Feeds:
Posts
Comments

Posts Tagged ‘fox’

The Tibetan fox (Vulpes ferrilata) is endemic to the Tibetan Plateau. Its exact position within vulpine phylogeny isn’t clear.

One of the more famous clips from the Planet Earth series is the sequence that shows the unusual-looking Tibetan fox hunting pika.

The fox’s square-muzzled features have intrigued many people, and on the internet, it is often used as a meme to convey messages in much the same way as the corgis and the so-called “LOL cats.” (I don’t find cats particularly funny, but then I’m an extreme ailurophobe.)

This fox is a pika-hunting specialist.

Yes.  You heard me correctly. It hunts pikas.

Pikas are not just found in western North America.  North America has only two species of these adorable little lagomorphs, but there are many more species in Eurasia.

They are particularly numerous in the Tibetan Plateau, and the Tibetan fox has evolved to be an efficient predator of pikas.

However, the exact function of the fox’s weird looking head isn’t exactly clear. One hypothesis goes that the Tibetan fox evolved its squared off head to make it easier for the fox to jam it into squared off crevices in rocks where a pika might be hiding. Another hypothesis is the fox evolved the head shape as a way of matching the angles of the rock formations in the Tibetan Plateau, which provides the fox greater camouflage when stalking pikas. Still another  hypothesis suggests that the head shape is nothing more than an  adaptation for retaining heat during the region’s frigid winters. (Arctic foxes, however, don’t have heads that are anything like those of Tibetan foxes, and they live in a much colder climates.)

The truth is none of these hypotheses have been tested.

We just know that the Tibetan fox has a weird head.

And  the head shape is not the only mystery behind this fox.

We don’t know where this fox fits in the canid phylogenetic tree.

The only genetic data I’ve been able to find on this species is a study that developed a genetic test for determining whether a fox scat had been left by a red fox or a Tibetan fox, and another study that analyzed the cytochrome-b gene from various carnivoran scats in the region, which found that sequences from Tibetan and Corsac foxes  (V. corsac) were virtually indistinguishable. Cytochrome-b gene is found in found in the mitochondria DNA, so what we have is a very narrow mtDNA study that suggests a relationship between the Tibetan fox and the corsac fox.

Corsac foxes are found in the steppe country of Central Asia. They are very much equivalent to our kit and swift foxes.

I don’t know of any other genetic studies on Tibetan foxes and where they might fit in the canid phylogenetic tree.

Tibetan foxes do have some features in common with red foxes.

If you look closely at the photo at the top of this post, you can see that Tibetan foxes have a red base color that is somewhat lighter than the typical red fox. However, in this part of the world, the only two reddish colored foxes are Tibetan and red foxes.

Reds and Tibetans also share a white tail tip, and some red foxes also lack the black legs we typically associate with this species.

This might mean that, despite what the narrow mtDNA studies suggest, the red and Tibetan foxes are close relatives.

In fact, the Tibetan fox might be nothing more than a specialized offshoot of the red fox lineage, in the same way that the arctic fox is a specialized offshoot of the swift fox lineage.

Of course, these two hypotheses are not necessarily mutually exclusive. The corsac fox is actually more closely related to the red fox than to the swift fox that it resembles in both morphology and ecological niche. It may be that the corsac and Tibetan fox may both be offshoots of the red fox lineage, and the corsac lost its red coat as it adapted to living in the steppes.

The truth is we need better genetic studies to see exactly where the Tibetan fox fits.

Its coloration suggests that its a close relative of the red fox, and the cytochrome-b gene analysis says they are related to corsacs.

And as a general rule, one needs to be skeptical of studies that look at mtDNA, especially those that  just a narrow sector of that DNA.

At the very least, a microsatellite  study is warranted to figure out where this very unusual fox fits.

Read Full Post »

A 35.5 pound fox! That’s the size of a typical coyote bitch in my part of the world.

Source.

Why are the foxes getting larger?

I would submit that they are simply evolving to fit a niche that has been left vacant when wolves were extirpated from the British Isles. Something very similar happened when wolves were killed off in the Eastern US, and Western coyotes wandered in. They grew larger in size to be more effective predators of deer.

