Squirrels:Predators or Dispersers of Marula Nuts?             Emma Alterman and Peter Macfarlane               Organizatio...
Introduction         Methods          Results       Discussion                          Marula               (Sclerocarya ...
Introduction       Methods          Results   DiscussionDispersal                       Bottlenecks                       ...
Introduction       Methods          Results   DiscussionDispersal                       Bottlenecks                       ...
Introduction   Methods             Results        Discussion                    Tree Squirrels               (Paraxerus ce...
Introduction    Methods          Results       Discussion              Janzen-Connell HypothesisI=SeedsShadowP=Probability...
Introduction   Methods   Results   Discussion                 Our Goals
Introduction     Methods             Results   Discussion                       The Set Up        “Near”             “Inte...
Introduction   Methods     Results   Discussion                  In the open                  Under trees                 ...
Introduction   Methods     Results   Discussion                         •Eaten                         •Scatter-hoarded   ...
Introduction     Methods   Results   Discussion               Scatter-hoarding
Introduction     Methods   Results   DiscussionUV Torch                    Scatter-hoarding
Introduction                         Methods            Results   Discussion                         12 Number of Marula N...
Introduction                                           Methods           Results          Discussion                      ...
Introduction                                      Methods       Results           Discussion                              ...
Introduction                               Methods               Results             Discussion                        40 ...
Introduction         Methods                 Results   Discussion         Janzen-Connell Hypothesis                 Critic...
Introduction         Methods                Results               Discussion                    Under Trees               ...
Introduction         Methods                  Results               Discussion                    Under Trees             ...
Introduction   Methods   Results   Discussion
Elephants!
Introduction             Methods      Results   Discussion        Can travel 6km per day     Food in gut for up to 46 hour...
Introduction   Methods   Results   Discussion
Introduction   Methods    Results            Discussion                              Nut found by squirrel                ...
Introduction            Methods      Results   Discussion     Why is this an effective      dispersal method?Seed mortalit...
Conclusions   •Janzen-Connell holding true              for savannas              •Trees as triggers              •Marulas...
Thank you!
Thank you!             Questions?
References•   Alterman, E. B. Lind, and A. Martinez. 2011. Where are my nuts? The role of elephants and squirrels in marul...
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Marula Dispersal

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This was a presentation I created with the help of a classmate for a course called "Field Research in Savannah Ecology" while I was abroad in South Africa through Duke University and the Organization for Tropical Studies (Spring 2011). After carrying out a self designed research project, my partner and I presented our findings to the employees of Kruger National Park (the park where the research was conducted) as well as our professors and fellow classmates. I created all the images in this presentation using powerpoint.

