Case studies in successful community-based deer control

Sue Sutherland and William Darrow MD PhD

The Fairfield County Deer Management Alliance 
held a public presentation on Wednesday September 17th 2008
at Redding Town Hall, on

Case studies in successful community-based deer population control

Speakers:

William R. Darrow, MD PhD, Chair, Bernards Township Deer Management Advisory Committee, New Jersey
 
Ms. Sue Sutherland, Chair, Wildlife Committee, Mumford Cove, Groton, CT


A DVD is available of this presentation. Contact us through the web site. Both speakers are available to explain details of their very successful programs to other communities.

A brief summary of the presentations:
Dr Darrow, former president of the Bernards Township Board of Health, described the community: 29,000 residents in a suburban commuter town in north central New Jersey, largely built out with few large pieces of land. The deer control program was started with a survey asking the question "Do we have a deer problem?" When the answer came back in the affirmative a deer committee was formed. The committee first looked at all other possible means to reduce deer numbers but concluded that there was no effective non-lethal means so a hunting program was selected. 

Goals: To reduce deer to 10 deer per sq mile, the identified cultural carrying capacity below which Lyme disease will no longer spread to humans, road accidents with deer will be minimal and property damage negligible as deer will not exceed their biological carrying capacity in the woods and natural areas.

Baseline measures:
First the deer numbers were estimated in a 2002 aerial overflight survey using infrared technology with high resolution imaging. This revealed 118 deer per sq mile or a total of over 2800 deer. The cost was $1200 per sq mile surveyed, resulting in a total cost of $30,000 for 24.5 sq miles. Police were asked to record all roadkills in addition to the reported accidents with deer: 289 were logged in the year before the program started in 2002.
Calculations based on reproductive capacity (35-40%), predation rates, road deaths and natural deaths were made and a goal for each year's harvest set. In addition to the planned hunts on town land there was additional private hunting occurring.
A deer damage survey was performed in 2003 of all single family homeowners (60% of town): $19.4 million had been spent on deer repellent sprays, deer tick sprays and landscape losses over the previous 3 years (over $6M a year).
A survey asking about Lyme and deer vehicle collisions (DVC) in the previous 5 years was performed in 2004: 40% of households had had a DVC at an average cost of $2166; 39% of households had one or more cases of Lyme diagnosed in the previous 5 years; the average cost per patient was $1500 with a maximum of $30,000; 20% had a pet diagnosed with Lyme.

An independent research team of NJ scientists measured tick populations at multiple sites throughout and followed Lyme case numbers before and during the program. This was not a planned part of the program but may provide valuable data when deer numbers have been reduced to the desired threshold levels  below which ticks cannot thrive.

The program:
Deer were removed by hunters in elevated tree stands over bait on 34 tracts of land across the township, including 6 larger tracts that were used by firearms hunters. The hunters chosen were two locally based volunteer groups, from Bernards Township and other nearby towns, a total of 65 hunters, including one group of 15 bow hunters and another using archery, shotgun and muzzleloaders. The firearms were only used on the 6 largest parcels of the 34. Professional sharpshooters were considered but not used. The first year of the program a commercial culling firm, Deer Management Associates, were used but they only use shotgun and we have very few sites that are large enough or unpopulated enough for shotgun use. 
A special season extension permit was used and 15 to 20% of the deer taken are taken in this extra 6 weeks to the end of March. The program began in the 2003 season.
Excess venison not taken by the hunters was butchered at the township's expense at $70 per deer and donated to the Food Banks of New Jersey, which is a central food bank that sources numerous community food banks across the state.

Safety: 
Shotgun and muzzleloader users were and are screened and tested by a certified firearms instructor. Archers are similarly screened and tested by a certified archery instructor. Tract closures by police while the area is in use by our hunting agents has not been necessary, although the program provides for it if/as needed.

