Before discussing the geographic distribution question (as I noted I would at the end of Part 1), I believe it's instructive to first ask whether, perhaps, bovids are targeted because they pose--or are perceived to pose--some type of ongoing threat to humans. After all, if humans are afraid of an animal, that would go a long way toward explaining why they'd target that animal or target a group of related animals.
For instance, it makes sense to me that we're leery of the canids (Canidae), which includes such animals as wolves, jackals, coyotes, and the many types of fox, all of whom are predatory hunters and are primarily meat eating carnivores; or that we fear other types of large, land-dwelling carnivores/omnivores like the felids (cat family), or the ursids (bear family), or even other, large, land-dwelling herbivores that, even though they don't eat meat whatsoever--like hippos or elephants--we fear just because to their enormous size; or even that we're uniformly scared of poisonous and/or venomous animals because, well, they can readily injure or even kill us. So, I see a lot of logic in viewing these sorts animals as a threat to the general welfare of human beings, and I believe there's a rational explanation to our fear of such animals. But, again, what about the bovids?
By any objective criteria, bovids cannot be regarded as a threat to humans (relative to a wide array of other types of animals). Bovids are not, for instance, poisonous or venomous animals; neither their bite nor their flesh will introduce something into our bodies that could cause us to go into shock or to die from the bite/poison alone. So, it seems to me that a threat of that sort needs to be ruled out from the get-go.
Likewise, for the most part, bovids are not enormous animals (like, say, the aforementioned hippos or elephants), so we shouldn't be killing them because they might kill us first. Small animals typically view larger animals as a threat solely because "size matters" all other factors being equal.* If two people, for example, possess comparable skills, but one of them is much larger or heavier than the other, the larger/heavier one will generally have a quantifiable advantage over the smaller/lighter one; and the same is true for animals because the heavier/larger one has an additional form of leverage by being able to pin the smaller/lighter one against a rock or a wall or whatever, or it can sit on top of its adversary/lighter animal; and if it is considerably heavier/ larger it can literally squeeze the smaller/lighter one into submission, if not eventual death by not letting it up. So, size is indeed something to fear. But, again, how large are the bovids?
While bovids come in all sizes--ranging from relatively large ones like the bison and yaks, or the largest bovid, the gaur, the majority indicated herein as poached--the gazelles, various types of antelopes, sheep, goats, impala, and duikers (a type of antelope)--are small, graceful animals that are typically a good deal smaller than an adult human. Hence, all things considered, I believe it's fair to say that size isn't--or shouldn't be--a significant factor when attempting to ascertain why bovids of all shapes and sizes are being poached in such large numbers.
Another type of threat is one that derives due to competition among species because of their comparable diets, so it seems fair to ask if humans and bovids have similar diets and therefore are clashing with one over available food sources. Well, with the exception of a few species of duikers who are frugivores and omnivores (they seem to enjoy selected insects, an odd combination but no doubt the result of living in tropical locales), all other bovids are herbivores that (like most ruminants) mainly consume grass and other fibrous plants, which most other animals, including humans, cannot easily digest. Moreover, bovids lack upper canine and incisor teeth, so the eating of flesh would be excessively difficult for any of the bovid, even the largest of them. Thus, unless they are starving and desperate, they'd have a highly difficult time trying to eat a human or any source of meat, and I consequently cannot envision how their diet and ours would in any way result in a conflict situation over available resources. Humans can easily kill and eat bovids, but bovids would have an exceptionally difficult time killing us; and even if the largest/heaviest of them ever did, it'd be all but impossible for them to then eat us (not to mention to digest animal flesh given the type of stomach they have), no matter how hungry and desperate they might be. So, again, from the perspective of dietary competition, I believe it's ludicrous to suggest that humans poach bovids in such large numbers because of some competitive, inter-species threat/conflict issue.
In sum, why are bovids being poached so much by humans? Clearly, as has already been discussed, it's not due to the fact that there are so many different species in the Bovidae "family" (in other words, it's not due to the large size of that "family"); and, as noted above, it's seemingly not due to some warranted, perceived threat humans have--or should have--of these animals, either. So, maybe it is due to their geographic distribution, which we shall explore in the next post.
*I see this all the time with my cat. She's terrified of the deer all around our property because they're so much larger and more massive than she is, even though it's fairly obvious that the deer couldn't care less about her--except to see what she's up to and what she smells like--and as such they pretty much just ignore her altogether.