Tucanes con GPS ayudan a estudiar la dispersión de las semillas/Toucans Wearing GPS Help to Study Seed Dispersal

El éxito reproductivo de cualquier frutal depende de la eficacia de la dispersión de sus semillas , pero el seguimiento y mapeado de las semillas individuales llevadas por el viento o ingeridas por los animales es casi imposible. Hoy, por hoy los ecólogos que estudian la dinámica del bosque confían sobre todo en modelos teóricos para determinar el área de distribución de semillas para plantas específicas. Las nuevas tecnologías de seguimiento están cambiando eso.
En la primera fase de un experimento llevado a cabo por científicos del Smithsonian Tropical Research Institute de Panamá , se recogieron semillas frescas de un árbol de nuez moscada común panameño (Virola nobilis) on las que se alimentó a tucanes (Ramphastos sulfuratus) cautivos del zoológico de Rotterdam. El tucán se traga entera la semilla de nuez moscada: la pulpa externa es digerida mientras que la pepita interna es regurgitada. Cinco tucanes del zoológico que se comieron 100 semillas de nuez moscada tardaron una media de 25.5 minutos para procesar y regurgitar las pepitas.
Después, en Panamá, los científicos capturaron seis tucanes salvajes ( cuatro R. sulfuratus y dos R. swainsonii) que se alimentaban de un enorme árbol de nuez moscada en la selva tropical de Gamboa. Les colocaron mochilas ligeras que contenían dispositivos GPS (que registraban la localización exacta del pájaro cada 15 minutos) y con acelerómetros que pueden medir la actividad diaria de las aves.
Al comparar con el tiempo medio de regurgitación de los tucanes del zoo, los datos GPS indicaron que los tucanes salvajes regurgitaban las pepitas una distancia media de 155 m del árbol madre. Cada semilla tenía un 56% de probabilidades de ser regurgitada como mínimo a 100 m del árbol y un 18% de serlo a 215 m
Además, el acelerómetro reveló que el pico de actividad y movimiento de los tucanes se producía por la mañana con un descanso a mediodía. un pico secundario de actividad por la tarde, e inactividad completa en la noche. Este es un patrón normal para los pájaros tropicales.
Según los científicos: “ La hora de la alimentación tenía una fuerte influencia en la dispersión de la semilla, Las semillas injgridas por la mañana (desayuno) y por la tarde (cena) tenían más probabilidad de ser dispersadas significativamente que las ingeridas al mediodía (almuerzo)."
Esta observación explica porqué los árboles de nuez moscada tropicales son "especialistas de la madrugada” y dan frutos que maduran a la madrugada y a la media mañana de manera que sean fácilmente ingeridos por los pájaros”.
El video corresponde a la canción 'El Tucán' del grupo español Esclarecidos

The reproductive success of any fruiting plant depends upon how effectively its seeds are dispersed, yet tracking and mapping individual seeds carried off by the wind or ingested by animals is nearly impossible. Today, ecologists studying forest dynamics rely mostly on theoretical models to calculate the area of seed distribution for specific plants. New tracking technology is changing that.
During the first stages of an experiment carried out by scientists at the Smithsonian Tropical Research Institute in Panama, fresh seeds from a common Panamanian nutmeg tree (Virola nobilis) were collected and fed them to captive toucans (Ramphastos sulfuratus) at the Rotterdam Zoo. Toucans gulp nutmeg seeds whole, the outer pulp is processed in the bird's crop, and the hard inner seed is then regurgitated. Five zoo toucans fed 100 nutmeg seeds took an average of 25.5 minutes to process and regurgitate the seeds.
Next, in Panama, the scientists netted six wild toucans (four R. sulfuratus and two R. swainsonii) that were feeding from a large nutmeg tree in the rainforest at Gamboa. They fitted the birds with lightweight backpacks containing GPS tracking devices (these devices recorded the birds' exact location every 15 minutes) and accelerometers which can measure a bird's daily activity level.
When matched with the seed-regurgitation time of the zoo toucans, the GPS data indicated the 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.
In addition, the accelerometer revealed that the toucans' peak activity and movement was in the morning followed by a lull at midday, a secondary activity peak in the afternoon, and complete inactivity at night. This is a normal pattern of tropical birds.
"Time of feeding had a strong influence on seed dispersal," the scientists write. "Seeds ingested in morning (breakfast) and afternoon (dinner) were more likely to achieve significant dispersal than seeds ingested mid-day (lunch)."
This observation explains why tropical nutmegs are "early morning specialists" with fruits that typically ripen at early and mid-morning so they are quickly removed by birds.
The video is the song 'El Tucán (The Toucan)' by the spanish band 'Esclarecidos'

Tomado de/Taken from Science daily

Resumen de la publicación/Abstract of the paper
The effect of feeding time on dispersal of Virola seeds by toucans determined from GPS tracking and accelerometers
Roland Kaysa, Patrick A. Jansenb,Elise M.H. Knechtc, Reinhard Vohwinkele and Martin Wikelskib
Acta Oecologica http://dx.doi.org/10.1016/j.actao.2011.06.007
Abstract
Seed dispersal is critical to understanding forest dynamics but is hard to study because tracking seeds is difficult. Even for the best-studied dispersal system of the Neotropics, Virola nobilis, the dispersal kernel remains unknown. We combined high-resolution GPS/3D-acceleration bird tracking, seed-retention experiments, and field observations to quantify dispersal of V. nobilis by their principal dispersers, Ramphastos toucans. We inferred feeding events from movement data, and then estimated spatio-temporally explicit seed-dispersal kernels. Wild toucans moved an average of 1.8 km d−1 with two distinct activity peaks. Seed retention time in captive toucans averaged 25.5 min (range 4–98 min). Estimated seed dispersal distance averaged 144 ± 147 m, with a 56% likelihood of dispersal >100 m, two times further than the behaviour-naive estimate from the same data. Dispersal was furthest for seeds ingested in the morning, and increased with seed retention time, but only up to 60 min after feeding. Our study supports the long-standing hypothesis that toucans are excellent dispersers of Virola seeds. To maximize seed dispersal distances trees should ripen fruit in the morning when birds move the most, and produce fruits with gut-processing times around 60 min. Our study demonstrates how new tracking technology can yield nuanced seed dispersal kernels for animals that cannot be directly observed