I thought its a well known fact that hig IQ males have a harder time mating with ANY female not just low IQ females.
The reason that IQ is falling is that socially high IQ males are not viewed as high status and even high IQ females would prefer a lower IQ, masculine male.
There seems to be an inverse correlation between IQ and masculinity and male fertility.
Moreover, socially men who outwardly engage in the victim olympics or who are higher status in the victim hierarchy (ie arab hoodlums) are more likely to mate with white females.
Finally, although physically fertile (capable of breeding), high IQ females do not seem to have a penchant for breeding as much as their lower IQ counterparts - some would argue they prefer less sex - but I do not agree with that point.
The point is - in both genders - high IQ seems to reduce their chances of breeding but this trend is especially common in men.