Reptile & Amphibian Forums

There are countless debates over nature verses nurture but what i am specifically interested in is opinions on the adult size of snakes given captive care conditions verses their natural conditions.

I have, for many years, been on a quest to find the dwarf eastern diamondbacks. i heard a report of an inland in the Gulf of Mexico that yields a race of reduced size EDB's. after years of research, i came across someone that knows it. He took a pair off of the island in 1959. he tells me that his never exceeded 30 inches and he has never heard of one that exceeded 3 feet. obviously, something in the island conditions has stunted the growth of the snakes. i am thinking most likely reduced food intake and perhaps a shorter feeding season.

i compare these snakes to the Timber Rattlesnakes off the mountains of the far northern range. i once had breeding size female from the Adirondack Mountains that was only 18 inches. i researched the yearly average temperatures for the region and based on my knowledge of timbers, i estimate they are only feeding about 5 to 6 months out of a given year. i was searching for a dwarf sized male, but i lost the female before we could breed her. i did not know the history of this female before she came to me, so i could not tell if he had been raised on a normal captive feeding regiment or if she was held to the shortened feeding season that was natural to her. what i was interested to see with her, and with these EDB's if i can find a pair, is this: if babies captive born from the naturally dwarfed parents, will remain dwarfed if given a normal captive feeding regiment.

In term of will they remain dwarfed, i think of the dwarf retics and burms. they come from populations that have been isolated from the mainland populations for generations, and when bread and raised in captivity, they remain dwarfs. on the other side, i recall a finding couple years ago that reported most of a rattlesnakes total adult size is determined by the amount of food intake in the first 18 months of life. So, babies produced in captivity from small parents, may not remain dwarfed if feed well for the first year and a half.

i guess what is boils down to is the question, will generation after generation of reduced feeding in the wild, lead to a genetically dwarfed rattlesnake, or will these snakes reach a normal adult size when feed the same as normal snakes when they are captive produced?
Chuck Hurd Serpentology

Very interesting question..............

I think that the genetics in the snake would limit the snake's maximum reach even if am ample supply of food is offerred. Let me explain.

The dwarfed populations are separated from the mainland and so naturally the food available is a little on the scarce side. Those individuals that fast and large soon died because they were unable to support their large bodies. However those that survived were able to because their growth was stunted whether it be from mutation or or plain increaser-decreaser alleles. Regardless, only the "dwarfed" individuals would be able to actually live and reproduce on the island, and any of their offspring that grew to large wouldn't survive....what you gradually end up with is a type of selective breeding enforced by the isalnds limitations, and what I would call the epitomy of natural selection. That is why I go so far as to say the dwarfed counterparts of the EDB would probably retain their dwarfism. However, not all of their offsping would exhibit the dwarfism to the same degree. So in the first breeding "clutch" there could very well be some intermediate-sized EDB or even normal-length EDBs(these of course would not survive in the wild, but now they are in captivity and are going to be given plenty of food) and you would have no way of telling until they start to grow or even perhaps until they sexually mature.

That's just my thoughts.....I could very well be way off on this one.
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All of the captive breedings combined are a miniscule sliver of a sampling of what has gone on in nature. Even with what little we really know, we can see a lot of variation in even the most inbred lines. By looking at the comparative speed with which the wolf became the teacup chihuahua, we could probably selectively breed snakes for equally outrageous characteristics. I think size preference would be fairly simple, both in nature and in captivity. I think you could get to the point, as in the wolf example, where no matter what, you can not selectively breed chihuahuas back into a wolf.

It really depends on things that we can't easily see or understand. It depends on what genes are responsible for the dwarfism, how they're responsible for the dwarfism, and how much influence they have on the size of the animal. In short, the best way to find out is by experimentally breeding and raising the animals. Dwarfism caused in different areas might have mechanisms in play that are different from other populations and more limiting.

Higher latitude squamate species always show the reverse of Bergmann's rule. This is a zoogeographical rule that states for any given species, body mass will increase with increasing latitude of that species within it's range. However, with any given snake or lizard species that covers a large geographical area, the adult sizes of individuals within this range will always decrease with increasing latitude, the opposite of Bergmann's rule. This is an inherited trait, breeds true, and it is highly possible that this timber rattler was expressing the basis for this concept. One reason for this smaller size of ectotherms in cooler climates has been linked to the ability to more efficiently thermoregulate. For an ectotherm, a larger body mass may hold heat longer, but a smaller body mass will heat more rapidly and efficiently. This will give the smaller animal the ability to remain more active over a longer period of time than an animal with a larger body mass. This concept has one exception, and that is for some dwarf reptile species found on very small isolated islands. These animals become inherently smaller so as to more efficiently utilize highly limited resources.

Kelly