High density housing: Termite mounds are more than just lumps of dirt

By Trish Fleming. Termites are amazing ecosystem engineers – they create massive changes in ecosystems that are far out of proportion to their size. A recent paper by Thompson and Thompson (2015; Pacific Conservation Biology) has captured how important termite mounds are for the Australian landscape.

At their study site in the Pilbara region of Western Australia, the authors found that 97% of the 158 termite mounds they sampled were home to a vertebrate. Mounds had an average of 30 vertebrate residents, but one mound had as many as 150. There was an average of one Stimson’s python per mound, and up to 109 Gehyra pilbara geckos in a single mound.

When termite mounds are removed from these sites to make way for mining, we lose a significant component of our biodiversity. Termite mounds can be hundreds of years old, and cannot be simply replaced in ‘restored’ sites.

A ~1.5m Varanus panoptes next to its refuge in a massive termite mound.
Termites can represent a greater biomass and therefore have greater contribution to nutrient cycling than grazing animals (Lee & Wood 1971), no mean feat when some of the landscapes they occupy are also frequented by extremely large herbivores, such as elephants and ungulates.

Termites play a pivotal role in converting indigestible fibre in plants into food for a diversity of animals. In Australian systems, these insect-driven (or more accurately, gut-bug-driven) nutrient cycles sustain a diverse and thriving reptile community, which in turn are food for larger vertebrates such as snakes, birds and mammals.

Individual termite mounds also provide substantial shelter resources for vertebrates (Fleming & Loveridge, 2003), providing cooler and wetter sites for refuge and breeding. The mounds provide shade against the heat of the day, and increased humidity that would reduce desiccation.

In many parts of the world, termite mounds also support dense plant growth that makes them even more suitable habitat for a range of animals. In savannah landscapes, where fire is a substantial and regular driver of change, termite mounds also create valuable refuges against flames that swiftly consume fire-adapted grasses.

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The large Macrotermes spp. mounds of Africa and Asia support vegetation completely different from the surrounding woodlands. Macrotermes construct massive conical mounds: up to 6m in height and some 30m in diameter. Mounds may be many centuries old and support dense vegetation, making them visible in aerial photographs such as this 1:50,000 aerial photograph (Carolina Wilderness, Zimbabwe). Vegetation on termite mounds is evident in grazing lands (black arrow) as well as for land that has never been cleared (white arrows).

The large Macrotermes spp. mounds of Africa and Asia support vegetation completely different from the surrounding woodlands.

Termites are the sole or major food for a number of weird and wonderful, rare and vulnerable mammalian species, including numbats, aardvark, aardwolf and pangolin (Delany & Happold 1979) and termites are also the major diet component for many reptiles (e.g. Mitchell, 1965).

Unpublished data from conservancies containing black rhino indicate that the vegetation upon termite mounds shows more sign of being browsed upon than surrounding woodland. The suggestion is that termite mound vegetation is either of greater nutritive value and therefore preferential to browsers, or else provides animals with shelter and the greater time spent in the area facilitates more herbivory. Either way, the resources provided by termite mounds may therefore increase the carrying capacity of the woodlands.

Termite mounds of a variety of sizes and shapes – homes to a range of vertebrates.

So next time you drive through northern Australia and you can’t see any large animals, think that every termite mound as a high-rise set of flats, alive with a myriad of small vertebrates.

 

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