, Volume 146, Issue 1, pp 57–67 | Cite as

Incorporating patterns of disperser behaviour into models of seed dispersal and its effects on estimated dispersal curves

  • David A. Westcott
  • Joan Bentrupperbäumer
  • Matt G. Bradford
  • Adam McKeown
Plant Animal Interactions


The processes determining where seeds fall relative to their parent plant influence the spatial structure and dynamics of plant populations and communities. For animal dispersed species the factors influencing seed shadows are poorly understood. In this paper we test the hypothesis that the daily temporal distribution of disperser behaviours, for example, foraging and movement, influences dispersal outcomes, in particular the shape and scale of dispersal curves. To do this, we describe frugivory and the dispersal curves produced by the southern cassowary, Casuarius casuarius, the only large-bodied disperser in Australia’s rainforests. We found C. casuarius consumed fruits of 238 species and of all fleshy-fruit types. In feeding trials, seeds of 11 species were retained on average for 309 min (±256 SD). Sampling radio-telemetry data randomly, that is, assuming foraging occurs at random times during the day, gives an estimated average dispersal distance of 239 m (±207 SD) for seeds consumed by C. casuarius. Approximately 4% of seeds were dispersed further than 1,000 m. However, observation of wild birds indicated that foraging and movement occur more frequently early and late in the day. Seeds consumed early in the day were estimated to receive dispersal distances 1.4 times the ‘random’ average estimate, while afternoon consumed seeds received estimated mean dispersal distances of 0.46 times the ‘random’ estimate. Sampling movement data according to the daily distribution of C. casuarius foraging gives an estimated mean dispersal distance of 337 m (±194 SD). Most animals’ behaviour has a non-random temporal distribution. Consequently such effects should be common and need to be incorporated into seed shadow estimation. Our results point to dispersal curves being an emergent property of the plant–disperser interaction rather than being a property of a plant or species.


Seed shadow Dispersal curves Gut passage rate Casuarius casuarius Cassowary 



We thank QPWS, in particular Andrew Dennis and Michael Cermak, for assistance in the field. Frederieke Kroon and Andrew Dennis contributed to the compilation of the cassowary foraging data used in the analysis and commented on the work generally. The Johnstone River Crocodile Farm and Rainforest Habitat allowed us to trial transmitter attachments on their valuable captive birds. Johnstone River Crocodile Farm, the Rainforest Habitat, Hartley’s Creek Crocodile Farm and Wild World allowed us to use their cassowaries in feeding trials and modified their routines to accommodate us. We are extremely grateful to them. The work was conducted under CSIRO Animal Ethics Approval OB15/12 and Queensland Department of the Environment Scientific Purposes Permit FO/001071/96/SAB. The research was in part supported by the Earthwatch Institute and we thank the volunteers for their assistance. JB received financial support from Environment Australia and the Wet Tropics Management Authority. Earlier versions of this paper were improved by comments by Louise Shilton, Andrew Dennis, Dan Metcalfe, Andrew Mack and an anonymous reviewer.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • David A. Westcott
    • 1
  • Joan Bentrupperbäumer
    • 2
  • Matt G. Bradford
    • 1
  • Adam McKeown
    • 1
  1. 1.CSIRO Sustainable Ecosystems & the Rainforest CRCAtherton QAustralia
  2. 2.Department of Tropical Environmental Science and Geography & the Rainforest CRCJames Cook UniversityCairnsAustralia

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