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South Dakota Hunters Concerned that Cougars May be Impacting Deer and Elk Populations

By Dr. John W. Laundré; Vice President, Cougar Rewilding Foundation



In a blatant attempt to use fear, South Dakota "sportsmen" are trying to influence cougar management by raising the specter of a bloodthirsty predator killing all THEIR deer and elk. In South Dakota is where cougars are making a valiant attempt to re-establish themselves in historical range, an effort we has humans would admire and hold in awe as an ecological wonder for any other non-predator native species. This selective and outright prejudice against predators has got to stop. Not just because it is ecologically disastrous but also because it is flat out logically wrong!  All across the West, so called sportsmen have been blaming predators, mainly cougars, for declines in deer populations that began in the early 1990's and have yet to recover to previous, probably unhealthy, highs in the 1980's. In the scientific literature, I demonstrated that if you go through the calculations and add the numbers up, it just does not make sense. Logically, given what cougars eat, the numbers of cougars, and the number of deer, cougars just can't eat enough deer to make a difference. To do so, there would have to be higher numbers of cougars than has ever been reported and they would weight over 700 pounds after one year!


As with the calculations I made for an area in Idaho, if we bother to do the calculations for the Black Hills of South Dakota, again, the numbers just don't add up. Let me show you. Now I know the numbers may get confusing but please bear with me because it is only by following this number trail that we can logically assess the impact cougars in the Black Hills can possibly have on the deer population. First, how many deer are there in the Black Hills? Based on a study out of Brookings, SD, there are approximately 43,000 mule and white-tailed deer there. Eighty percent of them are females (or about 34,000). Approximately 80% of them will give birth to an average of 1.5 young/year, or about 41,000 fawns. If 50% of them survive their first year, this is an addition of 20,500 new deer to the population each year!


The next thing to ask is how many cougars are there. According to the South Dakota Game Fish and Parks, there are about 250 cougars living in the Black Hills. If each of them eat only adult deer and kill on average 30 deer per year (this is actually high based on previous studies) then they will kill about 7,500 deer per year. This represents only about 17.4% of the adult deer population of 43,000 or only 34.3% of the surviving fawn crop would be needed to replace the adult loses to cougars! Human hunters take from 3000-4000 per year, still leaving a net gain of OVER 10,000 deer per year! So, unless there are twice as many cougars as estimated or they are eating twice as much as a normal animal (and thus weighing over 700 pounds!), the numbers just do not add up!


Of course this begs the question of whether there could be enough cougars in the Black Hills so that they do negatively impact deer numbers. Historically, we consistently found the largest ungulate populations, e.g. the plains of the Serengeti, the tundra of the arctic, the plains of North America, in the presence of healthy and "uncontrolled" predator populations. How can that be? Why in these cases didn't predators increase in number, as most population models would predict, to eventually cause the downfall of their prey populations? First of all, this would be evolutionarily unstable and any predator that did that would have long gone extinct along with its prey. So evolutionarily, there is pressure on a predator NOT to be too efficient. Secondly, they need to catch their prey with their TEETH and CLAWS! No spears, no high powered rifles, they have to come in physical contact with their prey and wrestle them to the ground! Given that and that the prey are not totally defenseless, it is not surprising that a predator's efficiency rate is only around 20%. Plus if we add the fact that in some habitat types the predators' efficiency is almost zero, we call them refuges, it makes logical sense that predators rarely can "decimate" prey populations the way hunters and ungulate biologists believe. What all this leads to is a system where only a small percent of the prey is actually realistically available to the predator. In this system, there can never be too many predators because there can never be enough of them!


Instead of decimating deer numbers, what cougars are more likely doing in the Black Hills is giving a long overdue reprieve to the forest vegetation of the area. As we have seen in Yellowstone Park and see too plainly here in the East, the mountains do indeed live in fear of the deer. Though I have not looked, I am sure I can find studies that show deer and elk have been severely overgrazing the Black Hills for decades. Freed of predation, and more importantly, the fear of predators, ungulates roam like cattle, overgrazing their favored food species and eventually reducing the productivity of the range and its ability to support the large numbers hunters seem to want! So, instead of being concerned that cougars might be impacting deer populations, hunters should be thankful that cougars are likely re-establishing a landscape of fear where deer are too afraid to go to certain areas, which will reduce the ecological damage their uncontrolled grazing has done. Thanks to the cougar, long overgrazed plant species can recuperate, enhancing productivity and biodiversity in the Black Hill forests for the benefit of multiple other species as well as the long term health of the hunters' beloved deer populations.


One last word on this. We have to stop thinking that ungulate populations exist only for human hunters! Although historically we relied on wild game animals, in the modern world hunting is a luxury, not a necessity. We should not sacrifice key elements of an ecosystem, the top predators, for this luxury. To do so is to destroy the ecosystem on which all of us, not just the hunting public, rely. An ecosystem functions by the flow of energy through all of its trophic levels, including the top predators. In a functioning ecosystem, deer live to feed cougars just as plants lives to feed deer. This is how ecosystems function. Break the chain of energy flow and you break the ecosystem. Break the ecosystem and we all suffer. The flow of energy from prey (deer) to predators (cougars) is the cost of operation in a functioning ecosystem. In a functioning ecosystem, there will be plenty of game for both humans and predators. We just have to not be so greedy!



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