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Ant safari

As summer reaches its height and the wattles shed their seeds, Australia's ants get really busy. Although some might consider them a nuisance, researchers are discovering that the bush couldn't do without ants.

Bullants with weevil

Bullants with weevil (Source: Bob Taylor/)

Australia, entomologists are proud to say, has the highest ant biodiversity in the world. In other countries where ants thrive, you might find 30 different species per hectare. In Australia, says ant expert Dr Alan Andersen, it’s more like 100 species.

“Only about 20-25 per cent of all ant species have been described,” he says of how little is known about this enormous group of insects.

“There are probably up to 300 new species being discovered every year!”

For anyone wishing to pursue a career in biology, ants are truly unexplored territory. Imagine if 300 new marsupials were still being discovered every year!

Andersen, who is a chief research scientist at CSIRO Sustainable Ecosystems, regularly collects ants and other insects in the tropical savanna country around Darwin. He traps them with a wide-mouthed jar, filled with a sticky liquid and buried up to the top in sand. The ants simply walk over the edge and fall in. With any another animal, you might trap one or two individuals if you’re lucky. But Andersen’s record is 27 ant species in two days.

Why does Australia have so many ants? One reason, suggests Alan Andersen, is our diverse soils. “In a 1km square area you might find a sandy soil, then a loamy area, then rock.” As time passes, the plants and animals isolated on each of these different soil types evolve to become new species uniquely suited to that particular micro-habitat.

Within Australia, there are particular areas which ants favour most, says Andersen. These include the semi-arid soils of southern Australia (such as Wyperfeld National Park in Victoria); the semi-arid mallee country of Western Australia (Stirling Ranges, Cape Le Grand); and particularly Kakadu National Park and surrounding areas, where the temperate and arid zones converge to form a rich and highly complex environment.

Fact file:

When: Most ant species are active in the warmer months; a few only emerge in winter.

Where: All over Australia including Tasmania (except in extreme deserts and very heavy clay soils)

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Ant watching

Pick a warm, not hot day, put on a pair of comfy old long pants, and take yourself out on an ant safari. You’ll find ants in almost every type of habitat, particularly the drier types of coastal forests and the scrub-lands of the semiarid areas.

Here are a few tips for ant watching:

  • What’s there? Sit on the ground, focus down and wait. You may find ants walking across the bare earth, or in leaf litter. Just simply by doing this, you’re likely to see at least a dozen different species of ant.
  • Drinking honey If you look along the branches of a wattle or other shrub, you might see ants clustered around aphids or scale insects. These creatures suck the sap from trees, some of which oozes out of their backside. This sweet sticky ‘honeydew’ as it’s called, is lapped up by ants and stored in their crop. They take it back to the nest and feed it to the worker ants.
  • Where’s your nest? If you drop tiny crumbs of food such as cake or meat on the ground, you won’t have to wait long for an ant to come along and pick it up. If you follow the ant, it’ll lead you back to its nest.
  • Renovation rescue Ants constantly tend their nests, making repairs and adjustments. Particularly after bushfires, ants can be seen in a fever of activity, carrying tiny stones to rebuild their nests. Ants also adjust the temperature of their nests by placing stones on top which heat up in the sun and keep the nest warm overnight.
  • Who’s boss? Drop a piece of food too large for an ant to carry (such as a piece of sausage) on the ground. Watch as the parade of different ant species come along and attempt to take the food away. The tiny ants try first, then the larger species, such as bull ants or sugar ants. But at the top of the ant hierarchy is the meat ant – although they aren’t as large as bull ants, they are far more aggressive.

If you’re really lucky in your ant-watching, you might see an ant carrying a seed back to its nest.

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Feeling seedy

It’s a fascinating system where the ant and the plant rely on each other. The seed has a special structure called an eliosome, packed with carbohydrate and protein. The ant is attracted to the seed, picks it up and takes it back to the nest, where the eliosome is chewed off and fed to the ant larvae. The seed is usually dumped elsewhere within the nest. The seed benefits because it is now safe from predators, but also because the interior of ant nests are usually moister, higher in nutrients and better aerated than the surface, making an ideal place to germinate.

