A scientific approach to limiting the wildlife population explosion

A Doe Participating in the Study courtesy National Wildlife Research Center/USDA

"Mother Goose" might soon be an anachronism.

In wildlife biology, concerns about animal populations often stem from unnatural declines; in a few cases, however, that concern can be a result of too many animals, not too few, as some once-threatened species have returned with a vengeance.

Now a group of researchers is fighting back with a familiar (to humans, at least) tactic: birth control.

Deer and Canada geese, in particular, have overtaken parts of North America in such magnitude that they're wreaking havoc on the environment, on human sanity and on public safety.

Just ask pilot Chesley "Sully" Sullenberger, whose U.S. Airways flight 1549 landed in the Hudson River after a flock of Canada geese took out the airplane's engines.

"A lot of the problems are occurring in urban areas, but people don't necessarily want the animals shot, so we're trying to be responsive to those kinds of issues," said Dr. Kathleen Fagerstone, research program manager at the National Wildlife Research Center in Fort Collins, Colo., where the contraception programs were developed.

A once-a-day birth control pill is now available for geese and pigeons, and wildlife researchers just submitted an application with the U.S. Environmental Protection Agency to market a one-time injectable immunocontraceptive for white-tailed deer.

The efforts complete a circle of sorts. Humans hunted geese and deer practically to extinction by the 1930s, but later helped restore native populations. Without natural predators and with an abundance of food and shelter, the animals have flourished. The continental United States is home to more than 17 million white-tailed deer, according to the Wildlife Research Center. By 2002, North America was home to 3.5 million resident Canada geese.

"Canada geese hit a low point in the '70s, partly because of DDT, partly because of hunting. That's when people started moving geese around and they would bring them in," Fagerstone said. "They didn't know they were supposed to migrate, so they didn't."

Like the mid-20th-century gosling boom, the goose contraceptive's discovery was somewhat of an accident. About 14 years ago, Erick Wolf was with a pharmaceutical company that worked with Merck to produce nicarbazin, a drug fed to chickens since the 1950s to prevent coccidiosis, a potentially fatal sickness.

The drug is only fed to broiler chickens that will be slaughtered, but on occasion, a breeding hen would snag one. Then her eggs wouldn't hatch. The drug changes an egg yolk's pH and allows it to mix with the albumin (the white part), which prevents an embryo from forming.

"For 50 years, the Merck guy went around and said, 'This is a great drug to protect your chickens from coccidiosis, but whatever you do, don't feed it to your breeders,'" Wolf said.

Eventually, a colleague convinced a skeptical Wolf to consider using the drug to intentionally prevent eggs from hatching. Wolf approached scientists at the Wildlife Research Center, who were already hoping to develop an oral contraceptive that could be fed to slippery species like feral hogs and birds, which are hard to capture and inject.

Pigeon Eating OvoControl Bait:  courtesy National Wildlife Research Center/USDA
Scientists at the wildlife center and Wolf's company, Innolytics, eventually developed a wheat-based, chewy bait for Canada geese, and the animals loved it. Gregarious geese are easy to train, so they quickly grew accustomed to workers feeding them daily birth control pills, Fagerstone said.

"They'll show up, actually, when the truck arrives, or when the feeder goes off. Then they're sitting there waiting for their morning feed, and then there's nothing left for anyone else," she said. That's good news for anyone worried about another creature picking up the treats by mistake.

Dale Humburg, chief biologist for the waterfowl and hunters' advocacy group Ducks Unlimited, said while contraception is humane and can be effective, it's not the only answer. He said longer hunting seasons, increased bag limits, and even relocation efforts should come into play.

"It doesn't help to employ methods of direct control if the attractant, the nest sites, or people feeding them or whatever, is in place," he said. "[Contraception] won't solve the problem unless the full range of tools are used."

A Biologist Checks a Goose Nest for Eggs:  courtesy National Wildlife Research Center/USDA

Though hunters do help, humans have tried for more than three decades to control wild populations of ungulates like horses, deer, and elk, without introducing predators that would also eat cows and sheep.

