Nature can turn a bit nasty Consequences: The overabundance of white-tailed deer has led to the proliferation of Lyme disease transmitted by deer ticks. It may be time to reassess some concepts about the out-of-control population.

On the Bay

September 19, 1997|By Tom Horton | Tom Horton,SUN STAFF

I'VE ALWAYS prized being close to nature, but in recent years I've been forcibly reminded that such associations aren't always benign.

The first time was in November 1995, when striking a white-tailed deer buck nearly totaled my Honda on U.S. 50 north of Easton. In November 1996, my Toyota collided with another deer near Cambridge.

Then, this spring, several days after walking in a Talbot County woods loaded with deer ticks, I came down with Lyme disease.

In all of this, I'm in plenty of company. The November rut, when deer have other things on their mind than traffic avoidance, is eagerly anticipated by auto body shops all over the state.

Several thousand motorists are estimated to strike deer on Maryland highways each year, and estimates nationwide range as high as a million such incidents.

That is astounding when you realize that around the beginning of this century, perhaps 300,000 white-tailed deer existed in all of North America. The species that in pre-Columbian times probably numbered 30 million in the United States and Canada had been almost 99 percent wiped out by intensive hunting and destruction of habitat.

In Maryland as recently as 1935, The Sun ran a full-blown article on the sighting of a single buck in Baltimore County. It was seen later in the company of two does, the paper reported, and said people hoped this would be the start of a new herd.

Another article in 1939 stated triumphantly: "Baltimore County deer now number a dozen."

And now? Maryland's herd numbers well over 200,000. Nationwide, one often hears the white-tails have rebounded to pre-Columbian numbers.

It may seem that, as deer invade every suburb (and suburbs invade every forest), a better estimate is probably 15 million to 17 million. That comes from brothers Thomas and Richard McCabe, wildlife biologists whose extensive historical analyses are the basis for most estimates of deer numbers.

A more serious consequence of the deer rebound than car-deer collisions (where death and serious injury to humans is infrequent) is Lyme disease.

Reported cases nationwide last year climbed to more than 16,000, the highest count since the federal Centers for Disease Control and Prevention began tracking the disease in 1982.

If detected soon after it is transmitted by tick bite, Lyme disease is usually treated successfully by antibiotics. Left untreated, it can lead to chronic, debilitating joint pain, fatigue, heart problems, brain infection and, in rare cases, death.

I was fortunate to have a doctor who diagnosed it from the rash caused by the deer tick's bite (expanding rings, sometimes almost a bull's-eye pattern) and began treatment. Sometimes, no rash is evident, and other symptoms often masquerade as the flu and are never treated as Lyme disease. Then it can become a lifetime affliction.

Lyme disease is caused by a bacterium that is most common in field mice and found in other creatures, ranging from robins to raccoons. Deer ticks pick it up by feeding on all the above and transmit it to humans. Far smaller than the common woodland tick (an adult is about the size of the "M" on a dime), they are almost impossible to see and pick off after an outing in the woods.

The role of deer might at first seem secondary. They function largely as "tick cities," maintaining year-round on their bodies thousands upon thousands of deer ticks.

The resurgence of deer, combined with the incursion of development into the countryside, has caused the rapid expansion of Lyme disease in recent decades, says Dr. Alan G. Barbour in his book, "Lyme Disease" (Johns Hopkins Press, 1997).

Where deer numbers are controlled, numbers of ticks eventually fall dramatically, and so does the incidence of Lyme disease in humans.

Of course, we fancy that we do control deer populations, largely through recreational hunting; but that is often fallacious, as noted in another book, "The Science of Overabundance" (Smithsonian Institution Press, 1997).

As this collection of scientific papers states: "All who have hunted deer, observed one in their yard, or seen an animated film on the subject consider themselves experts. No research endeavor contains more common knowledge than the study of deer."

A central "common knowledge" the book challenges is that of "overabundance." To the forest botanist, concerned about plant diversity and endangered species, deer in Maryland and other places might be out of control.

Ditto for the auto insurance industry and physicians seeing more and more Lyme disease; also farmers with mounting crop damage and suburbanites with ravaged azaleas.

But for sport hunters, for whom deer are largely managed (and whose licenses and other hunting-related fees largely finance wildlife management agencies), there is scarcely such a concept as too many deer.

Then there are the animal welfare advocates, whose views of hunting, our principal deer control, range from total opposition to viewing it as one among many tools, and preferably one of last resort.

"The Science of Overabundance" is pretty heavy going for a layman, but it is important enough and has enough readable pieces to recommend it.

It challenges a lot of concepts I'd always accepted -- that large predators used to control deer before we eliminated them; that the absence of population management always leads to out-of-control deer numbers; that hunting should always be the primary means of control.

The book offers no magic solutions, but makes a convincing case that it is high time to do the kind of research that can help us understand the true complexity of human-deer interactions.

Pub Date: 9/19/97

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