No-body knows for sure exactly why ants collect seeds, but they certainly go out of their way to do it. Until a few years back, the furthest an ant was known to have carried a seed was about 70m. Then, a few years back, a lonely meat ant carrying a seed in the middle of Kinchega National Park in Western NSW set a new world record. Researchers clocked the ant carrying its seed an exhausting 180 metres, from under the sandhill acacia where it had fallen, right back to the ant’s nest in the dunes. That’s the same distance as three Olympic swimming pools laid end to end, and almost twice as far as some birds have been known to carry seeds!

Alan York, a senior research fellow in ecology with the University of Melbourne, says Australian plants are especially reliant on ants. ‘Australian plants rely more so than anywhere else in the world on ants to disperse their seeds.’ He says this is possibly because Australia has so many mammals and birds that enjoy nothing more than a nice nibble on a seed, so it’s imperative for plants to find a way to get their seeds safely underground as quickly as possible.

The attraction that ants have for seeds has even been exploited by stick insects. One species lays eggs which look remarkably like plant seeds: the ant picks them up and takes them back to the nest, where they hatch safely!

Not only do ants do a great job of germinating native plants, they improve soil structure. The hard, compacted and desiccated soils of Australia’s inland are transformed under the patient, efforts of a billion tiny ants. They help soil turnover by bringing up deep soil and mixing it with the surface. They move organic matter from the surface to the subsoil, fertilising it in the process. They also relieve soil compaction when they build their tunnels, oxygenating the soil and creating space for water to penetrate deep into the soil.

So next time you’re out in the bush and ants invade your picnic, remember that without their silent toiling, the world would be a poorer place.

Ants at a glance

Meat ant (Source: Bob Taylor/)

Meat ant

These aggressive ants have powerful jaws and work together to defend their nest and attack invaders. They are so efficient that a dead animal such as a sheep, placed on top of a meat ant’s nest would be reduced to bones in a matter of weeks.

Honey-pot (or sugar-bag) ants (Source: Bob Taylor/)

Honey-pot (or sugar-bag) ant

These ants were traditionally eaten by the Aborigines of Central Australia – you pick it up by the head, put the abdomen in your mouth and bite it off. The ants harvest the tangy-sweet ‘honey’ from scale insects and other sap-suckers, who suck sap from plants. Some of this squeezes out the end and is collected in a crop by the honey-pot ant. Back in the nest, the honey is regurgitated to feed other ant-workers.

Red bull ant (Source: Bob Taylor/)

Red bull ant

With their huge pincer-like jaws, they might look scary, but bull ants are mainly vegetarian, although they also eat small insects and even other ants. They are among the largest of the ants, reaching nearly 4cm in length. Like their relative, the Jack Jumper, they grab their victim in their jaws, bend their tail around and sting it with their painful venom.

Jack Jumper (Source: Bob Taylor/)

Jack Jumper

A close relative of bees and wasps, the sting of a Jack Jumper ant can cause a severe allergic reaction that can even lead to death. These ants are found in Tasmania, Victoria, the ACT, the Snowy Mountains of New South Wales and coastal New South Wales, the Adelaide Hills in South Australia, and WA. They are easy to spot by the jerky movements.

Argentine ant (Source: Bob Taylor/)

Argentine ant

The introduced Argentine ant is such a pest that when it first appeared in Australia almost half a century ago, the government offered a reward to anyone who reported a nest. Today, Australia is still plagued with these tiny red ants, their latest assault being into the suburbs of Melbourne. They kill native plant seedlings and compete aggressively with native ants for food and nesting sites.  They also cause havoc in households by nesting in potplants, light sockets and wall cavities.

Green tree ants (Source: Bob Taylor/)

Green tree ants

Common in northern and western Australia. Unlike meat ants or bull ants, these ants make their nests in trees by weaving together leaves. Their main enemies are beetles and spiders, which they repel by spraying them with an irritating acid from their abdomen.


Special thanks to Alan Andersen and Alan York for expert advice on the world of ants.

Many thanks also to Bob Taylor for generously allowing the use of his photographs.


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Published 24 January 2008