Yellow journalism in Wall Street Journal pushing pesticide as “birth control” on wild horses?

Pm PZP Darts

Made with slaughterhouse pig ovaries PZP is dangerous to herd health

To:  Jacob Bunge, Wall Street Journal

Dear Mr. Bunge:  Regarding your article — They Shoot Horses (With Birth-Control Darts), Don’t They? — here are facts to correct the lies and disinformation you have been told.

Sting of the dart:  If it were only a sting!  Fact: Many wild horses develop an abscess at the dart-injection site.

Bogus ballooning population:  Wild horses are a slow-growth species when it comes to reproduction.  The gestation period lasts 11 months, and a mare produces just 1 foal.  While an independent study of BLM’s records confirmed an almost 20% birth rate, that study also found that 50% of foals perish before their first birthday.  Thus, the effective increase in population from new foals is just 10%.  But adult mustangs also die.  They succumb to illness, injury, and predation at a rate of at least 5% a year.  So, what is a normal herd-growth rate?  About 5%, probably less.

Fraudulent figures:  The Big Lie of “overpopulation” is the pretext for BLM’s war against the wild horses, and the wild horses are prisoners of that war.  It’s BLM’s version of the “Shock Doctrine,” wherein BLM concocted a phony crisis to push through policies antithetical to the Wild Horse Act against the will of The People.  There is no overpopulation except on BLM’s falsified spreadsheets.  Reviews of BLM’s population-estimates reveal biologically-impossible herd-growth rates.  For instance, in Utah, BLM claimed that the Conger herd grew from 156 horses to 285 horses in one year, an 82.7% increase, to which BLM tacked on another 20% by counting the unborn foals — the fetuses.  In Wyoming, BLM declared that the Salt Wells Creek herd grew from 29 horses to 616 horses in 6 months (yes, months), a 2,024% increase.  BLM’s “data” is chock-full of such preposterous growth-estimates.  So, when you hear talk of how the wild horses are reproducing “exponentially,” that’s a sure sign that BLM has falsified the data.

Wild horses are underpopulated:  Per the guidelines of BLM’s own geneticist, 83% of the herds suffer from arbitrary management levels (AMLs) set below minimum-viable population (MVP).  Low AMLs enable BLM to claim an “excess” in herds whose numbers, even if they were over AML, would still not reach MVP.  So being “over AML” is meaningless as well as misleading.  But the low AMLs, combined with falsified, biologically-impossible herd-growth estimates, give BLM an excuse to scapegoat those few wild horses for the range-damage done by the millions of livestock that overgraze the public lands.

Whose grass?  In fact, it is the livestock who are eating the wild horses’ grass.  Some background — the dedicated wild-horse habitats cover only 11% of BLM land.  Cattle are allowed to graze about 5 times that much, including within all but 4 of the wild-horse herd areas.  Yet in those official wild-horse habitats where livestock are given allotments, the mustangs are restricted to 18% of the forage while the cattle get 82%.

Bogus billion:  The wild horses being held in captivity are the “legacy” of former Secretary Salazar’s equid cleansing era, during which he had thousands of wild horses removed from the range.  However, the mortality rate of captive wild horses is about 8% a year.  So, obviously, since they are not reproducing, their numbers will steadily drop, showing that BLM’s billion-dollar figure for their care is just another Lie.  The Wild Horse and Burro program, if run per the minimum-feasible management-model specified by Law, would not cost much at all.  BLM does not lack for resources.  There are 22 million acres of legally-designated wild-horse herd areas — which BLM previously took away for expediency — that can be reopened as habitat.  The horses now held captive can be released to those areas, where the cost of their upkeep will be $0.

Adoptions:  Have not declined.  It’s just that BLM used to count sales-for-slaughter as “adoptions.”  Now, only “forever-family” placements qualify.  However, wild horses are not homeless horses.  They have a home — where they belong — on the range.

