Waking Up to Predators

By Howard Whiteman

Wolves are back in Colorado. There are many reasons why people might want wolves back on the landscape, and a variety of reasons why others might want to keep them off. Ranchers are obviously worried about their livestock and livelihoods, and increased costs of beef and lamb could affect a wide range of consumers. Others are worried about their pets, their children or even their own well-being, even though data suggests that it is only the first of those worries that has merit.

The more we learn about predators, however, the more the equation has shifted in their favor.  

In the 1970s, Robert Paine’s seminal experiments on starfish revealed one of the most fundamental discoveries in ecology: that some predators acted as “keystone” species, such that their presence keeps the surrounding community intact, and helps maximize the biodiversity of the ecosystem. Since then, scientists have discovered that a variety of predators act as keystones, including sea otters, sharks, salamanders and perhaps most famously, wolves.  

The Yellowstone wolf reintroduction was an experiment of epic magnitude that not only broadened our understanding of keystone predation, but another related ecological concept, the trophic cascade. Trophic cascades were first discovered in aquatic systems, where predatory fish have strong “top-down” effects on much of the food web below them. Largemouth bass directly affect species right below them in the food chain through consumption, but that direct interaction creates cascades of indirect effects that influence lower trophic, or feeding, levels. Bass eat smaller fish, which has a positive effect on zooplankton populations, which increase in size and consume more phytoplankton, reducing their populations. In this way, predators can affect lower trophic levels indirectly because of the direct effects they are having on their prey.  

Wolves act in similar ways. When wolves eat elk, that has a positive effect on the plants that elk eat, such as willows. Increased willow densities attract beaver, beaver create ponds, ponds create more habitat for cutthroat trout and songbirds, and so on.  When you have highly interactive predators, like wolves, sharks, otters and others, you get more diverse and resilient ecosystems.

Beyond these interactions, however, predators benefit our world in another fundamental way, one that has the potential to save wildlife from some of the most egregious problems that humans have created for them. Predators often pick the easiest prey to consume, such as the young, the old and the infirm. That last category includes animals that carry disease, and right now we need all the help we can get with disease, particularly in our deer and elk populations.

Chronic Wasting Disease (CWD) is a disease affecting a deer’s nervous system that leads to abnormal behavior, emaciation and eventual death. Once a deer gets CWD, it always dies, so no individuals recover. From its discovery in 1977, CWD has spread through 34 states and five Canadian provinces; it has become a problem of continental scope.  

One way to minimize the spread of CWD is to reduce our deer populations through hunting—which would also help reduce the damage they are doing to our forests and vehicles. Many state wildlife agencies have increased harvest quotas in CWD-affected areas in response to the spread of the disease.

But CWD also spreads because of the transfer of deer between game farms. Game farms are places where deer and elk are reared to provide meat, antlers or other products, just like any other farm. Some of them, however, are for humans (I won’t call them hunters, because they aren’t) that want to harvest a large-antlered buck or bull behind a fence without having to learn the skills necessary to do so in the wild. Such behavior is against all hunting ethics, and yet the urge to kill a trophy has led to the sale and movement of deer (and their semen) from all over the country, some of which have helped spread the disease. Deer and elk within the farm spread it to wild, local deer by interacting with them along fences. The regulation of such game farms has been lax at best, perhaps because the industry is so lucrative and economically important, and because they are regulated by state agriculture rather than wildlife departments.

This problem is only worsened by the fact that we currently do not have a CWD test for a live deer. That is, the only way to know if a deer or elk has CWD or not is to test it after it is dead. Infected deer may not show any symptoms for up to two years after being infected. It is thus impossible to know how many infectious individuals are out there without killing many deer, making our ability to understand the spread of CWD extremely difficult, particularly among game farms where each individual is too valuable to the owner to kill just for a test. Imagine if there wasn’t a reliable test for COVID-19, and you quickly understand the problem.

One way to reduce CWD is to stop the trade in deer and elk between game farms until a live test can be developed. I highly recommend writing your legislators about that, but it is an uphill battle. Another way would be to reintroduce predators.

Predators are a much more efficient solution than human hunters. Predators don’t have hunting seasons, and they don’t take days or even nights off. They are the only entity that has the potential to hunt 24/7, 365 days a year, and when they hunt, they minimize their time and effort by seeking out the weak links (young, old, and importantly for CWD, the sick) in a deer herd.  

Recent data, however, suggests that predators might be an even better solution than scientists initially thought. Early studies were aimed at determining whether predators and scavengers might spread CWD through their feces. Those studies showed that prions (the infectious agent of CWD) can make it through a predator’s digestive tract, usually in the first scat, which is unlikely to be very far from the carcass. However, the percentage of prions going out in feces is very small compared to the amount that the predator fed on, so predators are either destroying the prions or sequestering them in their own bodies, a disparity that is currently being studied. The data suggest, however, that predators may be helping to reduce the spread of CWD.

Somewhere, Michael Soulé is smiling. Soulé, who passed away in 2020, is considered by many to be the father of Conservation Biology, a field of study focused on biodiversity protection and ecosystem health. He was also a former Rocky Mountain Biological Laboratory (RMBL) researcher. During one of our conversations, we got to talking about predators and he opined that the emergence of CWD in western deer and elk herds had made it inevitable that predators would be reintroduced. Humans, he surmised, would finally understand how important predators are to them, when it became clear that they could save a resource that was both economically and socially valuable to us. It’s too early to know if his premonition was correct, but the resulting restoration would make him smile, nonetheless. It will be interesting to see whether the prevalence of CWD in Colorado declines as wolves increase in number, as he and others have predicted.

As a field biologist in these mountains, I have longed for wolves to be back, knowing the changes they may bring to the ecology of our montane ecosystem. I cannot wait for the moment when I am leaving my ponds at dusk, after a long day of sampling, and I hear a howl much deeper than the coyotes that frequent our valleys. Or, perhaps, when I walk out on the porch of a RMBL cabin at night and hear that same howl echoing off of Gothic Mountain. Or, perhaps, when I am paying a lot more attention to how I am hanging elk quarters in the fall so wolves, for the first time, won’t be tempted by them; they can have the rest of the carcass with my compliments.  

In each case I know that the hair on the back of my neck will stand at attention, and my senses will immediately be flushed, focused on this newly restored predator. In a real sense, the wolf reintroduction doesn’t just restore a predator, it restores wildness. Although we have abundant bear and cougar populations in the East River Valley, the howl of a wolf is a very different statement of wildness. If it weren’t, people wouldn’t be so divergent in how they interpret and react to that howl.

Whether due to their benefits to surrounding ecosystems through their keystone role and trophic cascades, or their ability to manage the spread of disease, it is clear that predators are a critical part of our ecosystems, and their restoration has thus become an important conservation goal. Such efforts have begun against much consternation and angst, but they have happened nonetheless. Many people will rightly disagree about the restoration and how to best manage wolves now that they are here, but again, at least we have them back on the landscape to argue about.  

Howard Whiteman is a professor of Biological Sciences at Murray State University in Kentucky and has been studying aquatic ecology at RMBL since 1990.