Some ant species farm. That is, they maintain fungal gardens or aphid herds, and in doing so, they sustain their food supply. Now, a new study suggests that a species of aphid-holding ants manages their herd(s) in ways that are eerily reminiscent of human farming practices.
The ant species under consideration is the Yellow Meadow ant (or Lasius flavus), common in Europe and also occurring in Asia, Northern Africa and the east of North America. Their nests are build underground and contain chambers where aphids are farmed. Like tiny cow-analogues, the aphids can be ‘milked’ by the ants for their honeydew, a sugary fluid. They can also be eaten.
The recent investigation looked at the genetic diversity of three aphid species in several ant mounds. It was shown that in more than half of the ant hills only one aphid species was present, despite availability of the others. And more, over 60% of these single-aphid-species ant colonies, contained only a single aphid clone (aphids reproduce mostly asexual, giving rise to clonal lineages). Even in colonies that contained more than one aphid species, the aphids were separated according to species in different chambers. In over 95% of these chambers the aphid presence was also limited to a single clone. These monocultures may reduce competition and maybe reflect husbandry, in which the aphids best suited for the ants’ needs are ‘selected’.
Further, it seems that the aphids ‘harvested’ for protein (a nice way to say ‘the aphids that get eaten’) are often young ones, ensuring that the aphid herd does not grow excessively and is subjected to intense competition for resources.
The authors see striking similarities with human cattle management:
The results of our study suggest that polyculture aphid husbandry in L. flavus follows similar efficiency principles as modern cattle husbandry practices in humans, where adult cows are kept in numbers that secure maximal milk-productivity in a competition-free environment and where surplus reproduction is slaughtered for meat-consumption soon after birth.
Maybe we can even learn something from these ants…
…ant farming practices for meat deserve more explicit study, as they may provide remarkable insights into sustainable farming practice.
Overall, the conclusion reads:
Many mechanistic details that govern the dynamics of this mutualism await further research. However, we feel that analogies with human husbandry practices based on similar cost-benefit considerations lend sufficient credibility to our interpretations to generate novel interest into natural selection processes that have produced ant farming practices for both meat and carbohydrates.
The words in bold are my doing, for it is important to note that while this might seem very clever of the ants, there is no reason to attribute any kind of conscious planning to our six-legged friends. If there is a benefit to the practice, say more food or a more stable food supply, natural selection can play its part and result in seemingly planned complex behaviors.
Ivens, A.B.F., Kronauer, D.J.C., Pen, I., Weissing, F.J., & Boomsma, J.J. (2012). Ants farm subterranean aphids mostly in single clone groups – an example of prudent husbandry for carbohydrates and protein? BMC Evolutionary Biology, 12 (106) DOI: 10.1186/1471-2148-12-106