August 13, 2011

Toucan tracking reveals rainforest secrets

 GPS devices show relationship between tree seed dispersal and tropical birds

Nutmeg seed eating toucans wearing GPS transmitters recently helped the Smithsonian Tropical Research Institute in Panama understand tree seed dispersal which could help rainforest protection and conservation. Data from the GPS revealed that toucans are excellent at dispersing seeds, particularly after breakfast. The same data now forms the basis of a map of the relative patterns and distances that toucans distribute the seeds of a nutmeg tree.

Until now, ecologists studying forest dynamics have relied mainly on theoretical models to calculate the area of seed distribution for certain plants. This new tracking technology is changing this. However, the first phase of this study fed fresh seeds from a common Panamanian nutmeg tree (Virola nobilis) to captive toucans (Ramphastos sulfuratus) at the Rotterdam Zoo to find out how quickly the hard inner seed is regurgitated. Five zoo toucans fed 100 nutmeg seeds took an average of 25.5 minutes to process and regurgitate the seeds.

The second phase was with 6 wild GPS tracked toucans in Panama, that were feeding from a large nutmeg tree in the rainforest at Gamboa. Compared with the seed-regurgitation time of the zoo toucans, the GPS data indicated that wild toucans were probably dropping nutmeg seeds a distance of 472 feet, on average, from the mother tree. Each seed had a 56 percent probability of being dropped at least 328 feet from its mother tree and an 18 percent chance of being dropped some 656 feet from the tree. Additionally, data revealed that the toucans’ peak activity and movement was in the morning. Conveniently, tropical nutmegs are “early morning specialists” with fruits that generally ripen during early and mid-morning, ideal for quick removal and effective dispersal by birds.


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