Should Deer Populations be Reduced to Control Lyme Disease?

Lyme disease has reached epidemic proportions in America, especially in the East.  An estimated >30,000 cases of Lyme disease will be diagnosed and reported in the U.Sl this year and many more cases will go undiagnosed or unreported. This issue is close to my heart because the daughter of a good friend continues her battle to survive with her case of advanced Lyme disease. Humans are infected when bitten by infected Ixodes ticks, deer ticks in the east and northern US, and black-legged ticks in the western US. The life cycle of the east coast deer tick and the west coast Black-legged tick, the primary vectors carrying the spirochete Borelia burgdorferi that causes Lyme disease primarily cycles between small rodents like mice and squirrels and large mammals, primarily deer.  Humans are essentially an accidental host for the spirochete.  The spread of Lyme disease is likely in significant part due to the dramatic increase in deer populations in areas where human populations have provided ideal deer habitat (edges with vegetation for food and adjacent wooded areas for cover) and markedly reduced natural predation by wolves and other large mammals. Bambi feeding on your garden may be frowned upon, but the wolves who historically kept deer herds in a natural balance have been extirpated from these same areas.  It’s little wonder that the ticks that spread Lyme disease also thrive in this area to an extent unheard of in decades past.

While visiting my Dad in Maine for the past week the local news programs, newspapers, and lots of web sites perseverate on how to avoid Lyme disease.  The primary recommendations include daily “tick checks”, keeping your lawn grass cut short and clearing your yard of tick hiding places like brush piles, leaves, and rock piles/walls, and keeping pets tick free and use of insecticides on lawns and yards. No one seems to be discussing what seems to me to be an obvious public health approach to this serious health concern.  There are just too many deer living in close proximity to towns and cities in much of the eastern and northern U.S.

In Southern New England white-tailed deer populations are out of control.  Although at about the turn of the 19th century and the early 20th century white-tailed deer had been nearly hunted out of existence, but with the institution of hunting seasons, and later annual “bag limits” this situation has more than reversed itself. Deer populations in some areas are at or above the “carrying capacity” of the land, and are so common on some southern Maine coastal islands as to be a menace to residents both because of increased populations of deer ticks, and hence Lyme disease, but also in deer-vehicular accidents and damage to crops and landscaping.

It seems that a better public policy of hunting permits to reduce deep populations in many areas would be an efficient, popular and safer way to reduce Lyme disease burden than asking everyone to mow their lawns short, remove habitiat for ticks (the same habitat used by many bird and other small animals), and spread insecticides on their properties.  The white-tailed deer has been a beneficiary of the mixed edge habitats and wooded areas for cover and the lack of natural non-human predators brought about by the gentrification of much of the east coast.  Although Maine residents and especially hunters desire a healthy white-tailed deer population keeping this population much lower in more populated areas seems like a good public policy to me.

I’d be interested to hear from readers from Eastern states stand on this issue. Is having robust populations of deer near your homes worth the cost of human life and suffering from the Lyme disease epidemic?  I’d say a loud no!

4 Responses to Should Deer Populations be Reduced to Control Lyme Disease?

  1. That was a thoughtful answer by Sue’s nephew above. I still favor suburban herd control after seeing first hand the way this disease challenges the survival of it’s victims. How about planting bushes the deer eats and changes it’s skin so it is not good tick habitat and the tick doesn’t survive?

  2. Thanks Dr. Pullen.. I passed your note along to Eli… I figured he would have something of value to add to the conversation. The really sad part of all of this is your friend’s daughter and I am so sorry she has to battle this awful disease. I sure wish a healthy recovery for her.

  3. Wow Sue, please thank your nephew for me for the very eloquent reply. Obviously much more well thought out than my position. I appreciate the reply and it is just what I was hoping for: an informed intelligent reader to reply. It sounds like this problem is just one more unintended consequence of our suburban utopia, green lawns, lush plantings, and city parks providing a very high carrying capacity for deer, and leaving humans at risk of Lyme Disease in those areas. My only issue is with the bucks only seasons still in place in lots of ME. Dr. P.

