The native red squirrel has been losing out to the invasive gray squirrel in Britain and Europe, but the pine marten may be helping the little squirrel forge a comeback. Photo by University of Aberdeen
March 7 (UPI) -- Conservationists and ecologists have been searching for ways to control the growth of gray squirrel populations across the British Isles. New research suggests they're getting some help from a native predator, the pine marten.
Scientists wanted to find out what environmental factors were linked with the successes and failures of the invasive North American gray squirrel. Why has the squirrel's invasion been more successful in some places and less successful in others?
The gray squirrel is outcompeting native red squirrel populations for resources, leading to a decline in the species. Researchers want to identify ways to better protect the red squirrel.
In analyzing the parameters of the gray squirrel invasion in Scotland, scientists found pine martens are helping to suppress the gray squirrel numbers. The data also showed a correlation between the presence of pine martens and the recovery of local red squirrel populations.
The European pine marten belongs to the mustelid family; the species most closely resembles a mink or weasel.
"Our state-of-the-art analysis suggests that we can achieve conservation objectives twice over by allowing a native species, the pine marten, to spread naturally while conserving our precious red squirrel," Christopher Sutherland, a researcher at the University of Massachusetts Amherst, said in a news release.
Scientists set feeder traps to collect DNA samples from squirrels and pine martens, allowing researchers to estimate the densities of the different animals. They used the data to build a complex model analyzing the interactions between the three species.
The data -- detailed in the journal Proceedings of the Royal Society B -- revealed the positive ecological impact of the pine marten, a traditional enemy of the red squirrel.
"The findings of this research are extremely encouraging," said Kenny Kortland, a species ecologist for Forest Enterprise Scotland. "It seems we have a very welcome ally in our efforts to protect red squirrel populations on the national forest estate. The research demonstrates that the return of native predators can have beneficial impacts for other native species."
