Solving the mystery of our 'native' fauna

ANOTHER LIFE:IN TIMES DOLED OUT digitally, second by second on stock exchange screens, there may be some calming grace in considering more leisurely intervals of change.

Let us start with 53 little skulls teased out by a sharp-eyed student from pellets of fur and bones regurgitated by the barn owls of Tipperary. The exceptional size of these ivory crania led to the trapping last spring of a brand-new animal in Ireland, the greater white-toothed shrew (Crocidura russula), previously known no nearer than the Channel Islands.

We already had the even more diminutive pygmy shrew, red in tooth if not in claw, and generally ranked among Ireland's "native" fauna - whatever we choose this to mean. Until very recently, it could be pictured as scampering across a transient landbridge from Britain some time after the ice went finally, 10,000 years ago.

DNA sampling offers fresh perspectives. Ireland's pygmy shrews have a mitochondrial heritage shared only with the pygmy shrews of the Pyrenean fastness of Andorra. Our animals are so identical as to suggest "an extreme founding event", which leaves us to imagine a whole nestful of pygmy shrews sneaking ashore from an early skin boat drawn up on the sands of Co Kerry. This makes them pioneer voyagers in the long list of mammals now seen to have been imported, accidentally or on purpose, in maritime traffic to Ireland. Badgers, foxes, pine martens, red squirrels, red deer, wild pigs, all for food and furs, and even possibly, baby wolves as pets, are seen now as early and purposeful introductions.

On the basis of fossil and genetic evidence, cold-hardy Irish stoats and mountain hares, as well as seals in the sea, were the only mammals around to greet the first Mesolithic humans. Later, probably, the otter swam here on its own. Advances in research technology and new findings on climate and Ice Age events have upset the key factor in the long debate on the post-glacial colonisation of Ireland. "It is no longer possible," runs a new verdict, "to believe in the sprint across a 'landbridge' that existed for a short time at the beginning of the so-called 'post glacial'." This comes from two Irish scientists who have marshalled the results of wide research into colonisation at two conferences at University College Cork, 25 years apart.

Prof Peter Woodman is the leading archaeologist of Ireland's early human settlement and the animals and fish people hunted, farmed and used for food and clothing. Dr Paddy Sleeman is a UCC mammal expert long concerned with how species arrived and how early predators survived with so limited choice of prey. They write together in Mind the Gap, a supplement to the current Irish Naturalists' Journal. This collects the papers of the last UCC conference in 2006, updated with current research into the "gaps" in question: that between Ireland and Britain or Europe, and that in the food supply for predatory carnivores.

In Drowning the myth of an Irish land-bridge?, Trinity College Dublin's Robin Edwards and Anthony Brooks use new modelling of the dramatic changes in post-glacial sea-levels to demolish any chance that our flora and fauna migrated over land from Britain. And Trinity's Fraser Mitchell, first to show that our trees returned by a southerly migration route rather than from Britain, still can't say exactly how it happened. A great deal remains to be discovered about land which may have been exposed beyond the southern reaches of Ireland's ice, as far as the Bay of Biscay.

Paddy Sleeman has been exploring the apparent mismatch between Ireland's early predators and prey - one so marked, that in his early stoat studies, it seemed hard to imagine how it existed without rabbits, voles or rats. Now, however, with accumulating examples of our stoats eating fish, he sees it as an early inhabitant of seashores and river banks and a predator of winter migrant waterfowl and waders. Before the trees arrived, Ireland's population of hares, an Arctic species, could have been immense, judging by the dense congregations still seen today in places like Ellesmere Island, off northern Canada.

Migratory salmon would have fed bears and otters as well as Mesolithic hunters. Ireland's estimated 2,000 Mesolithic wolves, with an appetite of 5.3 kilos a day, would have needed to wait for the wild pigs that arrived later.

The long history of Ireland's wildlife and plants has been complicated by the 20 or so warmer spells that brought amazingly rapid changes within the 100,000 or so years of the last cold spell we think of as the Ice Age. Trinity's Pete Coxon explores the significance of this global "flickering" of climate and environment. It heightens the main message of Mind the Gap, that rather than tying the recolonisation of Ireland to a single — now probably untenable — circumstance of a post-glacial landbridge from Britain, its study need to range through the changes of the whole 14,000 years since the ice began to melt.

EYE ON NATURE

On a trip to Donegal, my wife and I were spellbound by the sight of two eagles quartering the hills above Laghy. They were in close view for about 15 minutes and we could even hear the trailing eagle calling. Absolutely awesome!
Brian Mcloughlin, Swords, Co Dublin

I too have seen the lone raven at Redford cemetery in Greystones. He arrived for Ronnie Drew's funeral.
Brendan Byrne, Co Wicklow

I've had a fox visiting my garden for over a year now, and I spotted him last week with a mate. They've taken to digging holes and running around having fun in the sunshine. What should I do if they have a litter? I'm happy to leave them alone, just concerned I might be overrun and have more damage to the garden?
Sarah Callery, Walkinstown, Dublin 12

If your foxes have a litter the young ones will disperse eventually to find territories of their own.

I came across a very large spider climbing up the wall at home.(photo attached).
Paul Burns, Armagh

It wasTegenaria gigantea , a common house spider which spins a sheet web with a tubular retreat.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo; e-mail: vine@anu.ie. Include a postal address.