By Jay Ingram
Is it possible to calculate the social and economic benefits to humans of cougar predation of deer?
Where I live, just west of Calgary, cougars abound. Each September, children at the local elementary school are told that sometime during the school year a cougar will see them, but they won’t see the cougar. That the animals are out there creates an exciting and even unnerving sense of wilderness, but it is also problematic: how do we manage our relationship with their growing numbers?
Cougars are dangerous, although the number of human fatalities from cougar attacks in Canada is small: just seven in the last century. But a map created to show cougar movements through the nearby town of Canmore is an impressive spiderweb of trails, a pattern that, as populations grow, promises more intimate animal-human contact in the future. The usual response is to manage and control. The situation around Los Angeles is an example. (Los Angeles is the only large city in the Americas that has big cats living within the city limits.) Around L.A., a patchwork of mountain ranges and valleys is home to both cougars and humans, making inevitable the unnatural: cougars getting killed on freeways (not infrequently) and, in one extraordinary case, a cougar leaping a fence around the Los Angeles Zoo and fleeing with a koala.
There is no hunting of cougars allowed in California, but ranchers and farmers can apply for a “depredation” licence to kill cougars that attack their livestock. The options considered for maintaining healthy numbers of cougars around L.A. range from protecting or even expanding wildlife corridors (which have their own limitations) to accepting that the only solution is to manage the cougar population even more tightly than it is already. Neither seems ideal; perhaps new ways of thinking are needed. What about thinking of cougars as providing services to humans? There’s a complete about-face. A paper published in 2016 in the journal Conservation Letters titled “Socioeconomic Benefits of Large Carnivore Recolonization Through Reduced Wildlife-Vehicle Collisions” argues for more cougars, because they can, unbeknownst to them, help us.
The argument goes as follows: what animal is responsible for more human deaths than any other in North America? Deer. Not directly of course, but through deer-vehicle collisions. Hence the advice that if a deer bounds out in front of you on the highway, just keep driving. Trying to swerve out of the way risks hitting an oncoming car or the ditch, and either can be fatal.
A recent journal article examines the simple idea that predators are doing humans a favour: would more cougars lower the number of costly deer-vehicle collisions?
Obviously, such collisions are more common in areas where deer are abundant, and while it’s unlikely that vehicular traffic anywhere in North America is going to be reduced significantly in the future, it’s possible that the deer population could be. Yet relocating the animals, expanding the hunting season and even deploying contraceptives have not made much of a dent in those deer populations where collisions are a hazard. That’s where the cougars come in.
Cougars subsist on deer (some estimates are that deer make up at least 95 per cent of a cougar’s diet); the simple principle being evaluated in the Conservation Letters journal article is whether increasing the numbers of cougars in an area heavily populated with deer would actually lower the number of deer-vehicle collisions. The authors’ conclusion is yes.
They focused on the eastern United States, where cougars, although rare, are slowly returning after being extirpated a hundred years ago or so. They created a model that envisioned a much larger cougar population, then plugged in the numbers. Over 30 years, the simulation estimated there would be 700,000 fewer collisions, saving 155 lives and avoiding 21,000 injuries. Total overall cost savings (including medical expenses, vehicle repairs and cleanup) would be more than US$2 billion.
The model supposed that each cougar would consume 259 deer over a six-year period, but as the deer population declined, so would the cougars’. Eventually both would reach a stable equilibrium. These numbers were consistent with real experience in South Dakota, where cougars reduced collisions by nearly 10 per cent in eight years after being re-established.
The authors allow that there could be downsides, like cougars killing livestock and household pets or discouraging people from hiking or biking in the woods, but fewer deer would also mean less destruction of crops and landscape vegetation and possibly a lowered risk of contracting Lyme disease, of which deer are vectors. And, of course, there’s always the possibility of attracting trophy hunters.
It’s rare that conservation is seen through the lens of economic benefit like this, and who knows whether this would ever come to pass. But new thinking — of all kinds — is what we need as we confront the increasing pressure of mixing wildlife and humans, with minimal detriment to either.