  4. Hi Dr. Pullen: I read your blog this morning and found it interesting. So, I asked my nephew for his opinion as he is in this business both professionally as well as personally. FYI – Here is his response:

    Most people don’t have much experience with hunting as population control, nor knowledge of the chronology of wildlife management. We extirpated wolves a long time (100 years) ago, but that doesn’t necessarily correlate with the recent boom in deer populations. The wolf is a red herring. There’s actually a body of literature about the ecological effects of wolf reintroduction in Yellowstone that’s absolutely fascinating, but it’s also completely beside the point, because wolves wouldn’t live in suburbs, even if we allowed them to.

    While it is essentially true that white tailed deer are probably overpopulated in a lot of the US with regard to their interactions with humans, but to assert that increased hunting would solve that is pretty hard to take. The prevailing opinion in wildlife biology is that population is largely driven by available habitat. Populations swing widely throughout the year, but the number of critters that survive the toughest part of the year (late winter/early spring, typically) are really limited by available habitat–forage, cover, water, and space. In order to increase harvest enough to reduce populations substantially, you’d have to drop below the number of animals that could be supported by the available habitat. If you push too hard, you eradicate them, but usually, once you reduce herd size through hunting, they’ll bounce back to the carrying capacity of the land fairly quickly. This is the theory behind most harvest of fish and game–a “maximum sustained yield” that allows the population to be sustained over time without sending the population into extinction. Most hunts/fisheries are managed with a healthy buffer in place to ensure that we don’t mess up and send them over the brink to extinction on accident. In other words, we’re still allowing the habitat to be the primary limiting factor (the “bottleneck”) in the population. From an ecological perspective, if they’re truly overpopulated, then the population would self-correct; a 12-oz glass simply won’t hold more than 12 ounces of water, no matter how much you pour in. Overpopulation happens–but it isn’t sustained over time. Deer populations appear to be sustaining just fine at their very high levels.

    So – if it’s all about the habitat, the question is answered here. We made the habitat really, really good for deer. And in the process, we’ve put a whole bunch of people in and around the habitat that we’ve improved for deer. In fact, hunting access is the #1 problem for hunters based on a number of national surveys–not the lack of game. Hunter numbers have been decreasing despite increasing population, and most believe that the primary reason is that there isn’t enough habitat to support hunters–it’s been turned into rural/suburban residences. It doesn’t matter how many deer are available for harvest in a subdivision, because in order to hunt them, you’re shooting guns (or bows) in your backyard and then chasing mortally wounded deer through your neighborhood, or even more awkward, as a hunter you’re asking a stranger for permission to do that in their neighborhood. Even the most accurate, humane, lethal shot on a big game animal will allow it to live for ten seconds–plenty of time for it to race across several small properties. Many/most incorporated areas consider this antisocial behavior at best, and have instituted codes that prohibit or severely limit hunting within suburban boundaries. For example, we have several marauding bands of elk in suburban Longview that destroy lawns, knock down fences, stomp on dogs, and tear ornamental trees out of the ground. We also have a Longview City Code that prevents hunting inside of city limits. Issuing more hunting permits for the game management unit in which Longview is located wouldn’t do a bit of good to reduce elk damage inside of the city limits, which has been demonstrated here over the last ten+ years of liberal hunting seasons surrounding Longview.

    Most states with tons of whitetails already have liberal seasons with lots of antlerless harvest opportunities (killing bucks does almost nothing to the population). The problem is that suburbia isn’t a good place to hunt.

    Living in an area with a ton of deer, and concern about Lyme disease best calls for planting stuff that they don’t like to eat, dispensing with the lush green lawn, or surrounding your property with a decent deer fence. Bathing daily is also a really good way to make sure that you don’t have a tick burrowing into your flesh.

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