A stoat under the bed

OUR house is built upon a rock, or rather half the house is built on a raft of rocks that began life as a cow-byre. On the seaward side, the rocks at the base of the wall have been coated through the years with the odd trowelful of mortar from various jobs, left over as night was falling. Not all of these dollops have stuck very well, and the rain and wind have chipped away at them.

I tell you this to explain where a stoat may be thinking of having her babies - or not, as the case may be. In the middle of a rainy afternoon, at the bedroom window, I saw her - very small, dark as coffee, tail as stiff as a piece of old rope - ripple through a gap in the cold frame and disappear under my feet. And there, upon inspection outside, was this brand-new orifice, cleared of mortar crumbs.

Less is known about the dens of Irish stoats than one might think. Indeed, all field studies of these little animals are made more difficult because they are so widely dispersed: you'd have to trap 3040 hectares to catch one of them. Dr Paddy Sleeman, mammalogist at UCC, specialised in stoats before he moved on to badgers, and, using radio-tracking, he found three of them using a total of 19 dens.

Most of these were in underground burrows belonging to rats, rabbits or woodmice, but three were in piles of stones or sticks and one was up a lime tree in a witch's broom of twigs. All this was in the woods of the Fota Estate, but on our hillside the drystone wall is probably first choice, with its generous range of secure, dry spaces.

It is quite possible that, despite the noises Ethna insists she has heard in the night (little gravelly noises, she says, and definitely under the floor), there is no stoat under her bed. But March is the classic time for a first-time stoat mother to prospect for a maternal den, and she seems to have been rather emphatic in clearing its entrance.

It is not at all a good place for coming and going, being right beside the door to the greenhouse, built against the same wall. In spring it is a zone of brisk and necessary banging-about, mostly with the dog at my heels: this has probably put her off. But stoats do seem quite ready to move house, even complete with babies, if their first choice doesn't work out. A few years ago, staff at Glenveagh National Park, in Donegal, watched a nest-moving of the most laborious kind, described for me by the park superintendent, Dr Ciaran O'Keeffe.

It began, one day early in June, with the stoat taking her kits across a busy road and then some 700 metres to a bank thickly covered in whin bushes beside the entrance kiosk to the park. Most of the kits were carried by the scruff of the neck, but once she was seen carrying two kits, one astride her neck and another nipped in her teeth.

She used ditches, pipes at the side of the road and zones of deep shade to avoid people and traffic, and put on a spurt in the open whenever the coast was clear. After 90 minutes she had delivered six kits to her new nest and was visibly tiring, stopping for a rest every 10 metres or so. She was still on the move two hours later, so she may well have transferred up to 10 babies to the new nest.

Unfortunately, its entrance was in a bank between the kiosk and some picnic tables - a site she may have prospected early in the morning before the visitors arrive. Next day she was seen moving nest again, but nobody could take time to watch.

Female stoats have a very put-upon, lonely and rather short life. They are markedly smaller than male stoats, and ecologists have seen this as an adaptation that allows the sexes to share an area without competing for the same prey. But a newer idea argues that a small body needs less food to maintain: this lets the mother channel more of her energy into reproduction and feeding her babies. If our lodger really did take up residence under the bed and give birth there next month, she would be visited in due course by a male stoat which will mate not only with her but with all the females in her litter, eyes open or not. They are quite receptive to this peremptory sex; indeed, the oestrogens triggering their reproductive systems may reach them in their mother's milk.

None of them, however, will give birth for 280 days, since stoats share with badgers, seals and some other mammals a biological device known as delayed implantation. The fertilised ovum remains in a state of suspended animation until it is implanted into the wall of the uterus early the following year. The evolutionary function of this is to allow the male to mate when at his fittest to compete for females, and the female to give birth when there is plenty of food available.

There is great effort involved in chasing, killing and dragging rabbits home, or even the requisite number of mice and birds. (On two occasions, years ago, I took a freshly-killed rabbit from a stoat, and carried it home for the pot: I feel quite ashamed of that now.) Perhaps, as the local food supply thins out, it is better energetics just to move the family, and the sight of this in progress is certainly common enough to suggest that disturbance is not the only reason for relocation.

Wherever she settles, the new stoat is welcome. Gone are the brief and innocent years in which we thought we could raise ducklings, unmolested, on the stream in The Hollow. Now, we must suppose that, along with small, furry creatures in the acre's banks and wild corners, it is the abundance of nesting birds that earns us another resident predator. Stoat, magpie, the cat from down the hill, and their prey are all part of an elaborate ecological equation measured out in clutch-sizes, surplus fledglings and ready-fertilised kits.