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Marula Dispersal

  1. 1. Squirrels:Predators or Dispersers of Marula Nuts? Emma Alterman and Peter Macfarlane Organization for Tropical Studies May 2, 2011
  2. 2. Introduction Methods Results Discussion Marula (Sclerocarya birrea subsp. caffra)
  3. 3. Introduction Methods Results DiscussionDispersal Bottlenecks Adult Mortality Fire Trap/ Browse Establishment Time
  4. 4. Introduction Methods Results DiscussionDispersal Bottlenecks Adult Mortality Fire Trap/ Browse Establishment Time
  5. 5. Introduction Methods Results Discussion Tree Squirrels (Paraxerus cepapi subsp. cepapi)
  6. 6. Introduction Methods Results Discussion Janzen-Connell HypothesisI=SeedsShadowP=Probability of seedling survival because of lower predation
  7. 7. Introduction Methods Results Discussion Our Goals
  8. 8. Introduction Methods Results Discussion The Set Up “Near” “Intermediate” “Far”
  9. 9. Introduction Methods Results Discussion In the open Under trees In the bush
  10. 10. Introduction Methods Results Discussion •Eaten •Scatter-hoarded •Moved •Missing
  11. 11. Introduction Methods Results Discussion Scatter-hoarding
  12. 12. Introduction Methods Results DiscussionUV Torch Scatter-hoarding
  13. 13. Introduction Methods Results Discussion 12 Number of Marula Nuts 10 8 Untouched 6 Eaten 4 Scatter-Hoarded Missing 2 0 Near Intermediate Far Predation seen directly under the marula trees Mix of eating, scatter-hoarding and unknowns
  14. 14. Introduction Methods Results Discussion 10 Number of Marula Nuts left untouched 9 8 7 6 5 4 3 2 1 0 Under Marula Trees Under Other TreesSimilar predation rates under marula and non-marula trees
  15. 15. Introduction Methods Results Discussion 10 Number of Marula Nuts left untouched 9 8 7 6 5 4 3 2 1 0 In the Bush On the Golf Course Lower predation rates in the bush than on the golf course
  16. 16. Introduction Methods Results Discussion 40 35 30 25 20 15 10 Number of Marula Nuts 5 0 -4 0 4 8 12 16 20 24 Distance of Scatter-Hoarding (m) Most nuts were scatter-hoarded close to the tree
  17. 17. Introduction Methods Results Discussion Janzen-Connell Hypothesis Critical Point? “Near” “Intermediate” “Far”
  18. 18. Introduction Methods Results Discussion Under Trees In The Open Predation under marula and Fear predation non-marula trees same Feel safest in the trees -Trees as triggers
  19. 19. Introduction Methods Results Discussion Under Trees In The Open Predation under marula and Fear predation non-marula trees same Feel safest in the trees -Trees as triggers But… In The Bush To much cover might make it difficult for squirrels to find nuts
  20. 20. Introduction Methods Results Discussion
  21. 21. Elephants!
  22. 22. Introduction Methods Results Discussion Can travel 6km per day Food in gut for up to 46 hoursExcreted food deposited far from source Piles good foraging locations Can be filled with up to 700 nuts
  23. 23. Introduction Methods Results Discussion
  24. 24. Introduction Methods Results Discussion Nut found by squirrel Scatter-hoarded near dung pile Nut buried far away from parent trees!
  25. 25. Introduction Methods Results Discussion Why is this an effective dispersal method?Seed mortality in elephant gut very low • Seed can travel far safelyBuried seeds protected from threats • Risk of being burned • Predation
  26. 26. Conclusions •Janzen-Connell holding true for savannas •Trees as triggers •Marulas possibly dispersed by 2 modes of zoochory
  27. 27. Thank you!
  28. 28. Thank you! Questions?
  29. 29. References• Alterman, E. B. Lind, and A. Martinez. 2011. Where are my nuts? The role of elephants and squirrels in marula (Sclerocarya birrea subsp. caffra) seed dispersal. Organization for Tropical Studies report spring 2011. Skukuza, Mpumalanga Province, South Africa.• Butchart, D. 2009. Wildlife of South Africa | A Photographic Guide. Struik Nature, Cape Town, SA.• Davis, S. 2007. Endozoochory in Subtropical Thicket: comparing effects of species with different digestive systems on seed fate. MSc Thesis, Nelson Mandela Metropolitan University, South Africa.• Forget, P.M. 1990. Seed dispersal of Vouacapoua Americana (Caesalpiniaceae) by caviomorph rodents in French Guiana. Journal of Tropical Ecology 6:459-468.• Forget, P.M. and S.B. Vander Wall. 2001. Scatter-hoarding rodents and marsupials: convergent evolution on diverging continents. Trends in Ecology & Evolution. 16(2):65-67.• Gallaher, K.S.L. 2010. Marula (Sclerocarya Birrea Subsp. Caffra) Dispersal by Mammals: Are Squirrels Seed Predators Or Seed Dispersers? BSc. Honors Thesis. Botany Department University of Cape Town, Cape Town, SA.• Helm, C.V., S.L. Scott, and E.T.F. Witkowski. 2011. Reproductive potential and seed fate of Sclerocarya birrea subsp. caffra (marula) in the low altitude savannas of South Africa. South African Journal of Botany. in press.• Jacobs, O.S. and R. Biggs. 2002. The status and population structure of the marula in the Kruger National Park. South African Journal of Wildlife Research 32(1): 1–12.• Janzen, D. 1970. Herbivores and the Number of Tree Species in Tropical Forests. The American Naturalist 104(940):501-528.• Laorie, S.R., Van Aarde, R.J., and S.L. Pimm. 2009. Fences and artificial water affect African savannah elephant movement patterns. Biological Conservation 142:3086–3098• Midgley, J.J. and W.J. Bond. 2001. A synthesis of the demography of African acacias. Journal of Tropical Ecology 17:871–886.• Rees, P. A. 1982. Gross assimilation efficiency and food passage time in the African elephant. African Journal of Ecology 20(3):193-198.• Shackleton, C.M., J. Botha, P.L. Emanuel and S. Ndlovu. 2002. Inventory of Marula (Sclerocarya birrea subsp. caffra) Stocks and Fruit Yields in Communal and Protected Areas of the Bushbuckridge Lowveld, Limpopo Province, South Africa. Department of Environmental Science, Rhodes University, Grahamstown 6140, South Africa.• Schmidt E., M. Lötter, W. McCleland. 2002. Trees and Shrubs of Mpumalanga and Kruger National Park. Jacana, Johannesburg, SA.• Stuart, C. and T. Stuart. 2007 Field Guide to Mammals of Southern Africa. Fourth Edition Struik Piblishers, Cape Town, SA.• van Wilgen, B.W., W.S.W. Trollope, H.C. Biggs, A.L.F. Potgieter, and B.H. Brockett. 2003. Fire as a Driver of Ecosystem Variability. Pp 149-170 in J.T. du Toit, K.H. Rogers, and H.C. Biggs, editors. The Kruger Experience Ecology and Management of Savanna Heterogeneity. Island Press, Washington, DC, USA.

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