I believe those are the numbers. I'm just wondering if whatever it is that is generating the random numbers is doing something wrong. With those numbers, there should be a roughly 10% chance of a pair not reproducing. So if you do just single breeding pairs, you should expect roughly 1 in 10 to not produce offspring, which means bringing 7 species has roughly even odds of having at least one non-reproducing pair. Frequent enough I don't even bother trying that, so no data.
But 2 pairs, yes, that's every embark. I would expect a 50% chance of ending up with a non-breeding species roughly 1 out of 140. At 8 species per embark, roughly every 18th embark. Another way to look at it is that each embark has a shade below 4% chance of having at least one non-breeding species.
I might be just incredibly unlucky. Or at those ranges, it wouldn't take much of an error to add up. Say for example that the number being generated was rendered as an integer between 1 and 100. In that case, a 5% chance would be any number 5 or under. But if it were generating a number between 0 and 100, then checking for 5 and below means its really just a shade less than a 6% chance. That is simply not enough difference to notice unless you are talking about very rare events. In this case, a 5% chance would mean no kittens 6.25e-6, a 6% would mean no kittens 12.96e-6, less than half as often.
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I'm not complaining. Whatever the number is makes no difference. The game generates values as it does, and you get the outcomes you get. It doesn't really matter what those values are so long as it is still a playable game. And if you define that as almost guaranteed to get puppies, bring more than 1 pair.
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