Reduced food availability and predictability promote competition and decrease social cohesion

Patrícia Beltrão, Ana Cristina R. Gomes, Gonçalo C. Cardoso

This is a plain language summary of a Functional Ecology research article which is published here.

Searching for food in groups allows the sharing of information on food locations between individuals, which is most beneficial when those locations are scarce or unpredictable. Therefore, animals might choose to explore food sources in groups during challenging or changing environmental conditions. Alternatively, increased competition when resources are scarce might destabilize groups and compromise cooperative behaviour.

To evaluate these scenarios, we reduced the number of food sources (feeders with seeds) available to common waxbills in a large open-air aviary, and studied their feeding patterns, aggressive interactions and social connections. Decreasing the number of feeders caused increased aggression, weaker social connections between individuals and smaller foraging groups. Individuals also spent less time at the feeders per group visit and had to make more visits per day to the feeding area, meaning that they spent more energy and had a less efficient foraging behaviour. Similar results were observed when the number of feeders was reduced unpredictably across days, rather than permanently, indicating social effects longer than day-to-day adjustments.

Common waxbill ringed with a small tag on its leg, to monitor feeding behaviour, social connections and dominance relationships. A mesocosm population with tagged individuals allowed studying collective behaviour when facing ecological challenges (Credit: Patrícia Beltrão)

Although our results show what appears to be a less efficient behaviour upon changes in food availability and predictability, it is important to note that in nature these behaviours might actually be adaptive. Waxbills are adapted to unpredictable environments in their native habitat (sub-Saharan Africa), due to fluctuations in rainfall that affect the availability of seeds, and they may often need to look for and switch to alternative locations in search of food sources. In nature, the increased aggression and group fragmentation that we found might function as an early trigger to explore alternative locations before local food sources are severely depleted.

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