Hybrid fertility and vigor varies with the cross. In mammals, If a hybrid can be produced, the females range in fertility from fully fertile to so poorly fertile as to be essentially sterile. This depends apparently entirely on the degree of matching of chromosomes between the two parent species. In closely related species such as wolf and coyote, male progeny are fertile. Due to a phenomenon called Haldane's rule, sons of crosses between house cat and bobcat a sterile even though the chromosomes are essentially the same in both species and daughters are fully fertile. Once they are born and survive the first weeks of infancy, mammalian hybrids, especially mules, seem fairly hardy. Sheep-goat hybrids rarely survive to birth but one known hybrid had to be castrated even though he was sterile. He was just too hardy and very randy!



For every bird hybrid I've found, either the progeny are fertile in both sexes or it is claimed the hybrids are sterile. For number of these (chicken-pheasant, domestic-canada goose, etc.), the females are obviously sterile, but I don't know if anybody has ever tried backcrossing the sons to check for fertility. With regard to vigor, many hybrids are quite vigorous. On the other hand a chicken-turkey hybrid is one sick looking bird.



Some years ago, I bought an F2 of a cornsnake-bullsnake cross. She is not growing any faster than a cornsnake. She produces a small number of eggs but what she produces are huge! Unfortunately they mostly fail to hatch. I crossed her back to cornsnakes and got 3 babies one year and 1 baby the next. Nothing viable since then. The babies are fully fertile brother to sister and male with both cornsnake and bullsnake.



I don't have any hybrids old enough to tell if any will be getting larger than cornsnakes. I do have a pair of 7/8 corn-1/8 bull brothers in which one is twice the size of the other. This might be due to feeding differences when they were little, however.



Bigfoot

[ Show Entire Thread ]