Leaf-cutting ants stay sanitary with clever waste storage systems
Leaf-cutting ants are widely recognized for their ability to farm fungus, a feat that demands a high level of social organization. Some colonies contain as many as 8 million close relatives living in close quarters.
While it’s nice to be close with one’s family, leaf-cutter ants take it to the extreme. And such intense socializing puts the ants at great risk of transmitting diseases to one another. This risk is compounded by the deadly pathogens that multiply on their fungus farms, occasionally killing off the entire colony.
Thus, sanitation is a top priority for leaf-cutting ants, who have devised methods to deal with their waste. Some species dump the waste into refuse piles outside of the nest, while others chuck it into special storage chambers located within the nest.
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The waste chambers are handy because they can be completely sealed off, but digging them saps a lot of energy from the already hard-laboring ants. Dumping waste into piles outside of the nest does not require any digging, but the proximity to nest entrances means rain and wind could cause waste to leach back into the nest.
Though each strategy comes with its own advantages and disadvantages, researchers have questioned why leaf-cutting ant species have adopted such contrasting waste management solutions.
According to a new study published in Proceedings of the Royal Society B, which of the two waste management systems is most effective depends on where the ants live.
The researchers found that the fungal pathogens in the waste had trouble surviving when they were exposed to heat. This corresponded with data from 32 leaf-cutting ant species, which revealed that those living in hot and dry habitats tend to take the simpler approach of tossing refuse into heaps outside of the nest. In contrast, those in humid environments, where pathogens flourish, take extra precautions by digging refuse chambers within the nest.
“We proposed that LCA living in environments unfavourable for pathogens (…) avoid digging costs by dumping the refuse above ground,” the authors wrote. “Conversely, in environments suitable for pathogens, LCA species prevent the spread of diseases by storing waste underground, presumably, a behaviour that contributed to the colonization of humid habitats.”
By employing these differing waste storage strategies, the industrious leaf-cutting ants have been able to handle the hygienic challenges posed by their social lifestyles and their penchant for cultivating fungus across a range of habitats.
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