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Adult rattlesnake size: Nature verses Nurture.
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by ChuckHurd on November 20, 2008
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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?
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RE: Adult rattlesnake size: Nature verses Nurture.
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by FLAohHerper on November 20, 2008
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Chuck,
Great question.I live in S.Fla and heard about that isolated population on drawf EDB's,but never have been there or heard of any recent captures,oh well.To your question,I look at it similar to your burm and retic theory.You always hear breeders and dealers say,"The parents were huge", implying that the offspring will grow large as well.We have heard about this in regards to everything from snakes and lizards to crocodilians.So,if THOSE are genetic assumptions,why not assume the other way,also?I think that yes,the REASON for the drawf trait has to do with nature,but through breeding of a drawf speciman,it would make sense that regardless of feeding,temps,etc.Essentially that trait would carry on.
You could even think of it in humans.Typically,tall parents have taller children,regardless of the type of nurture,and vice versa.Not ALWAYS,but similar genetic trait passing on is assumed.
Just my thoughts
mike
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RE: Adult rattlesnake size: Nature verses Nurture.
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by yoyoing on November 21, 2008
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Hi Chuck,
This makes me think of the Urocoan Rattlesnake. These are said to remain quite small in the wild, but get much bigger on the typical diet of a captive animal. This also may apply to Hog Island Boas. The other consideration may be what the diet is and how it is changed in captivity.
Have you heard of the "Island Rule" in Biology?
Jim
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RE: Adult rattlesnake size: Nature verses Nurture.
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by FLAohHerper on November 21, 2008
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Jim,
Excellent point.It seems that would just mean that nature started the trait,then captivity changed the gene,however that gene kept on on being passed thought captivity,not changing.But then it could be argued,how did the trait EVER change in captivty,what made it change in the first place?Through feeding,food,temps,etc?So feeding and temps and certain diet may DETERMINE the gene originally,but once that gene is there,it may be assumed that the gene is then passed on by generation...keeping that animal at a similar size through breeding,but again,how did It originally change?.But taking another angle with what chuck brought up,location.Maybe most of the original collected specimans of many different species for captivity YEARS ago were from a certain area with a certain trait.They were bred for the pet trade and that trait is heavily bred originally and was being passed for years.For example.EDB's.Maybe X amount of years ago,EDB's were originally collected from north florida w/ a certain trait for the pet trade.Those were distributed to keepers and bred over and over keeping that LOCALES trait saturated in the pet trade.Then,someone discovers the EDB pop by the gulf and they are all similarly smaller,and this question arises.If the original EDB's were collected from the gulf area,maybe the majority of our EDB's we own would be 3 feet?That is my location theory I guess.
But this is all debatable,and im just throwing ideas out because it is an interesting topic.I may be way off on some of this for sure.But just my .02 cents
And what is the "island threory" jim?I have a criminal justice degree,so I biologically impaired.
mike
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RE: Adult rattlesnake size: Nature verses Nurture.
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by yoyoing on November 21, 2008
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The Island Rule in a nutshell is that animals which tend to be small on mainlands tend to be larger on islands and vice versa. Think of Galapogas tortoises and the boas found on islands off of Central America as examples.
Web search will explain this better.
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RE: Adult rattlesnake size: Nature verses Nurture.
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by Crotalusssp on November 21, 2008
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These traits arose because of natural selection towards smaller individuals requiring less resources for survival. The smaller individuals within the population were more successful and thus had higher fitness and reproduction rates. The individuals within a population have natural variations which are the sources for the mechanism of natural selection to act upon. The EDB's in these regions have gotten smaller due the increased fitness of being smaller and requiring less resources. This selected trait caused an overall change within the population over time. This change over time changed the genes/genotypes of the population. Organisms moved from this region and bred would retain the reduced size, but given an abundance of food/resources would not have the environmental pressures. The loss of environmental pressure would allow them to maximize their growth potentials, but since their genotypes were affected by the overall evolution of the population, their size would still be reduced from that of admanteus found in other regions. This is how I interpret this evolutionary change of those populations. I would love to hear more ideas from others who agree or disagree. Evolution of populations interests me greatly.
Charles
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