Sable Island horses have very shaggy coats, manes and tails, especially during the winter.

[6] Due to the lack of predators, older horses often die of starvation after their teeth are worn down by a lifetime of exposure to sand and marram.

The first recorded horses were brought by a Boston clergyman, the Reverend Andrew Le Mercier, in 1737 but most were stolen by passing mariners.

[5] After the government of Nova Scotia established a lifesaving station on Sable Island in 1801, workers trained some of the horses to haul supplies and rescue equipment.

Lifesaving staff recorded the importation of a stallion, Jolly, taken there in 1801, who was probably similar in type to the original Acadian horses released on the island.

[5] Other breeding stock, probably including horses of Thoroughbred, Morgan and Clydesdale breeding,[9] were sent to the island during the first half of the 19th century, in the hopes of improving the type of horses found on the island and raising the price for which they could be sold on the mainland.

The meat was primarily used for dog food by the late 1950s, and the island horses were in danger of extinction.

[3] The law requires that people receive written permission before they can "molest, interfere with, feed or otherwise have anything to do with the ponies on the Island".

Genetic erosion is a possibility within the Sable Island population, due to the small number of horses.

[13] A 2014 study by Parks Canada stated that the horses were under threat from their low numbers, excessive inbreeding and extreme weather due to global warming.

Nonetheless, some continue to view the horses as an invasive species which is not suitable in a protected region where ecological integrity should be preserved according to the National Parks Act.

[1] Necropsies of carcasses inspected in 2017 and 2018 showed that young horses died of starvation and hypothermia, particularly during extreme winters, as they would not have a sufficient reserve of body fat and suitable vegetation is sparse on the island during winter.

[1] The study also found that these horses incidentally consume significant quantities of sand, which gradually wears down their teeth and blocks their gastrointestinal tract.