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Posts Tagged ‘thylacine’

thylacine meets spaniel

I’ve seen this photo several times, but every time I’ve seen it, the left-hand side was always cut off.

Now that I see the full photo, you can see what was going here.

Someone wanted to introduce his spaniel (an English springer, by my estimation) to a captive thylacine.

I guess this would be the equivalent of a human meeting a Klingon or a Vulcan for the first time.

“You’re similar, but you’re not the same!”

 

 

 

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Remarkable discovery in the snow!

Thylacine sighting

 

 

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I’m so glad I caught it on camera!

thylacine sighting

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Female mainland thylacines that were living during the Holocene (skull at far left) were much smaller than dingoes from the same time period (skull at far right). This size difference means that dingoes could be effective predators of female thylacines on the mainland and could have been a cause of their extinction.

Thylacines went extinct on the mainland of Australia before European colonization.

They were around on Tasmania up until the twentieth century.

After the Thylacoleo (“marsupial lion”) species became extinct some 40,000 to 50,000 years ago, the thylacines were the largest marsupial carnivores.

And the largest terrestrial predators in Australia. The saltwater crocodiles clearly had them licked, but outside of riparian and coastal areas and in the southern part of the continent, the thylacine was the top “dog.”

However, the reason why the thylacine disappeared from the mainland has been up to conjecture.

Several hypotheses have been propsed.  Almost all involve some discussion of the dingo’s arrival on the continent– a date that is not exactly clear in either the genetic or paleontology literature.

The initial hypothesis was that dingoes simply outcompeted thylacines. Dingoes hunted in packs, and what’s more, as variants of domestic dogs, they would have had a very close relationship with humans.

Pretty much every study about thylacines has made comparisons with those that were in Tasmania during historical times.

These thylacines weighed as much as 70 pounds, and because we have historical accounts a thylacin splitting the skulls of a bull terrier with its jaaws,  it assumes they would have been a match for even a pack of dingoes that included individuals that weighed 30 to 45 pounds. (There is, however, some recent recent research that suggest thylacines had structurally quite weak jaws, so they may not have been all that effective in a combat situation with a mid-sized dog).

However, this is a bit of an unfair comparison.

If one assumes that thylacines that on the mainland when dingoes arrived were exactly like the ones in Tasamania, then it becomes more difficult to see how dingoes could have dominated them. Only by allowing for the dingo’s advantages– such as its association with people, who were on the increase throughout the continent, and the dingo’s pack hunting behavior which allowed it access to wider variety of prey– can we see how a dingo would have dominated the thylacine on the mainland.

However,  a recent study was just published in PLoS One.  In this study, researchers examined the body and skull size thylacine and dingo remains from Nullarbor Plain and the southwestern part of Western Australia that were dated to the early Holocene.

The results revealed something amazing.

Dingoes of that time were quite a bit larger and heavier than mainland thylacine.  The researchers found:

The smallest thylacines were 19.2% and 28.2% smaller than the smallest dingoes in the Nullarbor and southwest, respectively. The largest dingoes were estimated to be 36.8% and 54.1% heavier than the smallest thylacines in the Nullarbor and southwest, respectively.

If thylacines on the mainland were typically that much smaller than dingoes, then they certainly would have been killed by dingoes.

Dingoes are derived from domestic dogs, which are derived from wolves, and we know that wolves kill jackals and coyotes where their ranges overlap.

In fact, canids  in general will kill predators that are smaller than themselves.  Red foxes kill arctic foxes. Coyotes kill red foxes.

Even today, dingoes are effective at controlling fox numbers in Australia.

So it is very possible that larger dingoes were killing thylacines.

The authors of the recent study suggest that the smaller thylacines were female, and unlike Tasmanian thylacines, these mainland individuals had significant sexual dimorphism.

If the dingoes could easily kill these smaller ones, then they were likely killing many female thylacines, and without females, the population could not be sustained.

Of course, the authors point out that all of these relationships were likely much more complex than can be concluded through simple morphological studies.

Dingoes, as feral and semi-domesticated dogs, were attached to people, and the time in which thylacines became extinct is associated with a population increase among indigenous Australians. Indigenous Australians were using fire to manage lands in order to create landscapes that were filled with prey species. They may have even been using the dingoes as hunting dogs, which would make it much easier for them to catch prey.

