ÐÓ°ÉÔ­´´

Q: Why do sheep always run in a straight line in front of a car and
not to the side?

* * *

A: Sheep and other animals run ahead of cars because they do not realise
that cars cannot climb grassy banks. Ancestral sheep were pursued by wolves
and big cats. If an animal tries to turn aside some yards from the hunter,
the pursuing animal sees what is happening, makes an easy change of course
and intercepts the victim, which is presenting its vulnerable flank.

If, however, the prey dodges at the last minute, the outcome is different.
The hare is the master of this strategy: as the greyhound reaches out with
its jaws, the hare jinks to one side and the dog overshoots or, with luck,
tumbles head over heels.

The instinctive response of a sheep or a hare to an approaching car
is at least not as maladaptive as that of the hedgehog.

Christine Warman Clitheroe, Lancashire

* * *

A: Herbivores are killed by predators who normally grab them by the
throat while running alongside, so the prey will always do its best to keep
a potential threat behind its tail, swerving as the predator attempts to
overtake. That’s why a kangaroo, seeing a car drawing alongside, will jump
onto the road right ahead in order to keep the car directly behind it, and
often get run over in the process. As long as a car proceeds in a straight
line behind a sheep, the sheep will try to outrun it in a straight line.

G. Carsaniga Sydney, Australia

* * *

A: Sheep are much underrated. They don’t merely run in a straight line
– they run straight for a while, then dive to the side. This is not woolly
thinking, it’s perfectly logical. Sheep loose in the road are usually confined
to country areas, where roads are bounded by steep verges, cliffs, hedges,
fences and ditches. The sheep recognises that if it cannot beat the car
on the flat, it stands no chance whatsoever up a bank, so it attempts to
outrun the vehicle down the road.

What happens then is that the vehicle slows, and when it reaches a speed
that is slow enough for the sheep to think it might beat the car over the
obstructions at the side of the road, it swerves. And since most of the
time this action is proved correct (most vehicles don’t follow sheep off
the road), the sheep carries on behaving in this way. QED, by sheep logic.

Clearly, this is a much more successful approach to road safety than
that shown by humans. Humans rarely try to outpace the oncoming car. They
tend to dive to the side of the road. Since more people are run over than
sheep, one can conclude we have much to learn from sheep logic.

William Pope Towcester, Northamptonshire

* * *

A: Sheep, being clever animals with an instinctive grasp of psychology,
know that most drivers, though enjoying an occasional kill as long as they
can use the ‘it jumped in front of me, there was nothing I could do’ excuse,
are not so depraved as to deliberately run something down. Thus running
in a straight line has a distinct advantage over veering to the side.

Erik Decker National Institute of Animal Husbandry Department of Cattle
and Sheep Tjele, Denmark

Trunk drunk

Q: How do elephants drink? Elephants suck water into their trunks, but
how do they transfer the water into their mouths? If the elephant squirts
the water from its trunk by exhaling, how can it swallow at the same time?
Try it: it’s impossible to breathe and drink at the same time.

* * *

A: Elephants drink by sucking up to 10 litres of water into their trunks,
then placing the trunk tip in the mouth and squirting. Often they aid
the process by tilting their heads so the water flows downhill from trunk
to mouth. The breathing passages are separate from the oesophagus, as they
are in most mammals, so there is no conflict between drinking and breathing.
The only problem could occur at the point when the trunk is exhaling the
water and the mouth is receiving it but, after the trunk is emptied, a breath
can be taken by the trunk along with a swallow down the throat.

Indeed, small human infants are able to suck while at the same time
breathing through their noses, just like other mammals. After a few months,
changes in the soft palate cause the breathing and drinking passages to
be united in the mouth. This makes humans unusual and the questioner unable
to share breathing with drinking.

When elephants are very young, they cannot coordinate their trunk muscles
and resort to drinking directly with their mouths, squatting down on their
front knuckles. However, they still have no problem drinking and breathing
at the same time.

W. K. Lindsay Oxford

Run rabbit

Q: I was walking in the country with my dog when a rabbit crossed our
path. My dog did not see the rabbit, but on reaching the point where it
crossed our path he put his nose to the ground and followed the trail. After
10 metres, he sensed he was going the wrong way and turned around. How could
he smell which way the rabbit was running?

* * *

A: The dog does three things to enable it to follow the rabbit. First,
to locate the trail, it walks quickly, making a series of about 13 rapid
sniffs (at the rate of about 6 per second) while scanning its nose over
the area. Having located the trail, it embarks on the next phase of the
process. It slows down and makes a longer series of about 36 sniffs (again
about 6 per second) while following the trail in one direction. The nose
is held close to, but not touching, the ground, and it is now that the dog
decides which way the rabbit has gone. It needs only to sniff between two
and five footprints to decide in which direction to go.

It’s an amazing feat accomplished in about 4 seconds by sensing the
difference in the concentration of the scent in the air above consecutive
footprints, the theory being that the longer the print has been on the
ground, the fainter the scent. A dog’s perception of scent intensity depends
on the number of scent molecules detected per unit of time. In deciding
which way to go, the dog keeps his sniff frequency constant and the scent
a constant distance from its nose (about 1 cm) while it samples constant
volumes of air with each sniff.

D. P. Maitland Department of Pure and Applied Biology University of
Leeds

This week’s questions – Shocking TV

Shocking TV: After switching off a television in the dark why, when
the screen is touched, does static electricity discharge through the body
and the screen fluoresce at the point touched?

S. Mitchell Camborne, Cornwall

Bouncing along

Bouncing along: Do runners waste any energy output by raising their
bodies vertically every step? If so, what percentage is wasted, and why
do they do it?

P. B. Soul Reading, Berkshire