"Malcolm Kane" wrote in message
...
In message , BAC
writes

"Malcolm Kane" wrote in message
...
In message ,
writes
On Tue, 12 Apr 2005 08:47:22 +0100, "Tumbleweed"
wrote:


"Paul" wrote in message
...
Why do the RSPB and other conservation hooligan charities such as
the
Woodland Trust kill wildlife rather than manage it properly. We all
know killing large numbers of animals merely causes them to breed
more
and quicker.

Thats must be why there are lots of whales then?

No, It is always possible to slaughter a species almost to extinction.


But surely Angus when the main pressure was taken off a number of years
ago this principle you have quoted before that it causes faster
breeding
would by now have been making a really noticeable difference.

The concept of population rebound in some species may not be as far
fetched
as you seem to believe.

From Deer-UK's ecology of the Roe Deer,

http://www.deer-uk.com/roe_deer.htm

"In good conditions Roe have a high fecundity rate. In the South of
England
twins are the norm and in very good conditions triplets are not uncommon.
Many triplet fetuses are found during a post-mortem examination, though
not
all would necessarily have been born alive. But if all three fetuses are
the
same size, the indications are that all three will be live at birth.
Should
one or more be smaller than the others, then it is unlikely it would have
been born alive. In a particularly cold and/or wet early summer and
autumn,
the survival of all three triplets is greatly reduced and it is normally
buck kids that fare worst. This could be due to nature perpetuating the
species by saving the does for the following breeding season."

So, following extensive culling, it seems probable there would be reduced
competition for available fodder etc amongst the survivors, hence the
incidence of multiple births would be likely to increase, until the
population reached 'normal' densities for the prevailing conditions.

I do not know whether the near extinction of some of the planet's
cetaceans
will have had any effect on their species' birth rates, (it seems less
likely) but some experts are estimating the annual population growth of
some
species at between 7 and 8% since the general ban was introduced.


I would suggest that the climate etc. is far more of a difference
between North and South than the difference in fodder due to removal of
population. For example if we take deer which we have been discussing.
Roe are the commonest round here and getting commoner if the sightings I
have over the years are any guide. There is obviously more than ample
fodder after all they eat what the sheep and cattle eat. Using the
fodder theory killing off a significant proportion should increase the
numbers being born. I would see this as doubtful as they aren't at the
moment restricted by food supplies.

Population dynamics will be determined by the interplay between mortality
and recruitment within the population. If a local population is already in
optimal conditions for reproductive success, such that a reduction in the
population would be unlikely to lead to better conditioned females with an
increase in multiple births, and/or an increase in infant survival rates,
then I would agree no change would be likely to be evident, since
'recruitment' would already be at maximum rates.

However, if culling or a natural catastrophe were to create more favourable
conditions for multiple births and/or infant survival rates, then the
existence of the mechanism previously described suggests a faster than
anticipated 'rebound' would be possible.