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How long before feral animal is classed as native?

songhrati

Gone But Not Forgotten
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My mother works in landcare in a remote area of outback Australia (western Victoria for those with a handle on Australian geography). Part of her job is pest control, and one of the biggest problems is feral cats. When traveling through outback Oz, one of the things you notice is just how big the feral cats get (to the point where one could see people mistaking the cats for Alien Big Cats). My mother says that not only are the feral cats far bigger than the average domestic cat but their face looks different as well (eg. narrower, more pointy face).

Considering that domestic cats would have arrived in Australia in the 18th century (and possibly earlier) on visiting ships, have they been in Australia long enough to be classified as a) a seperate species and b) native? After all, the dingoes were originally introduced 30 000 odd years ago but is now considered native to Australia.

Zane
 
Well, the American mustang springs originally from Spanish stock imported during the Conquest in the 16th century, and they're still classified as feral, so your kitties probably have a ways to go.

This is going to sound like nitpicking, but the two terms you're using are not equivalent. Feral refers to members of a domestic species which run wild; native refers to species which originated in the area in question, and the equivalent terms are imported or invasive. Given that our ideas about what is and is not native is based largely on human time spans rather than the geological time spans appropriate to species history, sorting out "native" from "imported/invasive" can be awkward. It's an important question, too, because - as your mom can tell you about those cats - an invasive species can be devastating to the native ecosystem.

Examples abound. All modern North American megafaunal species except the black bear and (probably) the bison are Asian imports - the grizzly, the elk/wapiti, the musk ox, humans. One of the numerous unanswered questions about what was going on in North America at the end of the Pleistocene is, did these megafauna cause, or merely exploit, the demise of the native species? (Bison are problematic, because the present shorthorn bison closely resembles the extinct Eurasian shorthorn bison, so it's possible that Eurasian bison replaced American bison antiquus instead of antiquus speciating into the present form.) All of these animals are presently considered native, because at the time Europeans arrived they had adapted to the continent and the continent had adapted to them.

Although the horse developed in North America, the present horses running wild in the western states are feral, because they are descended from domesticates, and invasive, because they are distinct from the horse species that went extinct here. The degree to which they fit into the natural environment is problematic, because their introduction coincides with the introduction of Western culture (despite the name, an import from the East!), which tends to alter the environment in destructive ways. The impact of the mustang on the environment is difficult to guage in an ecology which is constantly changing under a variety of pressures.

Other invasive feral domestic species, such as the hog, and imported invasive wild creatures, such as the starling and sparrow, do demonstrable severe damage to native species with which they are in direct competition and are anathema to people like me who are interested in maintaining a viable ecology. (All the same, by far the majority of the birds I support with my bird feeder are European house sparrows. Let he who is guiltless cast the first stone.) Another accidentally and naturally imported species, the cattle egret, exploits a niche not exploited by native species, and is treated as if it were native, even though we know it blew over from Africa in historic times.

Any biologists in the crowd feel free to correct me, but if domesticates can ever achieve wild status, it presumably would take a geologically long time and would be marked by speciation - i.e., sufficient biological changes that breeding with the cats or horses or whatever kept by humans is no longer practical. Since any dog can breed viable offspring with any wolf, the breeding test has its weaknesses, and I'm not sure at what level of reproductive viability speciation would be held to occur. Since it's not likely to happen without a prolonged period of isolation from the domestic cat, and since as long as new cats are added to the feral population from the domestic stock, the point may be an academic one as far as Australian cats are concerned.

The changes your mother notes may be sufficient, however, for the Australian feral cat to count as a new breed (as the changes in the American feral horse have resulted in a breed called the mustang). Domesticates produce breeds readily, in time spans comprehensible to humans, as a result both of breeding pressure and environmental factors; which is not surprising when you think about it.
 
I reckon an Ice age, or so, would do.