Efforts to create a fertility control drug stem from the animals' fecundity -- in the wild, pregnancy rates reach 85 to 90 percent of all female elk, said Jenny Powers, a wildlife veterinarian for the National Park Service.

Initially, wildlife researchers tried using porcine zona pellucida, or PZP, a widely used, pig-derived immunocontraceptive. It spurs the production of antibodies that block sperm receptors on the egg.

But when scientists at the wildlife center tested it in white-tailed deer, they found that while it inhibits fertilization, it doesn't shut down reproductive hormones, so the deer were in the mood far longer than they should have been.

In 1996, Dr. Lowell Miller looked to the brain, and developed a vaccine for a hormone that starts the endocrine cascade leading to the reproductive cycle. He attached the hormone to a mollusk protein, fooling the immune system into attacking it. The successful result was that the deer's reproductive cycle simply didn't start. So far, the treatment hasn't been shown to have any adverse effects, Fagerstone said. And it keeps the does from attracting any suitors.

"The males just ignore them. It's like another young male or a young female that's not reproductive yet," she said.

The drug, called GonaCon, is especially promising because it doesn't require a booster shot, unlike most other vaccines, and one study showed it prevented pregnancy for up to five years.

It isn't commercially available yet, but scientists hope it could help in suburban areas where deer and elk cannot be hunted, as well as in national parks. In January 2008, Powers and other scientists injected 60 elk with GonaCon in Rocky Mountain National Park, 65 miles north of Denver, while also testing several animals for chronic wasting disease. Though the study's results aren't yet ready for publication, it seems to be working well one year later, she said.

Humburg said any attempts to control wildlife populations have trade-offs for the animals and for people.

"There's a large number of species that have been in relatively low abundance just in the past few decades," he said. "I can remember the first deer I saw; it was really quite a formative event for me. I can remember when Canada geese were not common at all. So these are conservation successes. But with conservation success, and in the context of growing human populations, there are tradeoffs, and there are challenges that we have to face."

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How right you are about the overpopulation of birds.....especially Geese. I fly a small homebuilt airplane and if I were to hit a goose in flight it would do a lot of damage. It's a problem all over this country. Glad to see someone is finally researching methods to stop the population explosion at the source, and in a humanitarian way. I know the bird lovers don't want to hear this but a few less pigeons would be a good thing too.

This is why I have subscribed to PopSci my whole life.....timely stories that are well researched and well written. Nice Job!!

Mike Cook

from Kent, WA

I have two problems with this concept. First, I am a hunter and there is nothing wrong with shooting walking or flying protein. Second, our environment is already becoming saturated with estrogen and other female hormones because so many millions of American women take this stuff and then it gets pissed out into the environment via waste water.

No one really knows the long-term effect of all this stuff. Maybe it is making American males more metrosexual. Maybe it is the real cause of autism, MS, lupus, Crohn's disease, or immune system disorders. Maybe all the ocean of hormones accumulating out there is really what is causing amphibians to disappear. Maybe the man-made hormones will cause super crocs and hogzillas to grow in the swamps until they are ready to ambush suburban school buses full of tasty little children.


from Grand Prairie, Texas

I think this would be a great addition to population control of birds within urban areas. Many businesses face the problem of birds such as crackles, pigeons, & crows by diverting them elsewhere--using tactics such as a fake owl to the strange noises blasted through speakers that mimics Jurassic Park. All temporary solutions for the areas that have this commodity, but very much so a problem for places with out. Thus the result is a black sky full of birds each time a train signals its over-pass or a car's alarm goes off; it's just a great nusiance. It'd be nice to enjoy a meal outside without having the feeling of my food being bombarded by poop from the sky.

this is SO messed up. It's one thing to contracept HUMAN species intentionally... but to try and interrupt other species is not only immoral, it's WRONG. Who are we to say how many animals should be on this Earth. We're humans. We don't have the right to limit other species!!! WE DO NOT OWN THIS EARTH!!!!! WE'RE ALL JUST ANOTHER ANIMAL, WITH LARGER, BUT DUMBER BRAINS!!!!!!


