Dispelling Myths About The Giant Gene: Part 1 – Weight

In a series of blog posts, I’m going to attempt to address some of the concerns I have about the information, and misinformation, that floats about the hobby concerning the giant gene.  The biggest misconception, by far, is the idea that the weight of an animal can somehow determine its genetic makeup.  This is where I will start.

Weight, by definition, is simply how much matter an object contains.  In the case of biology, we’re talking bones, tissues, muscle, fat, and blood.  Where geckos, and most pets, are concerned, we’re really looking at fat, as they need to sustain themselves through periods of fewer resources.  In captivity, these resources are typically plentiful, and in the case of a mealworm diet, oftentimes unlimited to the extreme of being excessive.  Now, I will state that the purpose of this article is not to criticize or condemn anyone for the way they maintain their animals, I’m simply providing some concrete groundwork for explaining weights and what they truly mean for leopard geckos, and for most animals in general.

Leopard geckos in captivity are prone to obesity, especially on a mealworm diet.  One simply need only to compare pictures and videos of wild leopard geckos, to those in captivity, to see a very striking difference.  So what is a healthy weight?  Who’s to say?  I’m not a big believer in rules where animals are concerned, as every single environment is likely different than the next.  Temperatures, humidity, light, dark, feeding regimen… all contribute to growth rates and ultimately to the general health of the animal.  In nature, the focus is simple:  recruit and reproduce.  These animals are on limited time, surviving predation and natural selection to further their species.  As such, sexual maturity is all that matters, and a female will accept a male at a very young age in order to produce offspring.  They don’t care about weight, the only rules they care about are the rules of survival.

Where the giant gene is concerned, it is thought that somehow an animal must reach a certain weight before a year of age in order to be “categorized” a giant, or super giant.  This is absolutely ludicrous.  That’s like saying a young person must be a certain height or weight at 15 years old, or they cannot play a sport in high school.  It’s completely illogical and erroneous.  The problem as I see it is in the interpretation of the original publication of this “requirement”.  It does not say MUST, anywhere.  It says “typically”.  It is also specific to THAT environment.  Meaning, the information is not compiled from various breeders, with any kind of diversity in husbandry or temperatures or other variations that will occur no matter what.  In short, there is no science involved in that determination, just generalization made from a very small data collection.

I have produced hundreds of animals the past three years, and nearly every single one is a giant, super giant or possible giant.  I can say beyond a shadow of a doubt that the gene is co-dominant, and I can also say beyond a shadow of a doubt that these animals will reach their size potential much closer to the two year mark or older, and not the one year mark.  I’ve purchased several super giant males that were less than 100 grams at near a year in age, and they all have matured into perfectly healthy, impressive beasts at two years or older, and some barely weigh 110 grams or more.  Under optimal circumstances and in good health,  they will be as big as they are going to be, and that’s just how it is.  The more they eat, the heavier they get, but an 11″ animal is just as impressive at 105 grams as he is at 130 in my opinion.  We don’t make our dogs, cats or kids fat on purpose, do we?  Why would geckos be treated any differently?

To wrap this up, I will say that I certainly appreciate those big, exceptional geckos.  But I also know how they got that big, and it’s just not genetics that accomplishes that.  A super giant is capable of weighing more, just as a 6’5″ human man is capable of weighing more, it’s only natural.  But when does obesity become a concern?  For me, I’d rather not find out.

Part 2 will discuss so called “giant lines”, and the intimation that there is somehow a line bred thing happening in lieu of true Mendelian genetics.  Thanks for reading!

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