Researchers studying the carcasses of Sable Island’s fabled wild horses have discovered many had unusual levels of parasites and sand, suggesting they are tougher than most horses, even as many died of starvation.
A team from the University of Saskatchewan and Parks Canada performed necropsies on more than 30 dead animals during trips to the isolated sandbar about 160 kilometres off Nova Scotia in 2017 and 2018.
“We showed up in 2017 not knowing whether there would be any dead horses to find,” said researcher Emily Jenkins.
“Scientifically we really didn’t know anything about the causes of mortality in this population because the last work that was done was in the 1970s.”
The horses have roamed there since the 18th century and become synonymous with the island’s romantic and untamed image.
Jenkins said conditions on the wind-swept, 42-kilometre long island were particularly harsh in the early spring of 2017, and that had an effect on the horse population.
“It was very hard on the horses,” she said. “When we got there they were taking shelter behind anything they could find.”
With the help of Parks Canada, Jenkins said she and other University of Saskatchewan researchers were able to find 30 carcasses that were suitable for examination during their initial foray to the island.
Jenkins said they estimated there were another 20 carcasses that were either unsuitable for examination or that were just too inaccessible to get to.
She said the overall findings were “very similar” to a previous study carried out by graduate student Daniel Welsh in 1972.
“The main finding was emaciation or starvation and hypothermia, especially for the young horses,” said Jenkins, who noted vegetation is sparse on Sable during that time of the year.
The researchers found the yearlings in particular, had little or no reserves of body fat to rely on.
“All of the young horses we looked at were just basically out of reserves,” Jenkins said. “They had nothing left, they were emaciated.”
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However, the adult animals, who would have higher social status and better access to the best grazing, were generally in better body condition and died of a combination of other causes.
Jenkins said Sable Island’s omnipresent sand tends to grind down teeth, affecting nutrient intake, and also ends up in the horses’ system, blocking their gastrointestinal tract.
“In several horses that we looked at there was quite a lot of sand. We were picking up the intestines and the stomach and saying ‘these weigh a tonne,’ because there was in many cases more sand than plant content.”
Jenkins also noted that some pregnant mares had died while giving birth.
The 2018 trip, meanwhile, focused more on looking for pathogens and diseases, and that’s where Jenkins said the researchers were able to find things such as respiratory and reproductive diseases including a parasite lungworm.
She said, in fact, research over the last 10 years has turned up astounding levels of parasitic worms in these small horses, many of whom are no bigger than 14 hands long. The average fecal egg count from the live horse study was 1,500 per gram.
“I just about fell over because we call a high fecal egg count in a domestic horse 500 eggs per gram,” said Jenkins. “So the average Sable horse is walking around shedding three times more parasites than our domestic horses.”
Jenkins said the horses’ genetic resistance to the parasites could render clues for horses in the domestic world, where veterinarians are “fighting a losing battle” to worms with a growing resistance to various treatments.
The scientist said she believes domestic horses are dewormed too much to begin with, and the Sable research could help bear that out.
“Look at what those guys are surviving with – massive levels of parasitism and no treatment. So we are probably overdoing it for most horses that are just companion animals.”
Jenkins said the overall mortality rate in 2017 was about 10 per cent of the population, while the 2018 figure represented about one per cent, which is more the norm.
She said the current population sits at around 500 horses, up from the 300 or so recorded in the 1970s.
From a scientific perspective, Jenkins said it’s fascinating to see a system of untreated and unmanaged horses living in what amounts to their ancestral conditions.
“But there’s the little girl in me who has always loved horses who can’t believe these horses are eeking out a living on this little sandbar,” she said.