So, give it about 10,000 years, roughly. ;)
 
An interesting question. I have been reading about how many different plants and animals were introduced to this island by the Romans, its quite a long list. Fallow deer, phesants, edible frogs and snails, horse chestnut trees....How many of these animals we regard as native?
Do we regard them as native if they `fit` in the ecology? or are just so widespread that we are used to them (such as rabbits)
What about invasive spiecies that do the job without human help (such as the Indian native collared doves, whom in the 50s and 60s decided to take a holiday in europe)

The degree to which they fit into the natural environment is problematic, because their introduction coincides with the introduction of Western culture (despite the name, an import from the East!), which tends to alter the environment in destructive ways.

I would question this. Studies in native culture show that they were very destructive of the enviroment (re the buffalo drives, which put paid to several larger versions of this tasty animal.) At least we have some inkling of how systems work.
 
This native/introduced species phenomena is a very tricky one. Perhaps the question should be put as "How quickly does an ecology adapt to the introduction or removal of a species?" The answer would seem to be quite rapidly. The Roman introductions seem to be in balance in Britain (including that archetypal British plant - the rose) and rhodedendrons seem to be approaching that. Certainly the wild fuscias of Cork are now considered to be an asset rather than an invasion despite displacing blackthorn from the hedgerows. What will happen with Japanese knotweed remains to be seen.

Horses on the american continent seem to have fitted in very rapidly although there is some dispute as to who introduced them. In Australia wild camels seem to be no problem although the dingo is often seen not fitting.
 
Homo Aves said:
Studies in native culture show that they were very destructive of the enviroment (re the buffalo drives, which put paid to several larger versions of this tasty animal.) At least we have some inkling of how systems work.

Buffalo drives killed large numbers of bison, but they occurred at the same places many times over thousands of years without endangering the species - a feat which industrial level hunting and habitat change accomplished in a few hundred years. Wasteful? Yes. Destructive of the environment? No. Bison antiquus, the extinct longhorn bison of the Ice Age, was *not* killed off by buffalo drives.

Certainly the Indians (I refuse to say Native American as my Muskogee friend laughs at people who do that) were not the New Age plaster saints that modern fantasy pictures them, but their hunting, gathering, horticulture, and agriculture were for the most part sustainable over time. The Mayas practiced slash-and-burn agriculture, but the high Maya culture died, not the jungles - and not the Mayas, who are still there. The Overkill Hypothesis for the megafaunal extinction, as originally postulated by Paul Martin, would seem to be falsified by the pushing back of the dates at Monte Verde, though we cannot rule out the possibility that hunting was a contributory factor. In that case, however, why did camelids, which were not hunted, die out when bison, which was hunted extensively, speciated instead? The environmental changes of the early Holocene were mediated by climate, not humans.

Ecology is a complex system, and no, we don't understand it now, though we understand some parts of it - primarily, the ones that have been broken in this or that place. The fact that we're not sure whether mustangs are good or bad for the environment they live in is, in itself, an indication that we don't understand well enough. It's not claiming excessive virtue or wisdom for the people who were already here in 1492 to acknowledge that, at the time of contact, they were part of a healthy ecosystem which we no longer have.
 
Peni said:
This is going to sound like nitpicking, but the two terms you're using are not equivalent. Feral refers to members of a domestic species which run wild; native refers to species which originated in the area in question, and the equivalent terms are imported or invasive.

Thanks for this; the heading should have been "How long before an imported animal can be classed as native?"

Zane
 
The Aesculapian snake is regarded by some as a Welsh native, following the survival of a population descended from a gravid female that escaped in the 60s.

Guess there'd be dangerously little genetic diversity in such a group though.
 
Captain Chunk said:
The Aesculapian snake is regarded by some as a Welsh native, following the survival of a population descended from a gravid female that escaped in the 60s.

I've never heard of anyone regarding this species as native- it's certainly listed as a non-native introduced species by DEFRA:

http://www.defra.gov.uk/paw/publications/law/appenda9.htm

Aesculapian snake bones have been found in pre ice-age deposits, so they were native a long time ago... as was the European pond terrapin, and the agile frog.

The pool frog was only accepted as native when bones were found at a site where they persisted into the early 1990s, which proved they had been present before the widespread introductions of pool and edible frogs in the late 18th century.
 
