Size of animals genetics?

So im looking to start my breeding project this coming season. I was thinking about how they make super dwarfs, i was wondering if it is something possible to selective breed for actually a larger size, id live to try and produce some 4’ boas ( Rosys) my boy is quite big so i wonder if that a genetic trait i could pass on? Or is it just going to be a random thing. Im not trying to produce “monster sized” Rosys but i think having above average lengths may be appealing. Is what im thinking even possible?

I like snakes on the small size hence why i chose Rosys over standard Boas. Im not sure i could get 5’ but 4 foot is possibility. Is this anything feasible?


I’d think genetics do play a role in how big a snake can get, just like how it affects their feeding responses and even their behavior.

It’s hard to tell exactly how big the offspring will be when they’re fully grown, but I’d pick the heaviest/biggest babies out of the clutch to raise up and essentially try to “line breed” to that bigger size.

Why I prefer to keep snakes that are not overly defensive and are good eaters, because most of the time their babies turn out similar to them.

My best example of the feeding thing is my hognose Scarlet, who I hatched out myself. Hognoses are notorious for being picky eaters, especially as babies.
Her mom is a monster when it comes to food… and turns out, Scarlet is nearly the same herself!
Both will readily eat mice (and my fingers) and when I do offer different food items like rat pinks/pups, scrambled egg, or chicken/turkey heart, they’ll happily snarf it all down.


This is fully possible, not sure how many generations it might take however.

Things to keep in mind:

  • You will want to make sure to use larger females. Using just large males kind of defeats the purpose because small females cannot safely/comfortably carry larger babies and are therefore likely to have breeding complications
  • Inbreeding depression is a real thing (contrary to the collective belief of much of the hobby) so you will probably want to amass a genetically diverse stock or be prepared to cull
  • There is a difference between a genetically large animal and an animal that has been powerfed to large size

Thats good to know thank you

@t_h_wyman is of course right on all statements. I just wanted to add that I even think it is more important to have large females, not just to handle the size of eggs, but as shown with retics the female size whether mainland, dwarf, super dwarf or a mix of all, the babies tend to follow the size of the female.


I know that with retics, the dwarf/super dwarf retics are descended from island populations that stay smaller than their mainland brethren. It’s an example of insular dwarfism, where a population is genetically isolated from other members of its species and stays smaller due to more limited resources, and the lack of any evolutionary advantage to growing larger in their isolated location (like having less prey, and/or a lack of large prey, so there’s no advantage to getting huge).

I don’t know much about rosy locales, but it might be worth looking into whether there’s a locality that’s known for growing larger, and trying to find the largest animals (especially females) from that locality. I feel like that might give you better odds of ending up with breeding stock that will pass on their size to their offspring, as opposed to ending up with large animals who were just power fed.


The coastal locality is the largest of all localities so i definitely have to go coastal designer lines like Carlson, Matrix, picassos Limburg and i believe monostripe are all coastal lineage so of course my quest start there. Just trying to obtain the biggest sub/adult adult specimens i can find. Im completely aware this may take many years and many generations but i believe making 4’+ animals is pretty obtainable, i think 4’ is a nice size not too small but meaty enough and not too big to handle however.

Right now im just in the beginning of my ambition to do this and make some incredible morphs. It will take time to aquire the best stock and enough so that they aren’t being all inbred where genetic problems may occur. To me having a 4’+ boa isn’t good if it has defects that make it unhealthy or deformed. Im prepared to be patient and be selective of the animals that will be part of the program. This could take a decade or more im sure.


I definitely agree about the genes over power-fed because the genes are the key, they new keeper may not feed to large size if the stock was power-fed for size, because thats not genetics it just a well fed animal.

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