Archive for the ‘snakes’ Category

For most of my life, we have thought of snakes as being closely related to lizards. Both snakes and lizards are squamates (the order Squamata), but all my childhood reptile books placed snakes as being part of a distinct suborder called Serpentes.

However, taxonomy has moved onto a cladistic model, where we group organisms based upon their common ancestry. A clade is defined as including all descendants of a common ancestor, and keeping snakes a specially defined entity distinct from lizards is problematic.

A recently published paper on the Komodo dragon genome reveals why this is a problem for a cladistic classification model.  The authors compared the genomes of komodo dragons with the Burmese python, several species of lizard and lots of other tetrapods.

A phylogenetic tree was drawn from the comparisons.

komodo dragon genome phylogenetic

The Burmese python does not fit outside of the “lizard” clade. It fits within that clade, and if we are to use cladistic classification, then we must place snakes within lizards.

Snakes are a particularly specialized form of lizard, and as it should be noted, they are not the only legless lizards known. There are glass lizards and worm lizards (some of which are not entirely legless) that have a similar sort of body design to the snakes.

Snakes are the most wildly distributed legless lizards, but we probably should recognize them as lizards and not some sort of special grouping distinct from lizards.

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Cottonmouths in Kentucky

These do not live in West Virginia at all.

Don’t let anyone tell you they have seen one in West Virginia. That’s the northern water snake, which always gets called a “cottonmouth” or a “water moccasin.”

The copperhead, which is in the same genus, really should be called the “copperhead moccasin,” just to avoid confusion with the elapid with the same name.

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Mary Copperhead with one her baby Jesuses.

Parthenogenesis is a form of asexual reproduction that is found in certain multicellular species, including vertebrates.

Certain species of whiptail lizard exist only as females that reproduce through “lesbian sex” (though it’s not technically “sex”). This mating behavior is thought to stimulate ovulation, and the female lizard lays eggs that consist only of other females. There is no male contribution to the offspring.

These lizards engage in obligate parthenogenesis. but another form of parthenogenesis also exists– facultative parthenogenesis.

In this form of parthenogenesis, the females switch between sexual and asexual forms of reproduction. This particular form has been observed in many species, including several species of shark and the Komodo dragon.

In squamates (snakes, lizards, and “worm lizards”), it was thought that facultative parthenogenesis happened only in captive females.

But a recent study of wild caught copperheads and water moccasins shows that even wild female squamates occasionally in parthenogenetic reproduction.  This was the first time facultative parthenogenesis had been observed in wild vertebrates.

Female snakes apparently produce only male offspring through parthenogenesis.

It was thought that isolation from males of their species would stimulate females to reproduce in this way, but this study shows that even females that have lived around males of their species will occasionally produce parthenogenetic offspring.

The researchers looked at microsatellites in the DNA of offspring born to 22 wild-caught female copperheads and 37 female water moccasins.

They found that one female in each species sample had given birth without having mated with a male, which means that as much as 5% of all litters produced by these snakes are produced through parthenogenesis.

Of course, another study with a much larger sample size will be needed to determine the full extent of this form of reproduction in these two snakes, but the fact that it was found it two distinct species suggests that it is relatively widespread in both of them. If it had been found only copperheads, we could say that the single parthenogenetic litter was just a fluke. It would have been the first time it had been confirmed in the wild, but it wouldn’t have been so interesting.

But finding it in both species raises important questions about exactly how widespread it is in squamates.

Copperheads and water moccasins (also called “cottonmouths”) are two close relatives.  The copperhead is found throughout the Eastern and Central US, while the water moccasin is found throughout the subtropical South and along the Mississippi drainage as far north as extreme southern Illinois and extreme southwestern Indiana.

They classified in the genus Agkistrodon.  The copperhead is A.  contortrix, and the water moccasin is A. piscivorus.  I don’t think the two species can interbreed, but I don’t know if any genetic studies have looked at when the two species last shared a common ancestor.

West Virginia has only copperheads, which are the less venomous of the two species. I have had a lot of experience with copperheads. When I was a kid, I was told never to go walking at night, because I’d likely be bitten by a snake. I did encounter several copperheads on my walks, but they always slithered away. They are very reluctant to bite.

However, we had more than a few dogs bitten by them. I remember one Jack Russell that my grandpa had custody over that never seemed to learn about copperheads. One time she bayed something under his building, and when she came out, she seemed fine. But about an hour later, the flesh on her lower jaw began to swell up, and it wasn’t long before she looked like a pelican. An emergency trip to the vet was in order, where she got an antivenin shot and antibiotics.

And that was only one encounter.

For whatever reason, golden retrievers tend to leave the snakes alone. Perhaps they have too much sense to waste time on snakes, but they just never seemed to cause problems with them. (I know that’s not a universal concept, but I’ve never seen a golden retriever go out looking for snakes in the way I’ve seen other dogs do it.)