I'd have to answer that the entire issue of "species that belong / species that don't belong" is a meaningless one. Species that have no business in a given environment will rapidly die out. You can't raise cows at the bottom of the sea.

The idea has somehow taken hold that there's only one "right" way for any particular part of the world to be. One perfect distribution of species, one perfect weather pattern, etc. Once you've convinced yourself of this, then any change to those patterns inevitably represents damage.

If a species can live wild in a part of the world, then I'd argue that it "belongs" just as surely as though its ancestors had been there for millenia.
 
You are perfectly right. I think we were more talking about the issue of `animals that are introduced and cause a lot of trouble`but there are plenty of perfectly natural examples of this.
(such as the interchange between N and S america.)

If you were to class all animals from the fossil record as native then this country would be full of polar bears and lions. (not to mention Iguanadon...)
 
Amoebas do not rapidly die out in my gut. That doesn't mean they have legitimate business there. If we regard me as an ecology for unicellular animals, amoebas are bad for their ecology!

Just because an animal's population expands into a new area does not mean it will do harm to that area (cf cattle egrets).

Just because an animal does harm to the environment in certain circumstances doesn't mean it will do harm to that environment under all circumstances (cf cattle, run on prairie land in sync with the natural progression of plant vs. cattle, kept on prairie land until every bit of grass is gone).

That environmental degradation can occur naturally does not mean that humans are wise to engage in activities which are known to cause environmental degradation.

The earth can get along fine without humans. The reverse has yet to be demonstrated.

I'm a misanthrope and I think it'll serve us all right when we go extinct because we've made the planet into an unsuitable habitation for ourselves, but I'd rather not still be alive when it happens. But I suppose in the nature of things I wouldn't be...

All right, done.

On the topic of the frogs that were considered non-native, until their fossil bones were found in a pond where they presently live -I wonder what tests, if any, were made to eliminate the possibility that, though the *species* was native in that it had been in place long enough ago to leave fossil traces, the present *population* was non-native. It is at least a logical possibility that the pond was viable frog habitat long ago, ceased to be for some reason (climate change; or a catastrophic disease wiping out the entire population of the pond), and, when it became viable again and the species re-expanded into the area, a new population reinhabited it.

Plants and insects are even more complicated to sort out than large animals, because of the ways they spread and the ways they leave their traces. When researching my story about Paleo-indians, although I was working with a well-defined term for once - "any species present in Texas at the end of the Ice Age" was suitable for my purposes - I was constantly plagued with uncertainty. Did the abundance of pine pollen in this area mean pine forests, or seasonal winds blowing in huge amounts of pine pollen from elsewhere? "Native American" pharmecopias and "Native plant" guides included lots of naturalized plants - weeping willow bark, for example, was not available to my Paleoindians; neither were dandelions. Neither were honeybees, though there are American honey producers - they're all tropical.

Oh, dear, definitely time for me to stop. I can go on about the Pleistocene all day; you'd think I'd be fed up with it by now, but it's like a disease. A really, really interesting disease (let me show you my symptoms...)
 
Peni said:
On the topic of the frogs that were considered non-native, until their fossil bones were found in a pond where they presently live -I wonder what tests, if any, were made to eliminate the possibility that, though the *species* was native in that it had been in place long enough ago to leave fossil traces, the present *population* was non-native.

This was considered- there's been quite a bit of work on their genetics, which has shown they are genetically distinct from continental populations, and most closely related to pool frogs from Scandinavia. None of the known introductions were from Scandinavia- most were from France. So it's very unlikely that they were replaced or succeeded by introduced frogs at the site in question.
 
There are a lot of British spieces that are more closely related to their Scandinaviain cousins rather than to mainland Europeon relatives, maybe dates back to iceage when North Sea landbridge was still there?,would seem a westward migration rather than a northerly one.Even Sea-trout in the South-east of England(few and far between) are more closely related to Scandinavian than those in the rest of UK,which would point to a more recent colonisation.
 
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