This might make you wonder, could tourists also be considered an invasive species?
SOURCE: The Star Democrat
Park Service reduces Assateague horse herd to 100
By JEREMY COX The Daily Times of Salisbury
BERLIN (AP) — Technically speaking, horses are as foreign to the sands of Assateague Island as phragmites, the reedy marsh plant that covers hundreds of the barrier island’s acres.
The National Park Service accuses both invaders — calling them out on an agency website from among a host of invasive species on Assateague — of inflicting “significant impact” on native plants and animals.
For its ecological crimes, phragmites have been marked for eradication. Park managers remove them by hand or spray them from the skies with a potent weed-killer designed for aquatic pests.
By comparison, the feral horses are treated with kid gloves. Twenty years into its horse-control program on the Maryland side of the island, the park service can claim victory. This year, the agency reached its goal of reducing the size of the herd to no more than 100 horses.
In response, biologists with the Assateague Island National Seashore are shifting strategies, taking steps to ensure the horses’ numbers remain stable instead of continuing their decline. If all goes according to plan, horses will be part of the island’s landscape for generations to come.
This week, the island’s other group of horses will take its place in the spotlight once again during the Chincoteague Volunteer Fire Department’s Pony Swim. For the 89th year, “saltwater cowboys” will gather the 150 “ponies” they own on the Virginia side of the island and swim them across the channel to Chincoteague, where the foals will be sold at auction.
There will be no Phragmite Festival. If there were, it would be a first.
The disparity in treatment between horses and phragmites demonstrates that land managers don’t always do what’s strictly best for nature. Sometimes, tradition trumps science.
“Everything has an impact,” said Jay Kirkpatrick, a Montana-based researcher who has studied Assateague’s horses for nearly three decades. “Three white-tailed deer will have an impact on the island. The issue is because the park service’s mission is wider, the question you have to ask is, ‘What is an acceptable impact?’”
Such considerations were almost surely not on the minds of European settlers when they introduced horses to the 37-mile-long island in the late 17th century. The arrangement enabled the horses’ owners to shirk taxes and fencing laws.
Over time, the horses adapted to the island’s harsh environment. Adjusting to the nutrient-poor diet of marsh grass, they shrank in stature to the size of ponies. They became like camels, drinking twice as much water as the typical horse to offset their salt intake. Their midsections grew plump and round.
Their shorter legs proved advantageous for navigating the island’s soft, unpredictable terrain, as well. A rangy thoroughbred would probably break a leg trying to hoof it among Assateague’s bogs and sugar-sand shores.
In modern times, the “Chincoteague pony” became recognized as a distinct breed, valued for its hardiness and easiness to train.
In all, about 250 horses live on the island. But since 1968, the population has been bisected by a barbed-wire fence running the length of the Maryland-Virginia border on the island.
The Virginia horses live in large “grazing compartments” in what is known as Chincoteague National Wildlife Refuge. Their fire department owner pays the federal government $1,500 a year for grazing rights.
Their cousins in Maryland, on the other hand, are owned by the park service.
They run freely, sometimes too much so. They’ve been known to raid campsites and beach blankets for food. Other times, humans are to blame, risking a nasty bite or trampling for the sake of a photo op.
Keeping horses on the island involves environmental concessions, park officials concede.
“We have plenty of vegetation to support a lot of horses,” said Allison Turner, a park service biological technician who has been working among the horses for years. “But it would destroy the natural barrier island habitat. What we’d have is just a horse farm.”
When the park service first took control of the Maryland portion of the island, it had just 28 horses. Like phragmites, their numbers multiplied — by 10-15 percent a year, to be exact.
The environmental damage seemed to grow at a similar rate.
The horses, being horses, compacted the soil beneath their hooves. Native fiddler crabs can’t burrow into overly trampled sand. And shorebirds, including the federally listed piping plover, found their nests at risk whenever the horses sought refuge from the biting flies on the bay side of the island in the summer.
The horses also ate just about everything green in sight.
That was bad news for a classification of birds known as rails, which depend on high marsh grass for resting and feeding. Park officials were so concerned about the potential effects on one endangered plant, the seabeach amaranth, that they began placing wire mesh cages around them to keep hungry horses at bay.
