Skip to main content

Influence of driver ant swarm raids on earthworm prey densities in the Mount Kenya forest: implications for prey population dynamics and colony migrations

Abstract

African driver ants are nomadic social mesopredators feeding on a highly diverse array of prey species at different trophic levels. Colonies of certain driver ant species have a biomass which can equal that of medium-sized mammalian carnivores and the ultimate cause of their nomadic life-style is thought to be local prey depletion. The impact of driver ant swarm raids is therefore expected to be strong but the degree to which they reduce prey populations has not been quantified and it is unknown whether these spectacular predators exert significant top-down effects. We examined the combined effect of driver ant (Dorylus molestus) and swarm-attending bird (Alethe poliocephala) predation on the population dynamics of earthworms, which constitute the ants’ main prey type in the montane forest of Mount Kenya. Pre-raid earthworm biomass densities in the soil layer down to a depth of 8 cm varied by a factor of 31. The immediate effect of swarm raids was a reduction in earthworm numbers in this layer, but 8 days later earthworm numbers had recovered to pre-raid levels. When earthworm biomass densities were compared, no significant effect of swarm raids was detected. The estimated proportion of earthworm prey biomass extracted from 0 to 8 cm layer by driver ants and birds together was about 2.2%. Although colony distribution was overdispersed as expected based on knowledge of D. molestus migratory behaviour, predation events were highly localized. Predation frequency was low (once every 62 days on average) and highly variable. These results indicate that earthworm prey is highly abundant but at the same time so difficult to harvest that swarm raids exert only a marginal influence on earthworm populations. Longer-term studies would be required to determine whether earthworm populations are limited by swarm raids. The small impacts of individual raids and rapid recovery of earthworm prey populations likely underlie the low frequency of migrations and short distances travelled by migrating colonies of D. molestus.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3

References

  1. Besag J. 1977. Contribution to the discussion of Dr. Ripley’s paper. J. R. Stat. Soc. B 39: 193-195

    Google Scholar 

  2. Brussaard L. 1998. Soil fauna, guilds, functional groups and ecosystem processes. Appl. Soil Ecol. 9: 123-135

    Article  Google Scholar 

  3. Bussmann R. 1994. The Forests of Mt Kenya – Vegetation, Ecology, Destruction and Management of a Tropical Mountain Forest Ecosystem. PhD thesis, University of Bayreuth, Germany.

  4. Chang C.-H., Rougerie R. and Chen J.-H. 2009. Identifying earthworms through DNA barcodes: pitfalls and promise. Pedobiologia 52: 171-180

    Article  CAS  Google Scholar 

  5. Dejean A., Schatz B., Orivel J. and Beugnon G. 1999. Prey capture behavior of Psalidomyrmex procerus (Formicidae: Ponerinae), a specialist predator of earthworms (Annelida). Sociobiology 34: 545-554

    Google Scholar 

  6. Dunham A.E. 2008. Above and below ground impacts of terrestrial mammals and birds in a tropical forest. Oikos 117: 571-579

    Article  Google Scholar 

  7. Fragoso C. and Lavelle P. 1992. Earthworm communities of tropical rain forests. Soil Biol. Biochem. 24: 1397-1408

    Article  Google Scholar 

  8. Frank D.A. 2008. Evidence for top predator control of a grazing ecosystem. Oikos 117: 1718-1724

    Article  Google Scholar 

  9. Franks N.R. 1980. The Evolutionary Ecology of the Army Ant Eciton burchelli on Barro Colorado Island, Panama. PhD thesis, University of Leeds, UK

  10. Franks N.R. 1982. A new method for censusing animal populations: the number of Eciton burchelli army ant colonies on Barro Colorado Island, Panama. Oecologia 52: 266-268

    Article  Google Scholar 

  11. Franks N.R. 2001. Evolution of mass transit systems in ants: a tale of two societies. In: Insect Movement: Mechanisms and Consequences (Woiwod I., Reynolds D.R. and Thomas C.D., Eds). CAB International Publishing, Wallingford, UK, pp 281-298

  12. Franks N.R. and Fletcher C.R. 1983. Spatial patterns in army ant foraging and migration. Eciton burchelli on Barro Colorado, Panama. Behav. Ecol. Sociobiol. 12: 261-270

    Article  Google Scholar 

  13. Franks N.R., Sendova-Franks A.B., Simmons J. and Mogie M. 1999. Convergent evolution, superefficient teams and tempo in Old and New World army ants. Proc. R. Soc. London B 266: 1697-1701

    Article  Google Scholar 

  14. Freitas A.V.L. 1994. Nest relocation and prey specialization in the ant Leptogenys propefalcigera Roger (Formicidae: Ponerinae) in an urban area in southeastern Brazil. Insect. Soc. 42: 453-456

    Article  Google Scholar 

  15. Gotwald W.H. Jr. 1974. Predatory behavior and food preferences of driver ants in selected African habitats. Ann. Entomol. Soc. Am. 67: 877–886

    Google Scholar 

  16. Gotwald W. H. Jr. 1978. Trophic ecology and adaptation in tropical Old World ants of the subfamily Dorylinae. Biotropica 10: 161-169.