maybe you have a dumber brain, but for the rest of us, i think our brains are as bright as ever. sure we are on here with everything else that is living but we do have a right to live comofortably and safetly. the next time you are out driving/flying remember that one of those species that reproduces extremely fast could come and get in your way and you could possibly die. hitting a deer going 60 is not something you would want to do.

of course on the other hand, how would you feel if someone came along and kept you from spreading your genes? wouldnt like it i suppose. well unless you realized what was going on which most of these animals dont. though i would try to keep some people from breeding because they dont do anything for our population.

maybe you have a dumber brain, but for the rest of us, i think our brains are as bright as ever. sure we are on here with everything else that is living but we do have a right to live comofortably and safetly. the next time you are out driving/flying remember that one of those species that reproduces extremely fast could come and get in your way and you could possibly die. hitting a deer going 60 is not something you would want to do.

of course on the other hand, how would you feel if someone came along and kept you from spreading your genes? wouldnt like it i suppose. well unless you realized what was going on which most of these animals dont. though i would try to keep some people from breeding because they dont do anything for our population.

I can't imagine how this is cost effective management on any level and not just pandering to the bleeding hearts with too much money and time on their hands.

It would make sense if these were species that were competeing for directly limited resources: the sterile would fill up an eco-nitch that would be replaced by a fertile adult if the sterile one was merely eliminated. The problem is, however, that these species are particularly those which have a super abundance of available food source and little to no competition or predation.

Also, how is this birth control safer or cheaper than good ole' fashioned lead (okay, tungsten then, for the plubio-phobiacs)? If you can drug it, you can shoot it, trap it, or poison it.

Considering that both Geese and Deer are delicious, opening seasons and bag limits will reduce populations. Urban areas can be safely harvest from in a variety of ways (baiting, archery, and trapping). Note that the article even mentions that the populations were critical only a generation ago through little more than consistant harvesting.

I was able to take a plague population of squirrels at my home (previous owners fed them in the middle of a hickory and oak forest) down to very few (a few individuals with clear teritories) in less than a year with a simple combination of traps and my 22. My neighbors run dogs and harvest the deer behind my house once a year. I do not see deer from October to May. When man removes the predators (which he does/did to reduce competition) then he must live up to the role which he created for himself.

When cattle and other forms of protein are energy intensive and take up much of our food supply and when so much of the world faces hunger, this is an absurd approach. We've got a few problems here and they have mutual even if partial solutions. I don't hunt, but this sort of thing makes me think that maybe I should. But then again, if they go ahead with pumping wildlife full of hormones, maybe I'd have second thoughts.

To combat the growing problem of these "animals", forced sterilization is the only answer. These inferior creatures have no right to interfere with the chosen species. The only option is to prevent them from passing on their primitive genes. We are the rightful heirs to this planet, to deny this is to deny one's great heritage! Survival of the fittest, no matter what the cost! Join us or suffer the same fate as the beasts. Human kind shall prevail!

I do not like this one bit. The animals are invading our homes. Didn't we invade theirs first? They were here first, what right do we have to control them like this. This is just completely wrong.

strwbrry993 - The problem is, we have eradicated their natural predators. If we brought back the eastern wolf and the mountain lion (I live on the East Coast), in sufficient numbers, they would control the population for us, but would also be snagging livestock, pets, and small children from time to time. If we just all left and gave the country back to the deer, they would expand to starvation levels in a few generation (remember, humans are still controlling the deer population through hunting and driving at night in the fall).

Compare current and historical deer populations and you will see that there are more deer now than ever before with less habitat than ever before.

The problem with reintroducing predators into the wild is that human populations have grown to such a level that there will inevitably more encounters with wild predators and consequently fatalities to humans. From a "natural" standpoint a balance between predator and prey would be ideal however from the human geographical standpoint, no one would want their child mauled or killed by a mountain lion who sees the little one as "fair prey." Its messed up to influence nature to this level but it seems like the best way to control the populations causing problems without harming uninvolved species.


from oakland, ca

"...immunocontraceptive. It spurs the production of antibodies that block sperm receptors on the egg."

a method of birth control which acts so specifically seems like it could avoid all the side-effects of traditional hormonal contraceptives.

Why isn't this being developed for human use?

