The role of scatterhoarding in the regeneration of rodent-dispersed rainforest trees in French Guiana

Project description

Many granivorous animals all over the world scatterhoard seed in fall or wet season for consumption in winter or dry season. These animals carry seeds away from the adult plant and siblings and bury them just below the surface, each seed at a different spot. This behaviour has early been recognised as a potentially effective mechanism of seed dispersal for nut-bearing tree species. The idea is that scatterhoarded seeds have far greater chances to establish than seeds remaining below the parent plant, if they escape recovery and consumption for whatever reason. The resulting advantage should outweigh the loss of many seeds being consumed by the scatterhoarder.

Scatterhoarding and tree regeneration
My research has focussed on the role of scatterhoarding rodents in the regeneration of nut-bearing trees. I tried to find out how scatterhoarding influenced plant reproductive success, and how scatterhoarding could be an effective seed dispersal mechanism. I was especially interested in selective pressures that scatterhoarding animals impose on plants in their roles of both seed disperser and seed predator. We expected that larger seeds would be more likely dispersed than smaller because rodents would prefer more nutritous food items. Also, we were interested in the effect of ambient seed abundance on the probability of seeds being successfully dispersed.

One approach was to follow different-sized seeds from a single tree species in space and time and compare the fate pathways of large and small seeds, and the ultimate fate of scatterhoarded and non-scatterhoarded seeds. We used battery-powered infrared-triggered video devices to monitor seed selection and harvest by scatterhoarding rodents and other granivorous animals without disturbing the animals. We then localised and tracked the harvested seeds using threadmarks attached to them, which protrude from the soil even when seeds are buried.

Most work was carried out at the Nouragues Biological Station in French Guiana, South America, where we study interactions between the red acouchy (Myoprocta acouchy) and several large-seeded trees, including Carapa procera (Meliaceae), Vouacapoua americana (Leguminosae) and Licania alba (Chrysobalanaceae). We have also been working at the Veluwe, The Netherlands, where we considered the interaction between oak (Quercus robur) and wood mouse (Apodemus sylvaticus).

Some results have been presented in a PhD thesis, and various papers. Please send an e-mail to Patrick Jansen if you want to be kept informed about this research program. 

Top 

• new paper on Carapa by Forget, P.-M. & P.A. Jansen (Conservation Biology, in press 2007) has attracted a very good and interesting attention. See: http://news.mongabay.com/2006/1220-ntfp.html

Top 

• Forget, P.-M. & P.A. Jansen (2007). Hunting Increases Dispersal Limitation in the Tree Carapa procera, a Nontimber Forest Product. Conservation Biology 21 (1): 106–113.
• Jansen, P.A., F. Bongers & H.H.T. Prins (2006). Tropical rodents change rapidly germinating seeds into long-term food supplies. Oikos 113: 449-458.
• Jansen, P.A. & J. den Ouden (2005). Observing seed removal: remote video monitoring seed selection, predation and dispersal. pp. 363-378 in: P.M. Forget, J.E. Lambert, P.E. Hulme & S.B. Vander Wall (eds.) Seed fate: predation and secondary dispersal. CABI publishing, Wallingford.
• Van der Hoeven, N., L. Hemerik, and P.A. Jansen (2005). Balancing Statistics and Ecology: Lumping Experimental Data for Model Selection. Pp. 233-265 in: Hemerik, L. and Reydon, T. A. C. (eds.), Current Themes in Theoretical Biology: A Dutch Perspective. Springer, Dordrecht.
• Jansen, P.A., F. Bongers & L. Hemerik (2004). Seed mass and mast seeding enhance dispersal by scatter-hoarding rodents in a Neotropical rainforest tree. Ecological Monographs (in press). 
• Hoeven, N. van der, L. Hemerik & P.A. Jansen (2004). Balancing statistics and ecology: lumping experimental data for model selection. Acta Biotheoretica (in press).
• Jansen, P.A. & J. den Ouden (2004). Observing seed removal: remote video monitoring seed selection, predation and dispersal. In: P.M. Forget, J.E. Lambert, P.E. Hulme & S.B. Vander Wall (eds) Seed fate: predation and secondary dispersal. CABI publishing, Wallingford (in press).
• Ouden, J. den, P.A. Jansen & R. Smit (2004). Jays, mice and oaks: predation and dispersal of Quercus robur and Q. petraea in north-western Europe. In: P.M. Forget, J.E. Lambert, P.E. Hulme & S.B. Vander Wall (eds) Seed fate: predation and secondary dispersal. CABI publishing, Wallingford (in press).
• Jansen, P.A. (2003). Scatterhoarding and tree regeneration. Ecology of nut dispersal in a Neotropical rainforest. PhD thesis Wageningen University, Wageningen, the Netherlands, X+166 pp. (Summary in Dutch).  ISBN 90-5808-777-8.
• Jansen, P.A., M. Bartholomeus, F. Bongers, J.A. Elzinga, J. Den Ouden & S.E. Van Wieren (2002). The role of seed size in dispersal by a scatterhoarding rodent. Pp. 209-225 in: D. Levey, W.R. Silva & M. Galetti (eds). Seed Dispersal and Frugivory: Ecology, Evolution and Conservation. CAB International, Wallingford.
• Jansen, P.A. & P.M. Forget (2001). Scatterhoarding rodents and tree regeneration in French Guiana. Pp. 275-288.
  In: F. Bongers, P. Charles-Dominique, P.M. Forget & M. Théry (eds). Nouragues: Dynamics and plant-animal interactions in a Neotropical rainforest. Kluwer Academic Publishers, Dordrecht.
• Jansen, P.A. & P.A. Zuidema (2001). Logging, seed dispersal by vertebrates, and the natural regeneration of tropical timber trees. Pp. 35-59 in: R.A. Fimbel, J.G. Robinson & A. Grajal (eds). The cutting edge. Conserving wildlife in logged tropical forests. Columbia University Press, New York.

• Nouragues Biological Station
• Programme on the Dutch television (in Dutch) about the research of Jan den Ouden and Patrick Jansen on seed dipersal of oak. After broadcasting on April 27 2003, the programme can be found on the TELEAC Jota! website.