Increasing Seal Pup Numbers Influence Feral-Horse Feeding Habits

Researchers reveal how seals affect vegetation patterns and influence the movement of feral horse populations on Sable Island in Canada.

Catherine Offord
Aug 1, 2016

SEA TO LAND: Feral horses on Sable Island, Canada, munch on marram grass that has been enriched with nitrogen from local seal populations. SARAH MEDILL


The paper
P.D. McLoughlin et al., “Density-dependent resource selection by a terrestrial herbivore in response to sea-to-land nutrient transfer by seals,” Ecology, doi:10.1002/ecy.1451, 2016.

Island living
Working on Sable Island, Nova Scotia, population ecologist Philip McLoughlin noticed that many of the local feral horses visited a small spit of land on the island’s west coast to eat marram grass and other vegetation. But flicking back through photos of the area, the University of Saskatchewan researcher found that 50 years ago, the spit had been just a strip of sand. “Something had happened since the 1960s to make this an important area for the horses,” he says.

Seal explosion
One thing the team knew had changed was the number of pupping...