Bambi's Impact

By Bob Engel
Marlboro College Professor Emeritus of Biology and Environmental Science

Years ago we had a Mexican exchange student living with us.  One evening we went by the edge of an orchard and saw two deer.  Our student went absolutely crazy.  She had never seen a deer because subsistence hunting by rural people in Mexico has just about eliminated anything large and edible.  I let her fawn over our find, but I kept my thoughts to myself.  I’m not a big fan of our deer, at least not at their current densities.

Some years ago, a rather extraordinary lawsuit was filed by several botanists against the U.S. Government’s Department of Agriculture.  The botanists had been working on the quantification of plant species in a northern Wisconsin National Forest, and then happened to do the same on a nearby Native American (NA) “reservation.”  It was like night and day!  Many plant species that were rare in the National Forest were common on the NA land.  These differences included woody species like Yew and a lot of herbaceous species.  What had caused the differences in plant abundance?  You got it; White-tailed deer.  It turns out that hunting is tightly regulated in the National Forests but allowed all year on NA land.  There were eight times as many deer in the forests as on NA nation.  The law suit held that the U.S. Forest Service was not upholding its legal mandate to maintain biodiversity in our National Forests.

In 2005, a paper appeared in Science magazine reporting on a reassessment of numerous historic Ginseng populations in the Northeastern and mid-Atlantic states. (The article isn't available unless you have a Science subscription, but you can read about this paper in a related National Geographic Magazine article.) Some ginseng populations had disappeared completely and the rest had declined.  By process of elimination, the finger was again pointed at deer.  The same finger reappears with a 100 year remapping of a natural area near Boston.  In the century between the two samples, a huge fraction of the historic species were simply gone.  Right, it’s Bambi… again. 

For that matter, we now have a lengthy list of herbaceous plant species that tell you whether deer herbivory in your neighborhood is intense.  If your property is covered with Jack-in-the pulpits and trillium, you don’t have a lot of deer.  The numerous painted trilliums along our drive are long gone.  So are the orchids.  I fence some gentians, which are doing fine.  Talk to any forester and s/he will tell you that deer are changing the composition of Vermont’s forests (the bugs will probably finish the job).  American beech is like chopped liver for deer, so it becomes disproportionately common as other tree species are browsed.

And there is also the nuisance factor: deer eat our flower and vegetable gardens.  There’s a multimillion dollar industry out there to help you with that.  I hope you’ve had more luck than we have.

Then it gets more personal.  We all know people who have had Lyme disease (or other tick-born diseases).  Some of these folks will struggle with often debilitating symptoms for life.  We can thank those very same deer for at least some of that.  Looking around the literature, there’s more than you want to read on deer and Lyme.  There’s a lot of circumstantial work that shows lyme to subside in prevalence with deer population reductions.  But there are also some people who think deer are free of blame.  There’s even a conspiracy theory that Lyme escaped from a Government lab in the south!  From where I sit, the jury is walking down the hall: young ticks feed on a variety of host species, from shrews to possums, the adults like bigger things like deer.  Both young and old can transmit the disease to us.  So how much do we blame the deer for our tick-born woes?  Again, its mostly circumstantial: for example, both mice and deer like acorns.  Acorns?  Yes, oak mast years has been connected to Lyme outbreaks.  Is this a case of trying to force a correlation into causation?  We simply don’t know yet.

So here’s the question: why not be safe instead of sorry?  Why don’t we regulate the deer herd downwards to see if that helps both us and our forests?  It’s a no-brainer, right?   More on that next time.