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Posts Tagged ‘bandicoot’

Dingoes are derived from domestic dogs that were brought to Australia between 4,000 and 6,500 years ago.

They are feral dogs.

In terms of classifying them through their phylogeny, they really shouldn’t be recognized as Canis lupus dingo but as Canis lupus familiaris. 

However, the question of whether they should be considered native wildlife in Australia has been a bit of a debate over the years. At times, experts have aligned them with dholes, while others have considered them the ancestor of the domestic dog– which is, of course, putting the cart before the horse. Dingoes are derived from dogs, not the other way around.   A dingo is more like a landrace of dogs that has evolved to live in the wilds of Australia.

Under normal circumstances, feral animals that derive from domestic species are not considered native wildlife.  They usually don’t get protections from governments. If they get anything, it’s normally a bounty on them or the government hires its own people to exterminate them.

We have lots of issues with invasive species all over the world.

This is not an issue to be taken lightly.

However, when an invasive species has been in a place for thousands of years, can we still think of them as an invasive species?

Because dingoes were introduced by man so long ago, should they be considered invasives like feral cats and red foxes?

Well, the answer is much more complex.

And there are many ways to examine this question.

Perhaps the most novel is to examine how other species react to a predator that is an introduced species. It

Have they evolved behavioral mechanisms that keep them from falling prey?

This a study using this new methodology was recently published in PLoS One.  It is entitled “When Does an Alien Become a Native Species? A Vulnerable Native Mammal Recognizes and Responds to Its Long-Term Alien Predator” by Alexandra J.R. Carthey and Peter J. Banks.

The authors examined the foraging behavior of long-nosed bandicoots on properties that were near national parks in the Sydney area.

They examined how often these bandicoots foraged in properties that contained dogs or cats. Cats are quite capable of killing one of these bandicoots, and if they had evolved an aversion to cats, it would be a major boon to their survival.

It turns out that the bandicoots tended to avoid properties with dogs on them. The tended to frequent those where cats were present.

The authors contend that the bandicoots have been able to evolve some natural aversion to Canis lupus through their thousands of years of predation from dingoes. Because of this aversion, they avoid domestic dogs are present, and because domestic dogs and dingoes are part of the same species, they had to have evolved this aversion in response to predation from dingoes.

Cats have been in Australia for only 150 years, and bandicoots have not evolved a similar aversion to them, which tells us that, at least when we’re dealing with long-nosed bandicoots, dingoes have the effect of a native predator upon them.  But cats do not.

The arrival of the dingo was not without ecological consquence for Australia’s fauna. Three species are thought to have disappeared on the mainland as a result of predation and increased competion from dingoes. Thylacines and Tasmanian devils went extinct on the mainland within a very short time of the dingo’s arrival, and the Tasmanian native hen, a type of flightless rail, also disappeared– probably as the result of dingoes killing them. These species persisted into modern times in Tasmania– the only place in Australia where dingoes never colonized.

But these mainland extirpations happened thousands of years ago.

And in that time, the other animals on the Australian mainland that didn’t become extinct had time to adapt to the dingo.

The dingo filled the niche of top mammalian carnivore, a niche that would have been left vacant with the extinction of the thylacine.

Lots of native marsupials in Australia existed alongside predatory dingoes.

Their numbers collapsed only when Europeans arrived and brought in all sorts of different domestic species. And then introduced the European rabbit and the red fox for sport hunting purposes. The grazing species changed the Australian landscape, causing lots of erosion and overgrazing of ground cover, and the cat and the fox began killing the small marsupials that dingoes generally ignored.

In fact, when dingoes exist in large enough numbers, they keep the fox and cat numbers down, and the small native marsupial population is able to thrive.

So Australia’s wildlife has had time to adjust to dingoes and dogs. It has not had time to adjust to all the other introduced species.

This is something would would have expected, but it is interesting to use it in this particular methodology to see if dingoes are truly native or not.

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My one little complaint with this study is that the authors state that they never asked the property owners if their cats killed bandicoots.

Although long-nosed bandicoots are in the size range that would make them vulnerable to cats, one really needs to know if the local cats actually consider them prey.

If the local cats don’t consider them prey, they aren’t likely to fear them.

And then you introduce a learned behavior variable into the study that isn’t entirely accounted for in the model.

The other problem with using this methodology to determine whether a species is native of nor is that invasive species usually affect ecosystems, not single species.

For example, one study that is often bandied about to defend the existence of feral cats in New Zealand found that feral cats kept down rats that preyed upon a certain species of seabird.  When the cats were controlled, the rats took a heavy toll upon the colony.

That’s an interesting find, but if one were to look at how cats affect various species in New Zealand from a cost-benefit perspective, one would clearly find that cats are an ecological disaster there. They have been implicated in the extinction or near extinction of so many different birds that one could hardly say that their benefit to this seabird colony justifies their existence.

So we need to look at how dingoes affect the ecosystem before making these pronouncements.

However, to me, it’s pretty obvious that dingoes are the top mammalian predator in Australia, and they do play a beneficial role for most native species.

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