Persecuted predators:  Contrary to BLM’s disinformation campaign, wild horses do have natural predators — mountain lions, bears, wolves, and coyotes.  But those predators are persecuted mercilessly.  The government exterminates what the hunters don’t shoot.  However, the International Society for the Protection of Mustangs and Burros — Wild Horse Annie’s foundation — notes that even without predators, wild-horse herds self-regulate their numbers, with population-growth in the single digits.

Science and Conservation Center:  Is the manufacturer and distributor of PZP / ZonaStat-H.  Thus, its information is not impartial.  PZP is a registered pesticide that was approved by the EPA for use on wild horses and burros “where they have become a nuisance.”   However, PZP was registered without the standard testing requirements.  There is currently a lawsuit challenging the legitimacy of the registration, especially in light of studies that have disclosed PZP’s many adverse side-effects.

Shooting wild horses:  PZP is a potent weapon in BLM’s arsenal — for its biological warfare against the wild horses.  But birth control for wild horses is unnecessary because there is no overpopulation.  Why would we contracept herds whose population is inadequate for genetic viability?  Why would we contracept herds based on falsified figures?  Logically we wouldn’t and ethically we shouldn’t.  Further, if PZP were going to stop the roundups, it would have done so long ago for the Pryor Mountain herd, which has been darted with PZP for nearly two decades.  Yet roundups have been scheduled there like clockwork every 3 years and, in spite of intensifying the PZP treatments recently, BLM tried to implement yearly roundups until stopped by a Friends of Animals lawsuit.

PZP — the anti-vaccine:  PZP causes auto-immune disease.  PZP “works” by tricking the immune system into producing antibodies that target and attack the ovaries.  The antibodies cause ovarian dystrophy, oophoritis (inflammation of the ovaries), ovarian cysts, destruction of oocytes in growing follicles, and depletion of resting follicles.  The mare’s estrogen-levels drop markedly as PZP destroys her ovaries.  Ultimately, PZP sterilizes her.  Because PZP stimulates the immune system, it ironically works “best” — sterilizes faster — in mares that have strong immune-function.  Such mares respond to the anti-vaccine and produce quantities of PZP antibodies that destroy their ovaries.  But, conversely, PZP may not work at all in mares whose immune-function is weak or depressed.  Those mares fail to respond to PZP.  They keep getting pregnant and producing foals who, like their dams, suffer from weak immune-function.  So, the PZP pesticide works against the very horses that Nature has best equipped for survival-against-disease while favoring and selecting for the immuno-compromised.  Worse yet, radioimmunoassay tests indicated that PZP antibodies are transferred from mother to female offspring via the placenta and milk.

Health-risks to volunteers:  As for the well-meaning volunteers who dart wild horses, EPA’s Pesticide Fact Sheet for PZP advises that Personal Protective Equipment requirements include long sleeved shirt and long pants, gloves and shoes plus socks to mitigate occupational exposure.  EPA specifically warns that pregnant women must not be involved in handling or injecting ZonaStat-H, and that all women should be aware that accidental self-injection may cause infertility.  Unfortunately, PZP’s manufacturer has misrepresented PZP as “so safe it is boring.”   But research shows that PZP is a powerful hormone disruptor.  Further, consider the magnitude of the risk — the PZP-in-question is a horse-size dose.  If volunteers think PZP is safe, they will be less likely to protect themselves from this dangerous pesticide.  Indeed, please note that in the photo accompanying your article, Ms. Bolbol is not in compliance with EPA’s safety-precautions.  She is not wearing the required protective gear.

Mengelian experiments:  Now, BLM wants to perform diabolical sterilization experiments on these equine POWs to develop a Final Solution to the “problem”.  BLM is handing out $11 million for sterilization-studies.  The grant money is surely intended to buy loyalty and silence potential criticism from academia.  Plus, BLM, a corrupt agency, gets to cloak itself in respectability by affiliating with prestigious universities.

The ugly side of PZP is humane-washed by feel-good features that describe it with humor, sweetness and light.  However, the true story of PZP is one of scandal, whose deceit and danger — to both horses and humans — must be exposed.  That is the story that needs to be reported.


