的地区，越来越多且往往不受管制的进入导致狩猎压力急剧增加，猎物密度下降，有时甚至达到局部灭绝的程度。毫不奇怪，许多研究发现，最近的进入点的距离与猎物密度之间存在相关性。在这里，我们假设，对于许多广泛分布的物种，与多个进入点相关的狩猎活动会导致当地数量减少，而不仅仅是最近的进入点。我们还假设，猎人进入点的分布决定了占据地区的占有模式和丰度，并且这两种模式（占有和丰度）对不同空间尺度的进入点做出反应。我们使用了有关中非五个国家公园内及周围的非洲森林象（Loxodonta africana cyclotis）丰度分布的数据，使用模型比较框架检验了这些假设。我们发现，包含基于多条道路距离的指数的模型优于包含其他基于进入的协变量的模型，包括仅基于最近道路距离的模型。我们还发现，允许我们分别对占有和丰度进行建模的模型优于更简单的模型。占有率对进入的反应与亚种中平均最大位移的先前估计值在同一尺度上，而丰度的反应尺度则更为模糊，但似乎更大。最后，我们表明，纳入基于多个进入点的指数并对丰度和占有量进行建模，对于我们理解整体区域丰度以及区域内丰度的分布具有重要的实际意义。
