Last week, a brother-in-law who lives in Cork city’s arboreal Montenotte filmed a red squirrel that has been visiting his bird table for months. News of such sightings is heartening for anyone who cherishes the hope that some, at least, of our rarer native species are still hanging on and living in the woods and wild places around us.
It is especially reassuring that, once protected — rather than proscribed — by legislation, animals will protect themselves and, by natural selection, even one another. There is surely a moral here.
Throughout the 1900s, two of our native forest mammals, the red squirrel and the pine marten were increasingly threatened with extinction, the former by a competitive non-native invader, the latter by man. Revised conservation legislation brought the pine marten back and, as a result, both species are now recovering and expanding their range. They are again our neighbours, rather than destined to be stuffed relics with glass eyes in the Natural History Museum.
It is significant that the legal protection of the one contributed to the salvation of the other. Big brother Pine Marten, now no longer proscribed by law has saved small brother, the Irish Red Squirrel, from replacement by the American Grey Squirrel. Where pine martens have thrived, grey squirrels have been decimated. Indeed, in many locations they have entirely disappeared. They had been gobbled up, in fact. Since greys were introduced from the UK in 1911, they had spread exponentially, colonising woodland, gardens and parks. Red squirrels arrived here at the end of the last Ice Age, or earlier. Within 15 years of the greys’ colonisation of any given habitat, the red squirrel had disappeared.
Greys are bigger and more omnivorous than reds; they can, for example, digest acorns (and discarded food in parks) which reds can not. They carry a disease, relatively harmless to themselves, but with 80% mortality for reds that contract it. In areas where reds are under pressure from greys, the reds’ breeding rate drastically declines.
Despite eradication programmes, the greys continued to spread. The red squirrel seemed doomed.
Then, around 2007, conservationists began to see reds in the Midland counties, in habitats where pine martens had re-established, and they were even expanding their range. In 2009, the connection between these two native woodland mammals was investigated by Emma Sheehy, of the Mammal Ecology Group of NUI, Galway in The Irish Squirrel and Pine Marten Project funded by the Irish Research Council. Since then, the predation of martens on grey squirrels has been acknowledged as an important factor in the latter’s control.
Red squirrels weigh 250g to 340g, greys weigh 400g to 600g. Greys often forage on the ground, where martens can more easily catch them. Reds largely feed aloft and, being lighter, can find refuge in treetops twigs where martens, weighing 1kg to 2kg cannot venture. Reds are extraordinary nimble and have evolved survival tactics. Martens are new to the greys who have not. The red squirrel and marten connection argues that leaving nature to its own balances rather than taking a creature (the marten) out of the chain is the best course. Take out the marten and we also lose the red squirrel.
The same might apply to the relationship of the Irish otter and another alien, the mink. Otter hunting became illegal in 1976 and Ireland has since become a European stronghold. Studies reveal otters expel mink from their territories. They sometimes kill and eat mink.
In Britain, mink had reduced the water vole population by 88%. However, Dr Don Jefferies of the Vincent Wildlife Trust, discovered that the voles were recovering. “The mink population is decreasing. There is a close correlation between it and the otter’s recovery.”
Mink decrease was most notable where otters were most widespread. Mink numbers in Wales dropped by 91%.