Is Natural Selection Stymied by this tactic?

[Paul C. Anagnostopoulos]

On the issue of how the snakes learn how long to wait, it is necessary to know that they have extremely keen olfactory senses. I surmise they can smell (even "taste")the difference between a potent poison and one which has lost its potency. Snakes actually smell as well as taste with their tongues, picking up odor molecules with each flick and thus retrieved draw it back into an olfactory organ in the roof of their mouth known as Jacobson's organ.

The snakes don't "learn" anything. Through mutations, some just happen to wait long enough for a particular poison, others don't. The ones that wait survive and the ones that don't die.

~~ Paul

 

[Dancing David]

This puzzles me. How is possessing bright colours an automatic advertisement for poison?

It isn't , but often it is. Some insects have bright colors, a bird that eats them gets sick and then associates those colors with being sick. Some things have stingers (bumble bees) and they have distinctive colors as well.

Then there is the mimicry stuff.

 

[Dancing David]

The snakes don't "learn" anything. Through mutations, some just happen to wait long enough for a particular poison, others don't. The ones that wait survive and the ones that don't die.

~~ Paul

Or they just get sick and don't eat the frogs again.

 

[SteveGrenard]

The snakes don't "learn" anything. Through mutations, some just happen to wait long enough for a particular poison, others don't. The ones that wait survive and the ones that don't die.

~~ Paul

This is a sensing issue ... the snake's olfactory sense tells them when its ok to eat a particular frog. This is how the same snake differentiates the times to safety for different types of poisonous frogs.

 

[Lucky]

It seems I was wrong to assume that the researchers were claiming learnt behaviour by the snakes. This article contains some quotes that aren't in the OP link or the press release:

Shine says that he's leaning toward the response being genetic because work he's doing on the way in which adders cope with other toxic prey is "frankly not impressing us with the learning ability of the snakes."

However, it seems to me that the following quote from the same article suggests a possible learning (or conditioning) mechanism:

In Phillips and Shine's experiments, an adder would sometimes strike at a Dahl's frog but would then release it immediately. As the frog died, the snake thrashed around too, sometimes lying on its back with its mouth open. "It's like the snake has just had a mouthful of chili pepper," says Shine. After recovering, the snake eventually would eat the frog

The snake could be learning to avoid a burnt mouth.

This is a sensing issue ... the snake's olfactory sense tells them when its ok to eat a particular frog. This is how the same snake differentiates the times to safety for different types of poisonous frogs.

That's very interesting, as it gives a clue to the information basis of the avoidance mechanism, but if correct it still doesn't tell us whether the behaviour itself is learnt or evolved. We don't know the biological basis for the link between a particular smell (or level of smell) and a "decision" to consume the prey. I'd be interested to know whether you think it's partly learnt or purely genetic.

 

[JoeTheJuggler]

(Also I don't think you need to postulate predators teaching their offspring to avoid a certain type of prey.)

Not necessarily. It could also be that they develop a distaste for red/yellow bugs.

Or each individual learns (is conditioned) by trying a few. Or it could be an inherited behavioral trait (as are other innate behaviors).

I doubt that parental teaching has much to do with it.

 

[Paul C. Anagnostopoulos]

Or they just get sick and don't eat the frogs again.

Aha, yes, that's possible. I was assuming we are seeing evolution at work, with snakes evolving to avoid the frogs until they are safe to eat.

This is a sensing issue ... the snake's olfactory sense tells them when its ok to eat a particular frog. This is how the same snake differentiates the times to safety for different types of poisonous frogs.

Yes, but does a snake learn to do this over its lifetime, or has it evolved an instinct?

~~ Paul

 

[SteveGrenard]

Yes, but does a snake learn to do this over its lifetime, or has it evolved an instinct?

~~ Paul

IMHO this is a strictly physical response based on the evolution of the vomeronasal organ or Jacobson's organ which is highly developed in snakes. They use this organ to sense chemosensory stimuli so it all depends on how you want to define "instinct." I am not sure you need to develop an instinct to know something smells and/or tastes bad but perhaps. Babies do it without learning or perhaps while in the process of learning. They grimace and make a ugh face. As you all know from watching snakes, they constantly flick their tongues in and out. When sticking their tongue out it gathers scents and, when retracted, it touches the opening of the organ conveying the scent to the olfactory processes.

Clearly they are born with this ability.....

For a good discussion of the vomeronasal or Jacobson's organ, see:

http://neuro.fsu.edu/~mmered/snake.htm

opt for diagram with text

 

[CFLarsen]

IMHO this is a strictly physical response based on the evolution of the vomeronasal organ or Jacobson's organ which is highly developed in snakes. They use this organ to sense chemosensory stimuli so it all depends on how you want to define "instinct." I am not sure you need to develop an instinct to know something smells and/or tastes bad but perhaps. Babies do it without learning or perhaps while in the process of learning. They grimace and make a ugh face. As you all know from watching snakes, they constantly flick their tongues in and out. When sticking their tongue out it gathers scents and, when retracted, it touches the opening of the organ conveying the scent to the olfactory processes.