Marybeth Devlin

 Marybeth Devlin is a member of the Protect Mustangs Advisory Board and a member of the Alliance for Wild Horses and Burros
This mare waits in the alley before being led into the chute where her age and body condition will be checked. After being treated with the PZP fertility control agent, this mare will be released back to the Owyhee HMA.

This mare waits in the alley before being led into the chute where her age and body condition will be checked. After being treated with the PZP fertility control agent, this mare will be released back to the Owyhee HMA.

Protect Mustangs is a 501c3 nonprofit organization who protects and preserves native and wild horses.

Groups who want Pesticide PZP used on America’s last wild horses


According to a press release by Return to Freedom Sanctuary, who seems to have received money from the BLM in the past, the following groups want to use PZP on wild horses:

Alliance of Wild Horse Advocates

American Society for the Prevention of Cruelty to Animals

American Wild Horse Preservation Campaign

Animal Legal Defense Fund

Animals Voice

Animal Welfare Institute

Black Hills Wild Horse Sanctuary

Center for Animal Protection and Education

Citizens Against Equine Slaughter

The Cloud Foundation

Corolla Wild Horse Fund

Friends of a Legacy

Front Range Equine Rescue

Habitat for Horses

Hidden Valley Wild Horse Protection Fund

Horses for Life Foundation

Humane Society of the United States

Jicarilla Mustang Heritage Alliance

Least Resistance Training Concepts

Lifesavers Wild Horse Rescue

Montgomery Creek Ranch

National Mustang Association, Colorado Chapter

Oregon Wild Horse & Burro Association

Photographers for the Preservation of Wild Horses and Burros

Pine Nut Wild Horse Advocates

Respect 4 Horses

Return to Freedom Wild Horse Sanctuary and Preservation

Salt River Wild Horse Management Group

Serengeti Foundation

Southern Sun Farm Sanctuary

Steadfast Steeds

Virginia Range Wildlife Protection Association

Wild Equid League (Colorado)

Wild Horses of America Foundation

Wild Horse Connection

Wild Horse Education

Wild Horse Observers Association

Wild Horse Preservation League

Pm PZP Darts


PZP = Slow Extinction


Don’t let yourself be fear mongered. Read the Science Against PZP:

The Fact Sheet on PZP:

PZP is Dangerous:


PM No Evidence Overpopulation

Protect Mustangs is an organization who protects and preserves native and wild horses.

Marybeth Devlin speaks out against PZP

Pm PZP Darts

Marybeth Devlin responds to PZP SPIN in High Country News titled: PZP: Where hope, science and mustangs meet

Ms. Wilder is disinformed. PZP does not “cause eggs to reject sperm.” That hypothesis has been disproved. PZP is a registered pesticide whose mechanism-of-action is to cause auto-immune disease. PZP tricks the immune system into producing antibodies that target and attack the ovaries. PZP’s antibodies cause the mare to suffer ovarian dystrophy, oophoritis (inflammation of the ovaries), ovarian cysts, destruction of oocytes in growing follicles, and depletion of resting follicles. Not surprisingly, estrogen levels drop markedly as the ovaries are slowly destroyed. But PZP’s adverse effects are not limited to the individual animal. As a recent study — which included the Little Book Cliffs, Colorado herd and the McCullough Peaks, Wyoming herd — found, PZP extends the birthing season to nearly year-round. Out-of-season births put the life of the foals and the mares at risk. Further, the same study disclosed that the pesticide causes a delay lasting 411.3 days (1.13 years) per each year-of-treatment before mares recover their fertility after suspension of PZP. However, some mares never recover — they are left permanently sterile, and quickly too. Indeed, yet another study found that sterility could occur in some mares from just three years of PZP injections or from just one treatment if the pesticide were given to a filly before she reached puberty. Because PZP messes with the immune system, it ironically works “best” — sterilizes faster — if the mare has a strong immune system. But, conversely, PZP may not work at all in mares whose immune function is weak or depressed. So, the pesticide discriminates against the very horses that Nature has best equipped for survival against disease while favoring and selecting for the immuno-compromised. Worse yet, tests performed via radioimmunoassay indicated that PZP antibodies are transferred from mother to young via the placenta and milk. The transferred antibodies cross-react with and bind to the zonae pellucidae of female offspring, as demonstrated by immunofluorescent techniques.