I also think that fox hunting ban in Britain has had an effect.  The fox hunts always exerted upon foxes a relatively strong selection pressure to remain small. If a fox is small enough, it can fit into the narrowest places and avoid the hounds. With the hunting ban, there is no longer much of a selection pressure to remain small.  A larger fox that exists hounds hunting it has certain advantages in obtaining access vixens and good hunting territory, and its prey choices become wider. A fox of that size might be a threat to some of the smaller deer species– and it certainly would be able to take relatively large lambs.

See related post:

Read Full Post »

This painting is called “Beagle and Fox,” and it was painted by Bruno Liljefors in 1885.

Liljefors was a Swedish artist, and the title is probably not translated correctly– because one can obviously see that the dogs attacking the fox are not beagles at all.

They are wire-haired dachshunds.

Read Full Post »

The following foxes have nothing to do with Dmitri Belyaev Siberian fox farm experiment:

Pearl foxes. Marked like border collies but not selected for tameness.

Irish marked marble fox, full body view.

Marbled fox. Almost entirely white.

Another marbled fox. These foxes are sometimes sold to rubes as arctic foxes. They are nothing more than red foxes with unusual coat colors. Arctic foxes are white only in winter. These foxes are always predominantly white.

These phases not result from their ancestors being systematically selected for flight distance or decreased aggression towards humans.

They resulted simply from unusual sports that popped up in farm fox breeding operations, and then the owners began to select for these color varieties. They normally aren’t uniform enough to make good pelts, but they often sold to roadside zoos.

These colors probably popped up as a consequence of being bred in captivity.  Belyaev suggested that his team was actually selecting for for genes that affect neurotransmitters that also affect melanin production.  So in this hypothesis, the selection for “tameness” increased the likelihood of producing spots.  But captivity produces a series of selection pressures on wild species that might be connected to selecting for both neurotransmitters and spots. It’s not tameness as defined by this experiment that affects morphology. It  is simply being bred in captivity that produced the spots.

Again, we actually don’t know the exact genetic basis behind the spotting, but we do know that these are phases that have been selected for in captivity.

Mark Derr in How the Dog Became the Dog points out that the control population of foxes in the Belyaev experiment also produced these spotted forms.  It was not the selection for tameness or docility that produced the spots.

The truth is we just don’t know why they are spotted.  The neurotransmitter-melanin hypothesis is worth exploring.

However, wild animals have been born with spots.

As I mentioned earlier, the leopard complex in horses existed when horses were wild animals. There were “Appaloosa” horses 25,000 years ago. People were hunting horses in those days. They weren’t selecting them to be tame at all.

There are also piebald white-tailed deer.  They are rare, but they are just as wild as the ones without spots.

It is possible that spotting is less of a problem for large ungulates in the wild than it would be for predatory mammals, even among those– such as wolves and foxes– that don’t use their coloration as camouflage.  Animals with lots of spots would have a hard time hunting for whatever reason, and nature would strongly select against these colors.

However  it may be that spotting is of no consequence with certain species of ungulate.

Of course, there is research that shows that most ungulates are uniform in color because predators tend to select those that are aberrant. That’s why you don’t often see white gnus or dalmatian-spotted gazelles.

The truth is we simply don’t know why some animals develop spotted pelts.

We have many hypotheses.

But the truth is likely quite complex.

And artificial selection is too often ignored as an agency.

The fox farm experiment likes to make a lot of hay out of the coat color changes in the domesticated foxes, but it doesn’t answer why marbled and pearl foxes turned up in populations that were never selected for tameness in this fashion.

We are simply not served well by such reductionism.

 

 

 

Read Full Post »

Foxes jump on trampoline

I think this might be an example of observational learning. I don’t know where foxes would get the idea to jump on the trampoline. They might pounce and play, but a trampoline is an unusual place to do the pouncing. My guess is they got the idea by watching children on the trampoline.

Source.

Read Full Post »

They got only one cat.

These animals do have feelings.

However, they don’t belong on this continent.

The native fauna is ill-prepared to deal with their depredations.

And the only way to save many species of native Australian wildlife is to create areas that are free of foxes and cats.

The only way to do that is to kill them.

They shouldn’t be tortured when they are killed. A single killing shot will do.

 

 

Read Full Post »

Albino Blandford’s fox

Blandford’s foxes are native to the Middle East to Pakistan.