Clearly they are born with this ability.....

In which case, no snake should ever die from eating poisonous frogs.

What if the poison doesn't taste bad to the snake?

 

[SteveGrenard]

In which case, no snake should ever die from eating poisonous frogs.

You hit it right. But it's "almost no" snake. Some snakes are very well adapted. I can't think of any frog or toad eating snake that hasn't adapted in some way which allows them to prey on poisonous frogs and toads if they are a principal or essential part of their diet. Of course snakes that don't, in nature, normally prey on poisonous frogs or toads and accidentally attempt to eat one can die from such an encounter. One group of Asian water snakes eat toxic toads and are believed to use the poison from the toad's glandular secretions as the substrate on which to produce their own venom.

And there are venomous snakes that have evolved immunities to their own poisons so if they bit themselves or a cohort bit them they would not die either. But there are a few venomous snakes not so lucky.

The non-venomous American King Snakes (Lampropeltis sp) habitually feed on rattlesnakes, copperheads and other snakes. They can endure being bitten and don't suffer from it. What is even more interesting is that rattlesnakes, smelling a king snake nearby, slither off to avoid it rather than engage it. It's almost as if the rattlesnake knows it is powerless against the king snake. How did they learn this?

http://asascott.com/snakes/pages/page02.html

What if the poison doesn't taste bad to the snake?

Again, while we can't ask the snake, it is obvious snakes that normally eat poisonous frogs and toads in nature and have adapted the means to do so don't find the poison so noxious they can't tolerate swallowing it. Snakes that don't normally eat these animals or haven't adapted the means to do so probably would find it unpalatable. You and I would.Then again we normally don't eat live poisonous frogs and toads. I would think that an unadapted snake who tolerates the taste would die from eating it. But this would be a rare ocurrence.

 

[CFLarsen]

You hit it right. But it's "almost no" snake.

Which is not what you said.

Some snakes are very well adapted. I can't think of any frog or toad eating snake that hasn't adapted in some way which allows them to prey on poisonous frogs and toads if they are a principal or essential part of their diet. Of course snakes that don't, in nature, normally prey on poisonous frogs or toads and accidentally attempt to eat one can die from such an encounter. One group of Asian water snakes eat toxic toads and are believed to use the poison from the toad's glandular secretions as the substrate on which to produce their own venom.

And there are venomous snakes that have evolved immunities to their own poisons so if they bit themselves or a cohort bit them they would not die either. But there are a few venomous snakes not so lucky.

Evolution isn't about luck.

The non-venomous American King Snakes (Lampropeltis sp) habitually feed on rattlesnakes, copperheads and other snakes. They can endure being bitten and don't suffer from it. What is even more interesting is that rattlesnakes, smelling a king snake nearby, slither off to avoid it rather than engage it. It's almost as if the rattlesnake knows it is powerless against the king snake. How did they learn this?

The same way any other animal learns to avoid a stronger opponent. Nothing special about snakes in this regard.

Again, while we can't ask the snake, it is obvious snakes that normally eat poisonous frogs and toads in nature and have adapted the means to do so don't find the poison so noxious they can't tolerate swallowing it. Snakes that don't normally eat these animals or haven't adapted the means to do so probably would find it unpalatable. You and I would.Then again we normally don't eat live poisonous frogs and toads. I would think that an unadapted snake who tolerates the taste would die from eating it. But this would be a rare ocurrence.

It would be a rare occurrence because such a species would be decimated, maybe even become extinct, unless it found a way to avoid eating such animals.

What do you think the answer is to your own question in the OP? Is this truly an example of a situation where natural selection is stymied?

 

[SteveGrenard]

Which is not what you said.

That's because I know there are over 2,000 species of snakes. It is pointless to generalize.
American hog nosed snakes (Heterodon sp) eat highly toxic toads that contain digitalis like poisons that slow and stop hearts. They have evolved the ability to do so by having bigger and more active adrenal glands than other non-toad eating snakes. The adrenal glands in hog nosed snakes are capable of producing more adrenalin than other snakes and adrenalin counteracts the effects of the toad's poison.

Evolution isn't about luck.

No? If you think so fine with me. If its not random luck, are your saying everything evolves according to a plan.? More details about this would be appreciated; more details about why you think chance or luck doesn't occur in evolution.

The same way any other animal learns to avoid a stronger opponent. Nothing special about snakes in this regard.

