Date:
August 4, 2016
Source:
University of Saskatchewan
University
of Saskatchewan (U of S) biologists have made a significant advance in
understanding the ecology of Sable Island and its iconic wild horses -- one
that underscores how intimately connected living systems are.
The
number of Sable Island horses is at an historic high -- now ranging from 450 to
550 horses compared with only 200 to 400 during the past 250 years. A team led
by Philip McLoughlin and Keith Hobson has been trying to find out why the
numbers have grown so much.
In
research featured this week in the journal Ecology McLoughlin, an
associate professor in Biology at the U of S and his team demonstrated a link
between burgeoning seal populations on Canada's east coast and the foraging
habits of feral horses along the length of Sable Island.
They
have found that grey seals, whose numbers on the island have swelled from fewer
than 1,000 in the 1960s to nearly 400,000 currently, have their pups on the
island and fertilize the sandy, wind-swept grasslands -- transferring nutrients
from the sea that promotes growth of the grasses where feral horses have now
chosen to feed.
McLoughlin
cautions that more research is needed to say definitively whether the increase
in seal numbers is increasing the survival and reproduction of the horses
feeding near seal colonies. But measurements prove the seals do enrich the
island's plant growth with nitrogen from feeding on fish in ocean, and computer
modelling has demonstrated that the horses preferentially select those
particular grassy areas to eat.
"What
is really interesting is that we show how the enrichment of grasses, which
occurs non-uniformly on the island, then affects how the horses move around the
island to eat," he said.
"This
speaks to the question of how seemingly distinct systems -- ocean and land --
can be interconnected by fundamental ecological relationships."
The
team's next step is to determine whether nitrogen originating from the sea is
detectable in the tissues or hair of the horses and to the extent it explains
their reproduction and survival.
He
noted the team included U of S graduate students Kenton Lysak and Tom Perry,
and post-doctoral fellow Lucie Debeffe.
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