What happened on Wisconsin highways after wolves returned


One of the benefits of starting my own newsletter has been greater freedom to pursue topical interests well outside the purview of what you can typically cover at the business desk of a major national newspaper. Judging by my output this year those interests include a lot of stuff about… deer and wolves, for some reason? Northern Minnesota must be imprinting on me, I dunno.

Regardless, I recently stumbled across a banger of a study that encompasses both animals and their relationship to humans. The study found that when wolves were reintroduced to parts of Wisconsin, driver collisions with deer dropped dramatically relative to the places in the state where wolves didn’t make a comeback. That’s a huge deal: deer cause roughly 18,000 car accidents in the state each year, wreaking tens of millions of dollars in economic damage.

The authors tracked deer and wolf populations at the county level in Wisconsin from 1980 through 2010. During that period wolves became more abundant and widespread across the northern and central regions of the state.

For data purposes that created two subsets of counties: those in which wolves were reintroduced, and those in which they weren’t. The authors then compared deer-vehicle accident trajectories in the wolf- and non-wolf counties.

The raw observational data shows a huge divergence: in counties without wolves, deer-vehicle collisions increased by roughly 80 percent between 1988 and 2017. In wolf counties, on the other hand, deer collisions essentially stayed flat over that period. In both sets of counties non-deer collisions followed a nearly identical trajectory, strongly suggesting the differences in deer collisions aren’t simply due to other, unseen road safety factors.

The authors go on to do some more complicated statistical tests to further iron out the association between wolves and deer accidents. They find, among other things, that the affects they observe aren’t primarily due to deer population changes — rather, the presence of wolves changes deer behavior, making them more cautious and less likely to go marauding about roadways. That’s good news because it’s further evidence against a common hunter complaint about wolves: that they decimate local deer populations. That’s simply not true, although it may be the case that the presence of wolves makes deer harder to shoot simply because they’re less likely to be out and about.

The paper notes that policymakers have tried their hands at a bunch of different interventions to reduce deer collisions over the years — road signs, wildlife corridors, reflectors, audio signals, etc. etc. They’ve tended to find that the cheap interventions don’t work well, with the ones that do work being ridiculously expensive.

Wolves, on the other hand: literally free! They do all the work for you! They’re cute!

Programming note

Here’s an unfortunate programming note: last week I tested positive for a breakthrough coronavirus infection. I’m fine, the whole experience has basically been like a beefy cold: congestion, cough, a little bit of achiness for a few days but no fever or breathing difficulties.

Better yet, for some miraculous reason nobody in my family’s gotten sick even though they’ve been breathing in my diseased miasma for days.

But everything in our lives has been nonetheless turned upside down. The kids are all out of school and daycare for several weeks of mandatory quarantine, so while I’m shepherding them through their schoolwork posting here might be a little on the light side. As I write this there’s a four-year-old in his jammies tugging at my leg and howling about lunch. So, I’m going to get on that.