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Assuring a Wild Future for Assateague Island Horses

The Humane Society of the United States

by Andy MacAlpine

Wild horses attract countless tourists to Assateague Island every year, each hoping to see some of the storied herd grazing in the distance or sauntering through a campsite.

Smaller and typically more people-friendly than wild horses on the western ranges of the United States, the Assateague horses have tolerated the harsh conditions shaping this windswept island where Virginia meets Maryland at the edge of the Atlantic for almost 350 years.

But as these horses multiply—from 21 horses counted in 1965 to 125 today—and run out of space, the herd and the island are both at risk.

Fortunately, there is a solution.

A Plan Conceived

After surveying the horse-related damage to island resources, including habitat for other animals, the National Park Service released an Environmental Assessment in May 2008, concluding that the herd needed to be reduced. The government outlined four strategies for bringing the population to between 80 and 100 horses in a timely manner.

An early favorite seemed to be a "one-time capture and removal" consisting of an—unavoidably—stress-filled roundup of between 15 and 30 horses and their transfer from their island home to an adoption program or horse sanctuary.

The Humane Society of the United States lent its voice to the process in favor of a more humane alternative: contraception.

In early 2009, the park service agreed and effectively spared dozens of horses the risky long-distance journeys to bewildering, and perhaps dangerous, new environs.  It will take between five and eight years to reduce the Assateague herd through birth control, but biologists concluded the outcome would be successful.

"It's the best outcome for keeping a free, wild and sustainable population," says John Grandy, Ph.D., a biologist and The HSUS' senior vice-president for wildlife and habitat protection.

Humane Solution

The Assateague Island decision underscores an emerging trend that deserves greater acceptance—the humane management of wild animals. The HSUS is a global leader in encouraging the use of proven contraceptive means as an alternative to culling, relocation or confinement.

Assateague has been a proving ground for such techniques. In 1988, a team led by Jay F. Kirkpatrick, Ph.D., the director of The Science and Conservation Center of Billings, Mont., introduced the use of porcine zona pellucida immunocontraceptive vaccine to the island.

Funded in part by The HSUS, the pilot project was so successful that the park service began to utilize PZP—a natural protein that blocks fertilization—as a population management tool in 1994.

Now unencumbered by annual pregnancies, the island mares are living longer than ever—some have even seen the ripe, old age of 30 years. This has allowed for natural family units to remain intact, and made it possible for visitors to catch an exceedingly rare glimpse of mothers, grandmothers, and even foals grazing together.

"I would call this [decision] a success because it takes another important step forward in the evolution of our management program for the feral horse population," says Carl Zimmerman, acting superintendent of the Assateague Island National Seashore. "We're committed to taking care of that population."

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