    Article  Google Scholar 

  17. Gotwald W.H. Jr 1995 Army Ants – The Biology of Social Predation. Cornell University Press. Ithaca and London. 302 pp

  18. Hebert P.D.N., Cywinska A., Ball S.L. and deWaard J.R. 2003 Biological identification through DNA barcodes. Proc. R. Soc. London B 270: 313–321

    Article  CAS  Google Scholar 

  19. Hendrix P.F. and Bohlen P.J. 2002. Exotic earthworm invasions in North America: ecological and policy implications. BioScience 52: 1-11

    Article  Google Scholar 

  20. Hölldobler B. and Wilson E.O. 1990. The Ants. Cambridge, Massachusetts: Belknap Press of Harvard University Press. 732 pp

  21. Hooper D.U., Bignell D.E., Brown V.K., Brussaard L., Dangerfield J.M., Wall D.H., Wardle D.A., Coleman D.C., Giller K.E., Lavelle P., van der Putten W.H., de Ruiter P.C., Rusek J., Silver W.E., Tiedje J.M. and Wolters V. 2000. Interactions between aboveground and belowground biodiversity in terrestrial ecosystems: patterns, mechanisms, and feedbacks. BioScience 50: 1049-1061

    Article  Google Scholar 

  22. Keith S., Urban E.K. and Fry C.H. 1992. The Birds of Africa. Vol. 4. Academic Press. London. pp

  23. Kingdon J. 1997. The Kingdon Field Guide to African Mammals. Academic Press. San Diego. 450 pp

  24. Kronauer D.J.C., Schöning C. and Boomsma J.J. 2006. Male parentage in army ants. Mol. Ecol. 15: 1147-1151

    Article  CAS  PubMed  Google Scholar 

  25. Kronauer D.J.C., Schöning C., Vilhelmsen L. and Boomsma J.J. 2007. A molecular phylogeny of Dorylus army ants provides evidence for multiple evolutionary transitions in foraging niche. BMC Evol. Biol. 7: 56. http://www.biomedcentral.com/1471-2148/7/56

  26. Lavelle P. 1997. Faunal activities and soil processes: adaptive strategies that determine ecosystem function. Adv. Ecol. Res. 27: 93-132

    Article  Google Scholar 

  27. Lavelle P., Bignell D., Lepage M., Wolters V., Roger P., Ineson P., Heal O.W. and Dhillion S. 1997. Soil function in a changing world: the role of invertebrate ecosystem engineers. Eur. J. Soil Biol. 33: 159-193

    CAS  Google Scholar 

  28. Leroux J.M. 1982. Ecologie des populations de dorylines Anomma nigricans dans la Région de Lamto (Côte d’Ivoire). Publ. Lab. Zool. 22. E.N.S. Paris.

  29. Moffett M.W. 1988. Nesting, emigrations, and colony foundation in two group-hunting Myrmicine ants (Hymenoptera: Formicidae: Pheidologeton). In: Advances in Myrmecology (Trager J.C., Ed). Leiden: E.J. Brill, pp 355-370

    Google Scholar 

  30. Perreault J.M., Whalen J.K. 2006. Earthworm burrowing in laboratory microcosms as influenced by soil temperature and moisture. Pedobiologia 50: 397-403

    Article  Google Scholar 

  31. Peters M.K., Likare S., Kraemer M. 2008. Effects of habitat fragmentation and degradation on flocks of African ant-following birds. Ecol. Appl. 18: 847-858

    Article  PubMed  Google Scholar 

  32. Raignier A., van Boven J.K.A. 1955. Etude taxonomique, biologique et biométrique des Dorylus du sous-genre Anomma (Hymenoptera: Formicidae). Ann. Mus. R. Congo Belg. Tervuren. Sc. Zool. 2: 1-359

    Google Scholar 

  33. Ripley B.D. 1976. The second-order analysis of stationary point processes. J. Appl. Prob. 13: 255-266

    Article  Google Scholar 

  34. Savage T.S. 1847. The driver ants of West Africa. Proc. Acad. Nat. Sci. Phil. 4: 195-200

    Google Scholar 

  35. Schoener T.W. and Spiller D.A. 1996. Devastation of prey diversity by experimentally introduced predators in the field. Nature 381: 691-694

