The present study provides detailed data on the foraging strategy of an ant that obligatorily exploits an unpredictable food source. To harvest fast-decaying mushrooms E. procera established a complex network of remarkably stable trails, which were used
only temporarily. Subsections of the trail network were abandoned over longer time spans and later followed again with high trail fidelity, leading us to reject our initial hypothesis of a fully flexible trail system consisting only of temporary trails. This hypothesiswas based on the assumption that mushrooms represent a spatiotemporally unpredictable food source. Our detailed, fine-scaled investigation of mushroom growth patterns in a Malayan tropical rainforest revealed, however, that mushroom growth was to some degree predictable. Predictability of mushrooms in space and time depended on the fungal species and on the timescale under consideration. The presence of most mushrooms harvested by the ants appeared unpredictable only when short time periods were
considered. Persisting for only a few days, they appeared to be
randomly distributed in space at any given point in time. Looking at
longer time periods, however, mushroom occurrence was to some
degree predictable because the same species frequently reappeared
in close proximity to its previous growth location within days or
weeks. Consequently, many mushroom species may be better
classified as a periodically regenerating resource with reasonable
spatial but low temporal predictability.
Our detailed examination of E. procera’s food preferences supports
the view of mushrooms being a regenerating food source for
the ants. Exclusively soft-bodied and mainly fast-decaying mushrooms
were harvested; these showed both a higher tendency to
reappear and a higher frequency of regrowth locally. Indeed, there
were almost always mushrooms available at our study site, offering
a reliable food supply to an animal that shows a rather generalistic
mushroom feeding habit, such as E. procera. Besides providing a
sufficient food supply, a general mushroom feeding habit is probably
also beneficial for achieving a balanced diet for an obligate