Selective Breeding for Size; Health Effects?

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Selective Breeding for Size; Health Effects?

Postby Scincus » Thu Jan 14, 2016 3:03 pm

I was trying to determine whether this belonged in advanced discussion or general discussion, but I suppose here would be more appropriate for more in depth discussion from breeders.

Anyway, the topic I want to discuss is selective breeding skinks to either be very small or completely massive compared to the normal counterparts of their species/subspecies.

I'm going to start with selective breeding for larger skinks. While I do not know too much about these cases, I have heard that there are "giant" leopard geckos and "giant" bearded dragons, so this concept has been explored in the hobby before. So let's I took two of the largest skinks I can find and breed them. I would then breed the largest offspring with either another very large relative or with new blood if possible. This brings along with it several concerns about health. If I simply bred for girth, I could eventually end up with a skink that has very awkward proportions and difficulty moving in a normal manner. This line of thinking would then bring me to selecting individuals that display largeness in length and that are proportioned correctly so to basically have a scaled up "model" of a normal sized skink. If we use that kind of selectiveness for breeding larger blue tongues, what kind of potential health problems might be seen in the future? Is there a limit to how big the skink could be bred for without health problems? If you look at Varanus sp. there is a vast difference of sizes including island gigantism. If such a thing over millions of years has happened would it be safe to do so in an artificial environment and significantly increased rates?

Now, tackling breeding for smaller sizes. As with breeding for larger size, let's assume that we breed for skinks that have shorter and shorter length while keeping anatomical proportions. This is where I think it gets tricky. How do we know if a small size is from either malnutrition (assuming wc, or unknown history) or just genetic? Would there be a point where they would start developing health problems?
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Re: Selective Breeding for Size; Health Effects?

Postby Edward » Fri Jan 15, 2016 7:37 am

Very interesting questions that I have contemplated myself for future breeding projects.
Hopefully, some of the experienced breeders will enlighten us with their thoughts/observations on this topic.
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Re: Selective Breeding for Size; Health Effects?

Postby Susann » Tue Jan 19, 2016 2:26 pm

I personally don't have any knowledge or experience with genetics when it comes to breeding, but just using logic, I would personally think that girth isn't something you can breed for... Other than purely head size, the girth of the skink would, with my thinking, be an environmental indicator --i.e. how healthy it is and how much food is provided.
Length however, is a different matter. I, myself, enjoy some serious size to my skinks, which is why I have in the past tried to use Milo as the sire for most of my litters. Milo (Merauke) is just under 28 inches long, and has produced offspring that have grown quite long. Unfortunately, in an effort to reduce work-load during a couple, very busy, years, I've sold off all of his offspring --so I can't line-breed any of them back to him to see what those offspring would show. But I can tell you that, in the litters that Milo has sired, even with my shortest female (23"), there have been some very inspiring-ly (not a word, but accurate, no?) long skinks.
I'm keeping my fingers tightly crossed that Austin (Scincoides) has luck this year with producing young from a couple, good sized, Milo-offspring. :goodluck:

Health-issues from size alone. I honestly think that, as long as proportion is maintained (meaning that you're not breeding skinks with, for example, freakishly long torsos but normal sized otherwise), it would take an extremely long time and many many generations before you run into health issues that stem purely from size. Line-breeding back to close relatives is likely to show health and vigor issues, I would think, long before you'd see them from basically selectively breeding large skinks together for size. If length/size was that easily accomplished, then we'd have seen a bigger range in size a long time ago. Just my logic though --no experience other than one generation so far. :)
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