    Article  CAS  Google Scholar 

  36. Schöning C., Njagi W. and Franks N.R. 2005a. Temporal and spatial patterns in the emigrations of the army ant Dorylus (Anomma) molestus in the montane forest of Mt Kenya. Ecol. Entomol. 30: 532-540

    Article  Google Scholar 

  37. Schöning C., Kinuthia W. and Franks N.R. 2005b. Evolution of allometries in the worker caste of Dorylus army ants. Oikos 110: 231-240

    Article  Google Scholar 

  38. Schöning C., Njagi W. and Kinuthia W. 2008. Prey spectra of two swarm-raiding army ant species in East Africa. J. Zool. 274: 85-93

    Google Scholar 

  39. Schmitz O.J. 2003. Top predator control of plant biodiversity and productivity in an old-field ecosystem. Ecol. Lett. 6: 156–163

    Article  Google Scholar 

  40. Sih A., Crowley P., McPeek M., Petranka J. and Strohmeier K. 1985. Predation, competition, and prey communities: a review of field experiments. Ann. Rev. Ecol. Syst. 16: 269–312

    Article  Google Scholar 

  41. Sims R.W. 1982. Revision of the eastern African earthworm genus Polytoreutus (Eudrilidae: Oligochaeta). Bull. Brit. Mus. (Nat. Hist.) Zool. Ser. 43: 253-298

    Google Scholar 

  42. Sinclair A.E. 2003. Mammal population regulation, keystone processes and ecosystem dynamics. Phil. Trans. R. Soc. Lond. B 358: 1729-1740

    Article  CAS  Google Scholar 

  43. Sokal R.S. and Rohlf F.J. 1995. Biometry. 3rd Ed. W.H. Freeman, New York. 887 pp

  44. Speck H. 1983. Mount Kenya Area. Ecological and Agricultural Significance of the Soils. Geographica Bernensia. African Studies A2

  45. Stevenson T. and Fanshawe J. 2002. Field Guide to the Birds of East Africa. T. and A.D. Poyser. 600 pp

  46. Swartz M.B. 1997. Behavioral and Population Ecology of the Army Ant Eciton burchelli and Ant-Following Birds. PhD thesis. University of Texas, Austin, USA

  47. Terborgh J., Lopez L., Nuňez P., Rao M., Shahabuddin G., Orihuela G., Riveros M., Ascanio R., Adler G.H., Lambert T.D. and Balbas L. 2001. Ecological meltdown in predator-free forest fragments. Science 294: 1923-1926

    Article  CAS  PubMed  Google Scholar 

  48. Vosseler J. 1905. Die ostafrikanische Treiberameise (Siafu). Der Pflanzer 1: 289-302

    Google Scholar 

  49. Weber N.A. 1943. The ants of the Imatong Mountains, Anglo-Egyptian Sudan. Bull. Mus. Comp. Zool. Harvard Coll. 93: 263-389

    Google Scholar 

  50. Wiegand T. and Moloney K.A. 2004. Rings, circles, and null-models for point pattern analysis in ecology. Oikos 104: 209-229

    Article  Google Scholar 

  51. Wilson E.O. 1958. The beginnings of nomadic and group predatory behaviour in the ponerine ants. Evolution 12: 24-36

    Article  Google Scholar 

Download references

Acknowledgments

We are grateful to Washington Njagi and Mwenda Tiraka for help during fieldwork and the Kenya Wildlife Service and the Kenyan Ministry of Education, Science and Technology for granting research permission. We thank Klaus Riech for preparing Fig. 1. C.S. wishes to thank Jacobus Boomsma and Eduard Linsenmair for fruitful discussions on the impact of driver ant predation on prey populations. Jon Fjeldså confirmed the ID of Alethe poliocephala based on pictures, and Titus Imboma kindly provided information on ecology of this bird. Two anonymous referees made useful suggestions that helped improve the manuscript. Financial support was provided by the Alexander von Humboldt-Foundation and the Danish National Research Foundation.

Author information

Affiliations

Authors

Corresponding author

Correspondence to C. Schöning.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOC 1271 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Schöning, C., Csuzdi, C., Kinuthia, W. et al. Influence of driver ant swarm raids on earthworm prey densities in the Mount Kenya forest: implications for prey population dynamics and colony migrations. Insect. Soc. 57, 73–82 (2010). https://doi.org/10.1007/s00040-009-0052-y

Download citation

Keywords

  • Ant-following birds
  • Army ants
  • Dorylus molestus
  • Nomadism