Another Life: Pine marten and its links with Spain

The second half of RTÉ's The Burren, a memorable enterprise, conjured brown bears, wolves and lynxes prowling Ireland's palaeolithic landscape. After thousands of years, these charismatic mammals are now "rewilding" areas of Europe that were once part of their natural range. A third of its landmass has at least one of them, protected and promoted in the wide rush of guilt about human treatment of the natural world.

Hopeful stirrings of rewilding in Ireland have been topographically modest: a few wolves and lynxes restored to the few wilder bits would control the excessive spread of deer. But while boosting predatory species in Europe could build on natural restoration, the animals for this island would need to be reintroduced.

“Much work would be required to undertake such efforts in Ireland,” conclude the authors of a challenging new genetic study. Conserving Ireland’s mammals, they say should concentrate on the resident species we have, such as stoat, hare, otter, fox and pine marten.

The last of these has drawn their special concern. Researchers led by Denise O'Meara of the Waterford Institute of Technology have produced the paper "Not Out of the Woods Yet: Genetic Insights Related to the Recovery of the Pine Marten (Martes martes) in Ireland", published recently in Oxford's Biological Journal.

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From DNA analysis of hair and tissue of 249 martens, many the victims of road kill, they found that while the marten has been recovering well from human persecution, it has relatively low levels of genetic diversity compared with other Irish carnivores. That could threaten its future, they suggest, in adapting to changes of habitat and climate.

Iberian back-up

The team explored the marten’s relatedness to those in Europe and found a particular affinity to those around northern Spain. They suggest genetically boosting the Irish population with Spanish “reinforcements”.

This is a novel recommendation for a species currently doing so well. But it’s also a reminder of how few mammals Ireland has compared with the rest of Europe.

Ireland has been an island twice as long as Britain, so failed to share in most of the recolonising, westward flow of mammals as ice retreated from Europe. Of the 219 terrestrial mammals found in Europe, only 27 are native or long established in Ireland, compared with 43 that made it to Britain.

Of the animals that locally survived the last ice age, only two are still part of our wildlife: the Irish hare and the stoat. For the hare, originally of mountain stock, a lack of predators allows it to graze the whole island’s grass, right down to sea level. The Irish lineage of the stoat is far older than in Britain and still gives its fur a distinctive pattern.

British mammals are related to the common stocks of Scandinavia and the Netherlands. Most of Ireland’s arrived with the island’s early human settlers. Brought from Britain and Europe, the animals can carry genetic forms now lost from their source populations.

This has shown up in the new and advanced genetic research of recent decades. Irish zoologists see conserving these early “native” species as potentially helping adaptation to future climate change.

Genetic heritage

It’s not known how or when pine martens arrived in Ireland, but the affinity of their genetic heritage with the martens of Iberia echoes similar molecular links in badgers and red foxes. Their luxurious fur was especially valued early, and the first evidence for their presence dates more than 2,800 years to the late Bronze Age.

A woodland specialist, with birds among its prey, it would have thrived in the forests of the time. But these were already beginning to decline and their later clearance hit woodland mammals. As a predator, the marten was already a quarry for gamekeepers and hunters.

Poultry were part of farming life, so persecution continued, and poison baits set for foxes killed martens as well. By the 1970s, woods around the Burren emerged as a rare sanctuary for a species with a dwindling stock of genes.

The animal’s recovery was helped by the banning of farm strychnine, the spread of forestry and the changing respect for wildlife that came with national and EU conservation measures. By 2019, an all-Ireland survey found dramatic increases in numbers in both Ulster and Leinster and a spread of their core midland range.

This range overlaps with and replaces that of its significant prey, the introduced grey squirrel, leaving the native red squirrel to reclaim much of its woodland world. The pine marten’s selective “rescue” of the reds by chasing and eating many more of the alien and invasive greys has helped to win it new credit as an agent of conservation.

Exactly how the selection works has been a mystery. But experiments with marten scent in Northern Ireland have shown red squirrels quicker to sniff, take alarm and scamper out of reach.