The Plight of the Bushbucks: Losing By Conserving – Part 2

O.K., so I guess the identical opinions of two very knowledgeable PHs, with decades of experience in game monitoring should have rendered my ‘expert’ intuition moot. Instead, I went down swinging. I wanted to know if scientific studies of interactions between Nyalas and Bushbucks saw competition resulting in Bushbucks losing ground to their more numerous cousins. We’ll return to how closely-related and inter-related Bushbucks and Nyalas are, but first let’s consider an analogous situation in North America.

As Europeans started settling North America, mainly from East to West Coast, they ate everything that didn’t get out of their way, especially everything that carried meat protein. It thus comes as no surprise that larger animals disappeared first, including bison, elk, moose, pronghorn antelope and whitetail and mule deer. Smaller, but still significant meat sources accompanied, or quickly followed the local extinctions of the bigger meat sources; included were rabbits, squirrels, turkey, ducks, pigeons, doves etc. Thankfully, beginning in the 20th Century, conservation efforts focused on protection of remnant populations. They also emphasized the reintroduction of species by their own natural movements and through human-led transfers of game species into previously occupied territories. For the most part, the natural and man-made expansions of game animals have gone smoothly, giving rise to healthy populations. But, there have been some unexpected consequences.

One of North America’s conservation success stories has been the geographic and numerical expansion of the Wapiti, a.k.a. Elk. Pre-European invasion across North America, this magnificent animal roamed from East-to-West coast. Thought of nowadays as a mountain-loving species, herds of Elk stood in the path of settlers making their way across the plains, the low-slung hills and the river bottoms between the Mississippi River and Rocky Mountains. That there are now huntable populations once again in places like Kansas, speaks to this species’ wide-ranging ecological preferences and adaptabilities. That’s the basis of the unforeseen, negative impact from Elk moved by humans, or using their strong legs to spread themselves into more and more places. Standing right in the path of the expanding Elk were populations of whitetail and mule deer.

The impact of the reoccupation of habitat by Elk herds on whitetail deer seems minimal. Likely due to their greater population sizes and habitats that overlap less with Elk than do mule deer, whitetails thrive. Though capable of utilizing the river bottoms and thick woods inhabited by whitetails, Elk are ruminants with multiple stomachs – like cattle – so are primarily grazers. Whitetails are browsers, and utilize woods for not only bedding, birthing, and hiding from predators, but also as their primary feeding sites. This begs the question of why then, mule deer, also a species that prefers browsing, experiences population declines in the presence of the grazing Wapiti?

Scientists in the know agree that declining Mule Deer numbers is not only because of the expansion of their larger cousin. They do, though, see a correlation with loss of prime mule deer habitat, making competition from the much bigger, more numerous, and more adaptable, Elk, a serious problem for the smaller, less-adaptable mule deer. Analogous to the Nyalas and Bushbucks, the large herds of Elk can reach higher into the overhead vegetation and browse off available food before the mule deer get a meal. This forces the deer into marginal, lower-nutritional areas to avoid the better competitor. The competition becomes most intense during harsh winters when the Elk switch to being browsers – with grasses for grazing buried under several feet of snow. This is when the large size difference comes into play, with the 500 – 800-pound Wapitis capable of pushing the mule deer that weigh half as much off the limited feeding areas. The deer die in droves during bad winters, likely in higher numbers when Elk are there to eat most of the available food.

Returning to Coutada 11 and the Nyalas and Bushbucks, we can ask why the latter are declining in numbers. Is it just because of competition with the swarms of Nyalas? Before we look at possible answers, let’s revisit the ‘cousin’ status of these two species. Unlike the Elk and mule deer, that belong to the general ‘deer’ category, Nyalas and Bushbucks are kissing-cousins. Seriously, back a few million years ago a Bushbuck and an Nyala, or more likely several of each, made babies. Scientists know this because some of the Bushbucks and Nyalas running across the African landscape of today share the same DNA. In biological terms, this closeness means that competition for food, mating sites, places to hide from predators, and nursery areas could be even more intense than seen for species like Elk and Mule Deer. Or, not…