Lion hunting and vegetation structure

Transcription

1 Lion hunting and vegetation structure Andrew Davies, Craig Tambling, Graham Kerley & Gregory Asner Carnegie Institution for Science & Nelson Mandela Metropolitan University

2 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

3 Protected areas Often do not encompass entire self-sustaining ecosystems Predator reintroductions

4 Hunting behaviour The interface of predator influence on ecosystems Affect prey (herbivore) undance, distributions and behaviour

5 Hunting behaviour Factors influencing hunting (kill sites) will influence herbivores

6 Vegetation structure 3D vegetation structure influences hunting patterns and kill sites

7 Vegetation structure 3D vegetation structure influences hunting patterns and kill sites Predator concealment Prey detection of predators Prey ility to escape

8 Vegetation structure Readily influenced by managers and under global change

9 Vegetation structure Readily influenced by managers and under global change How might structural changes affect predator-prey relationships?

10 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

11 Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure

12 Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure Consistent across ecosystems?

13 Lions Sexual dimorphism in appearance and behavior Sex-based differences in the use of savanna vegetation structure Consist across prey species and sexes?

14 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

15 Measuring structure

16 Lion kill and non-kill sites Minimum distance to downwind cover Wind speed Moonlight

17 Lion kill and non-kill sites Compared kill and resting sites between lion sexes Prey species Prey sexes

18 Viewshed (m 2 ) Viewshed (m 2 ) 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) Female Male 0 Female Male 2 Lion sex Lion sex

19 Distance to cover (m) Viewshed (m 2 ) Moon presence 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

20 Probility of kill a) b) c) Female Male Viewshed (m 2 * 1000) Average wind speed (m.s -2 ) Proportion of moon illumination

21 Probility of kill a) b) c) Viewshed (m 2 * 1000) Wind speed (m.s -2 ) Moonlight (proportion)

22 Probility of kill a) b) c) 100% 30% 5% Viewshed (m 2 * 1000) Wind speed (m.s -2 ) Moonlight (proportion)

23 Ambush style of attack Dense vegetation, high wind speeds and dark nights

24 Ambush style of attack Dense vegetation, high wind speeds and dark nights Vegetation cover more important than elsewhere

25 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

26 Lion sexes No differences between lion sexes Surprising given the strong sexual dimorphism and findings from elsewhere

27 Addo differences The availility of dense vegetation Females choose it over open landscapes elsewhere

28 Addo differences Social groups are smaller for females

29 Addo differences Social groups are smaller for females Females don t need to form groups Rely instead on dense vegetation

30 Addo differences Wind speed is more important in Addo

31 Addo differences Wind speed is more important in Addo Thick vegetation leads to increased rustling in windy conditions

32 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

33 Addo differences Darkness less important Thick vegetation makes reliance on dark nights less important

34 Viewshed (m 2 ) 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

35 Viewshed (m 2 ) 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

36 Viewshed (m 2 ) 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

37 Average wind speed (m.s -2 ) 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

38 Average wind speed (m.s -2 ) 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

39 Prey species in Addo Buffalo < 5% of kills, < 1% of male kills Small groups make buffalo hunting more difficult

40 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

41 Prey sexes Wind speed important for male prey Females are more vigilant, especially in risky conditions

42 Conclusion Vegetation structure is important in predator-prey relationships Effects of vegetation heterogeneity are not uniform across landscapes Ecosystem type (biome) affects lion hunting

43 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

44 Conclusion Careful consideration of how changes in vegetation structure might help or hinder predator-prey relationships

45 Acknowledgements CAO team Dave Knapp, Nick Vaughn, Chris Anderson, Robin Martin SANParks Angela Gaylard SA Weather Service Andrew Mellon Foundation Photographs by Craig Tambling