One of Turner’s jobs is to count as many horses as she can every other month. By last Tuesday, her July survey had found every Maryland horse except two: N9BO, an aging mare, and N6BKOS-H, a 5-year-old stallion.
She and Kelly Taylor, the park’s science communicator, followed a set of unreliable tire tracks down the beach in a park service pickup last Tuesday toward the last-known location of the pair.
A couple miles from the Virginia border, Taylor steered the truck down a bumpy path into the marsh, halting at a watery “gut” surrounded by lush, green marsh.
“This is one of the areas back in the day that was pretty heavily grazed,” Turner said. “It’s coming back pretty nicely.”
That comeback is one of the most surprising legacies of the park service’s horse-control efforts.
By the mid-1980s, land managers resolved to do something about the growing horse population. From media reports, they heard about a researcher out West who was experimenting with innovative methods of controlling the region’s exploding herd sizes.
For its part, Assateague offered Jay Kirkpatrick as perfect of a laboratory as he was going to find. Unlike the vast landscapes of the West, the skinny island reined in the horses, allowing them to be studied more reliably.
At first, he tried injecting steroids into the stallions to reduce their fertility. When that didn’t work, he tried it on the mares, but it had the opposite of the desired effect. Within the first year, every one that received injections got pregnant.
“They didn’t give up. They didn’t throw us off the island and tell us to go away. They said, ‘What else do you have up your sleeve?’ “ Kirkpatrick recalled.
Finally, in the third year, he settled on a vaccine for the mares that proved 95 percent effective at preventing foaling. Beginning in 1994, land managers used a dart gun to inject all of the female horses on the Maryland side with the vaccine.
Initially, the horse population continued to climb as the mares, freed from the stress of near-constant foaling, began to live into their 20s and 30s. But since reaching a high of 175 in 2001, their numbers have been steadily dropping.
This year, a major milestone was reached when the population fell to 100. Although it was short-lived — the birth of a foal bumped it back up to 101 — it was the first time the park service achieved its goal set in 2008 of maintaining a herd of 80-100 horses.
Turner said the park service is seeking to stay around 100 horses to provide some insurance against catastrophe, such as a major storm washing over the island. Keeping any fewer than 80 horses might lead to inbreeding, jeopardizing the herd’s future, the park service has determined.
For the past five years, she has stopped darting mares that haven’t gotten pregnant for at least seven consecutive years. Their infertility is likely permanent, she said.
For the first time, the park next year will enter an “adaptive management” stage — deciding how many fertile mares to dart based on the results of this fall’s pregnancy tests and the number of foals born this year.
Kirkpatrick has used the lessons learned on Assateague to apply his contraceptive methods around the world. The porcine zona pellucida, or PZP, vaccine has been used at 15 game parks in Africa, 250 zoos worldwide and elsewhere, he said.
“It’s a remarkable thing what they accomplished there” at Assateague, said Kirkpatrick, director of the Science & Conservation Center at ZooMontana in Billings, Montana.
Such an effort almost certainly wouldn’t have been expended for another non-native species.
Then again, the progeny of the North American horse is a matter of debate.
Officially, the park service has designated the horses as a “desirable feral species.” That opinion echoes the federal Bureau of Land Management in the West, which views North America’s horses as an invasive species and manages them as such.
Back on Maryland’s shore, “as far as we’ve been able to ascertain, horses were not part of the old Assateague,” said Jack Kumer, a wildlife specialist based at the park.
Scientists agree that North America’s horses died out about 11,000 years ago. But before they did, they migrated across a land bridge into Asia and eventually into Europe. The Spanish reintroduced them in the 16th century.
After that, things get murkier. Can a reintroduced species still be considered a native? Various groups, from the Park Service to the Wildlife Society, see today’s horses as outsiders. But many others, including Kirkpatrick, don’t.
“The genetics say this is the horse that originated here and was brought back here,” he said.
In June, two wildlife advocacy groups petitioned the U.S. Fish and Wildlife Service to have the horse listed under the Endangered Species Act because of encroaching development and the effects of government-led roundups.
On Assateague, they are protected for a different reason, Kumer said.
“In a sense, they represent early colonial North America,” he said. “The park service looked back and was sensitive to how do the people live within the park. How do they view that landscape?”
The answer was — and remains — obvious: with horses.
Information from: The Daily Times of Salisbury, Md., http://www.delmarvanow.com/