Ants Buczkowski G. And Bennett G. 2009

Ants

Buczkowski G. And Bennett G. 2009 July-August. Ethology: International Journal of Behavioural Biology. 115: 1091-9.

Buczkowski and Bennett are interested in studying movement of ant colonies. Previous research established that social organisms are capable of relocating en masse: authors devised ways to observe Pharaoh ants (Monomorium pharaonis). The Pharaoh ant is a highly polygynous species (a single male mates with many females) and makes little investment in nest construction: these two factors are what prompted authors to select this particular species for study, since they correlate with an increased propensity for both migration and "budding," the splitting off into separate smaller colonies. Authors discuss the reproductive strategy of the Pharaoh ant's budding, which they claim "dramatically increases the probability of successful colony founding." The causes and consequences of budding in an ant colony remain underexplored, and authors devised two experiments to investigate further. First, authors examined budding into multiple nests in order to "determine the effect of increasing the number of bud nests on the fragmentation pattern and the resulting colony social structure" (1092). Second, protein markers were utilized to look for possible changes in food allocation resulting from budding, by comparing pattern of food distribution in fragmented (i.e, those that had undergone "budding") and intact nests alike. Authors found that overall distibution of bud nests was uneven but within each bud nest there was no evidence of an uneven split between different specialized types of Pharaoh ant -- in other words, the Pharaoh ant can "exert social control over colony size and caste proportions during budding." It was additionally discovered that, even while undergoing multiple fragmentations, the Pharaoh ants themselves preferred to maintain a minimum group size, which they authors calculate as 469 +/- 28 individual ants. The food distribution experiment revealed that budding has no negative effect on the ability of the different groups to co-operate in the allocation of food resources. Authors conclude that individually budded nest units relate to one another cooperatively rather than competitively.

Buczkowski and Bennett's article is clearly written and lucid. Their research question was an interesting one, and their research methodology seemed appropriate. The use of the tables whereby the total number of individual ants in each colony was calculated -- and viewed comparatively to show the overall similarity in distribution -- was particularly effective. The revelation of a maintenance of a specific number in the budded populations is the most dramatic illustration of the control that ants have over their own population, and the fact that it could be calculated so precisely is the most impressive thing the authors here are able to do with their statistical data. Their results are hardly surprising or counterintuitive, though: it struck me in reading the article that, if the authors had permitted themselves to consider an ant colony -- or multiple colonies with a genetic commonality -- as a single organism, then the discovery that food resources were efficiently allocated would have seemed like a logical consequence rather than a surprise.