How Wild Horses Came To Be Animal Empires 106

Assateague is a barrier island running parallel to the east coast of the United States, from Maryland to Virginia. It's a narrow strip of sand and sediment almost 60 kilometers long. Another island with another species gone wild. Horses. Assateague's horses have free reign over the island's open meadows. Worldwide, the population of domestic and feral horses is estimated to be 58 million, with over 9 million in the United States alone. There are so many horses in the U.S. that if they were to form their own state, it'd be the 11th most populous in the country. Prior to their domestication, horses roamed the open plains and grasslands of the Eurasian steppes from Ukraine to Mongolia. First domesticated as a food source, humans eventually realized that tame horses made great workers. Over thousands of years, people brought horses with them across the globe, just like pigs and donkeys. Assateague Island's horses have been here since before the American Revolution. But how they got here is a mystery. Some say that the horses arrived when two Spanish galleons crashed into the island during the 1500s. Others believed that early colonizers stashed the horses on the island to avoid paying livestock taxes. Regardless of how they arrived, they've been roaming free for over three centuries. Today, 300 horses live on Assateague. Horses instinctively form herds like this one to protect one another and act as lookouts. Feral horse herds are often called bands. The bands are led by a dominant stallion. He's the herd's protector and enforcer of the band's rigid hierarchy, leading a harem of up to eight mares. In addition to a dominant stallion, every band has a lead mare, like this white horse. She decides where to graze and when to go find water. Horses are prey animals. They grow anxious and flighty when alone, even here where there are no predators. The company and hierarchy of the band keep everyone feeling secure. With winter on its way, this horse has begun shedding dead hair and growing in a thicker coat. The horse's pituitary gland recognizes the shift in daylight hours and produces a hormone that triggers the increased hair growth. It's an itchy process for the horse. Horses need to keep their coat well-groomed all year. It regulates body temperature and protects against the elements. Horses also produce pheromones that make it possible to identify other herd members from as far as 120 meters away. Of course, there's always an itch that you just can't reach without a little help. When animals clean each other, it's called allo-grooming. It's a sign of an intense bond between horses. The more horses an individual grooms, the higher her social status is within the herd. Scientists have even found that mares, who are the most gregarious groomers, also produce the most offspring. Horses spend between 15 and 17 hours a day grazing. Horses here eat the grasses that grow in the salt marsh or on the beach. This diet is high in salt content, so the horses drink twice as much water as other wild horses. All that water makes them bloated. The grasses are also low in nutrients, so the Assateague horses are shorter and stockier than other breeds. Adult horses eat 21,000 calories each day. Grazing the grass and trampling the field takes an enormous toll on the island and increases erosion. With no natural predators to control the population, these horses can eat themselves out of house and home. The sand that makes up Assateague Island's beaches comes from the ancient eroded rock of the nearby Appalachian Mountains. Waves pounding against the shore move the sand and keep this barrier island in a state of constant flux. But man-made barriers also shape life on this island for both people and horses. A state border runs across the island, separating it into two parks. The northern section of the island is Maryland's Assateague Island National Seashore. The southern part is in Virginia, where the horses live on the Chincoteague National Wildlife Refuge. A fence separates the two parks and divides the island's horses into two distinct herds. This is one of the Maryland horses. Now in his fourth year, he's just beginning to reach sexual maturity. He's on his own. The leader of his band, probably his own father, chased him away when he got old enough to become a threat to the stallion's dominance. For horses, this is an instinctual prevention against inbreeding. Stallions form their own band by drawing in females that have also been cast out, or by attracting a mare that's left her band to give birth. The Assateague Island horses are one of the few wild roaming herds in the United States. They're the subjects of ongoing studies by scientists striving to understand the secrets of wild horse herds. They found that individual horses form close bonds with each other, but these relationships are so prone to fallouts that researchers have compared life in the herd to a soap opera. The horses' reign on Assateague Island faces a similar set of threats as the empire on Bonaire. The horses are drawn to the rich grasses on the side of the road. Humans are drawn to the majestic horses. It's a dangerous and potentially deadly combination. Since 1982, traffic accidents have killed 29 horses on the island. But the horses themselves may be their own worst enemy. By pulling up the grass, the hungry horses are weakening the island's foundation. This salt marsh is regularly flooded by the tides. Assateague is a barrier island, and like all barrier islands, it's made from sand. The grass is the glue that keeps the island from washing away. When this area was made a national park in the 1960s, there were only 28 horses living on the Maryland side of the island. A nor'easter had decimated their numbers, and the park sought to protect the small herd. By 1997, the herd's numbers had risen to 165, and the park faced the opposite problem. The horse population was too high. To protect the horses and their home, the United States National Park Service put in place a plan to control the population. Most of the female horses on the Maryland side of the island are now on birth control. Mares who have given birth at least once are shot with a dart gun, containing a state-of-the-art equine contraceptive. For the first few years of the program, the population continued to grow. But officials were patient, and in 2014, the Maryland's horse population dropped to a sustainable 100 horses, with no call or relocation necessary. The female horses that receive the contraceptive even live longer, because they're spared the stress of pregnancy and nursing. The future of the Maryland horses has been secured. On the Virginia side of the island, the horse's appetite poses the same threat to the island's foundation. But officials there are trying a different solution to manage the population.