Results:
Deer have been reduced from 118 per sq mile to around 20 per sq mile as of Sept 2008, by removing approximately 250-300 deer a year through the controlled hunt program on town land, plus an additional similar number removed each year from private properties.
An annual population estimate calculation is done each spring after the sport hunting season ends in mid-Feb and our program ends at end-of-March. We start with the previous year's population estimate, which is a post-fawning estimate. We then subtract the program's sport hunting total (obtained from DFW tagging book numbers) and our program's total harvest. We then also subtract the last Deer Biological Year's (DBW = from April 1 to March 31 of the following calendar year) roadkill tally from the police logs, plus 15 % for estimated off-road deaths and a pro-rata estimated number of roadkill deaths on the two interstate segments in town. This gives us a pre-fawning estimate for the current year. We then have been adding 35 % for an assumed reproduction rate. But as evidenced by a resurgence in deer auto accidents noted in 2008, we now think that's too low and a more likely rate is 37 or 38% per year (but NOT as high as 40%).
Deer vehicle accidents had been reduced by 82% by 2007 but there was a slight resurgence in 2008. There is a much reduced rate of shrubbery damage observed. Tick numbers and Lyme case numbers are being followed by an independent research team in conjunction with the CDC. As deer numbers near the threshold level of 10 to 12 per sq mile dramatic falls in these two measures are expected within 2 years of deer densities being held at the threshold level.

The overall program cost in a typical year was $91 per deer removed, paid by the township. All the venison processed went to the needy. The community considered this a good investment and a win-win situation, considering the enormous costs incurred by residents prior to the program in medical and auto accident expenses, plus preventive spray programs.


With similar enthusiasm for the benefits of a deer control program, but in a very much smaller community, Ms Sue Sutherlanddescribed her small community of 150 homes in Mumford Cove which is part of Groton, Connecticut.

Goal of program: 
To reduce the risk and incidence of Lyme disease in residents.
In 1995 the residents were experiencing a high incidence of new Lyme cases every year. The community were concerned about having too many deer and how that related to Lyme Disease, damage to plantings, and deer-car accidents. They approached the state Dept of Environmental Protection who agreed to do a study in 1995. 

The Program:
Advice was sought from CT DEP's Wildlife Division and attempts were initially made to control deer numbers and hence tick numbers by treating deer with contraception. Unfortunately the fertility control failed and deer numbers and Lyme case numbers continued to rise. Between 1996 and 2000 there were between 20 and 30 cases of Lyme a year. 
In 1999, after the failed immunocontraception study, the community formed a deer-tick committee.  The committee talked to experts and provided the residents with options.  (see Kilpatrick and LaBonte 2003;  WSB 31:340-348).
A lethal deer management program was chosen and instigated in 2000 when deer were reduced from 100 per sq mile down to 10.4 per sq mile through controlled hunts from elevated tree stands. A combination of archery and shotgun hunting was used. Shotgun was used on tracts of 30 to 100 acres plus. The deer have been maintained at that same level of 10 per sq mile for the following 8 years by removing just 10 deer each year, also using tree stands in just 3 locations.

Benefits:
Ms Sutherland described that as Chair of the Wildlife Committee at Mumford Cove she has had people express surprise that she supported and helped organize the deer control program. She explains to them that she thinks about the entire animal kingdom not just one species. Mumford Cove is now a thriving, diverse ecosystem filled with butterflies, birds, native bees and the rare eastern tiger hummingbird moth and a lush and diverse understory of native plants such as milkweed and fruiting shrubs. She has not seen a tick in 8 years and like all the residents she now uses the trails, bike paths and does her (unfenced) gardening without worry of tick borne illness. Deer are still present and sighted but only at dusk or dawn in the quieter regions away from homes, as they were 30 or so years ago. Lyme case numbers have fallen dramatically to between zero and 2 per year, Ms Sutherland said. The results of the deer program here were published by Howard Kilpatrick of CT DEP in 2003 and a further extended follow up study of these extremely important results will be published shortly. An intermediate length follow up is described and graphed in the Ct DEP's "Managing Urban Deer in Connecticut", 2007 edition which is available online: http://www.ct.gov/dep/lib/dep/wildlife/pdf_files/game/urbandeer07.pdf

Conclusions: 
Controlling deer controls Lyme disease and encourages the re-emergence of key native species. Ms Sutherland highly recommends the Ct DEP program to advise and help control deer.

The overall program cost to the community was "one ream of paper for signage".