Red squirrels find a very unlikely saviour
IN the battle for survival against the rival grey squirrel, Scotland’s native red species has found an unlikely ally.
Predatory pine martens are boosting red squirrel numbers in Britain by reducing the number of non-native greys.
At present, North American grey squirrels outnumber the native red species by more than 15 to one – but the greys are more vulnerable to the pine martens.
Red squirrels are believed to be cautious when pine martens are around, as would be expected among two species that co-evolved together.
But grey squirrels have only been here since the 19th century, and their lack of experience could make them more likely to get caught and eaten. A study led by the University of Aberdeen found grey squirrel populations fall in areas where they are exposed to pine martens, yet red squirrels surprisingly thrive in the presence of the predator.
The study, published in the journal Proceedings of The Royal Society – B, is titled The Enemy of my Enemy is my Friend.
Lead author Dr Emma Sheehy said: ‘Our evidence that, in addition to their intrinsic value, pine martens provide an ecosystem service by suppressing invasive grey squirrel populations is good news for both red squirrel conservation efforts and the timber-growing industry, due to the detrimental impact of the invasive grey squirrel on both.’
Squirrel pox, carried by grey squirrels, has helped destroy 95 per cent of native reds in England and Wales since 1952. There are more than three million greys in the UK, while only 30,000 of their red cousins remain in England, 120,000 in Scotland and around 1,500 in Wales.
The study took place in the Borders, which the weasel-like pine martens have only recently begun to recolonise, and in the Highlands, where there are no grey squirrels but a long-established pine marten population coexists with native red squirrels.
The squirrels and pine martens were tracked using 223 feeders baited with nuts and seeds. Sticky pads collected their fur, whose DNA was used to identify individual animals and where they roamed.
Dr Sheehy said: ‘The detection component of our models showed that where pine marten activity was high, red squirrels took longer to use the feeders, which suggests red squirrels modify their behaviour to be more cautious.’