The mystery of Sable Island’s growing wild horse population – sciencedaily
Biologists at the University of Saskatchewan (U of S) have made significant strides in understanding the ecology of Sable Island and its iconic wild horses, highlighting how living systems are intimately linked.
The number of horses on Sable Island has reached an all-time high, now ranging from 450 to 550 horses, compared to just 200 to 400 in the past 250 years. A team led by Philip McLoughlin and Keith Hobson tried to find out why the numbers have risen so much.
In research featured this week in the journal Ecology McLoughlin, associate professor of biology at the U of S, and his team have demonstrated a link between burgeoning seal populations on Canada’s east coast and the feeding habits of wild horses along Sable Island.
They found that gray seals, which have grown in numbers on the island from less than 1,000 in the 1960s to nearly 400,000 today, have their young on the island and fertilize the sandy and windswept grasslands. – transferring nutrients from the sea which promotes growth of grasses where wild horses have now chosen to feed.
McLoughlin warns that more research is needed to determine with certainty whether increasing seal numbers increase survival and reproduction in horses that feed near seal colonies. But measurements show that the seals enrich the growth of the island’s plants with nitrogen by feeding on fish in the ocean, and computer modeling has shown that horses preferentially select these particular grassy areas to eat.
“What is really interesting is that we show how the enrichment of the herbs, which occurs unevenly on the island, then affects the way the horses move around the island to eat,” did he declare.
“This begs the question of how seemingly separate systems – ocean and land – can be interconnected by fundamental ecological relationships.”
The team’s next step is to determine whether nitrogen from the sea is detectable in the tissues or hair of horses and how it explains their reproduction and survival.
He noted that the team included U of S graduate students Kenton Lysak and Tom Perry, and postdoctoral fellow Lucie Debeffe.
Since 2007, McLoughlin, his students, and research collaborators have been naming and tracking the life history and movements of every horse that lives on Sable Island, with the goal of better understanding how populations function and how isolated populations can be conserved.
âSable Island is truly one of the most interesting outdoor labs a population ecologist can ask for,â he said.
The project was funded by the Natural Sciences and Engineering Research Council and the Canada Foundation for Innovation, with in-kind support from the Parks Canada Agency and Fisheries and Oceans Canada.
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