Lion hunting and vegetation structure Andrew Davies, Craig Tambling, Graham Kerley & Gregory Asner Carnegie Institution for Science & Nelson Mandela Metropolitan University
Predator-prey relationships Important top-down controls in ecosystems Imbalances can cause catastrophic regime shifts But maintaining or restoring sustainle predator-prey relationships is difficult
Protected areas Often do not encompass entire self-sustaining ecosystems Predator reintroductions
Hunting behaviour The interface of predator influence on ecosystems Affect prey (herbivore) undance, distributions and behaviour
Hunting behaviour Factors influencing hunting (kill sites) will influence herbivores
Vegetation structure 3D vegetation structure influences hunting patterns and kill sites
Vegetation structure 3D vegetation structure influences hunting patterns and kill sites Predator concealment Prey detection of predators Prey ility to escape
Vegetation structure Readily influenced by managers and under global change
Vegetation structure Readily influenced by managers and under global change How might structural changes affect predator-prey relationships?
Lions Lions are of particular interest in African ecosystems They contribute to the majority of prey mortality across prey sizes Tourism leading to predator reintroductions in small parks
Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure
Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure Consistent across ecosystems?
Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure Consist across prey species and sexes?
Lion kill and non-kill sites Addo Elephant National Park 405 kill sites and 477 resting sites 4 years of GPS clusters Majority of lion social groups Measured visibility (viewsheds) around each of site using CAO LiDAR
Measuring structure
Lion kill and non-kill sites Minimum distance to downwind cover Wind speed Moonlight
Lion kill and non-kill sites Compared kill and resting sites between lion sexes Prey species Prey sexes
0 2000 4000 6000 8000 Viewshed (m 2 ) Viewshed (m 2 ) 2000 4000 6000 8000 Average wind speed (m.s -2 ) Average wind speed (m.s -2 ) a) a) No kill Kill No kill Results 8 b) Kill No kill Kill 8 b) 6 6 4 2 4 Female Male 0 Female Male 2 Lion sex Lion sex
Distance to cover (m) 0 50 100 150 Viewshed (m 2 ) 2000 4000 6000 8000 Moon presence 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Average wind speed (m.s -2 ) c) Lion sex a) No kill Kill No kill Results Kill d) Lion sex No kill Kill 8 b) 6 4 Female Male Female 2 Male Lion sex Lion sex
Probility of kill 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 a) b) c) Female Male 0 2 4 6 8 Viewshed (m 2 * 1000) 0 1 2 3 4 5 6 7 Average wind speed (m.s -2 ) 0.0 0.2 0.4 0.6 0.8 1.0 Proportion of moon illumination
Probility of kill 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 a) b) c) 0 2 4 6 8 Viewshed (m 2 * 1000) 0 2 4 6 Wind speed (m.s -2 ) 0.0 0.2 0.4 0.6 0.8 1.0 Moonlight (proportion)
Probility of kill 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 a) b) c) 100% 30% 5% 0 2 4 6 8 Viewshed (m 2 * 1000) 0 2 4 6 Wind speed (m.s -2 ) 0.0 0.2 0.4 0.6 0.8 1.0 Moonlight (proportion)
Ambush style of attack Dense vegetation, high wind speeds and dark nights
Ambush style of attack Dense vegetation, high wind speeds and dark nights Vegetation cover more important than elsewhere
Ambush style of attack Dense vegetation, high wind speeds and dark nights Vegetation cover more important than elsewhere The characteristic thicket vegetation in Addo makes it feasible for lions to always choose dense vegetation for hunting
Lion sexes No differences between lion sexes Surprising given the strong sexual dimorphism and findings from elsewhere
Addo differences The availility of dense vegetation Females choose it over open landscapes elsewhere
Addo differences Social groups are smaller for females
Addo differences Social groups are smaller for females Females don t need to form groups Rely instead on dense vegetation
Addo differences Wind speed is more important in Addo
Addo differences Wind speed is more important in Addo Thick vegetation leads to increased rustling in windy conditions
Addo differences Wind speed is more important in Addo Thick vegetation leads to increased rustling in windy conditions The coastal location makes it more windy and winds are predictle
Addo differences Darkness less important Thick vegetation makes reliance on dark nights less important
Viewshed (m 2 ) 0 1000 3000 5000 Kill probility a) Female Female Male Male a a a a * ac a * ac * a * Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species
Viewshed (m 2 ) 0 1000 3000 5000 Kill probility a) Female Female Male Male a a a a * ac a * ac * a * Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species
Viewshed (m 2 ) 0 1000 3000 5000 Kill probility a) Female Female Male Male a a a a * ac a * ac * a * Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species
Average wind speed (m.s -2 ) 0 1 2 3 4 Kill probility Prey species c) Female Male Male > Female a a * * * a * ac Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species
Average wind speed (m.s -2 ) 0 1 2 3 4 Kill probility Prey species c) Female Male Male > Female a a * * * a * ac Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species Buffalo Eland Hartebeest Kudu Ostrich Warthog Zebra Prey species
Prey species in Addo Buffalo < 5% of kills, < 1% of male kills Small groups make buffalo hunting more difficult
Prey species in Addo Other species associated with dense vegetation are easier to locate and hunt Kudu and ostrich preferred Found in dense vegetation where are easier to catch
Prey sexes Wind speed important for male prey Females are more vigilant, especially in risky conditions
Conclusion Vegetation structure is important in predator-prey relationships Effects of vegetation heterogeneity are not uniform across landscapes Ecosystem type (biome) affects lion hunting
Conclusion Vegetation structure is changing Increased levels of CO 2 lead to vegetation thickening Clearing and herbivores can reduce vegetation cover Implications for predator-prey relationships
Conclusion Careful consideration of how changes in vegetation structure might help or hinder predator-prey relationships
Acknowledgements CAO team Dave Knapp, Nick Vaughn, Chris Anderson, Robin Martin SANParks Angela Gaylard SA Weather Service Andrew Mellon Foundation Photographs by Craig Tambling