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Effects of Vegetation Structure on the Location of Lion Kill Sites in African Thicket - PubMed

  • ️Fri Jan 01 2016

Effects of Vegetation Structure on the Location of Lion Kill Sites in African Thicket

Andrew B Davies et al. PLoS One. 2016.

Abstract

Predator-prey relationships are integral to ecosystem stability and functioning. These relationships are, however, difficult to maintain in protected areas where large predators are increasingly being reintroduced and confined. Where predators make kills has a profound influence on their role in ecosystems, but the relative importance of environmental variables in determining kill sites, and how these might vary across ecosystems is poorly known. We investigated kill sites for lions in South Africa's thicket biome, testing the importance of vegetation structure for kill site locations compared to other environmental variables. Kill sites were located over four years using GPS telemetry and compared to non-kill sites that had been occupied by lions, as well as to random sites within lion ranges. Measurements of 3D vegetation structure obtained from Light Detection and Ranging (LiDAR) were used to calculate the visible area (viewshed) around each site and, along with wind and moonlight data, used to compare kill sites between lion sexes, prey species and prey sexes. Viewshed area was the most important predictor of kill sites (sites in dense vegetation were twice as likely to be kill sites compared to open areas), followed by wind speed and, less so, moonlight. Kill sites for different prey species varied with vegetation structure, and male prey were killed when wind speeds were higher compared to female prey of the same species. Our results demonstrate that vegetation structure is an important component of predator-prey interactions, with varying effects across ecosystems. Such differences require consideration in terms of the ecological roles performed by predators, and in predator and prey conservation.

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Conflict of interest statement

Competing Interests: Bidvest Car Rental and Eveready provided support for vehicle and battery sponsorships used for kill site investigations. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Map of the study site showing the location of the Addo Elephant National Park within South Africa (upper left panel), the Nyathi, Main Camp and Colchester sections within the park (upper right panel) and lion resting (non-kill) and kill sites within the Main Camp section (lower panel).

Vegetation height derived from the LiDAR is also shown for Main Camp, as well as the botanical reserve, which lions do not have access to.

Fig 2
Fig 2. Example of a viewshed modelled from airborne LiDAR.

The lighter colors indicate areas that are visible and accessible in all directions from the location of a central GPS cluster. Lighter orange represents visible terrain whereas lighter green represents visible vegetation. Shaded (darker) colors represent areas that are occluded from view. Parts of the landscape that are farther can be visible even though closer areas are occluded from view by objects in the foreground.

Fig 3
Fig 3

Lion kill and non-kill sites in relation to a) the size of the viewshed, b) the average wind speed before the start of the GPS cluster, c) the distance to the nearest cover (ambush site) relative to the prevailing wind direction and d) moonlight at the start of the cluster of the moon (1 = moon present, 0 = moon absent). No interaction terms between vegetation and weather variables were significant in predicting the locations of kills. Error bars in d) represent standard error.

Fig 4
Fig 4

Probability of a site being a kill site for lions (lion sexes combined) in relation to a) viewshed area, b) average wind speed, and c) moonlight. Confidence intervals are too small to be shown due to the large number of iterations (10 000) performed during the analysis.

Fig 5
Fig 5

Kill site characteristics for each prey species and prey sex (juvenile prey animals are combined with females) for a) the viewshed, b) the minimum distance to cover (ambush site) in relation to the prevailing wind direction, and c) the average wind speed before the start of the GPS cluster. The solid red line indicates the mean of the characteristic of the non-kill sites; dashed lines represent standard error. Asterisks denote cases where a particular species differed significantly from the non-kill state, whereas letters denote significant differences between species in a) and b). Male prey kill sites were located at sites with significantly higher average wind speeds than female prey (c).

Fig 6
Fig 6. The minimum distance to cover relative to the prevailing wind direction grouped by lion sex, lion behavior (killing or resting), prey species (kill sites), and prey sexes (kill sites for the sex of each prey species).

Values for each prey species are taken from the combined measurements across lion sexes and arranged in descending order of prey body size. Asterisks denote significant differences; numbers are mean distance to cover in meters. Although large differences between prey sexes are evident for zebra and warthog, these were not statistically significant due to low sample sizes for those species.

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Grants and funding

This study has been supported by the Andrew Mellon Foundation, The International Foundation for Science, Avatar Alliance Foundation, Gordon and Betty Moore Foundation, John D. and Catherine R. MacArthur Foundation, Grantham Foundation for the Protection of the Environment, W. M. Keck Foundation, Margaret A. Cargill Foundation, Mary Anne Nyburg Baker and G. Leonard Baker Jr., William R. Hearst III, Bidvest Car Rental and Eveready. C.J. Tambling was funded by Post-Doctoral Fellowships from the National Research Foundation, the Claude Leon Foundation and the Nelson Mandela Metropolitan University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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