Rabbit Advocacy Animal Matters

 

Birth Control for Animals 

A scientific approach to limiting the wildlife population explosion
By Rebecca Boyle 03.03.2009
popsci.com

“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.

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."

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."

Comment:  Should we be interfering?  Do we have the right to reduce other species’ populations?  What about reducing our own?

Scientists investigate critter contraceptives

Meg Marquardt, Science News Examiner
March 7, 2009

Here's some strange weekend news for you: wildlife scientists are investigating a way to control exploding animal populations with birth control.

That's right: critter contraceptives.  It is odd to think of conservationists wanting to limit the population of animals, but the intentions are good.  Certain species in North America are out of control, such as Canadian geese, deer, and (if my backyard is any proof) rabbits.  Such an overpopulation is starting to strain the environment, not to mention causing public safety issues with the rise of deer-related car accidents, not to mention plane accidents such as the recent Hudson River incident that involved geese in the plane's engines.

According to the Popular Science article, the overpopulation is the fault of humans who overcompensated.  "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."

The hope is that these populations can be controlled in a peaceful manner instead of mass executions outside of hunting seasons.  So, unusually, scientists are turning to contraceptives.  Animal birth control was an accidental discovery in the 1950s when Merck created a drug, nicarbazin, to protect chickens from a fatal disease which had the odd side effect of non-hatching eggs.  "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,'" said Erick Wolf, who worked on the nicarbazin project. 

From there it snowballed.  Contraceptives now range from the daily ingestion of a commercialized form of a nicarbazin-like drug for geese to a vaccine that prevents deer from ever entering their reproductive cycle. That vaccine, GonaCon, is still in the testing phase, but so far there have been no adverse effects.  And Dr. Kathleen Fagerstone, research program manager at the National Wildlife Research Center in Fort Collins, CO said, "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."  [Popular Science] The best part about GonaCon is that "it doesn't require a booster shot, unlike most other vaccines, and one study showed it prevented pregnancy for up to five years."

However, there are those that think contraceptives aren't the only way to go.  "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."

And I'm sure there are still others who disagree with both points of view.  It can be safely assumed that in very little time, environmental scientists and activists who are concerned with human intervention in the natural reproductive cycle of animals will join those who are avidly against hunting as a form of population control.  And who knows, they may be right.  After all, as stated before, birth control is in response to devastating hunting that nearly wiped out the animals in the first place.  This may just be the continuation of the same conservation-cycle nightmare.

But any way you look at it, birth control for animals is a strange bit of science.

More on animal birth control 

Review of contraception in ungulate species  
AZA Wildlife Contraception Centre, St. Louis Zoo, Missouri & White Oak Cons. Centre, Yulee Florida 

Most ungulate species are herd animals. In captivity, and increasingly so in the wild, space constraints limit natural behaviors associated with group dynamics, possibly resulting in inbreeding and/or overpopulation. This situation has necessitated research regarding contraception of various species of hoofstock. Differing management situations mandate different contraception protocols to achieve optimal results. Fertility control in hoofstock has been achieved through a number of different contraceptive methods predominantly surgical sterilization, mechanical contraception, synthetic steroid hormones, and immunocontraception. In this study successes and limitations of these techniques are reviewed. Zoo Biol 26:311-326, 2007 Wiley-Liss, Inc. 

Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin  
CSIRO: 7 March 2006 Wildlife Research Management and Conservation 

Effects on reproduction, an excerpt: 

Eastern grey kangaroos are widespread on the east coast of Australia and frequently reach high densities in reserves and parkland near urban areas. Management of these populations is highly contentious and non-lethal fertility-control technologies are sought as an alternative option to manage population size. 

This study has demonstrated that slow-release deslorelin implants can successfully inhibit reproduction for extended periods in the female eastern grey kangaroos. This approach may have potential application in reproductive management of problem kangaroo populations.

April 2010 Dr. Donal Skinner, University of Wyoming, has remarked that injection of a hormone called deslorelin could potentially control the UVic rabbit population. According to Dr. Skinner, deslorelin injections were used to control the coyote population in Wyoming. Dr. Skinner has continued to research deslorelin use with other animals, including rodents. If deslorelin stops the production of sex hormones in rabbits for a period of time, usually two years, then it may render rabbits infertile for their reproductive life span. A tag and release program with a single dose of deslorelin administered in the wild (not in a lab) could control the rabbit population at UVic while keeping administrative costs down.

Pigeons On The Pill? HSUS Explores New Ways To Reduce Bird Populations 

Care2 May 10, 2010  

If someone asked you to name three things that set life in a big city like New York or Chicago apart from other urban environments, what would you say?

Most lists would probably resemble mine:
1. Traffic 2. Noise 3. Pigeons

Semi-domesticated animals (think: grey squirrels, starlings, and ducks) are attracted to big cities for obvious reasons (think: food, food, and food), but because they carry disease and have a tendency to congregate and deficate in public places, it's important to keep their populations under control.

A large part of the Humane Society's work as a national organization is to resolve conflicts between humans and wildlife in non-lethal ways, which is one reason they support the use of birth control technologies, as a means of humanely controlling animal populations.

Successful chemical contraceptives (products that prevent fertilization) and contragestives (products that prevent gestation) have already been developed for a variety of species, including elephants, brown bears, kangaroos, and even koalas.

Most recently, the concept has been applied to the control of bird populations, including geese, ducks, and pigeons, with the development of OvoControl-a kibble bait that uses the compound nicarbazin to effectively reduce egg hatching rates.

Although it might appear that OvoControl would have only positive effects for urban environments, it's important to remember that just like human oral contraceptives, there is an issue with what happens to them after passing through the bird's body.

Human birth control hormones like estrogen are turning up in our drinking water supply, and researchers have found evidence that "even extremely diluted concentrations of drug residues harm fish, frogs and other aquatic species, and have been shown in labs to impair human cell function."

With their free-wheeling ideas about when and where they can relieve themselves (think: everywhere), it's important to question whether feeding large amounts of chemical contraceptives to wild birds could exacerbate this issue.

Until quite recently, OvoControl was only available for use by licensed pesticide applicators, and though the Environmental Protection Agency did issue an approval for OvoControl for pigeons, they've been known to let some toxic pesticides slip through the cracks in the past.

For now, Nicarbazin (the active ingredient in OvoControl) does not appear to  bio-accumulate in the animals or the environment. Once in the environment, the compound binds to soil particles and breaks down over time.

It is reassuring to know that OvoControl has no effect on mammals, reptiles, insects or anything else that might accidentally consume it, and because its rooftop feeding system is designed to only attract flock-feeding birds like the pigeon, it is highly unlikely that it will have unintended effects on songbirds or other likeable flying species.

More news: Answers to Frequently Asked Questions About Wildlife Applications for SpayVac