EPOW - Ecology Picture of the Week

              Magnetic Termite Cemetery   --->

Magnetic Termite Mounds (Amitermes meridionalis), Family Termitidae
Litchfield National Park, Northern Territory, Australia

Explanation:  What remote graveyard is this?  We are exploring a corner of Litchfield National Park in tropical "Top End" of Northern Territory, Australia, and have come upon this apparently macabre scene.

But a cemetery it is not.  These are termite mounds!  More specifically, mounds of what is called the magnetic termite or compass termite.  

Built in vast cities of mud in seasonally wet grasslands, these mounds do resemble gravestones all neatly angled the same way -- along a north-south axis -- as if designed by some grim reaper.  But the true architects are tiny termites that have adapted to the harsh, dry, tropical heat sunshine and the seasonal flooding by building upward. 

The site is a "cold pocket" where, at night, cool temperatures settle to the ground.  But the termites do not burrow down into the soil to escape the cold, probably because their burrows would get seasonally flooded and destroyed.  So instead they construct gravestone-shaped mounds that are angled to catch the heat of the sun to the east, just enough to regulate the internal temperature.  It is as if the mounds themselves are a giant organism exhibiting "behavioral thermoregulation," much as an elephant will flap its ears to remain cool or orient itself to intercept the morning sun to warm up.

During the hot dry season, within their nests, magnetic termites move to the eastern face of their edifice to catch the warming sun, and then they move back to the warmer center of the nest as the temperature drops in the cool of the evening.  

Wait, it gets even more amazing.  

The termites will angle their mounds differently depending on local shade and wind, as well.  Instead of a perfect north-south axis, with local shade and wind conditions in more vegetated sites, the mounds are instead aligned anywhere from slightly west of true north, to ten degrees east as they are in the site shown in these photos. 

How do they know to do all this?  It is thought that the termites do not necessarily directly perceive local conditions of sun, temperature, shade, and wind, but instead over countless generations have evolved strict genetic codes to best build and adapt the orientation of their mounds to local conditions.  

If a colony of termites, for example was to construct a mound on the wrong orientation, it likely would overheat or underheat to the point of death of its inhabitants or at least far lower reproductive productivity.  This is adaptation and natural selection in action.  

It is thought that the termites also have a sense of magnetic orientation, as workers begin building a new mound along the correct local bearing conditions from the start.  

So this is the origin of the name magnetic (or compass) termite, seemingly able to detect directions like the magnetic poles of a compass.  How awesome is nature?