title: The spatial structure of hunter access determines the local abundance of forest elephants (Loxodonta africana cyclotis).
abstract: 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.
authors.affiliation: Department of Ecology, Evolution and Environmental Biology, 10th floor Schermerhorn Extension, 1200 Amsterdam Avenue, New York, New York 10027, USA. c_yackulic@yahoo.com
authors.forename: Charles B
authors.initials: CB
authors.lastname: Yackulic
authors.forename: Samantha
authors.initials: S
authors.lastname: Strindberg
authors.forename: Fiona
authors.initials: F
authors.lastname: Maisels
authors.forename: Stephen
authors.initials: S
authors.lastname: Blake
mesh_terms: D000350:Africa, Central; D000818:Animals; D003247:Conservation of Natural Resources; D017753:Ecosystem; D004606:Elephants / Q000502:physiology*; D008954:Models, Biological; D015233:Models, Statistical; D011156:Population Density; D014197:Trees