The West Virginia tradition was always to kill every copperhead one encountered, but I’ve often wondered about the wisdom of such a custom. One can teach a dog to leave copperheads alone, and as venomous snakes go, copperheads have fairly mild venom. They are also very unlikely to bite.

When I was a very young child, my dad killed one that was “pregnant.”   These snakes are ovoviviparous, which means that the embryos form in eggs inside the mother’s body. When they hatch, they are born. Unlike mammals, they are not fed by a placenta. It is an actual egg inside the mother’s body. Dad hacked open the snake’s body to reveal the developing embryos, and I distinctly remember that being one of the coolest things ever.

Maybe that female copperhead had been mated by male.

Maybe not.

But these snakes certainly deserve a little more respect than they have received.

They are not cute and cuddly.

They are not social animals.

They are not wolves, which remind of dogs and “noble savages.”

They are not panda, which remind of teddy bears.

They are the evil snake of Christian legend. Satan incarnate in the Garden of Eden.

The great irony is that humans can never have a virgin birth.

But the serpents can.





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Here’s the Rise Against Rattlesnake Roundups group on Facebook.

The rattlesnake is one of our national symbols.

Ever see this?


This is the Gadsden flag. It was designed by the South Carolina revolutionary Christopher Gadsden.

Timber and Eastern diamondback rattlesnakes were very common in the Thirteen Colonies, and they came to symbolize the colonist’s grievances.

The truth is rattlesnakes don’t attack people.

But if you tread on them and try to kill them, they will fight back.

Everyone living in the Thirteen Colonies would have recognized this.

They were not seeking a war with the mother country. Rather, the mother country had come to oppress them and take away rights that had long be established for British subjects.

So like a rattlesnake they struck back in defense of themselves.

But now, we’ve got all this messed up.  People think rattlesnakes attack.

Now, most rattlesnake species are not endangered, but the US Fish and Wildlife Service has suggested that the Eastern diamondback be put on the Endangered Species List. It is believed that its numbers have dropped dramatically in recent years, and if the snakes are protected, they won’t be subject to roundups or wanton killing.

Timber rattlesnakes now exist as a vestige of what they once were in the Northeast. Most states protect them, but of course, the one state that gives them no protection at all is also the one that made the species the official state reptile. Yes, West Virginia has no protections for this snake, even though the state legislature made the timber rattler an official symbol.

Primate evolution and natural history has left us with a strong natural aversion to snakes.

This aversion sometimes borders upon pathological hatred, and unfortunately, that’s what’s been fed into with these rattlesnake roundups.

These roundups could be wonderful educational opportunities.

But all you’re going to learn from seeing an animal with its mouth sewn shut is that cruelty is okay.

We have to have another message for the twenty-first century.

It’s certainly true that horses, cattle, and dogs get killed by snakebite.

And it’s true that people also fall victim to snakes.

But humans kill far more snakes than snakes kill us.

I have no problem with people wanting to control snakes on their properties.

But if people kill them, it must be done humanely.

We should not torture animals just because we don’t like them.

There are shocking parallels between what people do to rattlesnakes and what we once did to wolves.

It was not unusual for wolf trappers to bind the wolves’ jaws shut and then throw them to the dogs.

Or if they were particularly cruel, let them run off to die of dehydration or hyperthermia. (Remember that dogs and wolves must open their mouths to cool themselves.)

In both cases, people have allowed their irrational hatred to provide license for totally reprehensible behavior.

That’s not a good conservation ethic.

At all.

That’s an ethic that leads to destruction.

And one that we should not support.

Rattlesnake roundups must change.

They must be regulated to ensure a sustainable harvest.

And obviously cruel practices should be made illegal.

I guess it’s because we’re talking about snakes that it’s hard to get people concerned about these issues.

It’s hard to get people to be concerned with an animal that doesn’t really have  social life.

They aren’t wolves or mountain gorillas.

But if we lost them, we’d lose one of our national symbols.

Bald eagles represent liberty.

But ratttlesnakes represent our ability to defend our liberty.

It’s a symbol that has been embraced by the Tea Party Movement, which I know is not particularly fond of things like the ESA.

But if we’re not careful, someday we’ll be talking about the rattlesnake on the Gadsden Flag, and it will make no more sense than the dragon that St. George supposedly killed.

Let’s try to understand rattlesnakes as they are.

Let’s treat them with respect.

Don’t tread them.


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A juvenile black rat snake.

The adult looks like this:

black rat snake

I have more analysis here, which is partly based on some guesses I received on Retrieverman.

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baby snake

It was in a light fixture.

It was about 7 or 8 inches long. It was about twice the diameter of a pencil.

It didn’t try to bite.

Can you guess the species?

Leave answers in the comments.

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