Thamnophis species question

[Chris]

Hi Everyone,

I am currently enrolled in a graduate class in animal behavior and have chosen Thamnophis for a class project. This relates to an observation I made in childhood catching snakes.

I grew up in central Philadelpia where there were no wild snakes. Hence, when I was a boy I captured garter snakes in the wild in only two areas. One was on a couple of islands in Bucks County in S.E. Pennsylvania (boy scout camp). The other was in a rural area S.E. of Syracuse, New York (some land belonging to relatives).

Since I only played with the snakes for awhile and then let them go where I had found them, I never had the opportunity to compare the two side by side. They did appear very similar from memory, though.

My question is, based on the areas of capture, what would be the best guess of Thamnophis experts here as to the species/subspecies of these snakes. Is it possible that snakes from both areas were the same species? (That they were genus Thamnophis is clear).

Although visually the snakes from the two areas were quite similar, in behavioral terms they were distinct in one respect. All of the Pennsylvania snakes bit me but none of them released a particularly noticable odor. None of the upstate New York snakes bit even after a half an hour of handling but all released that famous odoriferous secretion from their post-anal glands. I wonder if this was an artifact of small sample size or if anyone knows anything more about differences in predator defense behaviors in garter snakes from different regions?

It would seem that biting might be an effective defense against predators only somewhat larger than the snake itself, such as bullfrogs. On the other hand, rendering oneself unpalatable would be effective against larger predators such as racoons. Just a thought.

I hope that these were the same species because then I could design an experiment to test the heritability of these two types of predator defense behaviors. Any insights/feedback from members of this forum would be appreciated. Thanks!

Chris

[ssssnakeluvr]

My guess is they would both be eastern garters. It's hard to say on the defense actions...I have caught garters of the same species in the same areas, some bite, some musk, some do both, and some do neither. I guess their defense would depend on what's after them....

[Chris]

Thanks ssssnakeluvr.

Thamnophis sirtalis sirtalis has the largest range of any T. subspecies and is found in both Pennsylvania and NY State. So it seems a likely I.D. for both populations of snakes I examined as a boy. I appreciate your help.

I am still keen to know if anyone here has observed any patterns relating to which Thamnophis individuals use biting/striking as their main defense when first handled by humans, as opposed to release of odoriferous musk. I wonder, is this difference learned or genetic? And if it is at least somewhat genetic, I wonder what selective forces conditioned each type of defensive response.

Chris

[ssssnakeluvr]

That's a good question......I have had them mostly musk. In Idaho, I found male wandering garters to be more mellow than the females and rarely bit. I had been bitten by more females, but I used to collect gravid ones to watch them give birth, so being gravid might have a little to do with the biting. I am interested to see what everyone else has seen.

[CrazyHedgehog]

See my photo on the biting thread.... little bugger musks and bites continuously!

[Cazador]

Activity levels and aggression patterns of males vs. females might be an easier study unless you're trying to center your thesis around this question. Some people say females are more active/aggressive, and others say males are. I think the variations in their observations are a factor of sample size, though.

The heritibility of defensive mechanisms would almost certainly be confounded by the size of the individual performing the defensive act, their recent diet, time since previous musking, physiological state, etc. Of course, these are all testable, but it's not the hypothesis you proposed. To do the "heritibility" study, you'll have to quantify frequency of defensive mechanism for several prospective parents, and I suspect these will vary along a continuum.

If this is simply a study for a single class, remember that the gestation time for a garter is approx 100 days. Just a few things to consider.
Rick

[tearmfah]

Re: Thamnophis species question Activity levels and aggression patterns of males vs. females might be an easier study unless you're trying to center your thesis around this question. Some people say females are more active/aggressive, and others say males are. I think the variations in their observations are a factor of sample size, though. The heritibility of defensive mechanisms would almost certainly be confounded by the size of the individual performing the defensive act, their recent diet, time since previous musking, physiological state, etc. Of course, these are all testable, but it's not the hypothesis you proposed. To do the "heritibility" study, you'll have to quantify frequency of defensive mechanism for several prospective parents, and I suspect these will vary along a continuum. If this is simply a study for a single class, remember that the gestation time for a garter is approx 100 days. Just a few things to consider. Rick

The nice answer!