FOR­EST FRIENDS IN HIGH PLACES

CAN PINE MARTENS RE­VERSE THE DE­CLINE OF RED SQUIR­RELS? A STUDY IN SCOT­LAND RE­VEALS ITS RE­SULTS.

BBC Wildlife Magazine - - Wild News - SOURCE Pro­ceed­ings of the Royal So­ci­ety B LINK https://bit.ly/2tntLmh

En­cour­ag­ing the spread of pine martens into their for­mer range across the UK might prove a god­send for another beloved na­tive mam­mal. New re­search shows that red squir­rels are able to re­colonise in their wake.

The story of the re­treat of red squir­rels in the face of the ad­vance of North Amer­i­can greys in­tro­duced to Bri­tain lit­tle more than a cen­tury ago is a fa­mil­iar one. But in 2014, bi­ol­o­gists work­ing in Ire­land doc­u­mented a grey squir­rel pop­u­la­tion crash – and a red squir­rel re­cov­ery – in a re­gion re­cently re­colonised by pine martens.

The sus­pi­cion that martens sup­press grey squir­rel pop­u­la­tions has now been con­firmed by a more thor­ough study of the three species’ in­ter­ac­tions in the Scot­tish High­lands.

“The re­sults were clear – the higher the ex­po­sure to martens, the less likely grey squir­rels were to be present,” says Emma Sheehy of the Univer­sity of Aberdeen, who was in­volved in both the Ir­ish and Scot­tish work. “Red squir­rels ac­tu­ally out­com­pete grey squir­rels where pine marten ac­tiv­ity is medium to high.”

The team found ev­i­dence that reds avoid feed­ing sta­tions fre­quented by martens, but that greys aren’t de­terred, which could make them more vul­ner­a­ble to at­tack. Such naivety could be the re­sult of the in­tro­duced greys’ lack of fa­mil­iar­ity or shared evo­lu­tion­ary his­tory with Euro­pean martens, which wouldn’t have been a prob­lem un­til martens started re­colonis­ing for­mer haunts.

En­cour­ag­ing the ex­pan­sion of pine martens could re­duce the need to cull greys. “Where pine martens are es­tab­lished and liv­ing in healthy num­bers, they elim­i­nate the need for grey squir­rel con­trol lo­cally,” Sheehy ex­plains.

Martens re­main rare in, or ab­sent from, most of Eng­land and Wales. “What por­tion of the UK may even­tu­ally be re­colonised by pine martens is yet un­known,” says Sheehy. “And suc­cess­ful re­coloni­sa­tion – to reach healthy enough num­bers to sup­press grey squir­rels – will take many decades.”

The pine marten is the red squir­rel’s ally and grey squir­rel’s en­emy.

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