The conventional wisdom is that hybrids are LESS prone to diseases, and there's even a term for it: "hybrid vigor" (although classically this refers to livestock and pet animals that aren't true species hybrids). This is especially true for animals that are extensively inbred due to linebreeding for specific traits - outcrossing to a different species minimizes the risks of deleterious gene combinations.

That having been said, I think that the further separated by evolutionary time the species are, the more likely that the particular set of genes won't function well for the offspring - very distant relatives (boa and python) won't produce viable offspring, more closely related animals produce sterile hybrids (mules), and very similar animals (kings and milks) produce hybrids that can reproduce themselves.

In summary, unless you're looking at terribly exotic hybrids, I wouldn't worry about their hardiness.

-Lee McMurtry

Hircus Circus

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