BALTIMORE (WJZ) — In a Friday Facebook post, Assateague Island National Seashore detailed the reproductive life of one of its “better-known horses,” Carol’s Girl, who recently passed away at the age of 23.
“She was the only horse that did not respond at all to the birth control vaccine PZP, and so she ended up producing 12 foals in her lifetime,” the post says. “Even more amazing, all but one survived and are still living!”
It goes on to explain how her feracious ways affected the genetics of the island’s herd.
To start with, the 11 living offspring of Carol’s Girl, along with their offspring, represent nearly 20 percent of the total population.
“Fortunately her foals were sired by seven different stallions, so they are not all full siblings,” the post says. “Six different stallions sired the second and third generations. There is no question that some good genetics have been passed on. However, for a managed population on a limited range, one of the things we need to consider is genetic viability and retention of genetic diversity.”
Island officials are currently completing a parentage and kinship analysis to include last year’s foals so they can reevaluate the “genetic status” of the population.
They expect that they should be able to maintain sufficient genetic diversity, but if they find the population becoming too closely related, they do have options (developed with public input), including selectively giving contraception to better-represented lines, or even introducing horses from similar barrier island habitats to refresh the genetics of the population.
“However, none of the options involve removing horses. Once the parentage and MK update is complete, if all is still well, we will continue with the current management plan,” the post says.