And if people were doing well, the dingoes likely were, too.  And if the dingoes were doing well, they could have been competing with thylacines for prey.

If their jaw structure meant that thylacines were reduced to preying on smaller animals, dingoes would have had an advantage.  They could hunt larger macropods that were out of the thylacine’s grasp, and they could very easily attack the same prey that thylacines were relying upon.

And if they were also killing thylacines, this would have been very bad for them.

After the extinction of the marsupial lions, the thylacine was the only predatory mammal of any size in Australia.

It evolved without competition.

Dingoes, as derivatives of domestic dogs that evolved from wolves, had derived from lineages that spent millions of years with lots of competition from other predators and very wily, recalcitrant prey.

The wolf had evolved pack-hunting behavior to deal with these challenges.

The thylacine, by all accounts, had not.

One way of interpreting the wolf’s success is that certain wolves evolved to have a relationship with humans. We call the descendants of these wolves domestic dogs. Dingoes are derivatives of domestic dogs, and virtually all accounts suggest that they had some sort of relationship with the indigenous people of Australia.

Thylacines had no relationships with anyone.

The cards were clearly stacked against the mainland thylacine when it went extinct.

Humans were changing the landscape through fire– which allowed human populations to increase.  But that same fire got rid of the forested habitat that thylacines preferred to use to ambush their prey.

And the success of humans also meant that the dingo’s numbers would increase.

And dingoes were much more efficient and generalized predators than thylacines were.

And the dingoes may have considered these mainland thylacines prey.

It was not a good situation for a predator that had spent so many thousands of years evolving without competitors.

And in this case, dingoes were an invasive species.

Over time, they became native, but not after being possibly implicated in the extinction of the mainland thylacine and Tasmanian devil.

It’s not a smoking gun, but dingoes certainly had the opportunity.

 

 

 

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Thylacine sighting!

Definitive proof they didn’t go extinct!

Source.

 

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"Scotch terrier" from Stonehenge's Dog in Health and Disease (1859).

The following account appeared in the Hobart Town Gazette (2 August 1823). It is quoted in Robert Paddle’s The Last Tasmanian Tiger.

Paddle explains that the thylacine probably could have defended itself against an attack by a small terrier, but it was so stressed by the four large dogs and the large number of men standing nearby that it didn’t focus its attention on the small terrier– which was a fatal mistake.

One should not assume that the dog called a “Scotch terrier” in 1823 or 1859 was exactly the same thing as the dog we call the Scottish terrier today. “Scotch terrier” was a term that referred to terriers from Scotland, which were varied in type from region to region and from strain to strain.

Australian native fauna was know for its naivete  when they first encountered European domestic and introduced animals. There was nothing on Tasmania that would have given the thylacine any clue that an animal of that size could have been a threat. I don’t think Tasmanian devils ever kill thylacines, but they may have been able to bluff them off their kills. I seriously doubt that any thylacine would have had reason to worry about them.

So why should it have worried about a small terrier? Especially when a pack of kangaroo dogs is nearby. Kangaroo dogs are a landrace of sighthounds that are roughly analogous to the staghounds of the American West. They probably could have killed a thylacine, but they were too scare of it.

I actually do wonder what dogs actually thought abut the thylacine. I know that dogs will respond to objects that are in roughly the same shape as another dog, and a thylacine superficially looked like dog. However, its behavior would have been remarkably different, and dogs might have been disconcerted when encountering it.  The thylacine had very powerful jaws that were structurally quite weak, which explains why there is a more famous account of a thylacine splitting open the skull of a bull terrier as the bull terrier charged in for the kill. It probably wouldn’t have bitten that hard had its life not been so threatened.

And one killed by the Scotch terrier didn’t have time to react to the attack– until it was too late.

 

 

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Cute thylacine

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From Live Science:

The extinct thylacine, more commonly known as the “Tasmanian tiger” or “marsupial wolf,” hunted more like a cat than a dog, meaning the tiger moniker may be the more appropriate nickname.

The thylacine had the striped coat of a tiger, the body of a dog and like other marsupials (including kangaroos and opossums) carried its young in a pouch. These carnivores were last seen in Australia 3,000 years ago, having died out after the introduction of dingoes by humans. The last remaining populations were sheltered by their isolation on the island of Tasmania, surviving until the 1900s, when a concentrated eradication effort wiped the thylacine out.

