I teach at a high school in Australia and I'm currently doing a unit on ants. One of the students in the class lives on a farm where there are lots of black ants. He and his family (I spoke to his father after school and he confirmed that his son was not kidding) have observed that ants seem to know when the rains are coming "weeks, even up to a month before they actually arrive." He says that they start preparing by storing food and building up walls around the nest.
The class found this fascinating and wanted to know how the ants could possibly know the rains were coming so far in advance. I told them that antweb are an authority on ants and that I would write to you for an explanation. My first question is: Is it possible that the ants could know the rains were coming so far in advance? Secondly, if so, how are they able to do this. Thirdly, if the student and his family are wrong, what are they observing that leads them to believe that the ants are long term weather changes?
My class and I would greatly appreciate any insights you are able to offer on this topic.
Thanks for your question!
There are a variety of ways that human meteorologists can predict the weather: they can look at trends in barometric pressure, they can note the wind direction and look at the clouds (from the ground or from satellites). But they can also make general predictions based on past trends. I suspect that any meteorologist in your area could predict to the nearest 10 days when the first monsoon rains are likely to hit southeastern Queensland, and they wouldn't need any information at all about the current weather! In many areas of the world, there are predictable times of year that organisms need to prepare for or migrate away from--times of year that are either too cold, too hot, too wet, or too dry for organisms to function well. Some organisms whose ancestors have been living in those places for millions of years are adapted to the annual rhythm of these seasons. The ants your student and his family observed are not "predicting" the weather any more than migratory birds or blossoming flowers are--they're just behaving in a way that is adaptive to long periods of rainfall.
Many animals and plants (and perhaps other organisms, like marine algae) have an instinctual response to seasonal cues like light levels or day length (photoperiod). For example, cherry trees from certain parts of Asia will always flower when days are as long as they are at the beginning of spring in that part of Asia. For other plant species, budding occurs only after some threshold of both photoperiod and temperature has been passed, and bird migration may be regulated by an even more complex interplay of cues, including food abundance. It has even been proposed that organisms might have "circannual clocks," the annual version of our circadian rhythms that get messed with when we travel to a new time zone. For many species, the exact cues used to regulate annual cycles of behavior and life history (or phenology) are not understood.
I'm sure you've guessed by this point that I don't know exactly what cues the ants on your student's farm are responding to. But as a class, you might be able to perform some scientific experiments to figure it out! My understanding is that your rainy season is the Austral summer--the warmer time of the year, with longer days. Thus, two cues the ants might be using (separately or together) are the length of the days and the temperature. If there are many of these ant nests, then you could set up lights around some nests about half way through the winter, and put them on a timer so that they turned on a half hour before dawn and again a half hour after dark. Near other nests, you could place some "heat rocks," like those used for reptiles. Some nests could receive both treatments, and some nests neither. Then you could see if any of the ant nests "predict" that the rains will come earlier than others. Unfortunately, you might have to wait until next year to perform this experiment, but, hey, it doesn't hurt to plan ahead, right?
One reason phenology and chronobiology are such "hot" topics lately is that global climate change is likely to make things difficult for organisms that use photoperiod as a cue to adjust to the changing of the seasons. Perhaps you and your class (or future classes) could help us better understand how the ants of Australia will react to climate change!
Hope this helps!
Jesse Czekanski-Moir & the AntAsk Team