Hmm. Snakes don't just use avoidance to back away from a confrontation with a more powerful animal, including humans, who are bigger or stronger. Many venomous snakes when they haved no other choice will attack. Rattlers know that to do so in the case of King snakes is pointless. King snakes are not bigger or stronger, they simply have an innate (evolved) immunity to the rattler's weapon, its venom. And that gives them the edge.

What do you think the answer is to your own question in the OP? Is this truly an example of a situation where natural selection is stymied?

I don't think natural selection is stymied or blocked but I was interested in what others might have to say. I already said this above.

 

[CFLarsen]

No? If you think so fine with me. If its not random luck, are your saying everything evolves according to a plan.? More details about this would be appreciated; more details about why you think chance or luck doesn't occur in evolution.

Evolution isn't random, Steve. That's a tired Creationist "argument".

I don't think natural selection is stymied or blocked but I was interested in what others might have to say. I already said this above.

But not in the OP.

 

[SteveGrenard]

Evolution isn't random, Steve. That's a tired Creationist "argument".

oookay. If not, what's the plan then?

 

[CFLarsen]

oookay. If not, what's the plan then?

There is no "plan", either.

Why are you using Creationist arguments?

 

[Lithrael]

There is no "plan", either.

Why are you using Creationist arguments?

Larsen, jeez. If you know from other threads this guy is insincere please say so, so that you don't come off as such a jerk to casual observers. It sounds to me like the guy is just referring to luck in the everyday sense, as in, the very hungry snake who does not normally predate upon poisonous frogs is experiencing a serious lack of 'luck' when a poisonous frog hops into its ambush range. It does not sound like he's claiming that evolution in general is random.

 

[CFLarsen]

Larsen, jeez. If you know from other threads this guy is insincere please say so, so that you don't come off as such a jerk to casual observers. It sounds to me like the guy is just referring to luck in the everyday sense, as in, the very hungry snake who does not normally predate upon poisonous frogs is experiencing a serious lack of 'luck' when a poisonous frog hops into its ambush range. It does not sound like he's claiming that evolution in general is random.

Someday, I will write about Steve Grenard.

 

[Lucky]

Evolution isn't random, Steve. That's a tired Creationist "argument"
...

No.

...
Why are you using Creationist arguments?

He isn't.

It is creationist (and incorrect) to claim that evolution by natural selection is impossible, because random events can't produce ordered, directional processes and an increase in complexity, but that's not at all what he said.

...
And there are venomous snakes that have evolved immunities to their own poisons so if they bit themselves or a cohort bit them they would not die either. But there are a few venomous snakes not so lucky.
...

...

Evolution isn't about luck.

No? If you think so fine with me. If its not random luck, are your saying everything evolves according to a plan.? More details about this would be appreciated; more details about why you think chance or luck doesn't occur in evolution.
...

CFLarsen, are you seriously claiming that mentioning the role played by chance in evolution is the same as supporting creationism? I'd be interested to see you defend that view.

Now, would you be so good as to answer this question: Do you have any evidence that Steve Grenard disbelieves in evolution, supports creationism or uses creationist arguments? Because there certainly isn't any in this thread.

If you want to discuss the general principle of randomness vs non-randomness in evolution then you should start a new thread. You're derailing this one, which is about a particularly interesting specific issue: how can natural selection produce a defence mechanism that only operates after death?

 

[SteveGrenard]

Lithrael got it when I said some snakes aren't so lucky. In fact they die, don't live to reproduce and hence are part of the natural selection process. Don't tell me this is part of god's plan or some other IDer's plan. It was pure chance or, if you wish, bad luck. The question is how this is supposed to occur post mortem where these frogs are concerned? These frogs have evolved a defense mechanism against snakes and then the snakes evolved a means of overcoming it and killing and eating the frogs anyway.

I review the various means by which venoms are evolving in American rattlesnakes here....

http://www.naturalhistorymag.com/features/0700_feature.html

None of the authors or researchers cited or interviewed are creationists. I am proud this appeared in a publication that was the regular venue of Steve Gould.

 

[CFLarsen]

No.

Yes, it is. Creationists try to shoot down Evolution by claiming that Evolution claims that species have come about by random processes.

CFLarsen, are you seriously claiming that mentioning the role played by chance in evolution is the same as supporting creationism? I'd be interested to see you defend that view.

I asked why he was using Creationist arguments. I didn't say he was supporting Creationism.

Lithrael got it when I said some snakes aren't so lucky. In fact they die, don't live to reproduce and hence are part of the natural selection process. The question is how this is supposed to occur post mortem where these frogs are concerned?

I review the various means by which venoms may evolve in American rattlesnakes here....

http://www.naturalhistorymag.com/features/0700_feature.html

Why do you think Evolution is random?