Leaf caching in Atta leafcutting ants: discrete cache formation through positive feedback

Area of Science:

• Animal Behavior
• Ecology
• Entomology

Background:

• Leafcutting ants exhibit complex foraging behaviors.
• Resource availability can fluctuate, impacting colony efficiency.
• Temporary bottlenecks at nest entrances can disrupt foraging.

Purpose of the Study:

• To investigate the occurrence, mechanism, and costs/benefits of leaf caching in leafcutting ants.
• To understand the factors influencing the formation of leaf caches.
• To evaluate the adaptive significance of leaf caching behavior.

Main Methods:

• Laboratory experiments with Atta cephalotes and A. colombica colonies.
• Observation of leaf caching at nest entrances and foraging trails.
• Manipulation of leaf cache sizes presented to foraging ants.
• Recording the probability of foragers dropping leaves on caches.
• Comparing retrieval times for cached versus scattered leaf pieces.

Main Results:

• Leaf caches form when foragers encounter temporary nest entrance bottlenecks.
• The probability of a forager dropping a leaf is positively correlated with cache size.
• Cached leaf pieces are more likely to be retrieved than non-cached pieces.
• Retrieval time from caches is longer compared to scattered leaf pieces.

Conclusions:

• Positive feedback mechanisms contribute to the formation of nest entrance leaf caches.
• Flexible nest entrance caching is an adaptive strategy for fluctuating resource availability.
• Leaf caching represents a trade-off between accessibility and retrieval efficiency for leafcutting ants.