FanOfGoodPics: Like most of post-nuclear creatures, Deathclaws are in almost all cases infertile. Although there are in fact, female Deathclaws, mostly found in dark caves, their bodies just can't accept irradiated semen of males, living on surface.
"Almost" all cases. One of 'claws, desperate to produce a progeny, became interested in one of the humans who made fatal mistake in wandering into caves.
For young human male it was at the same time the most horrifying and amazing experience of his life. Being a virgin, he didn't had previous experience, and now he never will, because female Deathclaw who captured him became pregnant, for the first time ever.
That was beginning of end of human domination on irradiated wastelands...