Limits...
Feeding and stocking up: radio-labelled food reveals exchange patterns in ants.

Buffin A, Denis D, Van Simaeys G, Goldman S, Deneubourg JL - PLoS ONE (2009)

Bottom Line: Our results show that, from the very first load that enters the nest, food present within the colony acts as negative feedback to entering food.Examining the position of these workers inside the nest, we found heavily loaded ants in the centre of the aggregate.Indeed the food-flow decreases proportionally to the food that has already been harvested, liberating the work-force for other tasks.

View Article: PubMed Central - PubMed

Affiliation: Unit of Social Ecology, Université libre de Bruxelles, Brussels, Belgium. aubuffin@ulb.ac.be

ABSTRACT
Food sharing is vital for a large number of species, either solitary or social, and is of particular importance within highly integrated societies, such as in colonial organisms and in social insects. Nevertheless, the mechanisms that govern the distribution of food inside a complex organizational system remain unknown. Using scintigraphy, a method developed for medical imaging, we were able to describe the dynamics of food-flow inside an ant colony. We monitored the sharing process of a radio-labelled sucrose solution inside a nest of Formica fusca. Our results show that, from the very first load that enters the nest, food present within the colony acts as negative feedback to entering food. After one hour of the experiments, 70% of the final harvest has already entered the nest. The total foraged quantity is almost four times smaller than the expected storage capacity. A finer study of the spatial distribution of food shows that although all ants have been fed rapidly (within 30 minutes), a small area representing on average 8% of the radioactive surface holds more than 25% of the stored food. Even in rather homogeneous nests, we observed a strong concentration of food in few workers. Examining the position of these workers inside the nest, we found heavily loaded ants in the centre of the aggregate. The position of the centre of this high-intensity radioactive surface remained stable for the three consecutive hours of the experiments. We demonstrate that the colony simultaneously managed to rapidly feed all workers (200 ants fed within 30 minutes) and build up food stocks to prevent food shortage, something that occurs rather often in changing environments. Though we expected the colony to forage to its maximum capacity, the flow of food entering the colony is finely tuned to the colony's needs. Indeed the food-flow decreases proportionally to the food that has already been harvested, liberating the work-force for other tasks.

Show MeSH
Spatial stability: shift of the centre of gravity.Displacement (in pixels) of the centre of gravity as a function of the time (minute, n = 15). Mean value (♦) and standard deviation (bars).
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pone-0005919-g006: Spatial stability: shift of the centre of gravity.Displacement (in pixels) of the centre of gravity as a function of the time (minute, n = 15). Mean value (♦) and standard deviation (bars).

Mentions: The mean distance between two centres of successive pictures rapidly decreases (fig. 6). After 25 minutes, the distance between the centre of two successive pictures is smaller than the mean distance between two random points of a square corresponding to the nest area (after 25 minutes, one sample t test, t75 = 68, p<0.0001, n = 77). We can therefore assert that the position of the zone of highest radioactive concentration is stable and that this stability arises quite early in the experiment.


Feeding and stocking up: radio-labelled food reveals exchange patterns in ants.

Buffin A, Denis D, Van Simaeys G, Goldman S, Deneubourg JL - PLoS ONE (2009)

Spatial stability: shift of the centre of gravity.Displacement (in pixels) of the centre of gravity as a function of the time (minute, n = 15). Mean value (♦) and standard deviation (bars).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691603&req=5

pone-0005919-g006: Spatial stability: shift of the centre of gravity.Displacement (in pixels) of the centre of gravity as a function of the time (minute, n = 15). Mean value (♦) and standard deviation (bars).
Mentions: The mean distance between two centres of successive pictures rapidly decreases (fig. 6). After 25 minutes, the distance between the centre of two successive pictures is smaller than the mean distance between two random points of a square corresponding to the nest area (after 25 minutes, one sample t test, t75 = 68, p<0.0001, n = 77). We can therefore assert that the position of the zone of highest radioactive concentration is stable and that this stability arises quite early in the experiment.

Bottom Line: Our results show that, from the very first load that enters the nest, food present within the colony acts as negative feedback to entering food.Examining the position of these workers inside the nest, we found heavily loaded ants in the centre of the aggregate.Indeed the food-flow decreases proportionally to the food that has already been harvested, liberating the work-force for other tasks.

View Article: PubMed Central - PubMed

Affiliation: Unit of Social Ecology, Université libre de Bruxelles, Brussels, Belgium. aubuffin@ulb.ac.be

ABSTRACT
Food sharing is vital for a large number of species, either solitary or social, and is of particular importance within highly integrated societies, such as in colonial organisms and in social insects. Nevertheless, the mechanisms that govern the distribution of food inside a complex organizational system remain unknown. Using scintigraphy, a method developed for medical imaging, we were able to describe the dynamics of food-flow inside an ant colony. We monitored the sharing process of a radio-labelled sucrose solution inside a nest of Formica fusca. Our results show that, from the very first load that enters the nest, food present within the colony acts as negative feedback to entering food. After one hour of the experiments, 70% of the final harvest has already entered the nest. The total foraged quantity is almost four times smaller than the expected storage capacity. A finer study of the spatial distribution of food shows that although all ants have been fed rapidly (within 30 minutes), a small area representing on average 8% of the radioactive surface holds more than 25% of the stored food. Even in rather homogeneous nests, we observed a strong concentration of food in few workers. Examining the position of these workers inside the nest, we found heavily loaded ants in the centre of the aggregate. The position of the centre of this high-intensity radioactive surface remained stable for the three consecutive hours of the experiments. We demonstrate that the colony simultaneously managed to rapidly feed all workers (200 ants fed within 30 minutes) and build up food stocks to prevent food shortage, something that occurs rather often in changing environments. Though we expected the colony to forage to its maximum capacity, the flow of food entering the colony is finely tuned to the colony's needs. Indeed the food-flow decreases proportionally to the food that has already been harvested, liberating the work-force for other tasks.

Show MeSH