The total population of the Maryland herd is currently at 76 horses, including 21 stallions and 55 mares. Three aged mares, N6BK (“Bessy Twister”), N6H, and X24M (“Patty”) are missing and presumed dead.
The National Park Service collects fecal samples in the fall of each year to test for pregnancy hormones in selected mares. There were four positives among the pregnancy test samples collected in November 2018, including N2BHS-A (“Gokey GoGo Bones”), N2BHS-AL (“Ms. Macky”), N2BHS-I (“Annie Laurie”), and N2BHS-M (“Susi Sole”), who foaled in January. The testing cannot predict due date, only that the mares were at least 3 months pregnant at the time the samples were collected.
The National Park Service completes a full census of the horse population in Maryland six times per year, in February, March, May, July, September, and November. Managed as a wildlife population, the Assateague horses are free to roam over approximately 27 miles of the barrier island and can be difficult to find at times.
During each census, horses are identified by their distinguishing characteristics, mapped, and counted. Individual horses that are not observed during multiple census periods are presumed dead. The census’ purpose is to monitor the herd’s overall population dynamics in support of the long-term fertility control program initiated in 1994.