Saunterings:  Walking in North-West England
Saunterings is a set of reflections based upon walks around the counties of Cumbria, Lancashire and
North Yorkshire in North-West England
(as defined in the Preamble).
Here is a list of all Saunterings so far.
If you'd like to give a comment, correction or update (all are very welcome) or to
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113.  White Stoats on Caton Moor
Our local hill, Caton Moor, received its first snow of the winter on New Year's Eve, so, as is
almost traditional, we walked up the hill as soon as we could, bright and early
on New Year's Day. We thus began the year as we are intended to carry on, that is,
by walking from home.
I had the ulterior motive of looking for white stoats but I didn't mention this to Ruth,
as I didn't want her to feel disappointed when we didn't see any.
The roads were still white and icy but we walked up gingerly, appreciating the views of the Lune valley
and the gradual revelation
of the surrounding hills. At first, we could see only the Howgills and Barbon Fell up the valley,
but eventually Gragareth, Whernside and, after passing Quarry House Farm, Ingleborough came into view.
Their tops were smudged by grey cloud but, as far as I could tell,
they appeared to
have less snow than Ward's Stone, just off to the south. But the highlight was behind us.
The Lake District hills appeared over the ridge on the north bank of the Lune and they too were
mainly under grey cloud except for a sunny patch that made the Coniston hills and then the
Langdales seem aglow.
Towards the Lake District hills (about 30 miles away), Black Combe on the left, Coniston hills in sunshine
Now, about those white stoats ...
Handel, Vivaldi and other composers of that vintage thought nothing of recycling
their compositions to meet their commitments. Writers nowadays are liable to re-use
their words in various forms - newspaper columns, books, anthologies, even in films
if they are lucky. I have more excuse than them for borrowing from myself.
I am supposed to be writing
about walking in the northern hills and dales but I can't walk there, for the
So, as it happens, I wrote something about white stoats five years ago which I
can regurgitate here (slightly edited) ...
You can’t really set out to see a stoat. Stoats are seen by chance,
if they are seen at all. But I had resolved that when the first
snow of the winter fell on Caton Moor then I would set off in
search of a white stoat.
By chance I have, during occasional visits in the last 35 years,
seen two white stoats on Caton Moor. I don’t know if I am lucky
to have seen as many as two, or unlucky to have seen only two. I
just don’t know how common white stoats are on Caton Moor. I
have also seen several brown stoats not on snow. I’ve never seen
a white stoat without snow nor, I think, a brown stoat with snow.
These observations, scanty though they are, provoke a number of
questions in my febrile mind.
As is well known, stoats in places where there is plenty of snow,
such as the Cairngorms, turn white in winter and stoats in places
where there is little snow, such as Dorset, do not turn white. But
how does the mechanism work in intermediate places like Caton Moor,
where snow is patchy and unpredictable?
What causes the change? Is it in anticipation of snow, or in
response to it? Does it occur gradually or quickly (like human hair
that turns white overnight as the result of some trauma)? Is it an
adaptation to the environment, like that of a chameleon? Does
turning white occur once each winter, or could a stoat turn white,
then brown, then white in response to snowy periods? If you took
a Dorset stoat to the Cairngorms would it turn white? If you took a
Cairngorms stoat to Dorset would it turn white? If turning white is
such a nifty strategy, then do other species adopt it? Do all stoats in
a particular location turn white or do they all not turn white? If not,
why not? Are the numbers of white stoats decreasing, in response
to climate change?
I have found the answers to some of these questions in the book
The Natural History of Weasels and Stoats (King and Powell, 2006).
It seems that the white stoat
provides a pristine case study on the interaction between genes and
First of all, some preliminaries. Stoats are members of the
Mustelidae family, which also includes weasels, minks, ferrets,
martens, badgers and otters. The stoat Mustela erminea and weasel
Mustela nivalis are within the Mustela genus of this family. Ermine
is an alternative name for the stoat, usually used for the white stoat
and for its fur.
In the United States, Mustela erminea (our stoat) is called the
short-tailed weasel and Mustela nivalis (our weasel) is called the
least weasel or common weasel. They also have a long-tailed weasel.
In Ireland Mustela erminea (our stoat) is usually called the
weasel. There are no Mustela nivalis (our weasel) in Ireland. You
could say that there are no weasels in Ireland, but the Irish might
say that there are no stoats. Clearly, outside the UK, the weasel is
not so easily distinguished and the poor stoat is totally confused.
Stoat and weasel have a huge range, across the whole northern
hemisphere from western North America to eastern Asia. Within
that range there are many climatic zones with prolonged snow
cover. Some stoats and weasels live at 3000 metres in permanent snow.
Snow is not a problem for stoats, as it is for many animals. With
its long, thin, sinuous body the stoat is well-adapted to burrowing
in grass and small tunnels and is therefore equally well-adapted to
burrowing within snow, where it may seek prey, find safety from
predators, and take refuge from the cold.
A stoat has quite an appetite, needing to eat up to one third of
its body weight every day. This is because it leads such a frenetic
life: it is alert, with rapid movements; its pulse runs at 500 beats per
minute; it digests and defecates within two hours; and it doesn’t
sleep for long.
It can kill rabbits twice its
weight. I once saw a stoat doing
a strange leaping dance beside
a hedge. I then noticed that it
had at its feet a dead rabbit. It
was leaping up trying to get the
rabbit into the hedge but it was
too heavy and the stoat lost its
grip. It eventually succeeded.