But there is no need for PZP or any other population-reduction measures. BLM’s wild-horse overpopulation “data” is a fraud. Reviews of BLM’s year-to-year growth-estimates for various herds disclosed biologically-impossible growth-rates. For instance, just recently in Oregon, BLM claimed that the famous Kiger herd’s population grew from 21 horses to 156 horses in just four years — an increase of 643%. Stealthily inserting bogus birth-rates into the data, then wrongly equating the birth-rate with the population growth-rate, and failing to factor in the mortality-rate — that is how BLM creates the false impression of a population-explosion. Another ruse BLM employs is restricting maximum herd-size below minimum-viable herd-size. Then, whenever a herd is made to appear — via false figures — to exceed the arbitrary management level, BLM screams “excess!” and declares an immediate need for mass-removals and sterilizations. It should be noted that more than 70% of the herds are “managed” below minimum-viable size, including Spring Creek Basin.

PZP Pushers are misleading the public as there is no evidence of overpopulation

PM PZP Auto-immune disease

PZP = Slow Extinction

While touted as a “vaccine,” porcine zona pellucida — PZP — is actually a perversion of a vaccine — an anti-vaccine — whose mode-of-action is to cause auto-immune disease. PZP tricks the immune system into producing antibodies that attack the ovaries, inducing ovarian dystrophy, oophoritis (inflammation of the ovaries), and ovarian cysts. Worse yet, per radioimmunoassay, the PZP antibodies are transferred from mother to young via the placenta and milk. The antibodies cross-react with and bind to the zonae pellucidae of female offspring. Although hyped as a “non-hormonal” method of birth-control, PZP causes estrogen-levels to plummet as the ovaries degenerate. Despite the manufacturer’s claim that PZP is “reversible,” its effects wear off unpredictably. In herds under PZP “management,” the birthing season extends to nearly year-round, putting the life of the foals and mares at risk. Because PZP messes with the immune system, it “works” best on the healthiest fillies and mares — those with strong immunity — ironically, rendering them sterile even with just a few treatments. Filles injected with PZP before they have reached puberty are particularly vulnerable to immediate sterilization. Conversely, PZP has little-to-no effect on fillies and mares with a weak immune system — they continue to become pregnant. Thus, a herd being treated with PZP is undergoing selective breeding for low immunity, which puts the population at risk for disease — and ultimately, extinction. ~Marybeth Devlin, member of The Facebook Forum on PZP for Wild Horses and Burros.

PZP = Slow Extinction

Alarm over behavioral and physiological side effects of wild horse birth control (PZP)




Cassandra M.V. Nuñez

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey


The advent of immunocontraception with porcine zona pellucida (PZP) has all but revolutionized wild horse management, providing a more humane method of population control than earlier strategies. Early studies on Assateague Island National Seashore have described it as an ideal form of fertility control in that it reduces the chance of conception to below 10%, can be delivered remotely, is reversible (after short-term use), lacks debilitating physiological side effects, cannot pass through the food chain, and shows minimal effects on social behaviors. However, recent research in other populations has revealed behavioral and physiological side effects of long-term PZP use. These results indicate that studies from one population may not necessarily be applicable to another, regardless of similarities in habitat and population structure. Careful study of the animals’ demography, physiology, and behavior is necessary prior to and during treatment to ensure that a) the potential effects of PZP can be assessed accurately, and b) within managerial constraints, PZP effects are ameliorated as much as is possible. Here I explain the history of PZP use in wild horses, its side effects on the horses of Shackleford Banks, North Carolina in comparison to other populations, and offer management suggestions based upon wild horse biology and behavioral ecology, which may minimize or prevent these side effects in other populations.

Read the full article here: PM Nunez 2010 management of horses with PZP


Posted for educational purposes only