Foxy fable
Question: A folk tale suggests that foxes get rid of fleas by swimming with a
mouthful of sheep鈥檚 wool taken from a hedgerow. The story goes that the fox
enters the water and the fleas quickly migrate to its head to stay above the
surface. The fox dips its head under the water, the fleas move onto the wool,
and the fox then releases the wool and swims ashore, minus fleas. Is there any
evidence to support this story?
Answer: This story dates back to the ancient Greek storyteller Aesop, if not
earlier. Such tales keep re-emerging and the wool story is told about other
animals, such as skunks. It is so charming that it is a pity there seems to be
no substance to it. Mammals are not generally good at copying such sophisticated
actions from each other, and it certainly does not seem to be instinctive, so
even if some four-legged Leonardo did develop such a strategy, the trick would
probably die with the inventor.
Personally, I am sceptical because foxes float and, in my experience,
parasites such as fleas do not flee rising water, preferring to hold on tight.
It takes a lot of immersion to drown a flea, and, anyway, if it does escape the
water, where is it to go after climbing onto the wool? Does it just float down
the river to catch the next passing fox? This is hardly likely. Surely it is
better to put up with a brief immersion.
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What does get fleas to abandon their transport very smartly is killing the
host. Fleas desert a dead rat faster than rats desert a sinking ship, and that
makes sense. Fleas faithful to a departed host are prone to wind up in the gut
of the predator responsible for its demise.
One cannot play dead convincingly enough to persuade fleas to disembark, so
we are left with the woolly fox story.
Jon Richfield
Dennesig, South Africa
Answer: If you take a flea-ridden animal and submerge it in cool water you
will find that the fleas, though immobilised, will stick fast to the animal鈥檚
skin. It may not be possible to wash all of them away even if you use a hose
with a pressure nozzle.
In summer I take my borzoi for a swim in the sea at least once a day.
On very hot days we swim for half an hour or more. I have never
noticed any fleas congregating on her head. However, when we come out of the
water I often notice one or two fleas on her abdomen.
While daily swims keep her white coat sparkling clean, they make it
impossible to use most flea products because these just wash away. Therefore I
examine her thoroughly after each swim. When her coat is wet the fleas are more
visible and are easily caught because they are still stunned by their recent
immersion.
Tristana Simon
Seaford, Victoria
Pain transfer
Question: Recently I had an itch on my right forearm. I scratched it hard
with a sharp left fingernail. While experiencing the usual momentary ecstasy of
an itch well scratched, I concurrently felt a stabbing pain just above the
waistline at the left side of my back. The more vigorously I scratched my arm,
the more intensely I felt the sympathetic stabbing in my back.
A few days later I found the scab I had created on my arm and attacked it
again, and found that the exact same point on my lower left back was being
stabbed once more. Why?
Answer: This is a not uncommon phenomenon known as 鈥渞eferral itch鈥� or
mitempfindungen (from the German mitempfinden, which means 鈥渢o
sympathise with鈥�). It was first described by the Reverend Stephen Hales, an
English cleric and experimental physiologist, in 1773. A more recent description
by P. R. Evans can be found in the second volume of the British Medical
Journal for 1976 on p 839.
Your correspondent鈥檚 experience was slightly atypical in that the referred
symptom was felt in the body below the level of the itch and contralaterally.
More usually it is on the same side at a higher level, but this is not
universal. The mechanism is not established, but the sensation is probably
transmitted by fibre tracts within the spinal cord and is dependent upon
temporary changes in nerve cell excitability.
P. K. Thomas
Former consultant in neurogenetics at the Institute of Neurology, London
This week鈥檚 questions
The truth is out there: Why do Martians have green skin? Or rather, how did
the science-fiction tradition that Martians have green skin begin?
Graham Stephen
Dunkeld, Perth & Kinross
Invisible guardians: On a recent visit to the Shetland Islands I noticed that
the young chicks of the great skua (Stercorarius skua), arctic skua
(Stercorarius parasiticus) and other ground-nesting birds such as
lapwing (Vanellus vanellus) appear to wander around their moorland
breeding sites far from any visible parent. How do the parents find and
recognise their individual offspring again? Or if we had tried to approach the
young birds would we have discovered the parents were, after all, keeping a
close eye on them? It is known that both species of skuas fearlessly attack
humans.
Chucky Blackpoint
London