of the plant left to identify. In the late spring and 

 summer, when the island's vegetation is the most 

 lush, too much green can make it difficult to 

 decipher specific plants. 



Staring through their binoculars, volunteers 

 watch as the ponies' lips sift through tufts of 

 seemingly indistinguishable plants to eventually 

 bite off something close to the ground. At first, 

 their rummaging seems random. After a while, a 

 certain level of meticulousness is apparent — the 

 ponies are after specific vegetation, but what are 

 they getting from it? 



Nutritional Mystery 



The main source of energy and nutrients in 

 a horse's diet comes from roughages, whether it 

 is in the form of grasses or hay, Yoder explains. 

 Research on domestic horses also shows that 

 mineral ratios play an integral role in optimum 

 health. If these ratios are too uneven, the body 

 cannot use nutrients properly. Take copper and 

 iron. Copper, along with zinc and vitamin D, is 

 tied direcdy to bone development in growing 

 animals, Yoder explains. 



"If we have an extremely high percentage 

 of iron in the diet, then that can bind copper," he 

 says, making the latter mineral unavailable for the 



body. Low levels of copper can cause abnormal 

 tendon and ligament development, he adds. 



Commercial feed companies serving North 

 Carolina markets are aware of our iron-rich soils 

 and supplement their products for domestic 

 horses, says Yoder. But commercial grains are 

 something the Shackleford ponies have never had, 

 and will never have. And that makes researchers 

 wonder whether the wild herd is surviving — and 

 apparently thriving — on different mineral ratios. 



"For these weanlings and yearlings on the 

 island, you'd like to think that they're getting 

 enough nutrients for normal development," Yoder 

 says. "Apparently, they're getting at least the bare 

 minimum, because they seem to be getting along 

 reasonably well." 



Study samples are analyzed for 10 to 12 

 different minerals, according to Yoder. In addition 

 to copper, iron, zinc and selenium, Yoder pays 

 special attention to calcium and phosphorous. 



"We know that with [domestic] horses, we 

 should always have two parts of calcium for every 

 one part of phosphorous in the diet," he says. 



If the diet doesn't provide enough calcium, 

 the body obtains it from the bones, which can lead 

 to brittleness and skeletal abnormalities. 



"If we don't see that [mineral ratio] in a wild 



situation like Shackleford Banks, that would lead 

 us to believe the ponies are functioning just fine 

 on different ratios," Yoder says. 



Could such ratios be why the Shackleford 

 horses look so different than their larger, more 

 proportional and carefully bred domestic 

 cousins? That, in combination with their 

 ancestor's genetic stock, might be a small part 

 of it, says Yoder. But there is so much about the 

 herd and its history we will never know. 



"These animals have been out here for who 

 knows how many generations," he says. "And 

 what Mother Nature has created is an animal that 

 she can sustain on this island." 



At the end of the day, when their coolers 

 are filled with plant and dung samples, the 

 volunteers trek back to the dock and wait for 

 their ride home. Tomorrow, their knees and 

 lower backs will be sore from crawling on the 

 ground to pick at tiny pieces of grass. But a few 

 short-term aches may lead to important long- 

 term knowledge of this fascinating herd. 



'It's going to give us a better idea of how 

 the ponies are surviving," Stuska says of the 

 study's significance. "It will show the uniqueness 

 of the wild horses in their adaptation to barrier 

 island living." □ 



Coastwatch I Early Summer 2006 I www.ncseagrant.org 1i9 