Plus: "it doesn't shut down reproductive hormones, so the [females] were in the mood far longer than they should have been."
Major bonus for husbands and boyfriends too.

There have been several comments posted on the risk of hormones in the drinking water or in the tissues of treated animals. For the record, the pigeon pill, OvoControl P, contains no hormones and does not act on any hormonal pathway. The product interferes with the hatchability of eggs by interupting vitelline membrane development. The active ingredient (nicarbazin) has been used for more than 50 years in chickens to control coccidiosis. It does not represent an environmental risk or contaminant which can impact other species. See www.ovocontrol.com for complete details.

Mike Cook

from Kent, WA

I suppose that if active bird population control via biological warfare does become official policy here in Washington, ravens would be targeted. These clever corvids draw a lot of criticism because they seem to be increasing in numbers and they drive out a lot of the smaller bird species. I have seen two crows hectoring a full-grown hawk in flight, playing such perfectly timed tag-team body checks that the poor hawk had to flee the area for his life.

The problem with demonizing these ominous black ruffians is that they ARE demons! They will find out and attack us!

Years ago on the "campus" of the institution where I work we had an over-population of fat geese and, consequently, messy sidewalks and lawns. Our superiors were driven nearly to distraction trying to find a politically correct solution to the problem that wasn't a budget buster. In the end the pond turned into a rock garden and all the bubbling fountains went dry.

I remember one of our workers (who had been born in Vietnam) insisting that there must not be a real problem with hungry homeless people in America, or there could not possibly be a problem of too many fat geese. He didn't understand how really hand-out trained are not only our pigeons, ducks, and geese, but many of our humans!

You also have to really understand who drives most environmental policy in America. This would be a silver-blue-haired woman who lives with her lap dog and a really fat cat on the 20th floor of swanky condominium tower. Her husband was a really fat cat himself, but he doesn't count even if he is still alive because long ago he turned a supplementary, totally useless vestigial appendage of his wife. Anytime SHE sees something that displeases her about the way she thinks animals are being mistreated in this world, she writes a really big check to some non-profit that actually is for the profit of some team of lawyers dedicated to litigating the world into compliance with any and all of the most outrageous wishes of the silver-blue-haired women.

A major point that is not discussed here is the costs associated with these products that will be charged to the homeowner, business, or tax payer. Having been trained in applying Ovocontrol for Geese here are some of the specifics for that particular product.

The product must be applied and ingested by the birds on a daily basis. Effectiveness of the product is based 100% on the amount consumed. Both male and female geese ingest the product although it only affects the females. It takes a minimum of 7 days feeding before the product becomes effective and feeding must be continued throughout the egg laying season. Here in Ohio that mean we need to start feeding as early as February 15 since we have eggs being laid as early as February 28. The label has been changed so I don't know the time and oversight criteria off the top of my head; however, it originally was 4 hours of oversight with collection and removal of any unconsumed product every day. With all these conditions, labor costs for just one individual can easily run between $2,000 and $15,000 or more based on the situation. Now add the costs of the products and their application and you easily have a project that runs in excess of $20,000 without any immediate results. As a side note, Canada geese can become active egg layers between three and four years of age and have a lifespan that can reach 20 years. So for any population effectiveness, the birthcontrol program would need to be performed for a minimum of 10 years to affect just the existing bird population. So when new birds continue to populate the area or take over abandoned nest sites more time is needed to try and achieve the population goal.

Another issue with these products is that they do not address the current problems the homeowner, business, or municipality is experiencing such as over browsing, fecal deposits, car and plane strikes, etc. When I deal with a property that has over 20 nesting pairs of geese, my clients are not looking at just the problems created with the goslings. Rather, they are looking at the problems 40 geese are causing and why they choose that property in the first place.

As with most things in life there is a time and place for everything. These products need viewed not as a solution to wildlife problems, but just as another tool that has it's time and place.

Eric Arnold, President
Bats, Birds, & More, Inc.

Who really wants to eat an animal that could have been natural but now has a foreign, new substance in its system. I like my deer natural and bulky. This way I know I am getting good quality meat since I shot the deer and know its habitat. Instead of a cow who could have been popping pills since the day it was weaned off its mother's milk.

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