Deer finding the good life in suburbia Helicopter survey by state provides population count

'How many is too many?'

Wooded areas offer refuge, residents' gardens give food

November 21, 1998|By Heather Dewar | Heather Dewar,SUN STAFF

Scientists using a helicopter equipped with ultrasensitive heat-detecting gear have found large populations of white-tailed deer hiding out in suburbia.

As suburban gardeners have long suspected, the deer thrive in the region wherever woods and fields are tucked between malls and townhouses. In a monthlong survey in March, researchers from the Maryland Department of Natural Resources counted an average of 13 deer per square mile along their 527 miles of flight path. In wooded areas, they found an average of 40 deer per square mile.

That's a lot, but it doesn't come close to the 160 deer per square mile DNR surveyors found in parts of Gunpowder River State Park in 1993. Still, it's more than enough to do harm, said Michael E. Slattery, director of DNR's wildlife division.

"How many is too many? When the public can't stand the damage happening in their neighborhoods," Slattery said. In parts of Baltimore and Montgomery counties and in suburban Annapolis, he said, "we're already at the breaking point."

The prolific creatures become a nuisance when they eat crops, damage nursery plants and collide with cars. And whenever deer populations climb above 20 per square mile, they cause obvious environmental damage, Slattery said. Their chomping makes it hard for shrubs and saplings to regrow, reduces the variety of plants, eliminates some rare types and encourages the spread of weedy, non-native species.

In rural parts of the state, hunting helps keep the population in check. But in urban and suburban areas, there are so few places where it's safe to hunt that the deer have plenty of refuges.

Because hunting-season tallies are the main method for tracking deer numbers, state officials haven't had a way to estimate how many there are in the suburbs.

To solve that problem, surveyors used a DNR Bell Jet Ranger helicopter equipped with a heat-sensing camera that can pick up temperature changes of less than one-fourth of a degree. The camera, mounted below the chopper body, can detect a poacher's still-warm gun and flashlight stashed in a patch of weeds -- and that's what it's usually used for, said Maryland Natural Resources Police Sgt. Scott Zimmerman.

DNR officials think this year's deer tally is probably the first time any state has used the heat-sensitive gear for a wildlife survey.

In March, when bare trees and cold temperatures made the creatures easier to spot, Zimmerman and other DNR pilots trained their cameras at the ground as they flew along 15 randomly selected east-west courses from northern Baltimore County to southern Anne Arundel. At 300 feet above the ground, the camera captured video images of all deer within a 221-foot-wide swath. Later, biologists watched the video and counted the deer, which are easy to distinguish from cows and horses.

The greatest number of deer, 55, turned up along a 221-foot-wide line that cut across Montgomery and Howard counties and ended at the southwest corner of Baltimore.

Populations were almost as big along a flight path that ended at the mouth of the South River and along a course in northern Baltimore County.

The results contained no surprises and reflected the high numbers indicated by residents' complaints, said biologist Paul Peditto.

State researchers want to repeat the surveys in February to check for accuracy and spot trends. The results will be used in meetings with neighborhood groups to help decide how to control the deer, Slattery said.

Other states are trying such methods as using professional riflemen or deer contraceptives, fired from dart guns. DNR wildlife managers aren't sure what Maryland's next steps might be, Slattery said.

"Fairfax County is using sharpshooters," he said. "We aren't there yet, but we may get there eventually."

Pub Date: 11/21/98

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