They were found dead of natural causes, according to a report posted today by the Maryland Coast Dispatch.
The herd consisted of 81 horses earlier in the month.
General Harker was a band stallion according to the AIA list dated December 6.
Yankee was unattached.
The loss keeps the sex ratio skewed in favor of females, a documented effect of PZP.
The list shows just two other bachelors, unusual for a herd of wild horses.
The article said the Park Service completes a full census of the horse population six times per year but did not mention that it stopped publishing the results to the Assateague news page four years ago, when the long-term effects of the fertility control program became obvious.
At the time the herd size was 75 and there were 2.4 mares for every stallion.
The darting program was shut off in 2016.
RELATED: If PZP Is Reversible, Why Hasn’t Assateague Herd Rebounded?
Western Horse Watchers Association 