Reptile & Amphibian Forums

How big a group of adult breeders do you need to have to have a truly diversified breeding group that can sustain itself indefinitely without further input of new genetic materials.

ALSO WHY DON'T SOME OF YOU OTHER FOLKS COME UP WITH SOME QUESTIONS FOR US TO DISCUSS AND SHARE ABOUT!!!!!

John Cherry
Cherryville Farms

i am not sure about needing a large group of breeders but if your hooked you sure will have one lol. I currently have close to 30 adults and am raising up about the same amount. Here is a question how many people truly know were their thayeri came from?

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i'm not over weight i'm under tall

where they came from as in the person who bred them? or thair relatives? i know 1 is from russ bates and the other i didnt really care b/c i found her at the reptile show for $10.
~kin
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~Sober Serpents~
Corns, Creamsicles, A Black Rat, Thayeri, Cal Kings, A Jungle Corn(Just A Pet), A Bearded dragon, Leopard Geckos, a Snapping turtle, and a white cheeked mud turtle

I have read some opinions (Dave Barker) that insinuate that inbreeding is not that big of a deal with snakes. So, as was my comment on "area of locality", I really don't think there has been enough research done in this area for anybody to give a definitive answer. I have heard the 2/3 ratio thrown out by some breeders, but that opinion is probably no better or worse than any other.
Have a Merry Christmas,
Jeff

all i know is: in corns(for sure) you can keep in-breeding for hets(and what-not) for about 3 times before they start getting deformed. as in grandmother x grandson. but its really not all that likely... i think it just depends on the incubation mostly and then genes.
~kin
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~Sober Serpents~
Corns, Creamsicles, A Black Rat, Thayeri, Cal Kings, A Jungle Corn(Just A Pet), A Bearded dragon, Leopard Geckos, a Snapping turtle, and a white cheeked mud turtle

"I have read some opinions (Dave Barker) that insinuate that inbreeding is not that big of a deal with snakes."

I once heard that it was OK to line breed sibling to sibling for 8 generation from a guy that had absolutely no records on his animals and could not offer non-sibling pairs. There may have been some merit to this view but I suspect that since he was invested in line breeding he saw no problem with it. Of course I try to avoid adverse inbreeding and am therefore invested in diversified stock so my view too is equally biased! Did any of that make sense?

Anyway, I think that whether inbreeding is a big deal or not relies on many factors, context being one. In the context of wild populations where natural selection pressures pick off all but the most fit offspring, inbreeding might not be a big deal. In the context of captive stock where a high level of survivability is expected it's likely to start having an impact.

Have I seen detrimental results from inbreeding, absolutely most likely!! I say most likely because I can only assume the cause when observed at a much higher frequency in highly inbred stock. Anyway here is the list:

Skeletal deficiencies throughout a clutch

Low metabolism, ie fat AND cage lazy no matter how they are fed

General lack of robustness, ie not very active and poor muscle tone

Poor fecundity

Zero nesting behavior

Egg binding

I think that the minimum number of breeding individuals necessary to maintain production of genetically healthy/robust/fertile offspring would be a function of the genetic diversity among the original group of breeders. The answer could be obtained empirically, but snakes are not fruit flies and I doubt there exist many with the patience and time to undertake the study. In addition to folks' speculation about the answer to the question, I'd like to learn from breeders out there who have long-standing colonies and have witnessed symptoms of inbreeding depression first-hand.

John - you asked for others to pose questions. What might the group think about these as examples:

1) What traits seem to be the most heritable? Examples of traits include pattern (phase), background color, saddle color, saturation of colors, saddle or band thickness/shape, feeding response, growth rate, temperament/nervousness, adult size, and clutch size.

2) What sexual dimorphism is evident in your thayeri? On average, which gender grows larger? grows faster? keeps juvenile colors better? is calmer? etc.

3) How cool (temperature, not appearance) do male thayeri need to get in order to optimize fertility?

I can come up with more, but thought I'd let others contribute.

BTW, I love this conversation. Great way to pass time during the chill of winter. Happy Holidays to all and best wishes for a happy, healthy New Year.

In his book A to Z of Snake Keeping, Chris Mattison describes a maximum avoidance system that requires starting with 8.8 unrelated individuals. Even then each succeeding generation incurs a loss of about 2% genetic diversity. I think that the longevity of a colony depends partly on the selection criteria of the next generation’s breeders. If color and pattern always take precedence over fitness then I would think the project would be shorter lived.

So here is my question, how do you describe fitness for a captive population and how if at all would the locality of founding stock have an effect?

I have really never thought of how many it would take to keep it diverse. But I feel diversity in the breeding group is extremely important. I have also read and talked to a few that said inbreeding would not cause issues. But from what I have seen with line bred animals they tend to be smaller and don't thrive as well, some have congenital issues. Some die off for no reason.

I would like to know from someone who line breeds them what are they finding if anything, like kinks or oddities? What are we not seeing for sale due to deformities?

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Michelle
All things bright and beautiful,
All creatures great and small,
All things wise and wonderful:
The Lord God made them all.

To us when putting together a breeding group that we intend to try and work with for a number of years. We really do not rest easy until we have a gorup of 3.5 or 3.6.

Which if you do the numbers will allow breeding to nonrelated individuals for 15 - 25 years if the mean average clutch size is 4.5 viable eggs and the clutches are split on sex at 50/50. Those are our normal goals anyway. And most fo the time we have been sucessful in achieving it.

John Cherry
Cherryville Farms

I seem to remember Ross and Marzec's Reproductive Husbandry of Pythons and Boas said you need 50 reproductive adults to establish long term viability.

I also read somewhere that all the hampsters in the USA descend from just a few pairs, but because they have such high fecundity they were able to get established.

I think you could generate quite a colony from just 2 pairs of snakes if you kept and controlled a large number of offspring. Think about this, if you wild collected 2.2 subadult graybands how many F1 offspring could you produce? If they had an average of 4 babies per year for 10 years you would have 80 f1's. Assuming they were even sex ratio, those 80 f1's could produce 1,600 f2's over a 10 year span(also assuming the same 4 babies per female per year). If one person were able to keep all those babies I would say you would have quite a base of f1's and f2's with which to "thread out" weak and delitious genes. I think if one were so motivated I think he/she could produce a colony that would remain strong for 100 years.