2024 Annual Horse Population Update for Assateague Island National Seashore

Horses in the salt marsh on the North End of Assateague Island.

NPS Photo

Background

Assateague Island National Seashore’s wild horses are managed as a wildlife population. Because they are an introduced species with no natural predators, park management had to step in to keep their numbers in balance with the barrier island ecosystem they now call home. The population census data is collected six times per year and provides the foundation for a solid management plan. The goal of each census is to locate each individual horse, and document band associations, births, and deaths.

The March census is particularly significant for several reasons. By the end of March, most winter deaths have occurred and been documented, and most foals have not yet been born. This allows a good comparison of changes in population size over the years.

March 2024 Census Results

In March 2024, the population was 73, consisting of 30 stallions and 43 mares, including one new foal this March (a colt). This is down from 75 in March 2023 and 76 in March 2022. In the year since the last March census, 10 deaths and 8 births have been documented.

Horse population growth on Assateague Island National Seashore, 1968-2024. Blue line - horse population, orange bar – target population range of 80-100 individuals, blank space - unavailable data

NPS image

Regular monitoring of population dynamics is necessary to support the long-term fertility control program that was initiated in 1994 to reduce the numbers of the Maryland herd, and now, management of the population close to the goal range of 80-100 individuals. A population of this size will remain genetically viable and still have minimal impacts on island vegetation and habitat. The population has since reached the new goal range, and the last mare to be contracepted was a single two-year-old, in 2016.

As new foals begin to appear on the island, we can all help to minimize our impacts on these animals by giving them plenty of additional space. We ask that all park visitors join us in support of efforts to protect these expectant mares from the added stress and disturbance that upcoming births tend to attract. Only one foal has been born so far in March 2024, but several are expected this season.

For more information on Horses at Assateague Island National Seashore visit: Assateague's Wild Horses - Assateague Island National Seashore (U.S. National Park Service) (nps.gov)