These rock-like monolithic mounds (also known as termitaria) which seem to litter Australia and many other parts of the southern hemisphere are an integral system of tunnels, galleries, climate control and a protective shell to the thousands of inhabitants that live within.
The wedge-shaped magnetic mounds before you are a most impressive sight, there are hundreds of termite mounds standing up to two metres high in a wide swathe of empty ground. These structures are up to 100 years old, with the magnetic mounds being unique to the northern parts of Australia. The mounds are aligned in a north-south direction as a response to the environment. They house a colony and provide protection for the colony to breed, care for the young and store food. The termites which build them feed on grass roots and other plant debris found in plains which are seasonally flooded. Therefore, the termites are forced to remain above the water, in the mound.
Inhabitants
For a delicate little insect, magnetic termites live in a pretty harsh environment, temperatures soar during the day and plummet at night and everything gets soaked during the wet season. There are two species of magnetic termites that regularly build magnetic mounds. One variety is found from the Cape York Peninsula and eastern Arnhem Land. They are named after the township of Laura, which is near the southern limit of magnetic mounds in Queensland. The other variety that builds magnetic mounds is the one found here in the Litchfield National Park area and towards Darwin in the Northern Territory.
Individual termites are not all the same, but belong to different castes that have different roles. These castes include the winged ‘reproductives’ that are males and females capable of breeding; and sterile males and females that are divided into ‘soldiers’ and ‘workers’. Reproductives that successfully mate are the founders of new colonies and become the king and queen. Usually there is only one queen in a colony. Soldiers are specially modified to defend the colony. Workers perform special tasks such as food gathering, mound building, and caring for the young.
Magnetic Mounds
The awesome spectacle of plains populated by giant thin mounds all lined up parallel to one another has caused considerable puzzlement. Why do the termites build magnetic mounds? The magnetic mounds are built from soil brought from beneath the ground. The soil is cemented together with the insects’ saliva and excreta. They require the sun’s temperature and humidity to maintain a consistent balance of internal temperature. By aligning the mound in a north-south orientation one side will always be in the sun or shade. This ensures there is always a place in the mound that is just right. It is believed that temperatures can vary up to 8 degree from one side to the other. To build ‘magnetic’ mounds the termites must be able to sense the direction of the earth’s magnetic field. It has been suggested that the termites do this by means of magnetite in their tissues, as has been shown in other animals, such as dolphins and pigeons that orient themselves without access to visual guides.
To claim a find for this earthcache:
You will need to visit the posted coordinates where you will obtain the answers to the following 2 questions. You should be standing at a bend in the fence-line looking towards the mounds.
- The first few mounds in front of you have a rough rocky top edge and have a changed colour along this top section. Why do you think this is?
- In your own words describe the soil type and colour. How is it different to that of other parts of the park?
The following answers can be obtained from the nearby information boards
- How did scientists test the theory that the termites have an in-built compass to guide them?
- Give the scientific name for the termites that build the magnetic mounds in this area.
- On what date and what newspaper did Randolph Bedford write an article about the mounds?
Optional: Include a photo of you with the Magnetic Mounds in the background.
Email your answers to me via my profile and log your find. If there are any issues with your answers I will contact you. Logs without emailed answers will be deleted.
References:
www.qm.qld.gov.au/Learning.../~/.../fact-sheet-magnetic-termites.pdf