Dr Don Ewart takes a look at Australia’s native animals that have acquired pest status.
Native animals can gain pest status in two ways. Firstly, when we move into their habitat and provide what they need in new forms. Secondly, they may also quickly appear as pests far away when they move to new habitats that we created. This is something worth exploring.
Of Australia’s native animals that have become pests, Ochetellus glaber, the black house ant stands out as a hitchhiker that’s now established across Asia, the Pacific and North America. Brushtail Possums, Trichosurus vulpecula, being bigger, smelly and noisy, haven’t been transported so widely (apart from deliberately to NZ) but have come to be masters of much of Australia’s urban forest. Similarly successful is Threskiornis molucca, the Australian White Ibis (pictured above). This bird once lived happily around the swampy rivers of central-western NSW but is now enjoying urban habitats such as Sydney, Brisbane and Perth.
We keep hearing about Mastotermes being a threat on the Gold Coast, much as Reticulitermes have been introduced and had some urban success in France, Hamburg in Germany and Devon in the UK. There’s a big difference between hanging on and thriving. The Hamburg termites thrived for decades tunnelling from the port to the town along subterranean municipal heating pipes.
Those in country Devon have also been tenacious but they apparently could not spread far. The American termites in Paris seem to be mostly living in buildings, having walked up the rail lines from Bordeaux where they arrived by ship from New Orleans.
A common factor is how well all these pests can cope with the cold of winter. Heated housing makes life very nice for some termites and was critical in Hamburg just as it is for keeping introduced Reticulitermes alive in housing in the cold Canadian cities of Guelph and Toronto. The Gold Coast is way further south than Mastotermes’ natural habitat (which peters out around Rockhampton) meaning that normal behaviour is restricted. If these Mastotermes can stay warm enough and avoid getting too wet, they too can hang on for extended periods and maybe even expand a bit by simply spreading out. Reproduction by alates (flyers) is hard for an introduced colony and so is not likely to work well for them down there. In the northern USA, colony budding replaces flights so some budding of Mastotermes colonies may eventually be detected.
Perhaps the best Australian urban-adapted termites are Schedorhinotermes. These have gone from being fairly uncommon house-eaters along the eastern seaboard to be often the most commonly reported. Is this because their numbers have built up or is it because better-trained pest managers can now tell their termites apart? Probably a bit of both. Coptotermes, which previously dominated reports, typically do best where there are large dimension timbers for their elaborate central nests. Coptotermes thrive in newly cleared areas or where large eucalypts are still around.
Schedorhinotermes don’t invest so much in their infrastructure and so they can be nomadic, moving between tree and soil nests and making the best of the season’s food over a broad area. A lack of commitment to a particular area or food source can make them tricky to bait. Disturbance or other factors may drive Schedorhinotermes away for extended periods. Schedorhinotermes do enjoy the modern, mulched garden. The old house yards with flower beds of bare-soil and expanses of short Victa-mowed lawns, are much less profitable places for Schedorhinotermes than modern gardens with efficient irrigation systems and areas of wood chip mulch through/under which they can simply walk rather than tunnel. So it isn’t just that suburbs have replaced bush, but the type of suburbs that matter.
Our native animal pests become pests because their place in nature has already given them the skills and abilities that suit what we provide. If we pay attention to the particular needs and abilities of each, we can make life much harder for them, and perhaps even achieve acceptable control. Cutting access to food is always the first consideration but looking at their environmental needs can pay big dividends. Think termites and available moisture. Making it a bit more dangerous/expensive to move around can greatly retard pest activity. Think how wide-open concrete aprons around factories can deter the rodents living nearby. Think too, of the success of the termite inspection zones that make recruitment much less likely.
Even within a suburb, the shape of the landforms, the drainage, shade/sun, elevation, wind exposure and soil types can have as much of an impact on pest distribution as the presence or quality of constructions. Land use history can also have big effects. There are suburbs of Melbourne that were once market gardens or orchards where termite numbers were very low compared to nearby cleared-bush developments. In Honolulu, housing in part of one suburb had lots more Coptotermes formosanus problems than the surrounding streets (that all looked just the same to me). Professor Tamashiro worked out that earlier use as for piggeries had made the truly local difference. Probably something to do with the richer soils. The same should work for our Coptotermes.
The bottom line with these native animal pests, be they insects, birds or mammals, is that a good knowledge of their life in the wild can greatly help you to profitably limit their suburban escapades. While nearly all the native species with pest potential have shown their hand, ever changing urban environments and the inevitable changing of our climate mean that other natives may pop up as pests to vex us.
Dr Don Ewart
*Dr Don Ewart, a doctor of termites, is a consultant to industry and pest managers, teaches pest management for Melbourne Polytechnic, Chairs the Standards Australia committee that’s currently re-writing AS 3660.2, helps AEPMA with Codes of Practice and still fits in the occasional scientific paper. You can find him at Dr Don’s Termite Pages.