Q: In the wild the average life span of weasels is about two years old
but when we pretend to have a domestic ferret to live up to 10-12 years
old, could it be a little adjustment in the percentage of protein would
be needed?  Probably their bodies are made to work perfectly fine with
the available diet in the wild considering that they are not supposed to
live so long, but in a long term, probably protein and other nutrients,
including carbohidrates, may need a bit different ratio among them
 
A: All I know is, each time I act wild, I shorten my own lifespan.  I
should have died decades ago maybe I did already, which is why I smell
so bad.
 
This is really a great question, because it illustrates the questioner
read something, thought about it, and rather than accepting it without
question, came up with a really good line of inquiry.  You win three
Attaboys for thinking.  Unfortunately, you are wrong, as I will explain,
so you get one Awwcrap, which wipes out all accumulated Attaboys.  Hey,
don't shoot the piano player; dems da rules! ;-)  All kidding aside,
this is an extremely insightful query, and I thank the questioner for
bringing it up.
 
It seems like you are bringing up two different points.  If you don't
mind, I ll rephrase them as
1) Do older ferrets have different nutritional needs?  and
2) What evidence do you have that the wild diet is the better one?
 
Before you can respond to either question, first thing you have to answer
is, What is the average age-at-death of polecats?  The answer is pretty
much the same regardless if you are looking at wild polecats or New
Zealand feral ferrets: roughly around 11 months of age.  However, that
is extremely misleading, as a look at a life table would show.
Zooarchaeologists, such as myself, are obsessed with the age of animals
when they die because we love constructing life tables.  When building
a life table you look at a large population and simply chart
(logarithmically) the number of individuals on one axis and their age on
the other.  When you look at the curve, what you see are the number of
survivors for each defined period of time.  For example, suppose you
counted the number of animals in a specific area every year, starting at
zero with the number born.  Imagine your numbers are 100, 40, 25, 12, 11,
10, 8, 6, 4, 3, 1, so at the end of 10 years you can expect to find a
single individual survivor.  If you carefully consider the numbers, it
would appear the species has high mortality in the first years of life,
but those that survive have a good chance of living a long life.  For
example, at birth the chance of an individual living 10 years is 100 to
1, but the chance of a 3-year-old living to 10 has improved to 12 to 1.
You can also look at this life table as inferring that in a population
of 226 individuals, 1 would be 11-years-old, 11 would be 4-years-old,
and 40 would be 1-year-old.  You would also know 60% the newborns can be
expected to die during their first year of life.
 
These types of tables give you three basic curves:
I: low-mortality until old age when death rates increase,
II: mortality doesn t change over time so death rate is the same for all
    age classes, and
III: high-mortality for the young with a lower death rate for the old.
 
Humans and pets in the USA have the first type of curve, but wild animals
tend to have the third type, with a high mortality rate for the young,
but once you survive to a certain age, your chances of living for a long
time are pretty good.  Unfortunately because so many infants are dying
that kind of a curve can have an average age-at-death that is extremely
young and doesn t reflect the lifespan of the survivors.  So, while the
average age at death for polecats might be 11 months, many survive to 4,
5, even 6 years of age or more.  Sort of sounds like ferrets, doesn't it?
The survivorship curve also reflects the polecat's reproductive strategy:
they put out a lot of babies.  If you assume a polecat jill has a litter
a year for three years (making her 4 years old), and the average number
of kits in a litter range from 4 to 7, the jill can produce as many as
21 babies or more in her lifetime.  She only needs two to replace herself
and the hob, so why all the extra babies?  Because they don t survive,
that's why; animals that overproduce babies do so to offset a high
species death rate.
 
Excluding human-caused mortality (road kill, hunting, etc.), the primary
causes of death for polecats are starvation and predation.  Disease and
injury are also factors, but to a lesser degree.  By far the biggest
challenge to any carnivore is getting enough food.  A single bad season
and the best polecat hunter will not survive the winter.  Predators kill
baby polecats in great numbers, but the greatest challenge after they
disperse is obtaining enough food, which few rarely do.  Most slowly
starve and in a weakened condition, either fall prey to predators or
disease.
[Posted in FML issue 4575]