Photo by Charlie Nelson

The wisdom of ants

On 26 August 2013, while walking through a park near my home in Brunswick, a suburb of Melbourne Australia, I observed some very unusual ant behaviour.  Three rivers of them were crossing from a treed area across a driveway, a footpath, and up a sports pavilion to a height of at least four metres.  Some were going up and some were going down but it was those going up who carried what I took to be either food or building materials.

I checked my own back yard and saw some ants also going up high.

Several times over the next three weeks I checked and they were always busy.

Naturally, it occurred to me that this behaviour may presage rain, possibly quite a lot of rain.  But there was only 11mm over the three weeks I had been watching the ants.

On the morning of 16 September the Bureau of Meteorology predicted 6 to 20 mm of rain for that day.  The 24 hour total was 33.6 mm.

By the end of September, it was the wettest September in Melbourne for 20 years (87.2 mm) with most of that in the second half of the month (76 mm).

But still, on 30 September, the ants were as busy as ever.  I had also observed similar activity at other buildings in the park.

It seems to me that the ants had made an accurate prediction, at least three weeks ahead.  They could have been active in this way for much longer as I usually walked through the park at night and so would not have noticed any earlier activity.

Perhaps the ant activity had no connection with the rain and it was just by chance that there was a wet fortnight three weeks after I observed the ants.

Perhaps the ants were reacting to an earlier extreme wet event.  On the night of 2 and 3 June 2013 Melbourne received 58 mm, which is a reasonably rare event.  But in Brunswick, where I and the ants reside, the total was 100 mm.  They may have been expecting more and, for all I know, had been on the move since.

Perhaps they reacted to a change in humidity or air pressure that they determined would be long-lived.

Or perhaps they had detected the imminent flipping of the sun's magnetic field, which happens at about the peak of the sunspot cycle and which can presage a change in rainfall.

I shall continue to observe and analyse.

Charlie Nelson
October 2013

UPDATE April 2014

On 27 March 2014, the ants suddenly resumed taking things up high in large numbers.  The first three months of 2014 were very dry in Melbourne - 65mm, less than half the average for this period.

Over 9, 10, and 11 April Melbourne received 41mm and Brunswick, where I and the ants live, had 50mm.  The Bureau of Meteorology said it was the wettest start to April since 1996.

The Bureau does not forecast more than 8 days ahead - but the ants do!