@flannan
As seen in the previous chapter the upper echelons of the orcs don't really care for the well-being of their underlings. Rousing them even after being struck and almost out of commission instead of fleeing in a unfavorable situation speaks a lot about their social structure and how their tribe survives and still thrives to this day. We still don't see any female orcs, so are they a tribe like harpies? One gendered, propagating through rape? Or are they a small male only army and just having "fun" raping, pillaging and stuffing their faces with their unfortunate victims?
Your argument about the orcs and their eating and mating habits makes sense. This may be me just speaking out of my ass, but I don't think the orcs in this manga, that we have seen so far, are capable of higher thought in the form of "this is for eating, this is for raping".
Speaking about the eating/mating habits of mantises, it is not well understood why they do it and there are speculations/evidence that it doesn't occur in all species or all the time. So it is possible for one male to mate with other females and more than one without being their next lunch or dinner.
@Liquidxlax
In a previous chapter it was mentioned between the elf daughter and her mother, that elves drink and eat a lot less than humans. And since the beastkin was there too, I think they also implicitly talked about her too. How much less is kind of vague. It could be like one gallon per week or it could be one gallon per half a week or month. Your thought about the gestation period of female elves raped by orcs brings another good point to the table. Is the gestation period different for different races? I.e. if a normal human pregnancy takes nine months and a normal elven pregnancy 18 months (assumptions just for the sake of argument), do they deliver orc babies at the same time or is a relative factor considered in?
There could be so much fun to be had, if Monster Musume were more like Dungeon Meshi with all the cultural implications of the different races and how they live their everyday lives.