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Archive for the ‘Rodents’ Category

Nearly a year after her TTA, Miley is back in action. She’s 8 years old, but she runs and looks like she’s five.

In past week, she’s dispatched a full grown rabbit and this chipmunk.

miley chipmunk

Golden retrievers never like to get dirty…

Never.

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Miley treed a squirrel today, but after it took to the trees, it let loose quite few alarm calls:

Source.

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I came across this little melanistic gray squirrel today, and naive as he is, he just sat there on that white oak branch and let me take a few photos and a few seconds of video of him.

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In this particular stretch of woods there are black variants and normal gray variants, but they come in more color variants than I can describe here.

Eastern gray squirrels have two litters per year. This one was born in the late winter winter litter.  Its mother is likely already pregnant with her midsummer litter which will be born some time next month.

As I mentioned, I did get a little bit of video of this squirrel before he darted off:

Source.

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I’ve had several people ask me about this article that appeared on a Finnish news website about introduced North American beavers losing their damming instinct. The story goes as follows:

Canadian beavers were introduced to Finland in the 1930s after the indigenous European beaver population had been hunted to extinction in the 19th century.

There are now an estimated 10-thousand beavers in the country, up to half of them in the South Savo region.

Population pressures, competition for living space and food, have brought more into large waterways such as Lake Saimaa. With a surface area of 4,400 square kilometres, Lake Saimaa provides plenty of room to spread out.

Beavers usually build damns in rivers and streams, to create ponds where they build their lodges. Those who have moved into Lake Saimaa, have had to adapt to a lifestyle of fluctuating water levels, rather than damming and regulating the waters themselves. In the process, they seem to have lost the desire to do so.

These beavers now create burrows or dens for themselves along the shores of the lake.

“They have had to adapt so that if the water level of Lake Saimaa falls, they change dens and diets. They change locations, and then if the waters rise too high for their dens, then they abandon them and build new dens higher up the shore,” explains Risto Hirvonen, a member of a local hunting club.

None of this should be of any surprise to anyone who knows about North American beavers.

We tend to think that beavers always build dams and then build lodges with underwater entrances.

The problem with this popular conception is that is not an absolute.

Most beavers in West Virginia don’t build dams at all. Instead, they dig dens into the sides of the banks of rivers. These dens always have an underwater entrance, which can sometimes be exposed if the water level in the river drops.

We call these beavers “bank beavers.”

beaver bank den

A beaver bank den in Kansas. Source for the image.

Does this mean that these beavers have lost their damming instinct?

I am very skeptical.

My guess is that these animals in Finland are now accustomed to the constant water levels in Lake Saimaa, just as they become accustomed to constantly shifting water levels in relatively slow moving rivers in the United States.

There is a way to test this hypothesis scientifically.

Catch some beavers from known populations that engage in bank denning, Put them in an enclosure with shallow rapidly running water and give them some material to make a dam.  Measure how long it takes for them to build a dam, if they built it at all.

Then do the same with beavers from known dam-building populations and run exactly the same test.

Then you’ll actually know if they’re actually losing the instinct.

My guess is that North American beavers, which are among the most successful of all large rodents, which have been introduced not just to Europe but Tierra del Fuego as well, are pretty good at adjusting their behaviors to fit their surroundings.

That hypothesis seems to fit with what we already know about them.

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squirrel monkeys ride capybaras

At a zoo in Japan.

(From Frans de Waal’s Public Page on Facebook).

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I saw this while out on the Coyote Highway:

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You’ll not see another rodent with a skull like this.

All other rodents known to science have chisel-shaped incisors that meet in the front. These teeth grow continuously, and their continuous grinding keeps them sharp and pointed.

All other rodents know to science have molars for grinding down food.

This rodent has neither of these features.

This all sounds bizarre, but this skull belongs to a new species of rat that was discovered on the Indonesian island of Sulawesi.

This animal was just described to science yesterday in the journal Biology Letters.

If one looks closely at the skull, one can see that it has no molars– at all.

This is very weird for a rodent.

It has incisors. The bottom incisors look very much like those of normal rodents, chisel-shaped, but the top incisors are little fangs.

This new species captured by a team of researchers who set up “pitfall traps”– buried buckets that are level with ground that allow small animals to fall in.

The researchers caught two of them, but they didn’t know until they examined the skull of a dead specimen that they had such weird dentition.

These rats live in high-elevation forests that are covered in moss.

The rats have evolved to live entirely on earthworms.

Earthworms aren’t very hard, so the rats have lost their rodent dentition.

Their teeth are now “worm grabbers.”

Their only purpose is to catch the worm, when the rat sucks it out of the ground with its long muzzle.

The species has been give the name Paucidentomys vermidax. Paucidentomys means “few-toothed mouse,” and verimdax means “worm-eater.”

This new species, which has not yet been given a common name, is closely related to the shrew rats that are found only on Sulawesi and the Philippines. Indeed, this animal is itself a new species of shrew rat. Shrew rats are largely insectivorous in their diet. They still have the typical rodent dentition. They have simply evolved into the shrew’s ecological niche.

This one, however, has become quite specialized to eating only worms.

It’s really unique among all rodents.

No other species of rodent has evolved such bizarre dentition to accommodate such a specialized diet.

Evolution produces lots of bizarre things.

But this is one of the most bizarre.

From a lineage that has produced the most diverse and successful order of mammals on the planet largely through its peculiar dentition, a species has evolved that has totally lost that defining characteristic of its order.

No longer can we say that all rodents have grinding incisors and molars.

We can only say all rodents but one.

And that’s this little shrew-like creature from Sulawesi.

The few-toothed, worm-eating mouse!

 

 

 

 

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