Their normal color is not at all like this.

This taxidermied specimen is displayed at the Natural History Museum at Tring, England.

Read Full Post »

From The Telegraph:

The male fox weighed two stone or 26.5lb and was four foot long, about the height of a seven-year-old child.

The giant fox was captured and killed in Maidstone after a cat in the local neighbourhood was killed.

It was trapped in a cage and put down in a humane way by Keith Talbot, a local vet.

He said foxes had been seen around his parents house days after their 19-year-old tabby cat was found killed on the doorstep.

Zoologists and experts said foxes said foxes could be growing bigger because of ‘easy pickings’ of food scraps in dust bins or even left out by animal lovers.

A dog fox will often grow bigger than the rest of the pack because the social system means the alpha male gets most of the food and the rest get leftovers.

There are thought to be at least 34,000 urban foxes in Britain.

Recently there has been concerns the animals could pose a threat after twins Isabella and Lola Kouparis were attacked in their beds in London.

However animal rights campaigners point out that most foxes live on insects and small mammals and pose no harm to humans unless they are frightened.

The Field Sports Channel is offering £100 for the best story of the largest fox. One taker has come forward with claims he shot a fox weighting 34lb in 2009, although this has not been confirmed with photographic evidence.

I guess the English have adopted one of our customs. In the US, there are coyote killing competitions. In the West, these competitions are about seeing who can kill the most coyotes within a given amount of time. In the East, where big coyotes are legendary, the goal is to see who can kill the biggest one. Anyone who kills a black, white, or otherwise unusually colored individual also gets plaudits. (Remember, the ones in the East have some wolf ancestry.)

Another reason why these foxes could be getting larger is that they have virtually no predation. Wolves no longer exist in England, and fox hunting has been banned. That means that foxes now exist at higher densities than they once did, and it may be that foxes that are bigger and tougher are better at competing for both vixens and food resources than smaller ones. With all of these foxes living in relative proximity to each other, it may be that a dog fox that has some size advantage might be better able to spread his genes, simply by muscling his way around smaller individuals.

And access to food would also play a role.  These foxes now have the nutrition to reach larger sizes.

The fact that this fox was killed in town means that he likely had access to really good nutrition his entire life. His ancestors may have been working their way towards the larger size as I describe may become possible when foxes exist at high densities.

Red foxes do vary quite a bit in size. A 26 to 34 pound fox is much larger than any fox around here. It actually would put  them in the same class as the smallest of coyote bitches.

Now, I’ve never seen one in North America of this size, but I did see one last week.

It was a taxidermied specimen at the German Hunting and Fishing Museum (Deutsches Jagd- und Fischereimuseum). I was shocked at how large this fox was. It was the size of a beagle.

Where I live, red and gray foxes are about the same size– 8-12 pounds. Virtually all red foxes here are derived from English imports to Maryland and Virginia in the seventeenth and eighteenth centuries. Genetically and morphologically, they are almost exactly the same as those foxes in England. Of course, there was a small native population of red foxes that lived in what is now the eastern US, but they were not that common before European settlement. (However, they did exist in Virginia during the Pleistocene).

The ones here also have very distinct black legs, which this particular fox does not have. Only its feet are black.

With 45 different subspecies of red fox,  we should see lots of variance between them. Not only do they come in several distinct phases in the wild, they also vary quite a bit in terms of size.

As wild dogs go, they are the true inheritors of the wolf’s empire. They are now more widely distributed than any other wild carnivore. Not only do they still maintain a vast Holarctic range, that also includes the Nile Valley, they are also found in Australia. Like wolves, they have the ability to rapidly respond to selective pressures and change their morphology and behavior to fit new ecosystems and new niches.

Large size may be of some advantage for certain populations, and that is probably the main reason why giant foxes are starting to appear in different European countries.

But if that readily available food supply disappears and the foxes find themselves suffering from both competition and predation from other animals, the large size may not be quite so advantageous.

 

Read Full Post »

Otis the Pug and a fox have a tail contest:

Source.

“You call that a tail? This is a tail!”

You know this film is very much fiction.

Easy to tell.

A pug survives months on its own in the wild?

I don’t believe that for two seconds.

Maybe for a second.

 

 

Read Full Post »

« Newer Posts

%d bloggers like this: