Stories tagged melanin

Apr
27
2008

Do you see what it's eating?: Fingers.
Do you see what it's eating?: Fingers.Courtesy lavendarlady
There’s big trouble in Little America (that’s what all the cool kids are calling England these days, that or “Olde America”).

It seems that Cambridge, Little America, is being invaded by black squirrels.

“Why is this a big deal?” you ask. I’ll tell you why. First of all, you have to keep in mind that most large, dangerous animals were hunted to extinction in England hundreds of years ago. So, while we North Americans are used to bears, wolves, mountain lions and cheetahs wandering our streets, it has been centuries since most Brits have had to deal with anything more dangerous that, say, a bunny. Squirrels, while often smaller than bunnies, can be slightly more dangerous—if necessary, a bunny can usually be avoided by going up stairs, or standing on a chair, but this won’t work for squirrels. The squirrel is, after all, nature’s monkey.

But it’s not the presence of squirrels alone that’s dangerous here. Cambridge had squirrels before, but these new squirrels are mutants. Mutant, melanistic, black-furred gray squirrels, and they are slowly but surely running the old-fashioned gray squirrels out of town.

Melanism, simply, is a genetic variation that causes skin, fur, or feathers to be consistently dark. It’s sort of the opposite of albinism. Black panthers, for instance, are just melanistic leopards or jaguars. Melanism is usually fairly uncommon in animals—if a species has evolved its fur or feathers to be camouflage within its natural environment, a melanistic individual might end up sticking out like a sore thumb and getting eaten before it can pass on its genes. This sort of selective pressure is probably less significant for your average city squirrel, and having black fur may not necessarily be detrimental, and other traits could determine a species’ success.

Red squirrels used to be common in Olde America, for instance, until the introduction of larger, more aggressive gray squirrel. Now red squirrels are largely extinct in Britain, except for certain small pockets in Scotland, forced out by the brutal gray squirrel armies. Oh, wait, something perfect just happened.

Right, so now the same thing is happening to the gray squirrels. There’s some evidence that in large cats melanism offers a certain amount of protection from viral infection, so it could be that the new melanistic squirrel population receives similar genetic benefits. It has also been suggested, though not yet proven, that the melanistic squirrels are more aggressive than their gray cousins due to higher testosterone levels.

Also, I just dug this link up the other day, but it seems appropriate here too. In Russia a couple years ago, there was a report of a pack of black squirrels killing and eating a big stray dog. A choice quote:

"They literally gutted the dog," local journalist Anastasia Trubitsina told Komsomolskaya Pravda newspaper. "When they saw the men, they scattered in different directions, taking pieces of their kill away with them."

In short, it may be that Little America’s days are now numbered. Consider canceling vacation plans, or at least packing squirrel repellent.

Sep
04
2006

Albino or not?: Is this an ablino squirrel or just a white variety of a regular squirrel. Check out the eyes to find out.
Albino or not?: Is this an ablino squirrel or just a white variety of a regular squirrel. Check out the eyes to find out.
Have I been working too hard lately, or was that a white squirrel I just saw?

The past couple weeks I’ve seen more white squirrels than I’ve ever see before and I was all excited that I was finding rare albino versions of the animal. After poking around on the Internet, however, I’ve discovered there’s a lot more to this than meets my eyes.

Thanks to information I found on the Minnesota Department of Natural Resources website, just because an animal is white (when it normally isn’t that color) doesn’t mean that it’s an albino. Conversely, an albino animal doesn’t have to be totally white, either.

The answers can all be found in the animal’s genes. Animals that have strong white coloration lack the genetics to produce the pigment melanin.

An albino member of a species inherits genes that interrupt the making of melanin. But other members of the same species may have other factors that block melanin production, making the animal look all white. The key difference can be found in the eyes.

An albino will have pink or light blue eyes, shades that are very uncommon to the animal. A white, non-albino will have eyes that are usual color of its species, usually black. From what I’ve seen lately, the white squirrels I’ve been seeing have black eyes. The estimated rate of albinism in squirrels is estimated at one in 100,000.

Of course, there are some other all white mammals. They’re called leucistic. Polar bears are leucistic year round, while snowshoe hares have a leucistic phase in the white, giving them good cover in the winter snows.

Getting back to the white squirrels, there are a number of towns across North America that celebrate their white furry critter. For instance, in Olney, Illinois, protects and fosters their growth. They’ve had laws on the books to protect the white rodents since 1902 and had a population that grew to 1,000 at one time. Today, there are about 200. Olney, along with towns in North Carolina, California, Texas and Ontario, use the white squirrels as tourist attractions.

The book is still out on if albinism is a detriment to survival. On first thought, being all-white would be a huge disadvantage to being spotted by a predator, you might think. But through more study naturalists have come to believe predators may not recognize a white-version of their prey as food. In studying albino birds, researchers have found that the white-feathered creatures have a hard time finding a mate -- another reason why the albino genes become so rare.