On another occasion I saw a
stoat disappear into a stone
wall. I stood by the wall and eventually the stoat popped its head
out, stared at me, squeaked, and went back inside. It repeated this
performance every minute or so. The squeaks became gradually
more threatening so, bearing in mind what a vicious killer the stoat
is, I thought I had better move on.
The stoat does not hibernate in winter. With its slim, fat-free
body, it needs twice as much energy to retain its body heat in
winter as it does in summer. It is therefore essential that the stoat
be adapted to survive harsh winters.
Now we can consider the change to white. Stoats moult twice
a year, in spring and autumn. The new fur, replacing the old, is
brown except for autumn moults in cold climates, when it is white.
The moult does not occur instantaneously and therefore stoats may
be seen at an intermediate brown-white stage. In mild climates
(such as here) the moult can take a month; in the Arctic it takes a
The moult is triggered by the hours of daylight. This is easily
demonstrated by manipulating the lighting over the cages of captive
stoats. They can be induced to moult at any time of the year, even if
the temperature is not consistent
with the apparent sunlight. In
this respect, the stoat is similar
to other animals that moult.
If the temperature or some
other environmental factor were
the sole determinant then stoats
transferred from, say, the Cairngorms to
Dorset (or vice versa) would turn white or not
according to the conditions in
their new home - but they don’t.
They moult at the usual time but into the ‘wrong’ coat. So the colour
of the new fur is controlled mainly, if not entirely, by heredity.
British weasels do not turn white. Why not? If it's a good idea for stoats to
turn white, why isn't it for weasels too? Swedish weasels do turn white - or at
least those in north Sweden do while those in south Sweden stay
brown (rather like the British stoat divide). However, the two sets
of Swedish weasels are two different subspecies (the two sets of
British stoats are not). British weasels belong to the same subspecies as the south Sweden weasels. Therefore the reason that
British weasels don’t turn white may be more to do with their genes
and evolutionary history than the climate.
In the United States it was
found that the boundary between
white and brown winter stoats
was at points where there was
an inch of snow for fifty
days of winter. In Britain stoats
whiten in somewhat milder
winters (Caton Moor normally
has an inch of snow for only a few
days of winter). The boundary
line divides Wales, Scotland
and parts of northern England
from the rest of England - but of
course it is not a precise, single
line, as mountain-top stoats are
more likely to whiten than low-level ones. Caton Moor, with a
highest point of 361 metres, is hardly
The boundary between white stoats and brown stoats is not a
line but a transition zone. Within that zone (which includes Caton
Moor) more or less stoats turn more or less white. Transition zone
stoats are usually pied, rather than fully-white or fully-brown
(actually, fully-white stoats are not fully white: they retain the
black tail tip). This suggests that our stoats are a hybrid of northern
fully-white genes and southern fully-brown genes. The colder or
snowier a region normally is, the more pied stoats there are (and, I
would guess, the more white they are).
In the transition zone female stoats are more likely to turn white
than male ones. Perhaps the gene that determines whitening is
dominant in one sex and recessive in the other. This would ensure
a genetic polymorphism so that the population always has some
individuals with every combination, in which case some will benefit
whatever the weather conditions turn out to be.
The reason that stoats turn white is obvious. It confers a clear
evolutionary advantage. Stoats have much to gain by being able to
live in snowy conditions but the penalty for being brown against
a white background or white against a dark background is large.
They become much more visible to their predators - hawks, owls
and foxes. Other species, such as the mountain hare, arctic fox,
ptarmigan and caribou, also turn white in winter. It is also clear
how this is a self-regulating mechanism. Those stoats that moult to
an inappropriate colour are more likely to be predated and therefore
less likely to pass on their ‘inappropriate’ genes.
I have found no discussion of the effect of climate change on the
transition zone for stoat-whitening - but I would expect the zone to
be moving north. Forty years
ago there were ski-orienteering events organised on the Howgills.
The organisers could be confident that there would be enough snow.
Today, the odds are that a winter date would see no or little snow
on the Howgills. Ski-orienteers are now more commonly found
further north. I expect white stoats are too.
So my expedition to snowy Caton Moor was made not in the
belief that the brown stoats would suddenly have turned white in
response to the fresh snow. My hope was that, after this exceptionally
mild and wet winter (so far), those stoats unfortunate to have genes
that have turned them white would have sufficient self-awareness
to have hidden themselves away over the last few weeks in order
not to make an easily-predated spectacle of themselves but that,
now that the snow has fallen, they would be gambolling about, in
Unfortunately, it proved not to be the case. I saw no stoats,
white or brown. On reflection, given the decreasing occurrence of
snow on Caton Moor, I think it unwise for any stoat to turn white
there. I suspect that white stoats have disappeared but I will keep
looking and if I see one I’ll let you know.
... Now, back in 2021, we saw no white stoats on our January 1st walk and I haven't seen
any in the intervening years either. Not to worry, it was an invigorating start to the New Year.
We walked up to beyond the windmills, which had just begun to be stirred into action by
a light breeze, and admired the snowy hills all around, with only a few in the glow of
sunshine. By the time we set off down, a thaw had set in, which made the roads more
slippery, but we made it safely back.
Clougha Pike and Morecambe Bay from above the windmills
Date: January 1st 2021
Start: SD543644, Brookhouse  (Map: OL41)
Route: SE, E on Quarry Road – picnic site – along the windmill track, to
the highest corner of the field – and back
Distance: 5 miles;   Ascent: 250 metres
114.   Never Mind the Danger
112.   Walking around Pilling with Pink Feet
A list of all Saunterings so far
© John Self, Drakkar Press, 2018-
Top photo: The western Howgills from Dillicar;
Bottom photo: Blencathra from Great Mell Fell