On the face of it, this question might sound as though it ought to be a simple one to answer. Are bovids widely distributed across the Earth's land surface and, if so, might that account for why humans are so actively hunting them down as a group, as an entire taxonomic "family"? However, the answer isn't as straightforward or as easy to come by as one would initially expect.
Yes, bovids are ostensibly found practically everywhere humans reside. They're not indigenous everywhere--and those that are indigenous vary quite a bit from one another--i.e., from one bovid species type to another, as well as from one land mass to another--but, today, one or more types (species) of bovid can be found in and around most human settlements (to varying degrees), even in the harsh tundra (e.g., the musk ox). Beyond this, though, it's important to provide some background, details, and context before proceeding further.
First, note that bovids are ungulates (hoofed mammals). Ungulates probably date from at least the end of the dinosaur era (65-66 mya), and they seem to have occupied niches on all of the then-configured, large land masses (which were notably different from today's land mass configurations), with the exception of Australia and the most frigid polar regions. The initial group of the more prosperous ungulates to multiply and disperse widely (once the dinosaurs began to die off) were the highly successful Perissodactyla (the odd-toed ungulates that today include the tapirs, the horses, the asses, the zebras, and the rhonoceri). Soon, not long after the downfall of the dinosaurs, these Perissodactylas came to be the planet's dominant, land-dwelling, large mammal grouping (in terms of absolute numbers) for millions of years.
Perissodactyla's foremost, contemporary "rivals," were the Artiodactyla (the even-toed ungulates that today include the camels, the pigs, the giraffes and okapis, the llamas, the deer, the pronghorns, the chevrotains, the bovids, and the hippos). (It should be noted that Artiodactyla's water-dwelling, very close relatives, the Cetacea [the whales, the dolphins, and the porpoises\ likewise began to prosper at this time, albeit by leaving the land for the water approximately 50 mya; in fact, some researchers lump these two, genetically close "orders"--Artiodactyla and Cetacea--together, and they classify them as the "clade" Cetartiodactyla.) The Artiodactyla shortly came to eclipse the Perissodactyla (in terms of absolute numbers) as Earth's dominant, land-dwelling, large mammal grouping by the start of the Miocene (20 mya). They did so, in part, by evolving to adapt to rapidly changing environmental conditions and by becoming less specialized, niche-specific mammals (as opposed to their relatives, the odd-toed ungulates that, based on the fossil record, seemed markedly less able to adapt to the new, changing climatic patters and, as such, they declined both in terms of numbers and in overall dominance).
Artiodactyla's rather quick evolution to become the primary grouping of large, land-dwelling herbivores (that could readily adapt whenever necessary to a variety of new biotopes) was faciliated because of their multi-chambered, complex stomachs that had evolved to consume and digest browse and extremely coarse grasses--grasses that had arisen first during the start of the Eocene (55 mya), but which had spread rather extensively across the Earth's surface by the close of the Miocene (5 mya). (It's perhaps worth mentioning in passing here that this is right on the cusp of the apex of the Great American Interchange, and that consequent to that so-called north-south "interchange," the southern hemisphere seems to have been the overall animal species "loser" following the majority of each, newly-arriving, north-south species "encounter." Moreover, kindred confrontations and "interchanges" elsewhere appear to have had the same net results, whether it was the north-south, Eurasia-Africa encounter/migration [which happened much earlier than the one in the Americas\, or the north-south, Asia-India encounter/migration [which transpired even earlier yet\ vis-a-vis overall faunal species adaptations/survival, albeit to less of an extent than what took place in the Americas.) Bovids appear to have originated--as a distinct grouping within Artiodactyla--somewhere on the margins of the Eurasia-African boundaries, and they dispersed out from that general area to the present day where they exist, if not thrive, on all continents (though introduced to Australia, Latin America, and to many remote islands, by humans, only during the last couple of centuries).
By the end of the Miocene (5 mya), the ruminants--this is an unranked subdivision of the Artiodactyla--as an entire grouping, but the bovids in particular, had evolved to become highly efficient consumers of these new, high-fiber grasses that few other animals could eat, better yet easily digest. The cervids (the deer [even-toed ungulates that are genetically linked to the bovids\) are extremely similar in this regard, but they differ, too, and in at least one crucial aspect. Yes, bovids and cervids both have similar teeth and stomachs designed to chew and digest the toughest of all grass types. Cervids, however, do not occupy as broad a range of ecological habitats as bovids, which means that cervids are more specialized than bovids, which in turn makes bovids more adaptable than cervids, and therefore bovids were--and still are--found in more locales/environments than cervids. In essence, wherever there are grasses or almost any type of coarse vegetation (roughage), there are bovids. They reached their peak in terms of diversity during the Plio-Pleistocene (along with the arrival of our hominid anscestors)--aptly termed the golden age of mammals--and it's at that point in time that bovids migrated as far as they could, being introduced by humans much later to other land areas inaccessible to bovids on their own.
Okay, returning to the question posed above, I believe it's now evident that bovids are admittedly widespread and are highly well suited/adapted to survive in almost any habitat this planet has to offer, so long as there's almost anything green available to eat. However, many other animals are likewise widespread and well adapted to their respective habitats, yet they're not systematically being poached--not as a group, not as a complete taxonomic "family," and not nearly to the same degree. For instance, Leporidae (rabbits and hares), Muridae (the rodent family), and Vespertilionidae (common bats) are, for all facts and purposes, just as--if not more--globally dispersed as are the bovids. However--based on the animal poaching news articles I've collected (circa 2009-the present day) and have since analyzed, all of which can be found in the animal poaching news portion of the site--none of these mammal "families" is being poached anywhere near the extent to which we find virtually all members of the Bovidae "family" being poached.
Ditto for non-mammals. Look at the insects: Insects are of course everywhere, and in far, far greater numbers than the bovids, but there's no indication that people are rushing out to poach them all, or even to poach a significant number of any one of the scores of zoologic "families" within the "class" Insecta. True, selected species of other mammal "families"--like elephants, rhinos, and even pangolins--are decidedly being systematically sought after and wiped out by poachers, for a multitude of reasons. And, in some cases, they're being poached in unbelievable numbers--in far larger numbers than the bovids are. But no single, entire taxonomic "family" as a whole is being singled out like the bovids are being targeted, irrespective of their geographic location or worldwide presence.
Hence, I do not believe that the almost ubiquitous nature of bovids can, by itself, account for this phenomenon. Something else is surely going on here. And in the next post we shall explore another possible factor--our prevailing perception of bovids--to ascertain whether that, perhaps, might be the key reason behind this sad situation.