Pioneer of PZP birth control in wild horses dies at 75

Dr Jay Kirkpatrick
Dr Jay Kirkpatrick. ©

Dr Jay Kirkpatrick, a pioneer of fertility control as a way to manage populations of wild horses, bison and urban deer, has died at the age of 75.

Kirkpatrick passed away on December 16 from a short but serious illness.

He was a leading figure in the use of the birth control vaccine porcine zona pellucida (PZP).

Kirkpatrick was the founder and director of the Science and Conservation Center in Billings, Montana, which produces PZP on a not-for-profit basis for use worldwide. It also trains volunteers in how to administer PZP.

His work presented an alternative to roundups, relocations, surgical sterilization and the culling of wild horses, bison, deer and elephants. His research in the field was published in many journals.

The use of PZP in wild horses has been controversial. While many volunteers and advocates have worked with him, believing birth control to be a sensible and humane way of managing wild-horse populations, others have opposed its use, saying they were worried about its long-term effects on the reproductive health of mares, and its influence on herd dynamics.

The Science and Conservation Center, in a letter last week, said Kirkpatrick had been the face of the wildlife fertility control endeavor for the past 45 years.

“He will be sorely missed in more ways than we can count,” its chief operating officer, Kimberly Frank, said.

“In a larger sense, however, the very effort and successful paradigm that he helped to create and build is alive and well.

“The Science and Conservation Center remains active and continues to produce and carry out the quality control for the PZP vaccine, distribute it, maintain the database, and train field personnel to deliver it effectively. In short, our operation and progress continues to move forth.

“We expect operations to go on as usual, for wild horses, urban deer, captive zoo animals, bison and with the collaboration of our African friends with regard to elephants.”

She said the loss of a key person in any endeavor was always a difficult transition, but it had been preparing for all sorts of contingencies for quite a few years.

“Perhaps the greatest tribute we can pay to Dr Kirkpatrick, is to continue this valuable work on behalf of our struggling wildlife in a seamless manner.

“Despite this tragic but temporary setback, we remain steadfast in providing the purest form of the porcine zona pellucida vaccine and facilitating its use in wildlife …”

The center produces about 3500 doses of PZP each year. Manufacturing the drug is a laborious and time-consuming process which must be done by hand.

Kirkpatrick grew up in rural Pennsylvania, where he had a pet crow and dozens of snakes.

He worked as a park ranger before a career in science beckoned, becoming an acknowledged international expert in animal contraception. He was, as he once put it, “there in the beginning”.

His foray into the field began more than four decades ago. Kirkpatrick was an assistant professor of physiology at Montana State University in Billings at the time.

Two cowboys knocked on his door, introduced themselves, and asked whether horses could be stopped from reproducing. The recently introduced Wild Free-Roaming Horses and Burros Act had recently been introduced, which ruled out culls as an option for controlling numbers.

Kirkpatrick was a pioneer in the development of PZP, and spent a good deal of time trying to convince federal authorities to use it on wild horses.

His efforts have gained traction in recent years, with worrying numbers of wild horses now held in captivity and budgets stretched paper-thin to pay for their ongoing care. Serious questions have also been raised over the sustainability of ongoing roundups to keep numbers in check.

Last year, the Bureau of Land Management gave PZP and PZP-22, which is a longer-lasting version, to 384 mares, and is looking more closely at mounting wider contraception programs.

Kirkpatrick’s Science and Conservation Center has supplied PZP for use on tribal lands and several sanctuaries. Some has been used for similar purposes overseas.

There is growing recognition of the potential of contraception as a means of controlling animal populations, and Jay Kirpatrick was “there in the beginning”.

He said in an opinion piece late last year: “Wildlife fertility control is here to stay. It will progress faster in some situations and with some species than others, but it will no longer go away.

“As new and open-minded personnel step into management organizations, public or private, attitudes have been changing.

“As the human population grows, wildlife populations face greater constrictions and challenges. Our responsibility to effectively and humanely provide stewardship becomes an imperative for the civilized mind.”

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