Researchers hypothesized that the dingoes were a main cause of the thylacine decline in Australia, because the two species were in direct competition — using the same hunting strategies to hunt the same prey.

Dingoes are a species [sic] of wolves, they are runners,” study researcher Borja Figuerido of Brown University said. “If the thylacines are ambushers, the hypothesis of the extinction of the thylacine outcompeted by dingoes is less probable.”

The elbow joint of the thylacine and the modern tiger, top, is wider and more rectangular than the dog-like wolf and fox, bottom, which are more toward the square. This suggests different styles of catching and subduing prey, cat-like or dog-like.

By looking at the elbow joint bones of the thylacine and 31 other mammals, the researchers noticed they resembled those of cats, which can rotate their paws upward to pounce and attack prey. Dogs and wolves don’t have this rotation capability.

“These anatomical characters reveal something about the hunting strategies of the thylacine. They are more ambushers than previously suspected,” Figueirido said. “Ambush predators usually manipulate the prey with the forearms, they have very good mobility. Running predators lack this ability, because the elbow is locked.”

The limited rotation of their arm bones makes dogs and wolves (including dingoes) faster runners, which changed their hunting behaviors. Dogs and wolves hunt in packs, following their prey over longer distances. The researchers determined that the thylacine was more of a solitary, ambush-style predator, similar to cats.

Marsupial mammals, found mainly in Australia and other areas of the Southern Hemisphere, are similar to placental mammals (such as humans, dogs and cats), but their evolution diverged from ours during the Cretaceous Period, the earliest example of a marsupial appearing about 125 million years ago.

The evolution of these two groups of mammals is an example of convergent evolution, where two separate groups in different locations evolve similar morphologies to deal with similar habitats. The thylacine was thought to be the marsupial equivalent, or ecomorph, of the wolf, with similar body size and eating habits.

Now, Figueirido said, “this designation will need to be revised.”

The study was published today (May 3) in the journal Proceedings of the Royal Society B: Biology Letters.

All of this information has been discussed before, so I don’t know why it’s making news now.  The convergence is in phenotype, not behavior or hunting style. I don’t think anyone ever made that claim.

The dingo outcompeted the thylacine because it was a pack-hunter. It was smarter, and it could attack both large and small prey.

It’s very similar to what happened to Hyaenadon when bear-dogs arrived in North America.

The notion of convergent evolution isn’t that animals from different ancestries evolve to be exactly the same. That’s a bizarre standard– and the one that seems to be put forth here.

But it is remarkable that the bulk of this animal’s adaptations– even if it were an ambush predator– closely resemble that of a dog.

It’s still convergent evolution. You’re never going to find convergent evolution that is 1:1 anywhere. Even with golden and marsupial moles, which are probably the closest anyone will ever get to that 1:1 convergence.

Convergent evolution can mean that only one trait is similar, such as the retractable claws in both modern cats and the thylacoleo, the extinct “marsupial lion,”  or the fact that koalas have the fingerprints, which are essentially a primate trait.

By this metric, the thylacine and the dingo are pretty strong examples of convergent evolution, for they share many traits, including the head shape, and the fact that both were digitigrade. Both use strong jaws that have evolved into the shape of a muzzle.

And a dingo isn’t a “species of wolf.”  Is is a subspecies that is sometimes called Canis lupus dingo or Canis lupus familiaris, which is probably more accurate, seeing as dingoes are more closely related to East Asian and Indonesian dog breeds than they are to wild wolves.

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Wilf Batty shot this thylacine on May6. 1930. It found it killing chickens in his hen house, so he shot it.

It is the last official wild thylacine.

He may have killed the last one, and I’m sure we’re all going to condemn him for doing so.

And we should.

But one should also keep in mind that this was a poor Tasmanian homesteader, who was trying to make a go of it in the bush.

The dog played no role in hunting this thylacine. Batty claimed that dogs always feared thylacines. After all, a thylacine had a much more powerful bite than any dog. When Batty brought the thylacine body home, his dogs took off and didn’t come back for three days.

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You can see the thylacine in the foreground has a bit of a distended belly. That is her pouch, and she has at least one joey inside.

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