Deer Contraceptives – It's All About the Math

Hilltop Conservancy Treasurer Theresa Trapp pens Letter to the Editor regarding county deer hunt.


Essex County’s 2013 deer hunt has come to a close, once again removing many of this over-abundant species from our reservations (Hilltop – 61, South Mountain – 43). Contrary to naysayers, deer have not become extinct because of the program, and there are small signs that our nature preserves are beginning to recover from decades of browse damage.

Contraceptives are sometimes proposed as an alternative to hunting. However, we need to acknowledge that non-lethal methods to control deer populations would involve significant investment of taxpayer dollars, particularly immuno-contraception (e.g., GonaCon).

Each GonaCon inoculation costs more than $1,000 per dose (including locating, immobilizing, inoculating and collaring). In addition, each doe requires at least 3 doses over her lifetime to render her infertile – driving the real unit costs above $3,000 per deer. This compares to about $600 per deer for the County’s current sharpshooting program. Claiming that “GonaCon only costs $10 per dose” is like saying the County’s program only costs $3 per deer because one can buy a 5-count box of shotgun slugs online for $15 – hardly a complete picture.

As a species, deer have a high reproductive rate (each doe will bear on average 1.75 fawns per year over her 10+ year lifespan). That, coupled with their low mortality rate in our area (10% including old age, disease, injury / accident, and no large predators) means that an uncontrolled herd can double in size within 4 years. And research shows that immuno-contraceptives do not always “take” – even after a full series of injections approximately 10% of inoculated does will still remain fertile and become pregnant. If the overall fertility rate of an immunized herd exceeds its mortality rate, then it will continue to increase in size.

Lastly, the above calculations do not include the fact that GonaCon cannot be administered to deer less than 1 year old ….. and yet 30% of female fawns become pregnant and bear on average 1 fawn each. Even assuming that an immuno-contraception program is able to locate and treat every single adult female in a target area – and subsequently follow through with year-over-year re-capture and re-dosing of each of those does – the program will not be successful at reducing the deer population. In a real-world situation, the number of female deer that need to be inoculated would continue to increase, driving the costs of the program ever higher.

Using the Hilltop to illustrate: over 4 years of sharpshooting, the County has removed 380 deer from the reservation. Assuming a 50% gender mix and applying a unit cost of $3,000+, a Hilltop-specific immuno-contraception program would have cost taxpayers almost $600,000 to date, and would still not have reduced the overall number of deer in the park.

No wonder the County is reluctant …..

Theresa Trapp, Treasurer
Hilltop Conservancy, Inc.

Andrea Lieberman February 23, 2013 at 01:46 AM
DiVincenzo stated that shooting South Mountain/Eagle Rock/Hilltop deer in 2011 "was accomplished at a total cost of $130,223.04, or $744.13 per deer. That cost included bait corn and butchering. The remainder was spent on staff and Sheriff's Department overtime, electronic message boards, food for the hunters, and an aerial infrared census." The alleged ecological benefits obtained at such a high cost of suffering and public treasure are indeed "small." The purpose of any bona fide and humane deer program should be a reduction in deer breeding rates. According to the U.S. Department of Agriculture, GonaCon, which Ms. Trapp opposes, obtains up to an "80 percent" success rate in reducing breeding rates. That is 80 percent more effective than any hunting program. Multiple studies show that baiting causes forest degeneration by concentrating deer, who continue to feed on natural browse in the area, and increases predation on ground nesting birds by attracting coyotes, opossums, raccoons and rodents. Bait contains invasive and exotic seeds that are deposited in the area by birds, animals, or wind, threatening the integrity of a forest community. Baiting encourages illegal activity and poaching, and increases auto/deer collisions as deer cross roads to reach food. Ironically, baiting improves reproduction in deer. Baiting increases risk for multiple diseases in deer and other wildlife."
Andrea Lieberman February 23, 2013 at 01:47 AM
The Division of Fish and Wildlife has allowed massive baiting for recreational deer hunting since 1998. In 1998-1999, hunters distributed one million pounds of food for deer throughout New Jersey. Since then, the percentage of hunters who bait has increased significantly. Secondly, contraceptives are mired in politics. Like most products, contraceptives require broader use to bring costs down. Merely gaining contraceptive trials meets hostility from gun and archery manufacturers and most hunting agencies partnered with same. Recently, certain conservation groups have partnered with the gun trade. Such groups mimic the trade's manufactured objections. The gun lobby opposes contraceptives for deer and in fact declared non-lethal methods "a declaration of war on sportsmen." It has actually sued to prevent contraceptive trials in Indiana. Susan Russell, Wildlife Policy Specialist, Animal Protection League of New Jersey
Essex Hiker February 27, 2013 at 12:49 PM
Again with the grand conspiracy ...... where does it end? Maybe it goes all the way up to President Obama??!! The scientific community are all consistent -- in the absence of predators, white-tailed deer numbers need to be controlled to remain in balance with their habitat. Anti-hunters never admit that there are other animals in the forest, and that those species are dying off because of their single-minded focus on Bambi. And they also seem to forget what the rest of us learned in middle school -- that prey species (including herbivores like deer) do not manage their own numbers, and that predators are needed to keep ecological balance. This concept is illustrated by the ecological food pyramid for each biome type -- including temperate deciduous forest (ours). It's sad that such basic biological principles are completely absent from anti-hunting screeds -- maybe due to their inconvenience?
MSS March 07, 2013 at 07:03 PM
You have made an astute observation. Deer are not native to Kenya, where Obama was born. Therefore, President Obama hates Deer and implemented the hunt! It makes perfect sense ;)
gregory l. mitchell March 29, 2013 at 09:15 PM
Talk to any policeman from any of The Caldwells,Essex Fells,Verona and Cedar Grove as they ride all through the aforementioned boroughs at night.Since the development of The Hilltop and now the county hunts the last several years,deer are now noticed in greater numbers than ever before.Obviously this makes sense,the deer will now head out to our yards for protection and that is exactly what they are doing.Let's stop trying to manage wildlife and let nature take it's course. Respectfully, Gregory L.Mitchell-West Caldwell


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